Eighteen cases of urachal abscess were studied with sonography. Their configurations were cone shaped in 11 cases, tubular in 4, curved club shaped, and oval and irregular in one each. Their complications, such as intraperitoneal spread, chronic cystitis, and adhesion to the omentum or the colon, could also be suggested by ultrasonography. Gas was found in 50% of the lesions, which were all larger than 1 cm in diameter. An abscess smaller than 1.2 cm in diameter (which can be as long as 5 cm) can be treated with antibiotics or incision and drainage without total excision. A lesion within the extraperitoneal fat space of abdominal wall a t the midline below umbilicus suggests the diagnosis of urachal abscess in cases of umbilical discharge and/or when-the lesion extends to the -Urachal abscess * Ultrasound Urachal anomalies are rare. Except for the congenital patent urachus, they are usually quiescent clinically until complicated by infection. Sporadic cases of urachal c a r ~i n o m a , ~ or abscess5 detected by sonography have been reported. We encountered 18 cases of urachal abscess that were studied by ultrasonography in the past three years. To our knowledge, this paper is the largest series dealing with urachal abscesses evaluated with ultrasonography. The objectives of this report are to describe the sonographic findings of urachal abscesses and their complications, and to assess the role of ultrasonography in the therapeutic management of such lesions. B. uniformis Bacteroides E. coli Salmonella Enterococcus Bacteroides Peptococcus Staph. epidermidis P. saccharolyticus B. fragilis Fusobacterium Unknown B. vulgarus B. distasonis Data not available Staph. epidermidis Strep. viridans Unknown Aerobic bacteria P. saccharolyticus B. melaninogonicus Staph. epidermidis Corynbacteriurn Bacteroides P. saccharolyticus B. fragilis