Renal System - Abnormalities

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Structural developmental anomalies of the urinary system

LB30 Structural developmental anomalies of kidneys LB30.0 Renal agenesis or other reduction defects of kidney | LB30.1 Renal dysplasia | LB30.2 Congenital single renal cyst | LB30.3 Renal tubular dysgenesis | LB30.4 Oligomeganephronia | LB30.5 Accessory kidney | LB30.6 Fusion anomaly of kidneys | LB30.7 Ectopic or pelvic kidney | LB30.8 Medullary sponge kidney | LB30.9 Multicystic renal dysplasia

LB31 Structural developmental anomalies of urinary tract - LB31.0 Congenital hydronephrosis | LB31.1 Congenital primary megaureter | LB31.2 Foetal lower urinary tract obstruction | LB31.3 Exstrophy of urinary bladder | LB31.4 Congenital diverticulum of urinary bladder | LB31.5 Duplication of urethra | LB31.6 Congenital megalourethra | LB31.7 Megacystis-megaureter | LB31.8 Atresia or stenosis of ureter | LB31.9 Agenesis of ureter | LB31.A Duplication of ureter | LB31.B Malposition of ureter | LB31.C Congenital absence of bladder or urethra | LB31.D Congenital vesico-uretero-renal reflux

KC01 Congenital renal failure A severe irreversible decline in the ability of kidneys to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism which existed at, or often before, birth.


Obstructive Defect of the Renal Pelvis
Horseshoe kidney
Horseshoe kidney

There are many different forms of renal development abnormalities associated with kidney, ureters, bladder and urethra. There are many genetic disorders associated with failure or abnormal renal development.

Prenatal diagnosis of obstructive and renal agenesis/dysgenesis disorders are also important for early reproductive decisions by the parents. For example, with bilateral renal agenesis, failure of both kidneys to development, is not compatible with fetal/neonatal survival.

"Horseshoe" kidney is the historic name for renal fusion, where the two kidneys are joined together usually by a single pole.

Because of their close developmental association, often described as the urogenital system, there can be an associated genital abnormalities.

There are also a range of branchiootorenal spectrum disorders (branchiootorenal syndrome and branchiootic syndrome) where both renal and auditory development are affected (for review see [1]).

Renal Links: renal | Lecture - Renal | Lecture Movie | urinary bladder | Stage 13 | Stage 22 | Fetal | Renal Movies | Stage 22 Movie | renal histology | renal abnormalities | Molecular | Category:Renal
Historic Embryology - Renal  
1907 Urogenital images | 1911 Cloaca | 1921 Urogenital Development | 1915 Renal Artery | 1917 Urogenital System | 1925 Horseshoe Kidney | 1926 Embryo 22 Somites | 1930 Mesonephros 10 to 12 weeks | 1931 Horseshoe Kidney | 1932 Renal Absence | 1939 Ureteric Bud Agenesis | 1943 Renal Position

Some Recent Findings

Mouse renal ureteropelvic junction obstruction[2]
  • Outcome after prenatal diagnosis of congenital anomalies of the kidney and urinary tract[3] "Congenital anomalies of the kidney and urinary tract are common findings on fetal ultrasound. The aim of this prospective observational study was to describe outcome and risk factors in 115 patients born 1995-2001. All prenatally diagnosed children were stratified into low- and high-risk group and followed postnatally clinically and by imaging at defined endpoints. ...Our study revealed a good prognosis in the majority of these children, in particular with prenatally low risk, i.e. isolated uni- or bilateral hydronephrosis, and revealed oligohydramnios and postnatal bilateral anomalies as risk factors for a non-favourable outcome, defined as need of surgery, persistent anomalies with impaired renal function, end stage renal failure or death."
  • Urothelial Defects from Targeted Inactivation of Exocyst Sec10 in Mice Cause Ureteropelvic Junction Obstructions[2] "Most cases of congenital obstructive nephropathy are the result of ureteropelvic junction obstructions, and despite their high prevalence, we have a poor understanding of their etiology and scarcity of genetic models. The eight-protein exocyst complex regulates polarized exocytosis of intracellular vesicles in a large variety of cell types. Here we report generation of a conditional knockout mouse for Sec10, a central component of the exocyst, which is the first conditional allele for any exocyst gene. Inactivation of Sec10 in ureteric bud-derived cells using Ksp1.3-Cre mice resulted in severe bilateral hydronephrosis and complete anuria in newborns, with death occurring 6-14 hours after birth."
  • Congenital urological anomalies diagnosed in adulthood[4] "Despite worldwide availability of prenatal ultrasound, many patients are diagnosed in adult life with congenital anomalies such as ureteropelvic junction obstruction (UPJO), undescended testicle (UDT), ureterocele, hypospadias, vesicoureteral reflux (VUR) and primary obstructing megaureter (POM)."
  • Etv4 and Etv5 are required downstream of GDNF and Ret for kidney branching morphogenesis[5] "Mice lacking both Etv4 alleles and one Etv5 allele show either renal agenesis or severe hypodysplasia, whereas kidney development fails completely in double homozygotes. We identified several genes whose expression in the ureteric bud depends on Etv4 and Etv5, including Cxcr4, Myb, Met and Mmp14. Thus, Etv4 and Etv5 are key components of a gene network downstream of Ret that promotes and controls renal branching morphogenesis."
More recent papers  
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Search term: Abnormal Renal Development

