COMSAE Renal and Urological Systems 1 — Questions and Answers
Question 1: A patient presents with oliguria, hematuria, and periorbital edema 2-3 weeks after a streptococcal throat infection. Urinalysis shows RBC casts. What is the most likely diagnosis?
- Post-streptococcal glomerulonephritis (Correct answer)
- IgA nephropathy
- Nephrotic syndrome
- Acute tubular necrosis
Correct answer: Post-streptococcal glomerulonephritis
Post-streptococcal glomerulonephritis presents with nephritic syndrome (hematuria, RBC casts, hypertension) occurring 2-3 weeks after Group A strep pharyngitis.
Question 2: On COMSAE, which diuretic is most appropriate for a patient with heart failure and severe symptomatic edema requiring rapid fluid removal?
- Furosemide (loop diuretic) (Correct answer)
- Hydrochlorothiazide
- Spironolactone
- Acetazolamide
Correct answer: Furosemide (loop diuretic)
Loop diuretics like furosemide act at the thick ascending limb of the loop of Henle, producing the most potent diuresis and are first-line for acute fluid overload.
Question 3: A 65-year-old man with diabetes presents with creatinine 3.2 mg/dL, hyperkalemia, and metabolic acidosis with a normal anion gap. Which acid-base disorder is most likely?
- Type 4 renal tubular acidosis (hyperkalemic RTA) (Correct answer)
- Type 1 RTA (distal)
- Type 2 RTA (proximal)
- High anion gap metabolic acidosis
Correct answer: Type 4 renal tubular acidosis (hyperkalemic RTA)
Type 4 RTA is the most common RTA in adults, caused by hypoaldosteronism (often from diabetic nephropathy) leading to hyperkalemia and normal anion gap acidosis.
Question 4: Which finding best distinguishes prerenal azotemia from acute tubular necrosis (ATN)?
- Fractional excretion of sodium (FENa) < 1% (Correct answer)
- BUN:Cr ratio < 15
- Muddy brown casts in urine
- FENa > 2%
Correct answer: Fractional excretion of sodium (FENa) < 1%
In prerenal azotemia, intact tubular function avidly reabsorbs sodium, yielding FENa < 1%, whereas ATN causes tubular dysfunction resulting in FENa > 2%.
Question 5: A 30-year-old man presents with recurrent hematuria coinciding with upper respiratory infections (synpharyngitic hematuria). Kidney biopsy shows mesangial IgA deposits. What is the diagnosis?
- IgA nephropathy (Berger disease) (Correct answer)
- Post-streptococcal GN
- Henoch-Schönlein purpura nephritis
- Alport syndrome
Correct answer: IgA nephropathy (Berger disease)
IgA nephropathy (Berger disease) is characterized by mesangial IgA immune complex deposition, presenting with gross hematuria during mucosal infections (within 1-2 days).
Question 6: Which electrolyte abnormality is the most immediately life-threatening complication of acute renal failure requiring emergent treatment?
- Hyperkalemia (Correct answer)
- Hyponatremia
- Hyperphosphatemia
- Hypocalcemia
Correct answer: Hyperkalemia
Hyperkalemia is the most immediately dangerous complication of acute renal failure because it can cause fatal cardiac arrhythmias including ventricular fibrillation.
COMSAE Renal and Urological Systems 1
A patient presents with oliguria, hematuria, and periorbital edema 2-3 weeks after a streptococcal throat infection.
Urinalysis shows RBC casts.
What is the most likely diagnosis?