1
Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
First Aid USMLE Step 1: Renal Questions with Detailed
Verified Answers (100% Correct Answers) /Already
Graded A+
With regard to kidney embryology:
What tissue is it?
What are the three kidney systems?
What is the uteric bud? What does it give rise to? What is the metanephrine
mesenchyma? What does it do?
2
Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
Ans: *What tissue is it?*
– derived from intermediate mesoderrm on the posterior wall of the
abdominal cavity
*What are the three kidney systems?*
– this tissue forms the following 3 kidney systems:
1. Pronephros
– rudimentary kidney that dissapears by week 4
2. *Mesonephros*:
– interim kidney for the first trimester, later contributes to the male genital
system
3. *Metanephros*:
– permanent kidney
– first appears in 5th week of gestation; nephrogenesis continues through 32-
36 weeks of gestation
*What is the uteric bud? What does it give rise to? What is the
metanephrine mesenchyma? What does it do?*
*uteric bud*: derived from the caudal end of the mesonephric duct ; gives
rise to the ureter, pelvises, calyces, collecting ducts; fully canalized by the
10th week
*metanephric mesenchyme*: the uterine bud interacts with this tissue;
interaction induces differentiation and formation of the glomerulus through
to the DCT
– note that aberrant interaction between these two tissues may result in
several congenital malformations of the kidney.
What is the pathophysiology behind Potter Sequence? What are its findings?
What causes it?
3
Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
What are the symptoms?
Ans: *What is the pathophysiology behind Potter Sequence What are its
findings? *
– in utero, babies swallow amniotic fluid, it passes through the GI tract and
is eliminated by the kidney where it is reintroduced into the amniotic fluid
as urine
– babies with renal agenesis are unable to recycle the swallowed amniotic
fluid resulting in a condition called *oligohydramnios* = decreased
amniotic fluid
– the fetus cannot float in the fluid thus gets —> *limb deformities and facial
anomalies*
– compression of the check and lack of fluid aspiration in the fetal lungs
results in *pulmonary hypoplasia* which is the ultimate cause of death
*What causes it?*
– ARPKD
– obstructive uropathy (posterior urethral valves)
– bilateral renal agensis
– chronic placenta insufficiency
*What are the symptoms?*
REMEMBER—> POTTER. Babies who can’t pee in utero get Potter!
P: pulmonary hypoplasia
O: oligohydramnios (trigger)
T: twisted face
T: twisted skin
E: extremity defects
R: renal failure
What is the defect in horseshoe kidney and what causes it?
4
Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
Associated findings or syndromes?
Ans: *What is the defect in horseshoe kidney and what causes it?*
– horseshoe kidney = when the inferior poles of the kidney fuse abnormally
– as they ascend form the pelvis during fetal development, horseshoe
kidneys get trapped under the IMA and remain low in the abdomen
– the kidneys, while attached, *function normally*
*Associated findings or syndromes?*
– associated with hydronephrosis, renal stones, infection, chromosomal
aneuploidy syndromes and rarely, renal cancer
What is the pathophysiology of unilateral renal agenesis?
When and how is it diagnosed?
Ans: When the uteric bud fails to develop and induce differentiation of the
metanephric mesenchyme resulting in complete absence of kidney and
ureter.
*When and how is it diagnosed?*
– often diagnosed prenatally via ultrasound
Remember normally:
*uteric bud*: derived from the caudal end of the mesonephric duct ; gives
rise to the ureter, pelvises, calyces, collecting ducts; fully canalized by the
10th week
*metanephric mesenchyme*: the uterine bud interacts with this tissue;
interaction induces differentiation and formation of the glomerulus through
to the DCT
What is the pathophysiology of multicystic dysplastic kidney?
5
Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
When and how is it diagnosed?
Ans: *What is the pathophysiology of multicystic dysplastic kidney?*
– when the uteric bud fails to induce differentiation of the metanephric
mesenchyma —> resulting in a nonfunctional kidney consisting of cysts and
connective tissue
*When and how is it diagnosed?*
– often diagnosed prenatally via ultrasound
What is the pathophysiology of a duplex collecting system of the kidney?
What are complications/associated risks?
Ans: *What is the pathophysiology of a duplex collecting system of the
kidney?*
– occurs when there is bifurcation of the ureteric budbefore it enters the
metanephric blastema creating a Y-shaped bifid ureter
– alternatively, duplex collecting systems can occur through two ureteric
buds reaching and interacting with metanephric blastema
*What are complications/associated risks?*
– strongly associated with vesicoureteral reflux and/or ureteral obstruction
– also increased UTI risk
What is the pathophysiology of a congenital solitary functioning kidney?
How does this affect kidney function?
