Page 623 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

Renal ` RENAL—EmbRyoLogy Renal ` RENAL—EmbRyoLogy SeCTIOn III 579

Horseshoe kidney Inferior poles of both kidneys fuse A
abnormally A . As they ascend from pelvis
Aorta
Horseshoe
kidney Renal artery during fetal development, horseshoe kidneys
get trapped under inferior mesenteric
artery and remain low in the abdomen.
Kidneys function normally. Associated with
hydronephrosis (eg, ureteropelvic junction
Ureter Inferior obstruction), renal stones, infection,  risk of
mesenteric
artery renal cancer.
Higher incidence in chromosomal aneuploidy
(eg, Turner syndrome, trisomies 13, 18, 21).

Congenital solitary Condition of being born with only one functioning kidney. Majority asymptomatic with
functioning kidney compensatory hypertrophy of contralateral kidney, but anomalies in contralateral kidney are
common. Often diagnosed prenatally via ultrasound.
Unilateral renal Ureteric bud fails to develop and induce differentiation of metanephric mesenchyme Ž complete
agenesis absence of kidney and ureter.
Multicystic dysplastic Ureteric bud fails to induce differentiation of metanephric mesenchyme Ž nonfunctional kidney
kidney consisting of cysts and connective tissue. Predominantly nonhereditary and usually unilateral;
bilateral leads to Potter sequence.

Duplex collecting Bifurcation of ureteric bud before it enters the metanephric blastema creates a Y-shaped bifid
system ureter. Duplex collecting system can alternatively occur through two ureteric buds reaching and
interacting with metanephric blastema. Strongly associated with vesicoureteral reflux and/or
ureteral obstruction,  risk for UTIs.

Posterior urethral Membrane remnant in the posterior urethra
valves in males; its persistence can lead to urethral
obstruction. Can be diagnosed prenatally by Kidney Hydronephrosis
bilateral hydronephrosis and dilated or thick- Dilated ureter
walled bladder on ultrasound. Most common Ureter Urinary reflux
cause of bladder outlet obstruction in male
infants. Associated with oligohydramnios in Bladder Distended bladder
cases of severe obstruction.
Urethra obstructed
Urethra
by posterior urethral
membrane
Normal Posterior
urethral valves

FAS1_2019_14-Renal.indd 579 11/7/19 5:42 PM