Genitourinary System and Renal Disorders
The genitourinary and renal domain tests acute kidney injury, chronic kidney disease, glomerular disease, urinary tract infection, stones, and bladder outlet obstruction, focusing on cause identification and medication safety.
Core rules
- Acute kidney injury follows KDIGO: creatinine rise of at least 0.3 mg/dL in 48 hours or 1.5 times baseline in seven days, or urine output below 0.5 mL/kg/h for six hours. Identify prerenal, intrinsic, and postrenal causes.
- CKD is kidney damage or eGFR below 60 mL/min/1.73 m² for at least three months. Control blood pressure, use ACE inhibitor or ARB with albuminuria, and avoid nephrotoxins.
- Nephrotic syndrome is proteinuria above 3.5 g/day, hypoalbuminemia, edema, and hyperlipidemia. Nephritic syndrome has hematuria, red cell casts, hypertension, and variable renal failure.
- Uncomplicated cystitis in women: nitrofurantoin for five days is first-line when renal function is adequate. Do not treat asymptomatic bacteriuria except in pregnancy or before urologic procedures.
Worked example
A 72-year-old man has urinary retention, a creatinine of 3.2 mg/dL, and a post-void residual of 600 mL. This is obstructive acute kidney injury. Place a urethral catheter, monitor urine output, and watch for postobstructive diuresis. Avoid NSAIDs and obtain renal ultrasound if the cause is unclear.
Traps
- Missing obstruction in AKI; check post-void residual and renal ultrasound.
- Continuing NSAIDs, contrast, or nephrotoxic drugs in CKD.
- Treating asymptomatic bacteriuria in older adults.
- Missing hematuria evaluation in adults without a clear cause.