Array ( [0] => {{short description|Organ that filters blood and produces urine in humans}} [1] => {{Other uses}} [2] => {{pp-semi-indef}} [3] => {{Infobox anatomy [4] => | Name = Kidneys [5] => | Latin = ren [6] => | Greek = nephros [7] => | Image = Blausen 0592 KidneyAnatomy 01.png [8] => | Caption = The kidneys lie in the [[retroperitoneal space]] behind the abdomen, and act to filter blood to create [[urine]] [9] => | Image2 = Gray1123.png [10] => | Caption2 = View of the kidneys from behind, showing their blood supply and drainage [11] => | Precursor = [12] => | System = [[Urinary system]] and [[endocrine system]] [13] => | Artery = [[Renal artery]] [14] => | Vein = [[Renal vein]] [15] => | Nerve = [[Renal plexus]] [16] => | Lymph = [17] => }} [18] => [19] => In humans, the '''kidneys''' are two reddish-brown bean-shaped blood-filtering [[organ (anatomy)|organs]]{{Cite web |title=Kidneys: Anatomy, Function, Health & Conditions |url=https://my.clevelandclinic.org/health/body/21824-kidney |archive-url=https://web.archive.org/web/20230629150732/https://my.clevelandclinic.org/health/body/21824-kidney |archive-date=2023-06-29 |access-date=2023-07-13 |website=Cleveland Clinic |language=en}} that are a multilobar, multipapillary form of [[mammalian kidney]]s, usually without signs of external lobulation.{{Cite book |last1=Zhou |first1=Xin J. |url=https://books.google.com/books?id=25_cDQAAQBAJ&pg=PA19 |title=Silva's Diagnostic Renal Pathology |last2=Laszik |first2=Zoltan G. |last3=Nadasdy |first3=Tibor |last4=D'Agati |first4=Vivette D. |date=2017-03-02 |publisher=Cambridge University Press |isbn=978-1-316-61398-6 |pages=19 |language=en |access-date=2023-08-16 |archive-date=2023-04-04 |archive-url=https://web.archive.org/web/20230404005725/https://books.google.com/books?id=25_cDQAAQBAJ&pg=PA19 |url-status=live }}{{Cite book |last1=Haschek |first1=Wanda M. |url=https://books.google.com/books?id=RXsdAAAAQBAJ&pg=PA1678 |title=Haschek and Rousseaux's Handbook of Toxicologic Pathology |last2=Rousseaux |first2=Colin G. |last3=Wallig |first3=Matthew A. |last4=Bolon |first4=Brad |last5=Ochoa |first5=Ricardo |date=2013-05-01 |publisher=Academic Press |isbn=978-0-12-415765-1 |pages=1678 |language=en}} They are located on the left and right in the [[retroperitoneal space]], and in adult humans are about {{convert|12|cm|in|frac=2|abbr=off}} in length.{{cite book | vauthors = Lote CJ |title= Principles of Renal Physiology, 5th edition|page=21|year=2012|publisher=Springer}}{{cite book | vauthors = Mescher AL |year=2016 |title=Junqueira's Basic Histology, 14th edition |publisher=Lange |page=393}} They receive blood from the paired [[renal artery|renal arteries]]; blood exits into the paired [[renal vein]]s. Each kidney is attached to a [[ureter]], a tube that carries excreted [[urine]] to the [[urinary bladder|bladder]]. [20] => [21] => The kidney participates in the control of the volume of various [[body fluid]]s, fluid [[osmolality]], [[Acid-base homeostasis|acid-base balance]], various [[electrolyte]] concentrations, and removal of [[toxins]]. Filtration occurs in the [[glomerulus (kidney)|glomerulus]]: one-fifth of the blood volume that enters the kidneys is filtered. Examples of substances reabsorbed are solute-free [[water]], [[sodium]], [[bicarbonate]], [[glucose]], and [[amino acid]]s. Examples of substances secreted are [[hydrogen]], [[ammonium]], [[potassium]] and [[uric acid]]. The [[nephron]] is the structural and functional unit of the kidney. Each adult human kidney contains around 1 million nephrons, while a mouse kidney contains only about 12,500 nephrons. The kidneys also carry out functions independent of the nephrons. For example, they convert a precursor of [[vitamin D]] to its active form, [[calcitriol]]; and synthesize the [[hormone]]s [[erythropoietin]] and [[renin]]. [22] => [23] => [[Chronic kidney disease]] (CKD) has been recognized as a leading public health problem worldwide. The global estimated prevalence of CKD is 13.4%, and patients with [[kidney failure]] needing [[renal replacement therapy]] are estimated between 5 and 7 million.{{cite book | vauthors = Lv JC, Zhang LX | title = Renal Fibrosis: Mechanisms and Therapies | chapter = Prevalence and Disease Burden of Chronic Kidney Disease | series = Advances in Experimental Medicine and Biology | volume = 1165 | pages = 3–15 | year = 2019 | pmid = 31399958 | doi = 10.1007/978-981-13-8871-2_1 | isbn = 978-981-13-8871-2 | s2cid = 199519437 }} Procedures used in the management of kidney disease include chemical and microscopic examination of the urine ([[urinalysis]]), measurement of [[kidney function]] by calculating the estimated [[glomerular filtration rate]] (eGFR) using the [[serum creatinine]]; and [[kidney biopsy]] and [[CT scan]] to evaluate for abnormal anatomy. [[Kidney dialysis|Dialysis]] and [[kidney transplantation]] are used to treat [[kidney failure]]; one (or both sequentially) of these are almost always used when renal function drops below 15%. [[Nephrectomy]] is frequently used to cure [[renal cell carcinoma]]. [24] => [25] => [[Renal physiology]] is the study of [[kidney function]]. [[Nephrology]] is the medical specialty which addresses diseases of kidney ''function'': these include CKD, [[nephritic syndrome|nephritic]] and [[nephrotic syndrome]]s, [[acute kidney injury]], and [[pyelonephritis]]. [[Urology]] addresses diseases of kidney (and urinary tract) ''anatomy'': these include [[kidney cancer|cancer]], [[renal cyst]]s, [[kidney stones]] and [[ureteral stones]], and [[urinary tract obstruction]].{{cite book | vauthors = Cotran RS, Kumar V, Fausto N, Robbins SL, Abbas AK |title=Robbins and Cotran pathologic basis of disease |publisher=Elsevier Saunders |location=St. Louis, MO |year=2005 |isbn=978-0-7216-0187-8 }} [26] => [27] => The word “[[wikt:renal|renal]]” is an adjective meaning “relating to the kidneys”, and its roots are French or late Latin. Whereas according to some opinions, "renal" should be replaced with "kidney" in scientific writings such as "kidney artery", other experts have advocated preserving the use of "renal" as appropriate including in "renal artery".{{cite journal | vauthors = Kalantar-Zadeh K, McCullough PA, Agarwal SK, Beddhu S, Boaz M, Bruchfeld A, Chauveau P, Chen J, de Sequera P, Gedney N, Golper TA, Gupta M, Harris T, Hartwell L, Liakopoulos V, Kopple JD, Kovesdy CP, Macdougall IC, Mann JF, Molony D, Norris KC, Perlmutter J, Rhee CM, Riella LV, Weisbord SD, Zoccali C, Goldsmith D | display-authors = 6 | title = Nomenclature in nephrology: preserving 'renal' and 'nephro' in the glossary of kidney health and disease | journal = Journal of Nephrology | volume = 34 | issue = 3 | pages = 639–648 | date = June 2021 | pmid = 33713333 | pmc = 8192439 | doi = 10.1007/s40620-021-01011-3 }} [28] => [29] => {{TOC limit|3}} [30] => [31] => == Structure == [32] => [[File:Surface projections of the organs of the trunk.png|thumb|300px|Image showing the human [[trunk (anatomy)|trunk]] with positions of the organs. The kidneys are at the [[vertebral level]] of T12 to L3. ]] [33] => In humans, the kidneys are located high in the [[abdominal cavity]], one on each side of the [[vertebral column|spine]], and lie in a [[retroperitoneal]] position at a slightly oblique angle.{{cite web|url=http://science.howstuffworks.com/environmental/life/human-biology/kidney.htm|title=HowStuffWorks How Your Kidney Works|date=2001-01-10|access-date=2012-08-09|archive-date=2012-11-05|archive-url=https://web.archive.org/web/20121105124818/http://science.howstuffworks.com/environmental/life/human-biology/kidney.htm|url-status=live}} The asymmetry within the abdominal cavity, caused by the position of the [[liver]], typically results in the right kidney being slightly lower and smaller than the left, and being placed slightly more to the middle than the left kidney.