# Case Report: Acute large bowel obstruction with actinomycosis of the sigmoid colon mimicking neoplasm

## TL;DR

A 68-year-old man with a sigmoid colon infection caused by Actinomyces was initially mistaken for cancer and required surgery and long-term antibiotics.

## Contribution

This case highlights the diagnostic difficulty of abdominal actinomycosis mimicking malignancy and the need for combined treatment.

## Key findings

- Actinomycosis of the sigmoid colon can mimic a malignant tumor, leading to emergency surgery.
- Histological confirmation is essential for accurate diagnosis and avoiding unnecessary procedures.
- Long-term antibiotic therapy is effective in treating complicated actinomycosis cases.

## Abstract

Actinomycosis is an uncommon inflammatory bacterial disease caused by Actinomyces species, especially Actinomyces Israeli. Abdominopelvic forms are relatively rare and may involve the colon as a solid mass, mimicking a malignant tumor.

A 68-year-old Tunisian man, with a history of diabetes, hypertension, penicillin allergy, and renal failure, presented to the emergency department with abdominal pain, vomiting, and bowel obstruction. CT scan showed an acute intestinal obstruction upstream with obstructive tissular mass at the sigmoid colon. Emergency surgery revealed a sigmoid mass and a pre-perforative cecum. Subtotal colectomy was performed, with ileostomy and distal end closure. Histological examination confirmed Actinomyces infection. The patient was then placed on long-term doxycycline and Bactrim, with no recurrence over a 9-month follow-up period.

Abdominal actinomycosis, though rare, presents diagnostic challenges. It can be mistaken for malignancy, leading to unnecessary surgery in non-complicated cases, since it is effectively treated by antibiotics. In complicated cases, a combined approach involving both surgery and antibiotic therapy is necessary until the infection is completely eradicated.