Presentation
Lower abdominal pain with a palpable mass
Patient Data
An ultrasound study shows lower abdominal well defined ovoid peritoneal lesion of complex echogenicity with no color flow in the duplex study.
CT study shows the lesion to be hypodense with internal small foci of fat. Other two partially calcified peritoneal lesions are seen at the upper abdomen adjacent to the liver.
MRI study shows the lower abdominal mass abutting the sigmoid mesocolon, displacing the sigmoid colon to the right, related to the superior urinary bladder wall and the rectus abdominis muscle. It elicits intermediate signal intensity in T1 with multiple hyperintense foci of fat that are suppressed in T1 fat sat. In T2, the lesion appears of heterogeneous high signal with internal serpentine undulant membranes "water lily sign". It elicits T2 shine-through on the diffusion study. The lesion shows no enhancement in the post-contrast study.
The lesion was surgically excised, it was cystic with internal membranes as shown in these photos. It was confirmed on histopathology to be a hydatid cyst.
Case Discussion
Peritoneal hydatid cysts may mimic neoplastic masses. Using multiple imaging modalities may be useful in differentiation as in this example where MRI gave the most reliable features compared to CT and ultrasound.
Primary peritoneal hydatid disease is rare while secondary spread from other organs especially the liver is much more common. The presence of other partially calcified peritoneal lesions adjacent to the liver was also a key for hydatid disease.
In this case, the imaging concern about hydatid disease guided the physician to review the patient's clinical history in detail, he gave a history of hepatic cystectomy a long time ago.
Intraoperative photos contribution by Dr.Adel Abdelwahed
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