{{cite web|url=http://www.indexedvisuals.com/scripts/ivstock/pic.asp?id=118-100 |title=Kidneys Location Stock Illustration |url-status=dead |archive-url=https://web.archive.org/web/20130927221414/http://www.indexedvisuals.com/scripts/ivstock/pic.asp?id=118-100 |archive-date=2013-09-27 }}{{cite web | title = Kidney | work = BioPortfolio Ltd. | url = http://www.bioportfolio.com/indepth/Kidney.html | archive-url = https://web.archive.org/web/20080210070807/http://www.bioportfolio.com/indepth/Kidney.html| archive-date= 10 February 2008 }}{{cite journal | vauthors = Glodny B, Unterholzner V, Taferner B, Hofmann KJ, Rehder P, Strasak A, Petersen J | title = Normal kidney size and its influencing factors - a 64-slice MDCT study of 1.040 asymptomatic patients | journal = BMC Urology | volume = 9 | issue = 1 | pages = 19 | date = December 2009 | pmid = 20030823 | pmc = 2813848 | doi = 10.1186/1471-2490-9-19 | doi-access = free }} The left kidney is approximately at the vertebral level [[thoracic vertebrae|T12]] to [[lumbar vertebrae|L3]],{{cite report | title = Bålens ytanatomy | trans-title = Superficial anatomy of the trunk | language = Swedish | vauthors = Dragomir A, Hjortberg M, Romans GM | work = Section for human anatomy at the Department of Medical Biology, Uppsala University, Sweden }} and the right is slightly lower. The right kidney sits just below the [[thoracic diaphragm|diaphragm]] and posterior to the [[liver]]. The left kidney sits below the diaphragm and posterior to the [[spleen]]. On top of each kidney is an [[adrenal gland]]. The upper parts of the kidneys are partially protected by the 11th and 12th [[rib]]s. Each kidney, with its adrenal gland is surrounded by two layers of fat: the [[adipose capsule of kidney|perirenal fat]] present between renal fascia and renal capsule and [[pararenal fat]] superior to the [[renal fascia]]. [34] => [35] => The human kidney is a bean-shaped structure with a [[wikt:convex|convex]] and a [[wikt:concave|concave]] border.{{Cite web |title=Renal system |url=https://www.britannica.com/science/human-renal-system |access-date=2022-05-22 |website=Britannica |language=en |archive-date=2022-05-31 |archive-url=https://web.archive.org/web/20220531015045/https://www.britannica.com/science/human-renal-system |url-status=live }} A recessed area on the concave border is the [[renal hilum]], where the [[renal artery]] enters the kidney and the [[renal vein]] and [[ureter]] leave. The kidney is surrounded by tough fibrous tissue, the [[renal capsule]], which is itself surrounded by [[adipose capsule of kidney|perirenal fat]], [[renal fascia]], and [[pararenal fat]]. The anterior (front) surface of these tissues is the [[peritoneum]], while the posterior (rear) surface is the [[transversalis fascia]]. [36] => [37] => The superior pole of the right kidney is adjacent to the liver. For the left kidney, it is next to the [[spleen]]. Both, therefore, move down upon inhalation. [38] => [39] => {|class="wikitable" [40] => |rowspan=2| '''Sex''' ||colspan=2 align="center"| '''Weight''', standard [[reference range]] [41] => |- [42] => |align="center"| '''Right kidney''' ||align="center"| '''Left kidney''' [43] => |- [44] => | Male{{cite journal | vauthors = Molina DK, DiMaio VJ | title = Normal organ weights in men: part II – the brain, lungs, liver, spleen, and kidneys | journal = The American Journal of Forensic Medicine and Pathology | volume = 33 | issue = 4 | pages = 368–372 | date = December 2012 | pmid = 22182984 | doi = 10.1097/PAF.0b013e31823d29ad | s2cid = 32174574 }} || {{convert|80-160|g|oz|frac=4|abbr=on}} || {{convert|80-175|g|oz|frac=4|abbr=on}} [45] => |- [46] => | Female{{cite journal | vauthors = Molina DK, DiMaio VJ | title = Normal Organ Weights in Women: Part II-The Brain, Lungs, Liver, Spleen, and Kidneys | journal = The American Journal of Forensic Medicine and Pathology | volume = 36 | issue = 3 | pages = 182–187 | date = September 2015 | pmid = 26108038 | doi = 10.1097/PAF.0000000000000175 | s2cid = 25319215 }} || {{convert|40-175|g|oz|frac=4|abbr=on}} || {{convert|35-190|g|oz|frac=4|abbr=on}} [47] => |} [48] => A Danish study measured the median renal length to be {{convert|11.2|cm|in|frac=16|abbr=on}} on the left side and {{convert|10.9|cm|in|frac=16|abbr=on}} on the right side in adults. Median renal volumes were {{cvt|146|cm3|cuin|frac=16}} on the left and {{cvt|134|cm3|cuin|frac=16}} on the right.{{cite journal | vauthors = Emamian SA, Nielsen MB, Pedersen JF, Ytte L | title = Kidney dimensions at sonography: correlation with age, sex, and habitus in 665 adult volunteers | journal = AJR. American Journal of Roentgenology | volume = 160 | issue = 1 | pages = 83–86 | date = January 1993 | pmid = 8416654 | doi = 10.2214/ajr.160.1.8416654 | doi-access = }} [49] => [50] => ===Gross anatomy=== [51] => [[File:KidneyStructures PioM.svg|thumb|300px|right| [52] =>
[53] => 1. [[Renal pyramid]] • [54] => 2. [[Interlobular artery]] • [55] => 3. [[Renal artery]] • [56] => 4. [[Renal vein]] [57] => 5. [[Renal hilum]] • [58] => 6. [[Renal pelvis]] • [59] => 7. [[Ureter]] • [60] => 8. [[Minor calyx]] • [61] => 9. [[Renal capsule]] • [62] => 10. [[Inferior renal capsule]] • [63] => 11. [[Superior renal capsule]] • [64] => 12. [[Interlobular vein]]{{citation needed|date=June 2022}} • [65] => 13. [[Nephron]] • [66] => 14. [[Renal sinus]] • [67] => 15. [[Major calyx]] • [68] => 16. [[Renal papilla]] • [69] => 17. [[Renal column]] [70] =>
]] [71] => The functional substance, or [[Parenchyma#Renal parenchyma|parenchyma]], of the human kidney is divided into two major structures: the outer [[renal cortex]] and the inner [[renal medulla]]. Grossly, these structures take the shape of eight to 18 cone-shaped [[renal lobe]]s, each containing renal cortex surrounding a portion of medulla called a [[renal pyramid]].{{cite book | vauthors = Boron WF |title=Medical Physiology: A Cellular And Molecular Approach |publisher=Elsevier/Saunders |year=2004 |isbn=978-1-4160-2328-9 }} Between the renal pyramids are projections of cortex called [[renal column]]s. [72] => [73] => The tip, or [[renal papilla|papilla]], of each pyramid empties urine into a [[minor calyx]]; minor calyces empty into [[major calyces]], and major calyces empty into the [[renal pelvis]]. This becomes the ureter. At the hilum, the ureter and renal vein exit the kidney and the renal artery enters. Hilar fat and lymphatic tissue with lymph nodes surround these structures. The hilar fat is contiguous with a fat-filled cavity called the [[renal sinus]]. The renal sinus collectively contains the renal pelvis and calyces and separates these structures from the renal medullary tissue.{{cite book | vauthors = Clapp WL | chapter = Renal Anatomy | veditors = Zhou XJ, Laszik Z, Nadasdy T, D'Agati VD, Silva FG | title = Silva's Diagnostic Renal Pathology | location = New York| publisher = Cambridge University Press | date = 2009 | isbn = 978-0-521-87702-2 }} [74] => [75] => The kidneys possess no overtly moving structures. [76] => [77] => [78] => File:Right kidney seen on abdominal ultrasound.jpg|Normal adult right kidney as seen on [[abdominal ultrasound]] with a pole to pole measurement of 9.34 cm [79] => File:CTscankidney.jpg|A [[CT scan]] of the abdomen showing the position of the kidneys. The left cross-section in the upper abdomen shows the [[liver]] on the left side of scan (right side of body). Center: cross-section showing the kidneys below the liver and spleen. Right: further cross-section through the left kidney. [80] => File:Slide42222.JPG|Image showing the structures that the kidney lies near [81] => File:Left kidney.jpg|Cross-section through a [[cadaver]]ic specimen showing the position of the kidneys [82] => [83] => [84] => === Blood supply === [85] => {{main|Renal circulation}} [86] => The kidneys receive blood from the [[renal artery|renal arteries]], left and right, which branch directly from the [[abdominal aorta]]. The kidneys receive approximately 20–25% of [[cardiac output]] in adult human.