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.