Australian Statistics

Australian abnormalities pie urogen.png

Statistics - Top Ten

Australian Data 1981-92

The ten most frequently reported birth defects in Victoria between 2003-2004.

  1. Hypospadias
  2. Obstructive Defects of the Renal Pelvis or Obstructive Genitourinary Defects
  3. Ventricular Septal Defect
  4. Congenital Dislocated Hip
  5. Trisomy 21 or Down syndrome
  6. Hydrocephalus
  7. Cleft Palate
  8. Trisomy 18 or Edward Syndrome - multiple abnormalities of the heart, diaphragm, lungs, kidneys, ureters and palate 86% discontinued.
  9. Renal Agenesis/Dysgenesis - reduction in neonatal death and stillbirth since 1993 may be due to the more severe cases being identified in utero and being represented amongst the increased proportion of terminations (approximately 31%).
  10. Cleft Lip and Palate - occur with another defect in 33.7% of cases.

Obstructive Renal Pelvis Defect

Renal outflow obstruction

Obstructive Renal Pelvis Defect (obstructive defects of the renal pelvis, uteropelvic junction obstruction, pelvo-uterero junction obstruction) is a term describing a developmental renal abnormality due to partial or complete blockage of the drainage of the kidney pelvis requiring surgical correction.

The blockage during development can be due to failure of recanalization of the outflow tract.

The blockage can have several anatomical causes including:

  1. ureter twisting or bending
  2. ureter compression by a blood vessel
  3. malformations of the muscular wall

The blockage leads to an accumulation of urine in the affected region, with several potential effects: nephron damage from compression (hydronephrosis); decreased urine output leading to lack of amniotic fluid (oligohydramnios); respiratory development effects due to the lack of amniotic fluid. The most common type of obstruction is at the uteropelvic junction (UPJ), between the junction of the ureter and the kidney. Blockage lower as the ureter enters the bladder, the ureterovesicular junction (UVJ), usually involves only one kidney and the back flow enlarges the affected ureter (megaureter).

Renal Agenesis or Dysgenesis

Q60 Renal agenesis and other reduction defects of kidney

Incl.: atrophy of kidney: congenital infantile congenital absence of kidney

  • Q60.0 Renal agenesis, unilateral
  • Q60.1 Renal agenesis, bilateral
  • Q60.2 Renal agenesis, unspecified
  • Q60.3 Renal hypoplasia, unilateral
  • Q60.4 Renal hypoplasia, bilateral
  • Q60.5 Renal hypoplasia, unspecified
  • Q60.6 Potter's syndrome
Potter's syndrome or sequence is a rare condition (1 in 2000-5000) resulting in bilateral renal agenesis and occurs more frequently in primigravid mothers and more commonly in male offspring. At birth affected infants have a characteristic facial phenotype known as "Potter facies", named after Potter (1946) original description.[6]
Renal agenesis. DTPA scan shows agenesis of the right kidney.[7]

Unilateral renal absence is relatively common and may be asymptomatic. In the complete form, bilateral absence, the child is not viable and dies within a few days of birth.