{{Citation |title=Urinary system |date=2015 |url=https://www.cambridge.org/core/books/design-of-mammals/urinary-system/E76848B86DA00C151DA92EDD8AB2F418 |work=The Design of Mammals: A Scaling Approach |pages=195–203 |editor-last=Prothero |editor-first=John William |place=Cambridge |publisher=Cambridge University Press |doi=10.1017/CBO9781316275108.016 |isbn=978-1-107-11047-2 |access-date=2022-06-25 |archive-date=2018-06-17 |archive-url=https://web.archive.org/web/20180617094738/https://www.cambridge.org/core/books/design-of-mammals/urinary-system/E76848B86DA00C151DA92EDD8AB2F418 |url-status=live }}{{Cite book |last1=Martini |first1=Frederic |title=Human Anatomy |last2=Tallitsch |first2=Robert B. |last3=Nath |first3=Judi L. |publisher=Pearson |year=2017 |isbn=9780134320762 |edition=9th |pages=689}} Each renal artery branches into segmental arteries, dividing further into [[interlobar arteries]], which penetrate the renal capsule and extend through the renal columns between the renal pyramids. The interlobar arteries then supply blood to the [[arcuate arteries]] that run through the boundary of the cortex and the medulla. Each arcuate artery supplies several [[interlobular]] arteries that feed into the [[afferent arteriole]]s that supply the glomeruli. [87] => [88] => Blood drains from the kidneys, ultimately into the [[inferior vena cava]]. After filtration occurs, the blood moves through a small network of small veins ([[venules]]) that converge into [[interlobular veins]]. As with the arteriole distribution, the veins follow the same pattern: the interlobular provide blood to the [[arcuate veins]] then back to the [[interlobar veins]], which come to form the [[renal vein]]s which exit the kidney. [89] => [90] => ===Nerve supply=== [91] => The kidney and [[nervous system]] communicate via the [[renal plexus]], whose fibers course along the renal arteries to reach each kidney.{{cite book |vauthors=Bard J, Vize PD, Woolf AS |title=The kidney: from normal development to congenital disease |publisher=Academic Press |location=Boston |year=2003 |page=154 |isbn=978-0-12-722441-1 |url=https://books.google.com/books?id=ctOm-cPwo60C&pg=PA154 |access-date=2020-10-19 |archive-date=2023-08-17 |archive-url=https://web.archive.org/web/20230817171609/https://books.google.com/books?id=ctOm-cPwo60C&pg=PA154 |url-status=live }} Input from the [[sympathetic nervous system]] triggers [[vasoconstriction]] in the kidney, thereby reducing [[renal blood flow]]. The kidney also receives input from the [[parasympathetic nervous system]], by way of the renal branches of the [[vagus nerve]]; the function of this is yet unclear.{{cite journal | vauthors = Schrier RW, Berl T | title = Mechanism of the antidiuretic effect associated with interruption of parasympathetic pathways | journal = The Journal of Clinical Investigation | volume = 51 | issue = 10 | pages = 2613–2620 | date = October 1972 | pmid = 5056657 | pmc = 332960 | doi = 10.1172/JCI107079 }} Sensory input from the kidney travels to the T10–11 levels of the [[spinal cord]] and is sensed in the corresponding [[dermatome (anatomy)|dermatome]]. Thus, pain in the flank region may be referred from corresponding kidney. [92] => [93] => === Microanatomy === [94] => [95] => {{citation needed span|date=November 2023|[[Nephron]]s, the urine-producing functional structures of the kidney, span the cortex and medulla. The initial filtering portion of a nephron is the [[renal corpuscle]], which is located in the cortex. This is followed by a [[renal tubule]] that passes from the cortex deep into the medullary pyramids. Part of the renal cortex, a [[medullary ray (anatomy)|medullary ray]] is a collection of renal tubules that drain into a single [[collecting duct]].}} [96] => [97] => Renal [[histology]] is the study of the [[microscopic]] structure of the kidney. The adult human kidney contains at least 26 distinct [[Cell type|cell types]].{{Cite Q|Q27013996}} Distinct cell types include: [98] => *Kidney glomerulus parietal cell [99] => *[[Kidney glomerulus podocyte]] [100] => *[[Kidney proximal tubule brush border cell]] [101] => *[[Loop of Henle thin segment cell]] [102] => *[[Thick ascending limb]] cell [103] => *[[Kidney distal tubule cell]] [104] => *[[Collecting duct system#Principal cell|Collecting duct principal cell]] [105] => *[[Collecting duct system#Intercalated cell|Collecting duct intercalated cell]] [106] => *Interstitial kidney cells [107] => [108] => == Gene and protein expression == [109] => {{Further |Bioinformatics#Gene and protein expression}} [110] => In humans, about 20,000 protein coding genes are expressed in human cells and almost 70% of these genes are expressed in normal, adult kidneys.{{Cite web|url=https://www.proteinatlas.org/humanproteome/kidney|title=The human proteome in kidney – The Human Protein Atlas|website=www.proteinatlas.org|access-date=2017-09-22|archive-date=2017-09-22|archive-url=https://web.archive.org/web/20170922194202/https://www.proteinatlas.org/humanproteome/kidney|url-status=live}}{{cite journal | vauthors = Uhlén M, Fagerberg L, Hallström BM, Lindskog C, Oksvold P, Mardinoglu A, Sivertsson Å, Kampf C, Sjöstedt E, Asplund A, Olsson I, Edlund K, Lundberg E, Navani S, Szigyarto CA, Odeberg J, Djureinovic D, Takanen JO, Hober S, Alm T, Edqvist PH, Berling H, Tegel H, Mulder J, Rockberg J, Nilsson P, Schwenk JM, Hamsten M, von Feilitzen K, Forsberg M, Persson L, Johansson F, Zwahlen M, von Heijne G, Nielsen J, Pontén F | display-authors = 6 | title = Proteomics. Tissue-based map of the human proteome | journal = Science | volume = 347 | issue = 6220 | pages = 1260419 | date = January 2015 | pmid = 25613900 | doi = 10.1126/science.1260419 | s2cid = 802377 }} Just over 300 genes are more specifically expressed in the kidney, with only some 50 genes being highly specific for the kidney. Many of the corresponding kidney specific proteins are expressed in the cell membrane and function as transporter proteins. The highest expressed kidney specific protein is [[Tamm–Horsfall protein|uromodulin]], the most abundant protein in urine with functions that prevent calcification and growth of bacteria. Specific proteins are expressed in the different compartments of the kidney with [[podocin]] and [[nephrin]] expressed in glomeruli, Solute carrier family protein [[SLC22A8]] expressed in proximal tubules, [[calbindin]] expressed in distal tubules and [[aquaporin 2]] expressed in the collecting duct cells.{{cite journal | vauthors = Habuka M, Fagerberg L, Hallström BM, Kampf C, Edlund K, Sivertsson Å, Yamamoto T, Pontén F, Uhlén M, Odeberg J | display-authors = 6 | title = The kidney transcriptome and proteome defined by transcriptomics and antibody-based profiling | journal = PLOS ONE | volume = 9 | issue = 12 | pages = e116125 | date = 2014-12-31 | pmid = 25551756 | pmc = 4281243 | doi = 10.1371/journal.pone.0116125 | doi-access = free | bibcode = 2014PLoSO...9k6125H }} [111] => [112] => == Development == [113] => {{Main|Kidney development}} [114] => [115] => The mammalian kidney develops from [[intermediate mesoderm]]. [[Kidney development]], also called ''nephrogenesis'', proceeds through a series of three successive developmental phases: the pronephros, mesonephros, and metanephros. The metanephros are primordia of the permanent kidney.