MD Renal and Urinary Systems 4 — Questions and Answers
Question 1: A patient with polycystic kidney disease asks about the risk to their children. What is the inheritance pattern of autosomal dominant PKD?
- Autosomal recessive, 25% risk
- X-linked dominant, 50% risk to sons
- Autosomal dominant, 50% risk to each child (Correct answer)
- Mitochondrial, 100% maternal transmission
Correct answer: Autosomal dominant, 50% risk to each child
ADPKD (PKD1/PKD2 mutations) follows autosomal dominant inheritance with 50% probability of transmission to each offspring.
Question 2: Which diuretic acts on the thick ascending limb of the loop of Henle and is most effective in patients with reduced GFR?
- Hydrochlorothiazide
- Spironolactone
- Furosemide (Correct answer)
- Amiloride
Correct answer: Furosemide
Furosemide (a loop diuretic) inhibits the Na-K-2Cl cotransporter in the thick ascending limb and remains effective even with low GFR, unlike thiazides.
Question 3: A patient presents with cola-colored urine, periorbital edema, hypertension, and hematuria 2 weeks after a strep throat infection. What is the most likely diagnosis?
- IgA nephropathy
- Post-streptococcal glomerulonephritis (Correct answer)
- Henoch-Schönlein purpura nephritis
- Membranoproliferative GN
Correct answer: Post-streptococcal glomerulonephritis
Post-streptococcal GN occurs 1-3 weeks after pharyngitis, presenting with nephritic syndrome and is the classic post-infectious GN in children.
Question 4: Aldosterone causes sodium retention primarily by upregulating which channel/transporter on the apical membrane of principal cells?
- Na-K-2Cl cotransporter (NKCC2)
- Na-Cl cotransporter (NCC)
- Epithelial sodium channel (ENaC) (Correct answer)
- Na/H exchanger (NHE3)
Correct answer: Epithelial sodium channel (ENaC)
Aldosterone increases transcription and membrane insertion of ENaC on principal cells of the collecting duct, promoting sodium reabsorption.
Question 5: A patient with renal cell carcinoma has polycythemia. What is the mechanism?
- Tumor secretion of EPO leading to increased RBC production (Correct answer)
- Dehydration causing hemoconcentration
- Paraneoplastic PTHrP secretion
- Iron deficiency causing compensatory erythropoiesis
Correct answer: Tumor secretion of EPO leading to increased RBC production
RCC can autonomously secrete erythropoietin as a paraneoplastic syndrome, stimulating erythropoiesis and causing polycythemia.
Question 6: Which acid-base disturbance is associated with contraction alkalosis caused by loop diuretics?
- Metabolic acidosis with increased anion gap
- Metabolic alkalosis with hypokalemia (Correct answer)
- Respiratory alkalosis with hypocapnia
- Mixed respiratory and metabolic acidosis
Correct answer: Metabolic alkalosis with hypokalemia
Loop diuretics cause loss of NaCl-rich fluid, volume contraction, and secondary hyperaldosteronism, leading to metabolic alkalosis and hypokalemia.
Question 7: A newborn is found to have bilateral renal agenesis, oligohydramnios, pulmonary hypoplasia, and limb deformities. What syndrome is this?
- Prune belly syndrome
- Potter sequence (Correct answer)
- VACTERL association
- Alport syndrome
Correct answer: Potter sequence
Potter sequence results from bilateral renal agenesis causing oligohydramnios, which leads to compression deformities (limbs, face) and pulmonary hypoplasia from lack of fetal urination.
MD Renal and Urinary Systems 4
A patient with polycystic kidney disease asks about the risk to their children.
What is the inheritance pattern of autosomal dominant PKD?