Primary meso-sigmoidal hydatid cyst: a rare presentation of echinococcosis: a case report

Echinococcosis, caused by Echinococcus species, is a parasitic disease typically involving the liver and lungs. Primary peritoneal hydatid disease is exceedingly rare, accounting for only 2% of cases. Atypical presentations, especially in nonendemic regions, can delay diagnosis and management. With increasing global migration, clinicians must be alert to uncommon manifestations. This report presents a rare case of a primary meso-sigmoidal hydatid cyst in a 64-year-old woman, emphasizing the importance of thorough diagnostic evaluation in patients with atypical abdominal symptoms. A 64-year-old diabetic woman presented with three months of intermittent colicky pain in the left lower quadrant, without systemic symptoms or notable clinical findings. Laboratory tests were unremarkable, and she had no history of animal exposure. ELISA serology was positive for echinococcosis. Abdominal CT revealed a 10 × 7.4 × 6.6 cm cystic mass in the left iliac fossa, consistent with a Gharbi type II and WHO CE3a hydatid cyst. Laparotomy revealed a solitary cyst embedded in the meso-sigmoid, displacing the left ureter but sparing adjacent organs. The cyst was excised intact to prevent spillage. Histopathology confirmed the diagnosis. The postoperative course was uneventful. This case highlights the diagnostic challenge posed by atypical hydatid disease. In patients presenting with nonspecific abdominal symptoms, especially in the absence of hepatic or pulmonary involvement, echinococcosis should remain a differential consideration. Combining serological testing with detailed imaging enables accurate diagnosis and guides surgical planning. Complete surgical excision without spillage remains the cornerstone of treatment. Heightened clinical awareness of rare presentations like meso-sigmoidal hydatid cysts is crucial for timely diagnosis and optimal outcomes, particularly in nonendemic areas.