Sonographic evaluation of children with urinary retention caused by an extragonadal pelvic mass.

Urinary retention in children is rarely caused by an extrinsic compression of an extragonadal pelvic mass. The sonographic appearance of these masses are divided into 3 categories: 1) solid, 2) fluid-filled, and 3) mixed. Familiarity with the sonographic spectrum of these lesions can limit the differential diagnosis, will suggest specific follow-up procedures needed for an accurate diagnosis and will eliminate the need for unnecessary invasive workups.