Bilateral renal infarction unmasking rheumatic mitral valve disease with left atrial appendage thrombus in sinus rhythm: a case report

Background Acute renal infarction mimics pyelonephritis and is frequently missed at first presentation. Rheumatic mitral stenosis can cause systemic embolism even in sinus rhythm. Case summary A 47-year-old Thai man presented with four days of evolving abdominal pain, previously attributed to gastroenteritis and treated symptomatically at a first emergency visit. He had fever without chills, left costovertebral-angle tenderness, and a bland urinalysis. Point-of-care ultrasound was atypical for pyelonephritis; computed tomography showed bilateral wedge-shaped cortical defects with a cortical rim sign but could not exclude focal bacterial nephritis. Contrast-enhanced ultrasound demonstrated an avascular left upper pole, confirming bland infarction, supported by lactate dehydrogenase 1194 U/L, procalcitonin 0.28 ng/mL, and sterile cultures. Echocardiography revealed rheumatic mitral valve disease with clinically significant stenosis (valve area 1.34 cm2 by planimetry; diastolic doming, commissural fusion, fish-mouth orifice) and moderate regurgitation. The left atrium was dilated, with dense spontaneous echo contrast and a left atrial appendage thrombus despite sinus rhythm. Enoxaparin with overlapping warfarin was started; a direct oral anticoagulant was avoided. At two months the patient was in New York Heart Association class II without recurrent embolism, but the international normalized ratio had not yet reached target; repeat transoesophageal echocardiography is scheduled at three months. Discussion Contrast-enhanced ultrasound can resolve the computed tomography ambiguity between infarction and focal bacterial nephritis at the bedside. In mitral stenosis, a prior embolic event or left atrial thrombus mandates vitamin K antagonist anticoagulation irrespective of rhythm, and an appendage thrombus and coexisting mitral regurgitation defer balloon commissurotomy.