Duplications of Alimentary Tract
Alimentary tract duplications, also referred to as mesenteric cysts, giant diverticula, or enteric cysts, are rare congenital malformations that develop during fetal life. These spherical or tubular structures may be single or, more frequently, multiple, and are equipped with all the layers of that part of the alimentary tract to which they are intimately attached, including the muscular coat. This is in distinction to diverticula, which lack a muscular coat. Gastrointestinal duplication cysts may or may not communicate with the adjacent lumen of the gastrointestinal tract.
Most intestinal duplications are diagnosed in newborn infants and children, but some can remain silent and present in adulthood. With the routine use of prenatal ultrasound, however, many are being diagnosed in utero. Associated anomalies are present in one third of cases and involve the spine and gastrointestinal tract.
Several theories have been proposed to explain the origin of the duplications, but no single hypothesis can explain all possible combinations of duplications, locations, and associated anomalies. Failure of recanalization can explain duplications located in the gastro- intestinal tract, which passes through a “solid” stage with temporary occlusion of the lumen around the 5th week of life. Other theories include intrauterine vascular accidents leading to duplications similar to intestinal atresia and incomplete twinning, which can explain duplications of the hindgut associated with genitourinary malformations.
Duplications can occur in all parts of the alimentary canal, from the tongue to the rectum, but are most frequently encountered in the jejunoileal area (65%), followed by the colon (20.5%), gastric region (8%), and duodenal region (6.5%). Small intestinal duplications are typically located on the mesenteric border and share a blood supply with the adjacent intestine.
The walls of the two structures (i.e., of the intestine and its corresponding duplication) are not sharply separated but have muscular fibers in common; hence, it is difficult to remove the duplicated segment without damaging the blood supply or the wall of the contiguous intestine.
Intestinal duplications may remain asymptomatic, and the diagnosis may be made incidentally by physical examination or during a radiologic or endoscopic procedure. Alternatively, abdominal pain, vomiting, and an abdominal mass are the most common symptoms and signs. Ectopic gastric mucosa is present in 24% of intestinal duplications, potentially leading to penetrating ulcers and severe gastrointestinal bleeding. Rarely, these cysts can serve as a lead point and cause intussusception or superinfection of the cyst. Malignant diseases arising from alimentary tract duplications, especially hindgut duplications, have also been reported. The diagnosis is confirmed by radiologic imaging, including ultrasound, barium studies, CT scanning, or MRI studies. Abdominal sonography typically shows a cystic structure situated next to the intestine with a “double wall,” consisting of a hyperechoic inner layer produced by the mucosa and a relatively hypoechoic outer layer produced by smooth muscle. The presence of peristalsis is also a helpful sign. When ectopic gastric mucosa is suspected,99m technetium pertechnetate scintigraphy should be performed to confirm the finding.
The definitive management of intestinal duplications is surgical resection, which is indicated even if the cysts are asymptomatic because the potential complications can be grave. Total resection of the duplication along with the adjacent bowel is preferred, if feasible. If the patient is in poor condition or if the procedure is technically unfeasible, the cyst may be excised or “shelled out” or mucosal stripping may be performed. Additionally, a simple exteriorization by the Mikulicz technique can be performed, with the final repair postponed to a later date. Minimally invasive surgery has been successfully employed, with a low rate of complications, including laparoscopic simple cyst excision and resection with end-to-end or end-to-side anastomosis. Endoscopic resection of duodenal duplications has been reported, but the long-term outcome has not been documented. Thoracoabdominal enteric duplications may require combined transdiaphragmatic thoracolaparoscopy.