The wandering mimic: Meckel's diverticulum with enterolith simulating an intraperitoneal hydatid cyst

Meckel's diverticulum (MD) is the most common congenital anomaly of the gastrointestinal tract and is often asymptomatic. Unusual complications such as enterolith formation or foreign body impaction are rare, particularly in pediatric patients, and may produce atypical imaging findings that mimic other intra-abdominal pathologies. We report a case of a previously healthy 4-year-old boy who presented with intermittent colicky abdominal pain and non-bilious vomiting. Contrast-enhanced CT demonstrated a cystic lesion in the left paracolic gutter containing multiple internal rounded low-attenuation structures, initially suspicious for hydatid daughter cysts. Follow-up MRI revealed interval migration of the lesion to the right lower quadrant with peripheral rim enhancement and internal floating components, raising suspicion for a mobile bowel-related process. The patient underwent surgical exploration, which confirmed an inflamed Meckel's diverticulum arising from the ileum. Histopathology demonstrated an intraluminal foreign body (watermelon seed) with surrounding enterolith formation, corresponding to the presumed daughter cysts on imaging. Complicated Meckel's diverticulum may closely mimic hydatid disease on cross-sectional imaging, particularly when enteroliths and inflammatory debris simulate daughter cysts. Recognition of lesion mobility and careful clinicoradiologic correlation are critical to avoid misdiagnosis and unnecessary antiparasitic therapy. This case highlights an important diagnostic pitfall in pediatric abdominal imaging.