During pregnancy, the umbilical cord passes through a small opening in the baby's abdominal muscles. The opening normally closes just after birth. If the muscles don't join together completely in the midline of the abdomen, this weakness in the abdominal wall may cause an umbilical hernia at birth or later in life.
Ileus may also be caused by an infection inside the abdomen, such as appendicitis or diverticulitis. Disorders outside the intestine, such as kidney failure, an underactive thyroid gland, or abnormal levels of blood electrolytes (low potassium levels or high calcium levels, for example), may cause ileus.
Adynamic ileus results in the dilatation of loops of bowel from smooth muscle dysfunction, as opposed to mechanical obstruction. Dilatation may be localized or diffuse, depending on the etiology. The colon may or may not also be involved.