Umbilical concretion.

Umbilical concretion is a rarely encountered benign entity. Concretions typically form within an umbilical cleft which is unusually deep and consist of keratinaceous and sebaceous material. Lack of attention to umbilical hygiene usually plays a role in their formation. Concretions are generally asymptomatic and may only present clinically when complicated by inflammation or infection. Their appearance on imaging studies may be problematic for the radiologist given their rarity, particularly in the setting of a known or suspected intra-abdominal malignancy.