[Mesenteric actinomycosis].

We present the case of a 46-year-old female, who presented with fever and abdominal pain. Abdominal ultrasound revealed a thickened-walled conglomerate near the transvers colon. Colonoscopy did not show any organic abnormality. Abdominal computed tomography described a retroperitoneal mass, so we decided on surgery based on the multidisciplinary team decision. One month after the onset of symptoms, laparotomy was performed, and it seemed that we found an approximately 5 × 8 centimetre tumour attached to the small intestine involving the ascending and sigmoid colon. We performed right hemicolectomy and sigmoid colon wall resection. Histology result showed mesenteric actinomycosis with no connection to the intestinal wall, no malignancy was revealed. Although the abdominal, mesenteric actinomycosis is a rare disease, it is important to think of it as a differential diagnostic option, so the patient can get proper treatment and cured sooner. Our aim with presenting this case report is to highlight the significance of this disease. Orv Hetil. 2021; 162(3): 116-119.