{{cite book | vauthors = Carlson BM | title = Human Embryology and Developmental Biology | publisher = Mosby | location = Saint Louis | edition = 3rd | year = 2004 | isbn = 978-0-323-03649-8}} [116] => [117] => == Function == [118] => [[File:Kidney Nephron.png|thumb|The [[nephron]], shown here, is the functional unit of the kidneys. Its parts are labelled except the (gray) ''connecting tubule'' located after the (dark red) distal convoluted tubule and before the large (gray) collecting duct (mislabeled ''collection'' duct).]] [119] => {{main|Renal physiology}} [120] => [121] => The kidneys excrete a variety of waste products produced by [[metabolism]] into the urine. The microscopic structural and functional unit of the kidney is the [[nephron]]. It processes the blood supplied to it via filtration, reabsorption, secretion and excretion; the consequence of those processes is the production of [[urine]]. These include the nitrogenous wastes [[urea]], from protein [[catabolism]], and [[uric acid]], from [[nucleic acid]] metabolism. The ability of mammals and some birds to concentrate wastes into a volume of urine much smaller than the volume of blood from which the wastes were extracted is dependent on an elaborate [[countercurrent multiplication]] mechanism. This requires several independent nephron characteristics to operate: a tight hairpin configuration of the tubules, water and ion permeability in the descending limb of the loop, water impermeability in the ascending loop, and active ion transport out of most of the ascending limb. In addition, passive [[countercurrent exchange]] by the vessels carrying the blood supply to the nephron is essential for enabling this function. [122] => [123] => The kidney participates in whole-body [[homeostasis]], regulating [[acid–base balance]], [[electrolyte]] concentrations, [[extracellular fluid volume]], and [[blood pressure]]. The kidney accomplishes these homeostatic functions both independently and in concert with other organs, particularly those of the [[endocrine system]]. Various endocrine hormones coordinate these endocrine functions; these include [[renin]], [[angiotensin II]], [[aldosterone]], [[antidiuretic hormone]], and [[atrial natriuretic peptide]], among others. [124] => [125] => ===Formation of urine=== [126] => [[File:Physiology of Nephron.png|thumb|260px|Four main processes are involved in the creation of [[urine]].]] [127] => [128] => ====Filtration==== [129] => Filtration, which takes place at the [[renal corpuscle]], is the process by which cells and large proteins are retained while materials of smaller molecular weights are{{cite book | vauthors = Hall JE |title=Guyton and Hall textbook of medical physiology |date=2016 |publisher=Elsevier Health Sciences |location=Philadelphia, PA |isbn=978-0-323-38930-3 |edition=13th | page = 1129 }} filtered from the blood to make an [[Ultrafiltration (kidney)|ultrafiltrate]] that eventually becomes urine. The adult human kidney generates approximately 180 liters of filtrate a day, most of which is reabsorbed.{{Cite book |last1=Alpern |first1=Robert J. |url=https://books.google.com/books?id=w5nEg7VLEQ4C&pg=1405 |title=Seldin and Giebisch's The Kidney: Physiology and Pathophysiology |last2=Caplan |first2=Michael |last3=Moe |first3=Orson W. |date=2012-12-31 |publisher=Academic Press |isbn=978-0-12-381463-0 |pages=1405 |language=en |access-date=2022-07-28 |archive-date=2023-07-22 |archive-url=https://web.archive.org/web/20230722105802/https://books.google.com/books?id=w5nEg7VLEQ4C&pg=1405 |url-status=live }} The normal range for a twenty four hour urine volume collection is 800 to 2,000 milliliters per day.{{cite web|url=https://www.mountsinai.org/health-library/tests/urine-24-hour-volume|title=Urine 24-hour volume|website=mountsinai|access-date=21 November 2022|archive-date=21 November 2022|archive-url=https://web.archive.org/web/20221121180728/https://www.mountsinai.org/health-library/tests/urine-24-hour-volume|url-status=live}} The process is also known as hydrostatic filtration due to the hydrostatic pressure exerted on the capillary walls. [130] => [131] => ====Reabsorption==== [132] => [[File:2618 Nephron Secretion Reabsorption.jpg|thumb|Secretion and reabsorption of various substances throughout the nephron]] [133] => Reabsorption is the transport of molecules from this ultrafiltrate and into the peritubular capillary. It is accomplished via selective [[Cell surface receptor|receptor]]s on the luminal cell membrane. Water is 55% reabsorbed in the proximal tubule. Glucose at normal plasma levels is completely reabsorbed in the proximal tubule. The mechanism for this is the Na+/glucose cotransporter. A plasma level of 350 mg/dL will fully saturate the transporters and glucose will be lost in the urine. A plasma glucose level of approximately 160 is sufficient to allow glucosuria, which is an important clinical clue to diabetes mellitus. [134] => [135] => Amino acids are reabsorbed by sodium dependent transporters in the proximal tubule. [[Hartnup disease]] is a deficiency of the tryptophan amino acid transporter, which results in [[pellagra]].Le, Tao. ''First Aid for the USMLE Step 1'' 2013. New York: McGraw-Hill Medical, 2013. Print. [136] => [137] => {| class="wikitable" [138] => |- [139] => ! Location of Reabsorption !! Reabsorbed nutrient !! Notes [140] => |- [141] => | Early proximal tubule || Glucose (100%), amino acids (100%), bicarbonate (90%), Na+ (65%), Cl− (65%), phosphate (65%) and H2O (65%) || [142] => * [[Parathyroid hormone|PTH]] will inhibit phosphate reabsorption. [143] => * [[Angiotensin II|AT II]] stimulates Na+, H2O and HCO3− reabsorption. [144] => |- [145] => | Thin descending loop of Henle || H2O || [146] => * Reabsorbs via medullary hypertonicity and makes urine hypertonic. [147] => |- [148] => | Thick ascending loop of Henle || Na+ (10–20%), K+, Cl−; indirectly induces para cellular reabsorption of Mg2+, Ca2+ || [149] => * This region is impermeable to H2O and the urine becomes less concentrated as it ascends. [150] => |- [151] => | Early distal convoluted tubule || Na+, Cl− || [152] => * PTH causes Ca2+ reabsorption. [153] => |- [154] => | Collecting tubules || Na+(3–5%), H2O || [155] => * Na+ is reabsorbed in exchange for K+, and H+, which is regulated by aldosterone. [156] => * ADH acts on the V2 receptor and inserts [[aquaporins]] on the luminal side [157] => |- [158] => ! colspan="3" |Examples of substances that are reabsorbed in the kidneys, and the hormones that influence those processes. [159] => |} [160] => [161] => ====Secretion==== [162] => Secretion is the reverse of reabsorption: molecules are transported from the peritubular capillary through the interstitial fluid, then through the renal tubular cell and into the ultrafiltrate. [163] => [164] => ==== Excretion ==== [165] => The last step in the processing of the ultrafiltrate is ''excretion'': the ultrafiltrate passes out of the nephron and travels through a tube called the ''collecting duct'', which is part of the [[collecting duct system]], and then to the ureters where it is renamed ''urine''. In addition to transporting the ultrafiltrate, the collecting duct also takes part in reabsorption. [166] => [167] => ===Hormone secretion=== [168] => The kidneys secrete a variety of [[hormones]], including [[erythropoietin]], [[calcitriol]], and [[renin]]. [[Erythropoietin]] is released in response to [[Hypoxia (medical)|hypoxia]] (low levels of oxygen at tissue level) in the renal circulation. It stimulates [[erythropoiesis]] (production of red blood cells) in the [[bone marrow]]. [[Calcitriol]], the activated form of [[vitamin D]], promotes intestinal absorption of [[calcium]] and the renal [[reabsorption]] of [[phosphate]]. Renin is an [[enzyme]] which regulates [[angiotensin]] and [[aldosterone]] levels. [169] => [170] => ===Blood pressure regulation=== [171] => {{main|Blood pressure regulation|Renin–angiotensin system}} [172] => [173] => Although the kidney cannot directly sense blood, long-term regulation of [[blood pressure]] predominantly depends upon the kidney. This primarily occurs through maintenance of the [[extracellular fluid]] compartment, the size of which depends on the plasma [[sodium]] concentration. Renin is the first in a series of important chemical messengers that make up the [[renin–angiotensin system]]. Changes in renin ultimately alter the output of this system, principally the hormones [[angiotensin II]] and [[aldosterone]]. Each hormone acts via multiple mechanisms, but both increase the kidney's absorption of [[sodium chloride]], thereby expanding the extracellular fluid compartment and raising blood