BACKGROUND: This is a case report of a male patient who presented with a history of right flank pain based on renal infarction. Initially the symptoms were misdiagnosed as acute pyelonephritis.

CASE REPORT: A 47-year-old male with a history of familial hypercholesterolemia and cerebral infarction presented at the Emergency Department with a 3-day history of acute right-sided flank pain. Physical examination revealed hypertension, subfebrile temperature, and costovertebral angle tenderness. Blood tests were unremarkable except for renal impairment, a high C-reactive protein level of 215 mg/L (normal <8 mg/dL) and an elevated lactate dehydrogenase (LDH) of 1289 U/L (normal <248 U/L). Renal ultrasonography was normal. He was admitted with a presumed diagnosis of acute pyelonephritis and treated accordingly. However, 2 days later, we rejected this diagnosis as the urine culture was sterile. Based on the acute onset of symptoms and the initial high LDH, renal infarction was suspected. A computed tomography scan confirmed right-sided partial renal and splenic infarctions likely due to spreading emboli from atherosclerosis of the descending aorta.

CONCLUSIONS: Acute renal infarction is often missed or delayed as a diagnosis because patients often present with flank pain that can resemble more frequently encountered conditions such as pyelonephritis and nephrolithiasis. Renal infarction should be considered in cases with acute flank pain accompanied by (low-grade) fever, high LDH level, increased C-reactive protein level, hypertension, and renal impairment, especially in those patients with an increased risk of thromboembolism.

Keywords: Flank Pain, Infarction, Splenic Infarction