Hydatid cysts in the psoas muscle are unusual. The authors report a ca
se of a hydatid cyst which had developed within the psoas muscle and w
as detected from a mass in the left iliac fossa which was diagnosed be
fore surgery by ultrasound and a CT scan, which remain the preferred p
rimary examinations for the investigation of masses of this type. The
authors discuss the various possible clinical and paraclinical context
s and recommend total pericystectomy of a closed cyst as the best trea
tment following extraperitoneal illac surgical opening.