History
The term ‘duplication was first used by Fitz, but more fully classified by Ladd in 1937.
Definition
75% are in the abdomen, 20% in the thorax, and 5% thoracoabdominal. 75% are enteric cysts without GI tract communication, and the other 25% are tubular duplications. Bleeding is more common in the latter (tubular) type. All of them share a common wall with the normal bowel, usually the mesenteric side. However, hindgut duplications are often on the antimesenteric side. They also share a blood supply with the GI tract.
Etiology
Some are felt to be partial twinning (esp. tubular duplications of the ileum and colon). There are 3 broad theories of formation: 1) split notochord – Early on in the embryo, there is only endoderm and ectoderm. Mesoderm comes later. At the primitive pit, the endo and ectoderma are in direct contact. There is an embryonic transient connection, the neuroenteric canal, between the future GI tract and the future neural tissue. The notochord forms in the mesoderm just caudal to this canal. Many abnormalities can occur (spina bifida, enteric duplications, diastematomyelia, spinal cyst, etc) if the process goes awry. 2) embryonic defect in recanalization (mostly this applies to the duodenum), and 3) embryonic diverticula for the bowel. This is shaky, since they often are transiently seen, but on the wrong side of the bowel.
Pathology
The lining is always some sort of GI mucosa, and overall, about 25% have heterotopic mucosa (often gastric). Colonic duplications don’t often bleed, since they rarely contain gastric mucosa. Malignant tumors (mostly adenoCA) have been reported in GI duplications, but usually after the age of 30 yrs. Colonic duplications account for about 15% of al GI duplications.
Associations
Tubular duplications of the colon / rectum are associated (sometimes) with GU or GYN abnormalities, duplications of the external genitalia, and rectovaginal or rectourethral fistulas. Also cloaca, spina bifida, omphalocele. Colonic duplications in particular have been associated with pulmonary sequestrations (Flye MW et al, Surgery 71:744-752, 1972).
Clinical
About 2/3rds of all GI duplications are identified by age 2 yrs. most commonly as a result of intestinal obstruction from lumen compression by a cystic duplication. Other symptoms vary by location. US, CT, and contrast studies are often obtained. GU and GI endoscopy are useful, particularly for colonic or rectal duplications. If a duplication is found in the abdomen, the chest should be screened, and vice versa (10% incidence of thoracic abnormality if abdominal duplication).
Treatment
For long colonic duplications, it may be necessary simply to provide a communication at the distal end. Cystic duplications can be excised.
