Abdomen

The abdomen constitutes that part of the body between the thorax and the pelvis. The abdominal cavity is bounded by the diaphragm above but is contiguous with the pelvis; the boundary is defined by the bony landmarks of the pelvic bones and lumbar spine. Anteriorly and laterally, the abdominal cavity is bounded by the soft muscular and fascial tissues of the anterior abdominal wall; posteriorly, the wall is more rigid, being formed by the parietal peritoneum that lies over the vertebral bodies with their muscular attachments. From a functional perspective, the abdominal cavity essentially acts as a repository for a number of organ systems responsible for metabolic processing. This includes the hollow tubular structure of the bowel, which enters cranially at the gastro-oesophageal sphincter and develops into the remaining parts of the digestive system, carrying and processing nutrients and waste before, at the caudal end, passing these products back to the external environment. Organ systems such as the liver and kidneys are developed through a number of embryologic stages bringing a variety of different cell lines together for functional effect. Other structures that pass through the diaphragm and run into the pelvis include the great vessels, lymphatics and peripheral nerves. Although prenatal assessment of the abdomen may not inspire clinicians as much as some other structures, this is the powerhouse of metabolic well-being and includes and is bounded by many complex structures that need to be coordinated with surrounding tissues. Abnormalities of these systems can be lethal or cause significant morbidity in a neonate, and there is significant value in prenatal diagnosis that allows timely and appropriate intervention after birth.