pressure. When renin levels are elevated, the concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of the extracellular fluid compartment, and an increase in blood pressure. Conversely, when renin levels are low, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure. [174] => [175] => ===Acid–base balance=== [176] => {{main|Acid–base homeostasis}} [177] => [178] => The two organ systems that help regulate the body's acid–base balance are the kidneys and lungs. [[Acid–base homeostasis]] is the maintenance of [[pH]] around a value of 7.4. The lungs are the part of respiratory system which helps to maintain acid–base homeostasis by regulating [[carbon dioxide]] (CO2) concentration in the blood. The respiratory system is the first line of defense when the body experiences and acid–base problem. It attempts to return the body pH to a value of 7.4 by controlling the respiratory rate. When the body is experiencing acidic conditions, it will increase the respiratory rate which in turn drives off CO2 and decreases the H+ concentration, therefore increasing the pH. In basic conditions, the respiratory rate will slow down so that the body holds onto more CO2 and increases the H+ concentration and decreases the pH.{{Citation needed|date=May 2022}} [179] => [180] => The kidneys have two cells that help to maintain acid-base homeostasis: intercalated A and B cells. The intercalated A cells are stimulated when the body is experiencing acidic conditions. Under acidic conditions, the high concentration of CO2 in the blood creates a gradient for CO2 to move into the cell and push the reaction HCO3 + H ↔ H2CO3 ↔ CO2 + H2O to the left. On the luminal side of the cell there is a H+ pump and a H/K exchanger. These pumps move H+ against their gradient and therefore require ATP. These cells will remove H+ from the blood and move it to the filtrate which helps to increase the pH of the blood. On the basal side of the cell there is a HCO3/Cl exchanger and a Cl/K co-transporter (facilitated diffusion). When the reaction is pushed to the left it also increases the HCO3 concentration in the cell and HCO3 is then able to move out into the blood which additionally raises the pH. The intercalated B cell responds very similarly, however, the membrane proteins are flipped from the intercalated A cells: the proton pumps are on the basal side and the HCO3/Cl exchanger and K/Cl co-transporter are on the luminal side. They function the same, but now release protons into the blood to decrease the pH.{{Citation needed|date=May 2022}} [181] => [182] => === Regulation of osmolality === [183] => The kidneys help maintain the water and salt level of the body. Any significant rise in [[plasma osmolality]] is detected by the [[hypothalamus]], which communicates directly with the [[posterior pituitary gland]]. An increase in osmolality causes the gland to secrete [[antidiuretic hormone]] (ADH), resulting in water reabsorption by the kidney and an increase in urine concentration. The two factors work together to return the plasma osmolality to its normal levels. [184] => [185] => ===Measuring function=== [186] => {{main|Kidney function}} [187] => Various calculations and methods are used to try to measure kidney function. [[Renal clearance]] is the volume of plasma from which the substance is completely cleared from the blood per unit time. The [[filtration fraction]] is the amount of plasma that is actually filtered through the kidney. This can be defined using the equation. The kidney is a very complex organ and [[mathematical model]]ling has been used to better understand kidney function at several scales, including fluid uptake and secretion.{{cite journal | vauthors = Weinstein AM | title = Mathematical models of tubular transport | journal = Annual Review of Physiology | volume = 56 | pages = 691–709 | year = 1994 | pmid = 8010757 | doi = 10.1146/annurev.physiol.56.1.691 }}{{cite journal | vauthors = Thomas SR |title=Modelling and simulation of the kidney |journal=Journal of Biological Physics and Chemistry |volume=5 |issue=2/3 |pages=70–83 |year=2005 |doi=10.4024/230503.jbpc.05.02}} [188] => [189] => ==Clinical significance== [190] => {{Main|Kidney disease}} [191] => [[Nephrology]] is the subspeciality under [[Internal Medicine]] that deals with kidney function and disease states related to renal malfunction and their management including [[Kidney dialysis|dialysis]] and kidney [[Organ transplantation|transplantation]]. [[Urology]] is the specialty under [[Surgery]] that deals with kidney structure abnormalities such as kidney [[cancer]] and [[cysts]] and problems with [[urinary tract]]. [[Nephrologists]] are [[internists]], and [[urologists]] are [[surgeons]], whereas both are often called "kidney doctors". There are overlapping areas that both [[nephrologists]] and [[urologists]] can provide care such as [[kidney stones]] and kidney related [[infections]]. [192] => [193] => There are many causes of [[kidney disease]]. Some causes are acquired over the course of life, such as [[diabetic nephropathy]] whereas others are [[congenital]], such as [[polycystic kidney disease]]. [194] => [195] => Medical terms related to the kidneys commonly use terms such as ''renal'' and the prefix ''nephro-''. The [[adjective]] ''renal'', meaning related to the kidney, is from the [[Latin language|Latin]] ''rēnēs'', meaning kidneys; the prefix ''nephro-'' is from the [[Ancient Greek]] word for kidney, ''nephros (νεφρός)''.{{cite book | vauthors = Maton A, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD | title = Human Biology and Health | publisher = Prentice Hall | year = 1993 | location = Englewood Cliffs, New Jersey, USA | url = https://archive.org/details/humanbiologyheal00scho | isbn = 978-0-13-981176-0 | url-access = registration }} For example, surgical removal of the kidney is a ''[[nephrectomy]]'', while a reduction in kidney function is called ''renal dysfunction''. [196] => [197] => ===Acquired Disease=== [198] => [199] => *[[Diabetic nephropathy]] [200] => *[[Glomerulonephritis]] [201] => *[[Hydronephrosis]] is the enlargement of one or both of the kidneys caused by obstruction of the flow of urine. [202] => *[[Interstitial nephritis]] [203] => *[[Kidney stone]]s (nephrolithiasis) are a relatively common and particularly painful disorder. A chronic condition can result in scars to the kidneys. The removal of kidney stones involves [[ultrasound]] treatment to break up the stones into smaller pieces, which are then passed through the urinary tract. One common symptom of kidney stones is a sharp to disabling pain in the middle and sides of the lower back or groin. [204] => *[[Kidney tumour]] [205] => **[[Wilms tumor]] [206] => **[[Renal cell carcinoma]] [207] => *[[Lupus nephritis]] [208] => *[[Minimal change disease]] [209] => *In [[nephrotic syndrome]], the [[glomerulus (kidney)|glomerulus]] has been damaged so that a large amount of [[protein]] in the blood enters the [[urine]]. Other frequent features of the nephrotic syndrome include swelling, low serum albumin, and high cholesterol. [210] => *[[Pyelonephritis]] is infection of the kidneys and is frequently caused by complication of a [[urinary tract infection]]. [211] => *[[Kidney failure]] [212] => ** [[Acute kidney failure]] [213] => ** [[Chronic kidney disease|Stage 5 Chronic Kidney Disease]] [214] => * [[Renal artery stenosis]] [215] => * [[Renovascular hypertension]] [216] => [217] => ===Kidney injury and failure=== [218] => {{main|Acute kidney injury|Chronic kidney disease|Kidney failure}} [219] => [220] => Generally, humans can live normally with just one kidney, as one has more functioning renal tissue than is needed to survive. Only when the amount of functioning kidney tissue is greatly diminished does one develop [[chronic kidney disease]]. [[Renal replacement therapy]], in the form of [[Kidney dialysis|dialysis]] or [[kidney transplantation]], is indicated when the [[glomerular filtration rate]] has fallen very low or if the renal dysfunction leads to severe symptoms.