A 36-year-old man presents with right-sided flank pain for three days. No other symptoms are present. His medical history is significant for at least four urinary tract infections (UTIs) over the last two years, which were treated with short courses of antibiotics. Despite medical advice to the contrary, he opted against further investigations. Exposition of his family history reveals that a maternal uncle was diagnosed with end-stage renal disease at the age of 50; the causative etiology is not known to the patient. He only drinks socially, does not smoke, and denies using recreational drugs. A complete blood count (CBC) is significant for a leukocyte count of 12,000/mm3, with 82% neutrophils.
Albumin: 80 mg/d (<150) RBC: 10/hpf (<3) WBC: 8/hpf (<5) Leukocyte esterase: Positive Nitrites: Negative Culture reports will be available in 48 to 72 hours.
The ultrasound reveals both kidneys to be enlarged (right kidney: 16x9 cm; left kidney: 13x6 cm) with multiple fluid-filled cysts. A large staghorn calculus is seen in the right renal pelvis. There is no evidence of renal malformations or of urinary tract obstruction.
Creatinine: 0.75 mg/dL (0.6 - 1.2) BUN: 15 mg/dL (7 - 20) Na: 138 mEq/L (135 - 145) K: 4.6 mEq/L (3.5 - 5.3)
The CT reveals enlarged, cystic kidneys and a staghorn calculus in the right renal pelvis. There are no features suggestive of urinary tract obstruction.