Features associated with this anomaly are:

  • Oligohydramnios
  • Amnion nodosum (small warty amnion with accretions of squamous cells on the inner wall). This is tangible evidence for oligohydramnios.
  • Facial deformities: This results from uterine moulding around the head. The ears are low slung and simple, the mandible is small, the nose flattened and the eyes exhibit Pre-epicanthic folds. This is a horseshoe shaped flap of skin from the upper lid to the cheek in front of the epicanthus. (Downs syndrome has an epicanthic fold). Note that the genesis is occasionally incomplete allowing survival (e.g.) Causal factors are largely unknown although there is some familial predisposition. There has been described a mutation in the enzyme, heparan sulfate 2-sulfotransferase, that generates a similar phenotype in the mouse.

Note that upper G.I.T. obstruction is associated with POLYHYDRAMNIOS whereas failure of fetal micturition is associated with OLIGOHYDRAMNIOS with consequent firm uterine moulding on the fetus, leading to facial, locomotor and palatal deformities.

Renal agenesis 01.jpg

Renal agenesis. I.V. pyelography showing right renal agenesis (or dysplasia) (>). The right hip dysplasia is also shown (>>).[8]

Links: OMIM - Urogenital Adysplasia, Hereditary

Renal Fusion

A Horseshoe.

ICD - Q63.1 Lobulated, fused and horseshoe kidney

Also described as Horseshoe kidney.
  • fusion of the lower poles of the kidney.
  • During migration from the sacral region the two metanephric blastemas can come into contact, mainly at the lower pole.
  • The ureters pass in front of the zone of fusion of the kidneys.
  • The kidneys and ureters usually function adequately but there is an increased incidence of upper urinary tract obstruction or infection.
  • Some horseshoe variations have been described as having associated ureter abnormalities including duplications.
Horseshoe kidney 01.jpg

Renal fusion (pathology specimen)


Eisendrath DN Phifer FM and Culver HB. Horseshoe Kidney (1925) Ann Surg. 82(5): 735-64. PubMed 17865363

Boyden EA. Description of a horseshoe kidney associated with left inferior vena cava and disc-shaped suprarenal glands, together with a note on the occurrence of horseshoe kidneys in human embryos. (1931) Anat. Rec. 51(2): 187-211.

Renal-Adrenal Fusion

A rare anomaly of the upper pole of the kidney historically first described by Rokitansky in 1855[9]. Intrarenal ectopic adrenal tissue can also occur and in such instances consist of adrenal cortical tissue with no adrenal medullary tissue. Other organ fusions can occur with splenogonadal fusion the most commonly reported.

Triad Syndrome

Prune Belly Syndrome

Also described as Prune Belly Syndrome.

The Triad is:

  1. Agenesis of abdominal wall muscles
  2. Bladder outflow obstruction
  3. Bilateral undescended testes

The condition was first described by Frolich[10]and then called "prune belly syndrome" as a descriptive, because the intestinal pattern is evident through the thin protruding abdominal wall in the infant.[11]

Survival of the prune belly child depends on the number of functioning remaining nephrons at birth and the operability of the obstruction.

In some cases there are vestiges of muscle in the abdominal wall and it is not known whether this represents (a) destruction of muscle, or (b) failure of development of muscle. The causes of this malformation are little known, but maternal therapy with estrogens in the first trimester has been implicated frequently.

Polycystic Kidney Disease

Multicystic kidney
Multicystic kidney
Multicystic kidney and histology
Multicystic kidney and histology[12]
  • diffuse cystic malformation of both kidneys
  • cystic malformations of liver and lung often associated, Often familial disposition
  • Two types
    • Infantile (inconsistent with prolonged survival)
    • Adult (less severe and allows survival)
  • Autosomal dominant PKD disease - recently identified at mutations in 2 different human genes encoding membrane proteins (possibly channels)
  • Defects in the genes encoding PC1 or PC2 lead to aberrant gene transcription, cell proliferation, and ion secretion, which in turn result in the formation of fluid-filled cysts.
  • As cysts balloon out from individual nephrons, their collective effect leads to the displacement of the normal renal parenchyma and the formation of a cyst-filled kidney with reduced functional capacity.
Polycystic kidney disease cartoon.jpg

Cyst formation at the level of the cell, nephron, and kidney[13]

Nephroblastoma (Wilms' Tumor)