{{cite journal | vauthors = Kalantar-Zadeh K, Jafar TH, Nitsch D, Neuen BL, Perkovic V | title = Chronic kidney disease | journal = Lancet | volume = 398 | issue = 10302 | pages = 786–802 | date = August 2021 | pmid = 34175022 | doi = 10.1016/S0140-6736(21)00519-5 | s2cid = 235631509 | url = https://researchonline.lshtm.ac.uk/id/eprint/4663580/1/Kalantar-Zadeh_etal_2021-Preserving-Kidney-Function-in-People.pdf | access-date = 2022-05-22 | archive-date = 2022-05-17 | archive-url = https://web.archive.org/web/20220517153016/https://researchonline.lshtm.ac.uk/id/eprint/4663580/1/Kalantar-Zadeh_etal_2021-Preserving-Kidney-Function-in-People.pdf | url-status = live }} [221] => [222] => ===Dialysis=== [223] => [[File:Peritoneal dialysis.jpg|thumb|258x258px|A depiction of [[peritoneal dialysis]]]] [224] => {{main|Kidney dialysis}} [225] => Dialysis is a treatment that substitutes for the function of normal kidneys. Dialysis may be instituted when approximately 85%–90% of kidney function is lost, as indicated by a glomerular filtration rate (GFR) of less than 15. Dialysis removes metabolic waste products as well as excess water and sodium (thereby contributing to regulating blood pressure); and maintains many chemical levels within the body. Life expectancy is 5–10 years for those on dialysis; some live up to 30 years. Dialysis can occur via the blood (through a [[central venous catheter|catheter]] or [[arteriovenous fistula]]), or through the [[peritoneum]] ([[peritoneal dialysis]]) Dialysis is typically administered three times a week for several hours at free-standing dialysis centers, allowing recipients to lead an otherwise essentially normal life.{{cite web|title=Dialysis|url=https://www.kidney.org/atoz/content/dialysisinfo|website=National Kidney Foundation|access-date=8 November 2017|date=2015-12-24|archive-date=2017-09-26|archive-url=https://web.archive.org/web/20170926224542/https://www.kidney.org/atoz/content/dialysisinfo|url-status=live}} [226] => [227] => ===Congenital disease=== [228] => *Congenital [[hydronephrosis]] [229] => *Congenital obstruction of urinary tract [230] => *Duplex kidneys, or double kidneys, occur in approximately 1% of the population. This occurrence normally causes no complications, but can occasionally cause urinary tract infections.{{cite news |url=https://www.theguardian.com/society/2008/feb/19/health |title=How many people have four kidneys? |work=The Guardian |location=London |vauthors=Sample I |date=2008-02-19 |access-date=2016-12-19 |archive-date=2016-08-17 |archive-url=https://web.archive.org/web/20160817203659/https://www.theguardian.com/society/2008/feb/19/health |url-status=live }}{{cite web |url=https://abcnews.go.com/Health/girls-kidneys-fail-doctors-find-double-valves-saving/story?id=10668525 |title=Kidneys Fail, Girl Survives with Spare Parts |publisher=Abcnews.go.com |date=2010-05-18 |access-date=2011-01-03 |archive-date=2010-05-21 |archive-url=https://web.archive.org/web/20100521092403/http://abcnews.go.com/Health/girls-kidneys-fail-doctors-find-double-valves-saving/story?id=10668525 |url-status=live }} [231] => *[[Duplicated ureter]] occurs in approximately one in 100 live births [232] => *[[Horseshoe kidney]] occurs in approximately one in 400 live births [233] => *[[Nephroblastoma]] (Syndromic Wilm's tumour) [234] => * [[Nutcracker syndrome]] [235] => *[[Polycystic kidney disease]] [236] => **[[Autosomal dominant polycystic kidney disease]] affects patients later in life. Approximately one in 1000 people will develop this condition [237] => **[[Autosomal recessive polycystic kidney disease]] is far less common, but more severe, than the dominant condition. It is apparent ''in utero'' or at birth. [238] => *[[Renal agenesis]]. Failure of one kidney to form occurs in approximately one in 750 live births. Failure of both kidneys to form used to be fatal; however, medical advances such as amnioinfusion therapy during pregnancy and peritoneal dialysis have made it possible to stay alive until a transplant can occur. [239] => *[[Renal dysplasia]] [240] => *Unilateral small kidney [241] => *[[Multicystic dysplastic kidney]] occurs in approximately one in every 2400 live births [242] => *Ureteropelvic Junction Obstruction or UPJO; although most cases are congenital, some are acquired.{{Cite book | vauthors = Novick AC, Gill IS, Klein EA, Rackley R, Ross JH, Jones JS |chapter=Ureteropelvic Junction Obstruction |title=Operative Urology at the Cleveland Clinic |journal=Urology Annals|publisher=Humana Press|year=2006|isbn=978-1-58829-081-6|volume=8|location=Totowa, NJ|pages=S102–S108|doi=10.1007/978-1-59745-016-4_16|pmc=4869439|issue=Suppl 2}} [243] => [244] => === Diagnosis === [245] => Many renal diseases are diagnosed on the basis of a detailed [[medical history]], and [[physical examination]].{{cite journal |vauthors=Gaitonde DY |title=Chronic Kidney Disease: Detection and Evaluation |journal=Am Fam Physician |date=15 December 2017 |volume=12 |issue=96 |pages=776–783 |url=https://www.aafp.org/afp/2017/1215/p776.html |access-date=1 March 2021 |archive-date=26 February 2021 |archive-url=https://web.archive.org/web/20210226140126/https://www.aafp.org/afp/2017/1215/p776.html |url-status=live }} The medical history takes into account present and past symptoms, especially those of kidney disease; recent infections; exposure to substances toxic to the kidney; and family history of kidney disease. [246] => [247] => [[Renal function|Kidney function]] is tested by using [[blood test]]s and [[Clinical urine tests|urine tests]]. The most common blood tests are [[creatinine]], [[urea]] and [[electrolyte]]s. Urine tests such as [[urinalysis]] can evaluate for pH, protein, glucose, and the presence of blood. Microscopic analysis can also identify the presence of [[urinary cast]]s and crystals. The [[glomerular filtration rate]] (GFR) can be directly measured ("measured GFR", or mGFR) but this rarely done in everyday practice. Instead, special equations are used to calculate GFR ("estimated GFR", or eGFR).{{cite journal |title=KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease |journal=Kidney Int Suppl |date=2013 |volume=3 |pages=1–150 |url=https://kdigo.org/guidelines/ckd-evaluation-and-management/ |access-date=2021-01-25 |archive-date=2019-05-01 |archive-url=https://web.archive.org/web/20190501124111/https://kdigo.org/guidelines/ckd-evaluation-and-management/ |url-status=live }}{{cite web|vauthors= Post TW, Rose BD|veditors= Curhan GC, Sheridan AM|title= Diagnostic Approach to the Patient With Acute Kidney Injury (Acute Kidney Failure) or Chronic Kidney Disease|website= www.uptodate.com|date= December 2012|url= http://www.uptodate.com/contents/diagnostic-approach-to-the-patient-with-acute-kidney-injury-acute-renal-failure-or-chronic-kidney-disease|access-date= 2016-12-19|archive-date= 2015-11-10|archive-url= https://web.archive.org/web/20151110144346/http://www.uptodate.com/contents/diagnostic-approach-to-the-patient-with-acute-kidney-injury-acute-renal-failure-or-chronic-kidney-disease|url-status= live}} [248] => [249] => ==== Imaging ==== [250] => [[Renal ultrasonography]] is essential in the diagnosis and management of kidney-related diseases.Content initially copied from: {{cite journal | vauthors = Hansen KL, Nielsen MB, Ewertsen C | title = Ultrasonography of the Kidney: A Pictorial Review | journal = Diagnostics | volume = 6 | issue = 1 | pages = 2 | date = December 2015 | pmid = 26838799 | pmc = 4808817 | doi = 10.3390/diagnostics6010002 | doi-access = free }} [https://creativecommons.org/licenses/by/4.0/ (CC-BY 4.0)] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }} Other modalities, such as [[CT scan|CT]] and [[magnetic resonance imaging|MRI]], should always be considered as supplementary imaging modalities in the assessment of renal disease. [251] => [252] => ==== Biopsy ==== [253] => The role of the renal biopsy is to