Renal Actinomycosis Camouflaging as Malignancy: A Diagnostic Challenge

Abstract

Actinomycosis is an unusual infection that typically appears in the thoracic, cervicofacial, and abdominal areas. However, the occurrence of renal actinomycosis in adults remains rare, with few cases reported since 1990. Actinomycosis is often considered “the most misdiagnosed disease” due to its tendency to be overlooked even by experienced clinicians. Hereby authors report a case of a 55-year-old male with pyrexia of unknown origin and weight loss, presenting with pallor upon general examination. Further investigation revealed microcytic hypochromic anaemia and neutrophilic leukocytosis on peripheral blood smear. A heterogeneous mass with internal vascularity in the left kidney was identified on abdominal ultrasound. Subsequent Computed Tomography (CT) abdomen confirmed an ill-defined lesion in the mid and lower pole of the left kidney, with extrarenal extension into the perinephric space, and a filling defect in the left renal vein. A provisional diagnosis of a left renal tumour infiltrating the spleen and splenic flexure of the colon was made. The patient then underwent a left radical nephrectomy, splenectomy, and limited colonic resection. Histopathological examination confirmed actinomycosis with abscess formation in the kidney and colon. The patient was treated with crystalline penicillin for eight weeks until considered disease-free. Renal actinomycosis poses challenges in diagnosis due to its ambiguous clinical and laboratory features. Often mimicking malignant neoplasms on imaging, it can confuse even experienced clinicians. Early detection is crucial for precise medical intervention and to reduce unnecessary surgeries.