Table I. Nonsyndromic human CAKUT (Part 1) Type of Cause Anatomical and histological Gene malformation characteristics Renal agenesis No interaction between Absence of the ureter and kidney Ret, GDNF the UB and MM Renal hypoplasia Aberrant interactions Reduced number of UB branches and Pax2, Sall1 among the UB, MM nephrons that are fully formed Six2, BMP4 or stroma Small kidney size HNF1β UMOD Renal dysplasia Aberrant inteactions Reduced number of UB branches and Pax2 among the UB, MM nephrons. Presence of undifferentiated HNF1β or stroma stromal and mesenchymal cells, cysts or UMOD cartilage. Frequently associated with Nphp1 kidney hypoplasia BMP4, Six2 XPNPEP3 Polycystic Aberrant tubular and Cysts in tubules and collecting ducts Pkd1, Pkd2 kidneys collecting duct patterning Normally formed glomeruli HNF1β NPHP1 Multicystic Aberrant interactions Absence of glomeruli and tubules HNF1β dysplastic among the UB, MM or Presence of large size cysts UPIIIA kidneys stroma Poorly formed atretic ureters Aberrant patterning Small remnant kidney (if organ involutes

Table I. Nonsyndromic human CAKUT (Part 2) Type of Cause Anatomical and histological Gene malformation characteristics Medullary Aberrant tubular and Tubular atrophy, interstitial fibrosis, UMOD cystic kidney collecting duct patterning cysts in distal tubules and disease 2 medullary collecting ducts Duplex Supernumerary UB Duplex ureters and kidneys or Robo2 ureters budding from the ND duplex ureters and collecting FoxC1, FoxC2 systems BMP4 May be associated with VUR or obstruction if UB budding is ectopic Horseshoe Defects in renal capsule Kidneys are fused at inferior lobes HNF1β kidney Failed migration and located lower than usual VUR Ectopic UB budding from Movement of urine from the bladder Robo2 the ND or insertion into into the ureter or kidney Slit2 the bladder Can be due to urethral atresia or PUV Pax2 Can be associated with dysplastic UMOD Kidneys PUV Retention of the remnants Folds of posterior urethra in males ACE, AT1R of the urogenital membrane Associated with bilateral VUR, hydroureter, hydronephrosis, dysplastic kidneys