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578 SeCTIOn III Renal ` RENAL—EmbRyoLogy Renal ` RENAL—EmbRyoLogy

` RENAL—EmbRyoLogy

Kidney embryology Pronephros—week 4; then degenerates.
Mesonephros—functions as interim kidney for
1st trimester; later contributes to male genital Degenerated
pronephros
system.
Metanephros—permanent; first appears in 5th
week of gestation; nephrogenesis continues Mesonephros
through weeks 32–36 of gestation. Mesonephric
ƒ Ureteric bud (metanephric diverticulum)— Metanephric duct
derived from caudal end of mesonephric mesenchyme
duct; gives rise to ureter, pelvises, calyces, Metanephros
collecting ducts; fully canalized by 10th Ureteric bud
week Ur
Urogenital sinusogenital sinus
ƒ Metanephric mesenchyme (ie, metanephric
blastema)—ureteric bud interacts with this
tissue; interaction induces differentiation
and formation of glomerulus through to
distal convoluted tubule (DCT)
ƒ Aberrant interaction between these 2
tissues may result in several congenital
malformations of the kidney (eg, renal
agenesis, multicystic dysplastic kidney)
Ureteropelvic junction—last to canalize
Ž congenital obstruction. Most common
cause of prenatal hydronephrosis. Detected by
prenatal ultrasound.

Potter sequence Oligohydramnios Ž compression of Babies who can’t “Pee” in utero develop Potter
(syndrome) developing fetus Ž limb deformities, sequence.
A facial anomalies (eg, low-set ears and POTTER sequence associated with:
retrognathia A , flattened nose), compression Pulmonary hypoplasia
of chest and lack of amniotic fluid aspiration Oligohydramnios (trigger)
into fetal lungs Ž pulmonary hypoplasia Twisted face
(cause of death). Twisted skin
Causes include ARPKD, obstructive uropathy Extremity defects
(eg, posterior urethral valves), bilateral renal Renal failure (in utero)
agenesis, chronic placental insufficiency.

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