Anomalies of the midgut

Atresias and stenoses can appear anywhere in the midgut and they have several causes. One of the most common anomalies of the intestine is diverticulum ilei (Meckel's diverticulum). A part of the omphalo-enteric duct persists. The result is that in the adult a diverticulum forms about 40 to 60 cm from the ileocaecal valve. This anomaly has different forms and varying degrees of severity. The diverticulum can be connected to the anterior abdominal wall by means of a fibrous cord, which, in turn, can contain a cyst. It can develop a fistula, which may open from the intestine toward the outside through the abdominal wall. Stomach mucosa or pancreatic tissue can also be found in the diverticulum, sometimes causing it to ulcerate or perforate.
Intestinal malrotations can lead to different forms of incomplete rotation. When only a part of the intestine rotates, this can cause blood vessels to become strangled (volvulus).
Following rotation, the caecum can fail to attach firmly to the posterior abdominal wall, or the mesocolon can persist. In this condition, the caecum is able to move slightly (caecum mobile). Subhepatic caecum causes the caecum to lie beneath the liver because the last phase of intestinal rotation has not been performed.
Omphalocele is a condition where the intestinal loops fail to return into the peritoneal cavity after a physiological hernia. The intestinal loops in the membranous hernial sac are then covered in the inside with parietal peritoneum, and on the outside with amnion. Omphalocele very often occurs in combination with other congenital anomalies and chromosomal aberrations. In gastroschisis, intestinal loops protrude from the abdomen near the umbilicus. This phenomenon is caused by a weakness in the abdominal wall. Neither the umbilicus nor the umbilical cord is involved and so there is no hernial sac. Gastroschisis does not occur in combination with other congenital malformations or chromosomal aberrations.