Wilms tumor
  • (nephroblastoma) Named after Max Wilms, a German doctor who wrote first medical articles 1899
  • most common type of kidney cancer children
  • WT1 gene - encodes a zinc finger protein[14][15]
  • Both constitutional and somatic mutations disrupting the DNA-binding domain of WT1 result in a potentially dominant-negative phenotype
  • some blastema cells (mass of undifferentiated cells) persist to form a ‘nephrogenic rest’
  • Most rests become dormant or regress but others proliferate to form hyperplastic rests
  • any type of rest can then undergo a genetic or epigenetic change to become a neoplastic rest
  • can proliferate further to produce a benign lesion (adenomatous rest) or a malignant Wilms’ tumour

Renal Cysts

The Bosniak classification system (I - IV) was designed to separate identified cystic renal masses by analysis of computed tomography (CT) features into surgical and nonsurgical categories.[16] Named after Morton Bosniak, Yale University School of Medicine, the developer of this classification system.

  1. Category I lesions are simple benign cysts showing homogeneity, water content, and a sharp interface with adjacent renal parenchyma, with no wall thickening, calcification, or enhancement.
  2. Category II consists of cystic lesions with one or two thin (<=1 mm thick) septations or thin, fine calcification in their walls or septa (wall thickening > 1 mm advances the lesion into surgical category III) and hyperdense benign cysts with all the features of category I cysts except for homogeneously high attenuation. A benign category II lesion must be 3 cm or less in diameter, have one quarter of its wall extending outside the kidney so the wall can be assessed, and be nonenhancing after contrast material is administered.
  3. Category IIF consists of minimally complicated cysts that need followup. This is a group not well defined by Bosniak but consists of lesions that do not neatly fall into category II. These lesions have some suspicious features that deserve followup to detect any change in character.
  4. Category III consists of true indeterminate cystic masses that need surgical evaluation, although many prove to be benign. They may show uniform wall thickening, nodularity, thick or irregular peripheral calcification, or a multilocular nature with multiple enhancing septa. Hyperdense lesions that do not fulfill category II criteria are included in this group.
  5. Category IV lesions with a nonuniform or enhancing thick wall, enhancing or large nodules in the wall, or clearly solid components in the cystic lesion. Enhancement was considered present when lesion components increased by at least 10 H.

Urorectal Septum Malformation

Urorectal septum malformation thought to be a deficiency in caudal mesoderm which in turn leads to the malformation of the urorectal septum and other structures in the pelvic region. Recent research has also identified the potential presence of a persistent urachus prior to septation of the cloaca (common urogenital sinus).

Clinically the condition is described as a urorectal septum malformation sequence (URSMS): female disorder of sexual development; ambiguous external genitalia; imperforate anus, vagina, and urethra; renal, colonic, and lumbosacral anomalies.

Renal Vascular Anomalies

There is an excellent recent 2010 review[17] of renal vascular anomalies shown in adults using computed tomography. The images below are from that review.

Renal Arteries

Multiple renal arteries 01.jpg Accessory renal artery.jpg
Multiple renal arteries Accessory renal artery

Renal Veins

Supernumerary renal vein 03.jpg

Supernumerary right renal vein

Supernumerary renal vein 01.jpg

Supernumerary right renal vein

Supernumerary renal vein 04.jpg

Multiple right renal veins

Supernumerary renal vein 02.jpg

Multiple right renal veins

Renal Vascular Anomalies: Multiple renal arteries | Accessory renal artery | Supernumerary right renal vein 1 | Supernumerary right renal vein 1 | Multiple right renal veins 2 | Multiple right renal veins 2 | Cardiovascular System Development

Bladder Exstrophy

 ICD-11 LB31.3 Exstrophy of urinary bladder - Bladder exstrophy (or classic bladder exstrophy) is a congenital genitourinary malformation belonging to the spectrum of the exstrophy-epispadias complex and is characterized by an evaginated bladder plate, epispadias and an anterior defect of the pelvis, pelvic floor and abdominal wall.
  • developmental abnormality associated with bladder development.
  • origins appear to occur not just by abnormal bladder development, but by a congenital malformation of the ventral wall of abdomen (between umbilicus and pubic symphysis).
  • There may also be other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies).


  • absent or small bladder - associated with renal agenesis.

