[Infected urachal cyst].

There is a wide variety of pathologies associated with the presence of urachal remnants. We describe a case of infected urachal cyst in a young adult male, with classical symptoms of dysuria, lower abdominal pain, and fever. Ultrasound, cystography and CT are described, ultrasound being often the modality of choice. Differential diagnosis of acute abdominal and pelvic pain or a midline lower abdominal mass at this age should include infection of an urachal remnant.