Renal · Year 2 · from Renal
Case 1: Polycystic Kidney Disease
Patient Presentation
A 38-year-old male presents to his primary care physician for evaluation of flank pain and hypertension. He reports intermittent dull aching in both flanks for the past 6 months. His father died at age 52 from kidney failure requiring dialysis, and his paternal aunt is currently on dialysis.
History of Present Illness
- Bilateral flank discomfort, worse on the left
- Recent onset of headaches
- Occasional blood in urine (gross hematuria)
- No dysuria or urinary frequency
Physical Examination
- Blood pressure: 156/98 mmHg
- Bilateral palpable abdominal masses in the flanks
- No lower extremity edema
- Cardiac exam: Normal S1/S2, no murmurs
Workup
Laboratory Studies:
- Serum creatinine: 1.4 mg/dL (elevated)
- eGFR: 58 mL/min/1.73m2 (CKD Stage 3a)
- Urinalysis: 2+ blood, trace protein
- BUN: 24 mg/dL
Imaging:
- Renal ultrasound: Bilateral enlarged kidneys (right 16 cm, left 17 cm) with multiple cysts of varying sizes throughout the cortex and medulla
- Total kidney volume: >1500 mL
Diagnosis
Autosomal Dominant Polycystic Kidney Disease (ADPKD)
Discussion
This case illustrates key anatomical concepts from the lecture:
- Cortex and Medulla: The cysts in ADPKD arise from tubular epithelium and can develop in both cortical nephrons (85% of nephrons) and juxtamedullary nephrons (15%)
- Nephron Structure: Cysts develop from all segments of the nephron, including proximal tubules, loops of Henle, and collecting ducts
- Renal Size: Normal kidney length is approximately 11 cm; the bilateral enlargement to 16-17 cm reflects progressive cyst expansion
Treatment
- Blood pressure control with ACE inhibitor (target <130/80 mmHg)
- Tolvaptan (vasopressin V2 receptor antagonist) for rapidly progressive disease
- Genetic counseling for family members
- Monitoring for complications: hepatic cysts, intracranial aneurysms
Clinical Pearl
The anatomical location of cysts determines clinical manifestations: cortical cysts cause flank pain and hematuria from capsular stretching, while collecting duct cysts contribute to concentrating defects and polyuria.