Water-lily sign on MR imaging of primary intramuscular hydatidosis of sartorius muscle.

Primary hydatidosis of muscle is very rare and can cause a variety of diagnostic problems, especially in the absence of typical radiologic findings. This is the report of a case of primary intramuscular hydatid cyst in a 35-year-old woman, who presented with a 1-year history of a painless lump in the distal left thigh. The authors document the pathognomonic water-lily sign that has not previously been reported in a case of intramuscular hydatid disease.