Parietal hydatid cyst of the rectus abdominis muscle: case report and literature review.

INTRODUCTION AND IMPORTANCE: Hydatid disease is a zoonotic infection caused by the larval stage of Echinococcus granulosus. It remains endemic in Morocco and represents a significant public health concern. Although the liver and lungs are the most frequently affected organs, muscular involvement is rare. This report aims to describe an unusual case of a hydatid cyst in the rectus abdominis muscle and highlight the role of imaging in diagnosis and management. CASE PRESENTATION: A 37-year-old woman presented with a progressively enlarging hypogastric swelling evolving over 5 months. Clinical examination revealed a soft, non-inflammatory mass in the lower abdominal wall. Hydatid serology was positive, while other laboratory findings were unremarkable. Imaging demonstrated a multilocular intramuscular cystic lesion separating the fibers of the left rectus abdominis muscle, consistent with a type III hydatid cyst. No hepatic or pulmonary involvement was identified. The patient underwent complete pericystectomy. Histopathological examination confirmed the diagnosis by demonstrating hydatid membranes and protoscolices. Postoperatively, albendazole was administered for 4 weeks. The clinical course was favorable, with no residual lesion detected on follow-up imaging. DISCUSSION: Primary muscular hydatid cysts are uncommon and may pose a diagnostic challenge because of their nonspecific clinical presentation. Imaging, particularly ultrasound and computed tomography, plays a crucial role in establishing the diagnosis, assessing lesion extent, and planning treatment. Surgical excision remains the treatment of choice, while albendazole may be used as an adjunctive therapy. CONCLUSION: Hydatid cyst of the rectus abdominis muscle is a rare entity that should be considered in the differential diagnosis of abdominal wall masses in endemic regions. Early diagnosis and complete surgical excision provide an excellent prognosis.