Primary care physicians often see patients with complaints of acute abdominal pain. The differential diagnosis for the acute abdomen is complex and requires not only precise clinical skills but also a high index of suspicion for a specific disease state. Uncommon disorders must be considered when the signs and symptoms observed are unusual or the pathologic entity suspected is not found on diagnostic workup or during surgery. A urachal cyst abscess, although rare, may have the signs and symptoms of an acute abdomen.