Bladder Duplication

Neonatal duplicated bladder MRI 01.jpg

Bladder duplication

An extremely rare abnormality. This Magnetic Resonance Image (MRI) shows a complete bladder duplication with urethra duplication, diphallus, anorectal malformation and rightsided renal agensis with ipsilateral gonadal agenesisis.[18]
  • red arrow - collapsed right bladder
  • blue arrow - distended left bladder
  • orange arrow - midline septum
  • yellow arrow - right phallus
  • green arrow - left phallus


The distal ureter balloons at the opening into the bladder and forms a sac-like pouch. Often associated with other ureter abnormalities.

Ureter and Urethra

Ureteral duplication. Frontal radiograph from an intravenous urogram study shows bilateral complete ureteral duplication.[7]
  • Ureter - Duplex Ureter, ectopic ureter
    • Meyer-Weigert Rule - clinical term for the arrangement of the ureter in a completely duplicated renal system, the ureter from the upper renal pole enters the bladder more medially and caudally than the ureter from the lower renal pole.
  • Urethra - Urethral Obstruction and Hypospadias

Female genital and ureter abnormality 03.jpg

Ectopic and dilated left ureter (small arrows) inserting ectopically into the obstructed left hemivagina (asterisk) on MR imaging in a 17-year-old girl.[19]

See also Genital System - Abnormalities


  1. Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A & Smith RJH. (1993). Branchiootorenal Spectrum Disorders. , , . PMID: 20301554
  2. 2.0 2.1 Fogelgren B, Polgar N, Lui VH, Lee AJ, Tamashiro KK, Napoli JA, Walton CB, Zuo X & Lipschutz JH. (2015). Urothelial Defects from Targeted Inactivation of Exocyst Sec10 in Mice Cause Ureteropelvic Junction Obstructions. PLoS ONE , 10, e0129346. PMID: 26046524 DOI.
  3. Nef S, Neuhaus TJ, Spartà G, Weitz M, Buder K, Wisser J, Gobet R, Willi U & Laube GF. (2016). Outcome after prenatal diagnosis of congenital anomalies of the kidney and urinary tract. Eur. J. Pediatr. , 175, 667-76. PMID: 26805407 DOI.
  4. Halachmi S & Pillar G. (2008). Congenital urological anomalies diagnosed in adulthood - management considerations. J Pediatr Urol , 4, 2-7. PMID: 18631884 DOI.
  5. Lu BC, Cebrian C, Chi X, Kuure S, Kuo R, Bates CM, Arber S, Hassell J, MacNeil L, Hoshi M, Jain S, Asai N, Takahashi M, Schmidt-Ott KM, Barasch J, D'Agati V & Costantini F. (2009). Etv4 and Etv5 are required downstream of GDNF and Ret for kidney branching morphogenesis. Nat. Genet. , 41, 1295-302. PMID: 19898483 DOI.
  6. POTTER EL. (1946). Facial characteristics of infants with bilateral renal agenesis. Am. J. Obstet. Gynecol. , 51, 885-8. PMID: 20984673
  7. 7.0 7.1 Alorainy IA, Barlas NB & Al-Boukai AA. (2010). Pictorial Essay: Infants of diabetic mothers. Indian J Radiol Imaging , 20, 174-81. PMID: 21042439 DOI.
  8. Acién P, Galán F, Manchón I, Ruiz E, Acién M & Alcaraz LA. (2010). Hereditary renal adysplasia, pulmonary hypoplasia and Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome: a case report. Orphanet J Rare Dis , 5, 6. PMID: 20388228 DOI.
  9. Rokitansky K. A manual of pathologic anatomy. Vol II. Philadelphia, Pa: Blanchard & Lea, 1855; 188.
  10. Frolich, F. Der Mangel der Muskeln, insbesondere der Seitenbauchmuskeln. Dissertation: Wurzburg (pub.) 1839.
  11. Osler, W. Congenital absence of the abdominal muscles with distended and hypertrophied urinary bladder. Bull. Johns Hopkins Hosp. 12: 331-333, 1901.
  12. Kumar M, Gupta U, Thakur S, Aggrawal S, Meena J, Sharma S & Trivedi SS. (2012). Prenatal sonographic evaluation and postnatal outcome of renal anomalies. Indian J Hum Genet , 18, 75-82. PMID: 22754226 DOI.
  13. Chapin HC & Caplan MJ. (2010). The cell biology of polycystic kidney disease. J. Cell Biol. , 191, 701-10. PMID: 21079243 DOI.
  14. Call KM, Glaser T, Ito CY, Buckler AJ, Pelletier J, Haber DA, Rose EA, Kral A, Yeger H & Lewis WH. (1990). Isolation and characterization of a zinc finger polypeptide gene at the human chromosome 11 Wilms' tumor locus. Cell , 60, 509-20. PMID: 2154335
  15. Sharma PM, Yang X, Bowman M, Roberts V & Sukumar S. (1992). Molecular cloning of rat Wilms' tumor complementary DNA and a study of messenger RNA expression in the urogenital system and the brain. Cancer Res. , 52, 6407-12. PMID: 1330293
  16. Israel GM & Bosniak MA. (2005). How I do it: evaluating renal masses. Radiology , 236, 441-50. PMID: 16040900 DOI.
  17. Kumar S, Neyaz Z & Gupta A. (2010). The utility of 64 channel multidetector CT angiography for evaluating the renal vascular anatomy and possible variations: a pictorial essay. Korean J Radiol , 11, 346-54. PMID: 20461189 DOI.
  18. Gajbhiye V, Nath S, Ghosh P, Chatterjee A, Haldar D & Das SK. (2015). Complete duplication of the urinary bladder: An extremely rare congenital anomaly. Urol Ann , 7, 91-3. PMID: 25657554 DOI.
  19. Wang ZJ, Daldrup-Link H, Coakley FV & Yeh BM. (2010). Ectopic ureter associated with uterine didelphys and obstructed hemivagina: preoperative diagnosis by MRI. Pediatr Radiol , 40, 358-60. PMID: 19924410 DOI.


