A Rare but Critical Presentation in Primary Care: A Case Report on Unilateral Ureterolithiasis Leading to Postrenal Acute Kidney Injury.

Distal ureteral calculi measuring ≤5 mm are generally expected to pass spontaneously and are commonly managed conservatively. However, persistent obstruction may occur and can result in renal impairment. A 31-year-old previously healthy male presented with lower abdominal discomfort, dysuria, and penile pain. Initial noncontrast computed tomography (CT) revealed a 4 mm calculus at the left ureterovesical junction without hydronephrosis. He was discharged with conservative management, including nonsteroidal anti-inflammatory drugs (NSAIDs), oral cefixime 400 mg daily, hydration advice, and follow-up instructions. Ten days later, he re-presented with severe flank pain and reduced urine output. Laboratory evaluation demonstrated elevated serum creatinine consistent with acute kidney injury (AKI). Repeat CT showed the persistent distal ureteral stone with new hydronephrosis and periureteric fat stranding. The patient underwent urgent placement of a double-J ureteral stent, resulting in rapid clinical improvement and normalization of renal function within four days. Although small distal ureteral stones are often considered low risk, this case demonstrates that even a 4 mm calculus may lead to persistent obstruction and postrenal AKI. Clinicians should remain cautious for complications in patients with ongoing symptoms and consider timely reassessment and repeat imaging when clinical deterioration occurs.