diagnose renal disease in which the etiology is not clear based upon noninvasive means (clinical history, past medical history, medication history, physical exam, laboratory studies, imaging studies). In general, a renal pathologist will perform a detailed morphological evaluation and integrate the morphologic findings with the clinical history and laboratory data, ultimately arriving at a pathological diagnosis. A renal [[pathologist]] is a physician who has undergone general training in anatomic pathology and additional specially training in the interpretation of renal biopsy specimens. [254] => [255] => Ideally, multiple core sections are obtained and evaluated for adequacy (presence of glomeruli) intraoperatively. A pathologist/pathology assistant divides the specimen(s) for submission for light microscopy, immunofluorescence microscopy and electron microscopy. [256] => [257] => The pathologist will examine the specimen using light microscopy with multiple staining techniques (hematoxylin and eosin/H&E, PAS, trichrome, silver stain) on multiple level sections. Multiple immunofluorescence stains are performed to evaluate for antibody, protein and complement deposition. Finally, ultra-structural examination is performed with electron microscopy and may reveal the presence of electron-dense deposits or other characteristic abnormalities that may suggest an etiology for the patient's renal disease. [258] => [259] => ==Other animals== [260] => {{Main|Kidney (vertebrates)}} [261] => In the majority of vertebrates, the [[mesonephros]] persists into the adult, albeit usually fused with the more advanced [[metanephros]]; only in [[amniote]]s is the mesonephros restricted to the embryo. The kidneys of [[fish]] and [[amphibian]]s are typically narrow, elongated organs, occupying a significant portion of the trunk. The collecting ducts from each cluster of nephrons usually drain into an ''archinephric duct'', which is [[homology (biology)|homologous]] with the [[vas deferens]] of amniotes. However, the situation is not always so simple; in [[cartilaginous fish]] and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the [[bladder]] or [[cloaca]]. Indeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in the adult. [262] => [263] => In the most primitive vertebrates, the [[hagfish]] and [[lamprey]]s, the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct. Invertebrates may possess excretory organs that are sometimes referred to as "kidneys", but, even in ''[[Amphioxus]]'', these are never homologous with the kidneys of vertebrates, and are more accurately referred to by other names, such as [[nephridia]]. In [[amphibian]]s, kidneys and the [[urinary bladder]] harbour specialized [[parasite]]s, [[monogenea]]ns of the family Polystomatidae.{{cite journal | vauthors = Theunissen M, Tiedt L, Du Preez LH | title = The morphology and attachment of Protopolystoma xenopodis (Monogenea: Polystomatidae) infecting the African clawed frog Xenopus laevis | journal = Parasite | volume = 21 | pages = 20 | year = 2014 | pmid = 24823278 | pmc = 4018937 | doi = 10.1051/parasite/2014020 }} [264] => [265] => The kidneys of [[reptile]]s consist of a number of lobules arranged in a broadly linear pattern. Each lobule contains a single branch of the ureter in its centre, into which the collecting ducts empty. Reptiles have relatively few nephrons compared with other amniotes of a similar size, possibly because of their lower [[metabolic rate]].{{cite book | vauthors = Romer AS, Parsons TS |year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|pages= 367–376|isbn= 978-0-03-910284-5}} [266] => [267] => [[Bird]]s have relatively large, elongated kidneys, each of which is divided into three or more distinct lobes. The lobes consists of several small, irregularly arranged, lobules, each centred on a branch of the ureter. Birds have small glomeruli, but about twice as many nephrons as similarly sized mammals. [268] => [269] => The human kidney is fairly typical of that of [[mammal]]s. Distinctive features of the mammalian kidney, in comparison with that of other vertebrates, include the presence of the renal pelvis and renal pyramids and a clearly distinguishable cortex and medulla. The latter feature is due to the presence of elongated [[Loop of Henle|loops of Henle]]; these are much shorter in birds, and not truly present in other vertebrates (although the nephron often has a short ''intermediate segment'' between the convoluted tubules). It is only in mammals that the kidney takes on its classical "kidney" shape, although there are some exceptions, such as the multilobed [[reniculate kidney]]s of [[pinniped]]s and [[cetacea]]ns. [270] => [271] => ===Evolutionary adaptation=== [272] => Kidneys of various animals show evidence of evolutionary [[adaptation]] and have long been studied in [[ecophysiology]] and [[comparative physiology]]. Kidney morphology, often indexed as the relative medullary thickness, is associated with habitat [[aridity]] among species of mammals{{cite journal | vauthors = al-Kahtani MA, Zuleta C, Caviedes-Vidal E, Garland T | title = Kidney mass and relative medullary thickness of rodents in relation to habitat, body size, and phylogeny | journal = Physiological and Biochemical Zoology | volume = 77 | issue = 3 | pages = 346–365 | year = 2004 | pmid = 15286910 | doi = 10.1086/420941 | url = http://www.biology.ucr.edu/people/faculty/Garland/Al-kahtaniEA2004.pdf | access-date = 2009-03-28 | url-status = dead | s2cid = 12420368 | citeseerx = 10.1.1.407.8690 | archive-url = https://web.archive.org/web/20100617221052/http://www.biology.ucr.edu/people/faculty/Garland/Al-kahtaniEA2004.pdf | archive-date = 2010-06-17 }} and diet (e.g., carnivores have only long loops of Henle). [273] => [274] => ==Society and culture== [275] => [276] => ===Significance=== [277] => [278] => ====Egyptian==== [279] => In [[ancient Egypt]], the kidneys, like the heart, were left inside the mummified bodies, unlike other organs which were removed. Comparing this to the biblical statements, and to drawings of human body with the heart and two kidneys portraying a set of scales for weighing justice, it seems that the Egyptian beliefs had also connected the kidneys with judgement and perhaps with moral decisions.{{cite journal | vauthors = Salem ME, Eknoyan G | title = The kidney in ancient Egyptian medicine: where does it stand? | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 140–147 | year = 1999 | pmid = 10213808 | doi = 10.1159/000013440 | s2cid = 35305403 }} [280] => [281] => ====Hebrew==== [282] => According to studies in modern and ancient Hebrew, various body organs in humans and animals served also an emotional or logical role, today mostly attributed to the [[brain]] and the [[endocrine system]]. The kidney is mentioned in several biblical verses in conjunction with the heart, much as the [[bowels]] were understood to be the "seat" of emotion – grief, joy and pain.{{Cite web|url=http://www.adath-shalom.ca/body_metaphors_bib_hebrew.htm|archive-url=https://web.archive.org/web/20030322082801/http://www.adath-shalom.ca/body_metaphors_bib_hebrew.htm|url-status=dead|archive-date=March 22, 2003|title=Body Part Metaphors in Biblical Hebrew by David Steinberg|date=March 22, 2003|access-date=July 21, 2019}} Similarly, the [[Talmud]] (''Berakhoth'' 61.a) states that one of the two kidneys counsels what is good, and the other evil. [283] => [284] => In the sacrifices offered at the biblical [[Tabernacle]] and later on at the temple in [[Jerusalem]], the priests were instructedLeviticus 3: 4, 10 and 15 to remove the kidneys and the adrenal gland covering the kidneys of the sheep, goat and cattle offerings, and to burn them on the altar, as the holy part of the "offering for God" never to be eaten.ie Deut 3:4,9,10,15... or the Babylonian Talmud, Bechorot (39a) Ch6:Tr2... [285] => [286] => ====India: Ayurvedic system==== [287] => In ancient India, according to the [[Ayurveda|Ayurvedic medical systems]], the kidneys were considered the beginning of the excursion channels system, the 'head' of the ''Mutra Srota''s, receiving from all other systems, and therefore important in determining a person's health balance and temperament by the balance and mixture of the three 'Dosha's – the three health elements: Vatha (or Vata) – air, Pitta – [[bile]], and Kapha – [[mucus]]. The temperament and health of a person can then be seen in the resulting color of the urine.