A soft bulge of tissue or a small, localized swelling on the abdomen. This is caused by failure of the muscular ring around the navel to close completely.
Umbilical hernias are more common in babies with a low birth weight , including premature babies.
See also gastroschisis . Incisional hernias may not appear until after straining, heavy lifting, or a prolonged period of coughing . A ureteropelvic junction obstruction may also feel like a lump in the abdomen. Considerations Most often, a lump in the abdomen is caused by a hernia. An abdominal hernia occurs when there is an area where the muscles are weak, and this allows the internal organs to bulge through the abdominal wall.