Obstructive kidney disease: which is the culprit, prostate or stone?

A 94-year-old man was admitted to the nephrology department with acute kidney injury. His medical background included arterial hypertension and a gastric ulcer, treated with candesartan and pantoprazole, and his recent medical history included dysuria with macroscopic hematuria, treated three times with antibiotics for suspected prostatitis by his general practitioner. Physical examination showed no signs of dehydration: no fever, normal blood pressure  (134/64 mmHg), and no abdominal pain, diarrhea or vomiting. He weighed 55.2 kg. Laboratory tests showed serum urea nitrogen 33.7 mmol/l, creatinine 1189 µmol/l, hyponatremia 133 mmol/l [136–145], hyperkalemia 5.8 mmol/l [3.2–4.9], bicarbonate 19 mEq/l [22–29], C-reactive protien (CRP) 13 mg/l (N < 5), Prostate Specific Antigen (PSA) 15 ng/ml (N < 4 ng/ml). Cytobacteriological urine test revealed no leukocyturia or hematuria, and culture was sterile. Natriuresis was 103 mmol/L. …