It is not exciting but it is common--a hernia. Hernias represent an outpouching of peritoneum through a defect or weakness in the abdominal wall. This is most typical in the inguinal region, but it can also occur in the umbilical region, as seen here. An "internal" herniation of bowel can result from an abnormal opening formed by adhesions, as in the previous image. The defect may be large enough to admit omentum or bowel. In this abdominal incision can be seen a small hernia sac that contains adipose tissue from omentum. The external appearance of the umbilical hernia is seen below.