A 35-year-old woman was urgently admitted to a hospital due to severe abdominal pain lasting for 2 days. Physical examination revealed a painful tumor localized within the umbilical region, mimicking incarcerated umbilical hernia. Abdominal ultrasonography demonstrated a heterogeneous, hypoechogenic lesion measuring 7.6 cm × 4.3 cm × 55 cm, potentially corresponding with incarcerated abdominal hernia. Plain abdominal X-ray revealed no gas-fluid levels or free air beneath the diaphragm (Figure 1A). Complete blood count showed an elevated level of C-reactive protein (26.7 mg/l; reference range [RR], 0–5 mg/l) and a white blood cell count close to the upper limit of normal (10.77 × 103/µl; RR, 3.9–11 × 103/µl), while all other parameters fell within the normal range.

Figure 1. A – plain abdominal X-ray revealing no gas-fluid levels or free air beneath the diaphragm; B – intraoperative photograph showing a tumor arising from the greater omentum and infiltrating the parietal peritoneum; C, D – histopathologic analysis revealing actinomycosis colonies (black arrows); hematoxylin and eosin staining, mangnification × 50 (C) and × 100 (D)

Anamnesis revealed laser ablation of the uterine cervix. The patient had also undergone removal of an intrauterine contraceptive device (IUD) several months ago due to recurrent paronychia. She had no history of abdominal surgeries or any comorbidities.

The patient was scheduled for urgent laparotomy. Intraoperatively, a tumor arising from the greater omentum was observed to infiltrate the parietal peritoneum in the umbilical region (Figure 1B). Resection of the omental tumor along with the adjacent parietal peritoneum was performed. Furthermore, examination of the abdominal cavity showed enlarged uterus with a palpable tubercle tumor. No other pathologies were detected, and no macroscopic abnormalities were noted in the liver. Due to nonspecific intraoperative findings, a postoperative computed tomography scan of the abdomen and pelvis was performed to rule out any potential malignancies. The scan showed multiple enlarged lymph nodes along the right side of the uterus, within the pelvis, and in the small bowel mesentery. No other abnormalities were found. The postoperative recovery was uneventful, and the patient was discharged 3 days after the surgery. Histopathologic analysis showed abdominal actinomycosis (Figure 1C and 1D).

Actinomycosis is a rare, chronic disease caused by gram-positive anaerobic bacteria.1 The most common form of actinomycosis is orocervicofacial disease, comprising 50% of reported cases.2 The abdominopelvic form represents up to 20% of actinomycosis cases, usually as a result of complications associated with IUD use or previous gastrointestinal tract surgery.3 Signs and symptoms of the disease are nonspecific, involving abdominal pain, fever, and weight loss. Consequently, its chronic progression may lead to infiltration of surrounding organs and the abdominal wall, mimicking the presence of a palpable tumor. In prolonged infections, painful tumors may be observed, imitating inflammatory or neoplastic pathologies. Blood test results often lack specificity, with mild anemia, leukocytosis, and other inflammatory markers being the most typically ascertained abnormalities. Similarly, there are no specific features of actinomycosis observed in imaging studies. Only 10% of abdominal actinomycosis cases are diagnosed preoperatively. Direct isolation of the pathogen is challenging and has an over 50% failure rate.2 Histopathologic examination of surgical specimens remains the most frequent method for reaching a final diagnosis. In a majority of symptomatic abdominopelvic actinomycosis cases, the recommended approach involves surgical removal of the affected tissue in conjunction with long-term targeted antibiotic therapy, reflecting the management utilized in the presented case. This combined approach boasts a curative rate exceeding 90%.4