{{Cite web|url=http://www.ayurvedacollege.com/articles/drhalpern/Vata_Doshas|title=What is Vata Dosha? Tips and diet for balancing vata | CA College of Ayurveda|website=www.ayurvedacollege.com|date=7 April 2010|access-date=July 21, 2019|archive-date=9 November 2019|archive-url=https://web.archive.org/web/20191109092730/http://www.ayurvedacollege.com/articles/drhalpern/Vata_Doshas|url-status=live}} [288] => [289] => Modern Ayurveda practitioners, a practice which is characterized as pseudoscience,[[List of topics characterized as pseudoscience]], according to the [[American Medical Association]]'s Report 12 of the Council of Scientific Affairs (A-97) and [http://www.skepdic.com/ayurvedic.html claims by skeptics] {{Webarchive|url=https://web.archive.org/web/20160810061129/http://skepdic.com/ayurvedic.html |date=2016-08-10 }} ('The Skeptics Dictionary' website) have attempted to revive these methods in medical procedures as part of Ayurveda [[Urine therapy]].{{cite journal | vauthors = Sangu PK, Kumar VM, Shekhar MS, Chagam MK, Goli PP, Tirupati PK | title = A study on Tailabindu pariksha – An ancient Ayurvedic method of urine examination as a diagnostic and prognostic tool | journal = AYU | volume = 32 | issue = 1 | pages = 76–81 | date = January 2011 | pmid = 22131762 | pmc = 3215423 | doi = 10.4103/0974-8520.85735 | doi-access = free }} These procedures have been called "nonsensical" by skeptics.{{cite web | title = A Few Thoughts on Ayurvedic Mumbo-Jumbo | vauthors = Barrett S | author-link = Stephen Barrett | url = https://www.old.quackwatch.org/04ConsumerEducation/chopra.html | access-date = 2022-05-22 | archive-date = 2020-09-29 | archive-url = https://web.archive.org/web/20200929051141/https://www.old.quackwatch.org/04ConsumerEducation/chopra.html | url-status = live }} M.D, head of the [[National Council Against Health Fraud]] NGO and owner of the QuackWatch website. [290] => [291] => ====Medieval Christianity==== [292] => The Latin term ''renes'' is related to the English word "reins", a synonym for the kidneys in [[Shakespearean English]] (e.g. ''[[Merry Wives of Windsor]]'' 3.5), which was also the time when the [[King James Version]] of the [[Bible]] was translated. Kidneys were once popularly regarded as the seat of the [[conscience]] and reflection,{{cite book |author3-link=William F. May (ethicist) | vauthors = Ramsey P, Jonsen AR, May WF |title=The Patient as Person: Explorations in Medical Ethics |date=2002 |publisher=Yale University Press |location=New Haven |isbn=978-0-300-09396-4 |page=60 |edition=Second}}{{cite book |title=History of Nephrology 2 |date=January 1997 |publisher=Karger Medical and Scientific Publishers |isbn=978-3-8055-6499-1 | page = 235 | veditors = Eknoyan G, Marketos SG, De Santo NG }} International Association for the History of Nephrology Congress, Reprint of ''American Journal of Nephrology''; v. 14, no. 4–6, 1994. and a number of verses in the Bible (e.g. Ps. 7:9, Rev. 2:23) state that God searches out and inspects the kidneys, or "reins", of humans, together with the heart.{{citation |url=https://intertextual.bible/text/revelation-2.23-berakhot-119.29 |title=intertextual.bible/text/revelation-2.23-berakhot-119.29 |access-date=2022-12-15 |archive-date=2022-12-15 |archive-url=https://web.archive.org/web/20221215081525/https://intertextual.bible/text/revelation-2.23-berakhot-119.29 |url-status=live }} [293] => [294] => ==History== [295] => Kidney stones have been identified and recorded about as long as written historical records exist.{{cite journal | vauthors = Tefekli A, Cezayirli F | title = The history of urinary stones: in parallel with civilization | journal = TheScientificWorldJournal | volume = 2013 | pages = 423964 | date = November 2013 | pmid = 24348156 | pmc = 3856162 | doi = 10.1155/2013/423964 | doi-access = free }} The urinary tract including the ureters, as well as their function to drain urine from the kidneys, has been described by [[Galen]] in the second century AD.{{cite journal | vauthors = Nahon I, Waddington G, Dorey G, Adams R | title = The history of urologic surgery: from reeds to robotics | journal = Urologic Nursing | volume = 31 | issue = 3 | pages = 173–180 | date = 2011 | pmid = 21805756 | doi = 10.7257/1053-816X.2011.31.3.173 }} [296] => [297] => The first to examine the ureter through an internal approach, called ureteroscopy, rather than surgery was [[Hampton Young]] in 1929. This was improved on by [[VF Marshall]] who is the first published use of a flexible [[endoscope]] based on [[fiber optics]], which occurred in 1964. The insertion of a drainage tube into the [[renal pelvis]], bypassing the uterers and urinary tract, called [[nephrostomy]], was first described in 1941. Such an approach differed greatly from the [[open surgery|open surgical]] approaches within the urinary system employed during the preceding two millennia. [298] => [299] => ==Additional images== [300] => [301] => File:Slide4nn.JPG|Right kidney [302] => File:Slide5pp.JPG|Kidney [303] => File:Slide3ppp.JPG|Right kidney [304] => File:Right kidney.jpg|Right kidney [305] => File:Left kidneys.jpg|Left kidney [306] => File:Kidneys.jpg|Kidneys [307] => File:Left kidney.jpg|Left kidney [308] => [309] => [310] => == See also == [311] => *[[Artificial kidney]] [312] => *[[Holonephros]] [313] => *[[Nephromegaly]] [314] => *[[Organ donation]] [315] => *[[Organ harvesting]] [316] => *[[Pelvic kidney]] [317] => *[[World Kidney Day]] [318] => *[[List of distinct cell types in the adult human body]] [319] => [320] => == References == [321] => === Citations === [322] => {{Reflist|30em}} [323] => [324] => === General and cited references === [325] => * {{Cite book |vauthors = Barrett KE, Barman SM, Yuan JX, Brooks H |year=2019 |title=Ganong's review of medical physiology |edition=26th |location=New York |isbn=9781260122404 |oclc=1076268769 |ref={{harvid|Ganong's Physiology|2019}}}} [326] => [327] => == External links == [328] => {{Commons category|Kidneys}} [329] => * [https://www.proteinatlas.org/humanproteome/kidney Kidney at the Human Protein Atlas] [330] => * [http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMNiereE.html Electron microscopic images of the kidney (Dr. Jastrow's EM-Atlas)] [331] => [332] => {{Urinary system anatomy}} [333] => {{Authority control}} [334] => [335] => [[Category:Kidney| ]] [336] => [[Category:Endocrine system]] [] => )
good wiki

Kidney

The kidney is an essential organ in the human body responsible for filtering waste products and excess water from the bloodstream, producing urine, and maintaining proper levels of electrolytes and fluids. This vital organ also plays a crucial role in regulating blood pressure and red blood cell production.

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This vital organ also plays a crucial role in regulating blood pressure and red blood cell production. Located in the abdominal cavity, kidneys are bean-shaped and are composed of millions of tiny units called nephrons. Defects or diseases affecting the kidneys can lead to various health problems, including kidney failure, which may require treatment such as dialysis or kidney transplantation. This Wikipedia page provides comprehensive information about the anatomy, function, diseases, diagnosis, and treatment options related to the kidney. It also delves into the historical background, development, and research conducted on this organ.

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