Renal Embryology B&B Flashcards
from which embryonic layer are the kidneys derived, and what are the 3 stages of embryonic renal development
intermediate mesoderm - 3 embryonic renal structures form in utero, first 2 degenerate:
- pronephros: week 4
- mesonephros: 1st trimester, contributes to vas deferens in males
- metanephros: appears 5th week, permanent kidney
what do the embryonic ureteric bud and metanephric mesenchyme become, respectively?
ureteric bud: outgrowth of mesonephric (Wolffian) duct, becomes ureter/pelvis/calyxes/collecting ducts
metanephric mesenchyme (aka metanephric blastema): interacts with ureteric bud to form glomerulus to distal tubule
*aberrant interaction between ureteric bud and metanephric mesenchyme = kidney malformation!
Wilms’ Tumor
proliferation of metanephric blastema/mesenchyme - embryonic glomerular structure
associated with mutations of WT1 - expressed in metanephric blastema
most common renal malignancy in young children
most common renal malignancy in young children, caused by proliferation of metanephric blastema
Wilms’ Tumor - associated with mutations in WT1
what causes renal agenesis and what is the physiologic consequence of this?
ureteric bud fails to develop, therefore fails to signal to mesenchyme
if single kidney, other kidney compensates —> hypertrophy, hyperfiltration, risk of focal segmental glomerular sclerosis, risk of renal failure (decades later)
if both kidneys —> oligohydramnios, Potter’s syndrome
multicystic dysplastic kidney
abnormal ureteric bud-mesenchyme interaction in utero —> kidney replaced with cysts
no/little functioning renal tissue
what is the consequence of ureteropelvic junction (UPJ) obstruction?
ureteropelvic junction is last renal connection to form in embyro
obstruction —> narrowing at proximal ureter at junction
—> hydronephrosis, poor urinary flow —> kidney stones/UTIs
*common cause of single kidney obstruction, often detected in utero, can be treated with surgery after birth
describe what occurs in a duplex collecting system?
duplicated ureter due to 2 ureteric buds or a bifurcated ureteric bud —> upper and lower kidneys form
—> poor urine flow, hydronephrosis, UTIs, vesicoureteral reflux
primary vs secondary vesicoureteral reflux
backward urine flow from bladder to kidneys, causes recurrent UTIs
primary: abnormal closure of ureterovesical junction (UVJ), associated with duplex ureters, occurs in children
secondary: caused by high bladder pressure, seen with posterior urethral valves
Patient is a 2yo M presenting with vesicoureteral reflux, with a history of recurrent UTIs. The mother did not receive prenatal care due to limited healthcare access. What is likely the cause of these symptoms?
likely primary vesicoureteral reflux (abnormal closure of ureterovesicular junction) in association with duplex ureters (2 ureteric buds or bifurcation of ureteric bud in utero)
what is Potter’s Syndrome/Sequence and how/when does it present?
due to absent/low amniotic fluid (fetal urine) —> loss of fetal cushioning to external forces and compression of fetus
—> limb deformities, flat face, pulmonary hypoplasia, often fatal
1st trimester (1-12w): rare
2nd trimester (13-27): most common, due to decreased formation of fetal urine
3rd trimester (28+w): due to rupture of membranes
how can bilateral renal agenesis cause Potter’s Syndrome?
Potter’s: absent/low amniotic fluid —> loss of fetal cushioning/ compression of fetus
bilateral renal agenesis: ureteric buds fail to develop —> amniotic fluid cannot be produced
how can posterior urethral valves cause Potter’s Syndrome?
Potter’s: absent/low amniotic fluid (fetal urine) —> loss of fetal cushioning/ compression of fetus
posterior urethral valves: in males, valve tissue obstructs bladder outflow (both kidneys effected), dilated bladder/kidneys on ultrasound
what is the inheritance pattern of polycystic kidney disease and how can it cause Potter’s Syndrome?
Potter’s: absent/low amniotic fluid —> loss of fetal cushioning/ compression of fetus
polycystic kidney disease: juvenile form of cystic kidney disease (AR), both kidneys effected —> if severe, cysts can cause oligohydramnios
if less severe, can cause renal failure and HTN in childhood
which 2 genetic conditions is horseshoe kidney associated with?
horseshoe kidney: inferior poles fuse, kidney cannot ascend pelvis (trapped by inferior mesenteric artery)
associated with 1. Turner Syndrome and 2. Down Syndrome
what causes a horseshoe kidney to develop?
inferior poles fuse both kidneys into one —> kidney cannot ascend pelvis because it is trapped by the inferior mesenteric artery (stays in retroperitoneum)
most patients are asymptomatic, but associated with vesicoureteral reflux
what does the urachus become after birth?
urachus: connects dome of bladder to the umbilicus, obliterated at birth to become medial umbilical ligament
if failed/incomplete obliteration —> urine can leak and cause infections, cyst/sinus/diverticulum can form
Patient is a 38yo F presenting with painless hematuria. Imaging reveals a tumor at the dome of the bladder, and pathology confirms adenocarcinoma. Where did this tumor come from?
remnant of urachal cause formation of adenocarcinoma of bladder …
urachus: connects dome of bladder to the umbilicus, obliterated at birth to become medial umbilical ligament
if failed/incomplete obliteration —> urine can leak and cause infections, cyst/sinus/diverticulum can form
how does the intermediate mesoderm differentiate/develop to become the kidneys?
intermediate mesoderm differentiates into urogenital ridge which runs vertically along the length of the posterior body wall…
a. pelvic/sacral cells form metanephros, which becomes nephrons
b. ureteric bud sprouts off the mesonephric duct and becomes collecting ducts, calyces, and ureters
nephron + collecting system = uriniferous tubule
from what embryonic structure does the urinary bladder and urethra develop?
the urinary bladder and urethra develop from the embryonic urogenital sinus
what does the embryonic cloaca become?
cloaca: caudal end of the embryo’s endoderm-lined gut tube
mesoderm wedge called urorectal septum divides cloaca into anterior urogenital sinus and posterior anorectal canal
superior part of urogenital sinus becomes the urinary bladder, and inferior parts becomes urethra
how does a urachal fistula form and what is the consequence of this?
urachus/allantois is continuous with the superior part of the urogenital sinus (which becomes urinary bladder) and it courses into the umbilical cord
if urachus is not closed after birth, patent urachal fistula forms and urine can leak at the umbilicus
what is bladder exstrophy and how does it occur?
bladder exstrophy: bladder forms outside of the body wall, due to defective anterior body wall fusion in the pelvic region during lateral body wall folding
what embryonic structure forms the trigone in the bladder?
trigone: part of urinary bladder where mesonephric ducts fuse into the wall