Chariatte V, Ramseyer P & Cachat F. (2013). Uroradiological screening for upper and lower urinary tract anomalies in patients with hypospadias: a systematic literature review. Evid Based Med , 18, 11-20. PMID: 22815315 DOI.

Woodhouse CR, Neild GH, Yu RN & Bauer S. (2012). Adult care of children from pediatric urology. J. Urol. , 187, 1164-71. PMID: 22335866 DOI.


Fernando MA, Creighton SM & Wood D. (2015). The long-term management and outcomes of cloacal anomalies. Pediatr. Nephrol. , 30, 759-65. PMID: 25217327 DOI.

Chowdhary SK, Kandpal DK, Sibal A & Srivastava RN. (2014). Management of complicated ureteroceles: Different modalities of treatment and long-term outcome. J Indian Assoc Pediatr Surg , 19, 156-61. PMID: 25197194 DOI.

Search Pubmed

Search Pubmed: Obstructive Renal Pelvis Defects | Renal Agenesis | hydronephrosis | Ureterocele


  • anterior urethral valve - uncommon real abnormality.
  • bilateral renal agenesis - (BRA) failure of both kidney development and is not compatible with life and is associated with oligohydramnios and pulmonary hypoplasia.
  • CAKUT - congenital anomalies of the kidneys and urinary tract.
  • cystic dysplasia - term used in renal dysplasia if cysts are present.
  • Meyer-Weigert Rule - clinical term for the arrangement of the ureter in a completely duplicated renal system, the ureter from the upper renal pole enters the bladder more medially and caudally than the ureter from the lower renal pole.
  • posterior urethral valve - (congenital obstructing posterior urethral membrane) a common male renal abnormality (~1 in 10,000-25,000 live births) classified into 3 types. Membrane from mesonephric (Wolffian) duct origin forms of a thick, valve-like structure.
  • renal agenesis - term for a complete absence of renal development.
  • renal dysgenesis - term for several forms of abnormal kidney development, which includes aplasia, hypoplasia, dysplasia, and cystic disease.
  • renal aplasia - term for a rudimentary kidney without any functional nephrons.
  • renal hypoplasia - term for a small non-dysplastic kidney that has less than the normal number of calyces and nephrons.
  • renal dysplasia - term for focal, diffuse, or segmentally arranged primitive structures, specifically primitive ducts, resulting from abnormal metanephric differentiation. There can also be non-renal elements present.
  • renal adysplasia - term is used when aplasia and severe dysplasia are aspects of phenotypic spectrum.
  • unilateral renal agenesis - (URA) failure of a single kidney development, often asymptomatic if not detected by prenatal screening.

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