Alimentary Tract Duplications Flashcards
Which bowel segment is the most common site of intestinal duplication?
A. Esophagus
B. Stomach
C. Duodenum
D. Ileum
E. Rectum
ANSWER: D
COMMENTS: Intestinal duplication is a common finding at autopsy, with an incidence of 1 in 4500. Duplications have been described throughout the entire GI tract; however, the most frequent sites are the jejunum and ileum.
The exact etiology of these duplications is unknown. Several theories including twinning, disorders of recanalization, and environmental factors have been proposed.
Duplications are often identified as large intraabdominal cystic structures on prenatal ultrasound.
After birth, large intestinal duplications, especially blind pouch duplications, should be resected within the first few months of life. If the duplication causes symptoms such as obstruction or jaundice, resection should be performed sooner. Small duplications may present later in life or may never become symptomatic.
A duplication is defined by three histologic features:
1) a well-defined smooth muscle coat,
2) the presence of intestinal epithelium, and
3) attachment to the alimentary tract.
How are duplication cysts different from Meckel’s diverticula?
Duplications are found on the mesenteric aspect of the bowel, which differentiates them from a Meckel diverticulum.
Duplications may be cystic or tubular, with the former comprising the large majority.
Whereas cystic duplications typically share a common wall, but not a lumen, with the adjacent bowel, tubular duplications often have a luminal communication.
Incidence of types of alimentary tract duplications?
1) Small bowel 50% (majority ileocecal)
2) Esophagus 20%
3) Foregut 15%
4) Colon 15%
5) Rectal 5%
6) Thoracoabdominal <3%
Intestinal duplication is different from mesenteric cysts on the following bases, except:
A. Duplication cyst shares common blood supply with adjacent bowel.
B. Duplication cyst has different mucosal layer from adjacent bowel.
C. Duplication cyst shares muscular layer from adjacent bowel.
D. Duplication cyst is macroscopically different from mesenteric cyst.
E. Duplication cyst is microscopically different from mesenteric cyst.
B. Duplication cyst has different mucosal layer from adjacent bowel.
Regarding duplication cysts, which of the following is true?
A. Most of the duplication is thoracoabdominal.
B. Ectopic gastric mucosa is commonly seen.
C. Most duplication is solitary.
D. Most are communicating with bowel.
E. Ectopic pancreatic tissues are present in 20 percent of cases.
C. Most duplication is solitary.
Regarding duplication cysts, which of the following is false?
A. They possess at least one coat of smooth muscle.
B. They share a common wall with GIT.
C. They contain some sort of GIT lining.
D. Tubular variety is usually communicating and cystic variety is unusually non-communicating.
E. Tubular variety usually occurs in the stomach and proximal small intestine.
E. Tubular variety usually occurs in the stomach and proximal small intestine.
(cystic)
The following are different options of treatment of duplication cysts of GIT, except:
A. Resection and end to end anastomosis
B. Injection sclerotherapy
C. Partial resection with internal drainage of distal end
D. Partial excision and mucosal stripping
E. Some duplication cysts may need Roux-en-y drainage
B. Injection sclerotherapy
What are the five prevailing theories on the embryology of alimentary tract duplications?
Alimentary tract duplications take many forms, and one unifying embryologic theory is unlikely to encompass all variations. The associated findings of vertebral, spinal cord, and genitourinary (GU) malformations, as well as malrotation and intestinal atresia, suggest a multifactorial process in their development.
There are five prevailing theories: partial twinning, split notochord, diverticular defects, canalization defects, and environmental factors.
The partial twinning theory states that organs can be doubled as a result of partial twinning. This theory may be pertinent in hindgut duplications associated with GU tract duplications.
The split notochord theory centers around notochord separation in the first month of gestation. This theory postulates that gaps in the notochord develop and allow gut endoderm to herniate and form diverticula. This theory could account for the association of duplications with spinal defects.
A persistent embryonic diverticulum from the gastrointestinal (GI) tract was the first theory described in the literature, and a defect in lumen canalization was proposed years later. The theory of defective canalization is based on the finding that GI organs begin as solid tubes and vacuolate to form lumens. During this process, diverticula form but regress during fetal life. If they persist, duplications could form.
Finally, environmental factors including hypoxia, vascular accidents, and trauma have been implicated in the development of these anomalies.
What are imaging findings expected for duplication cysts?
Multiple imaging modalities are utilized to make the diagnosis.
Prenatal ultrasound (US) can be followed with US postnatally, which may be sufficient, especially for distal small bowel lesions. The typical sonographic appearance of a duplication (the double wall sign) demonstrates a cystic rim of hyperechoic serosa and an inner hyperechoic rim of mucosa and submucosa with a hypoechoic muscular layer sandwiched between the two hyperechoic layers.
For foregut lesions, more information in the form of computed tomography (CT) or magnetic resonance imaging (MRI) may prove valuable in operative planning.
Plain radiographs may reveal a mediastinal mass, which requires further workup with either CT or MRI.
Contrast studies may show a mass effect or communication with the alimentary tract and can help with the diagnosis, particularly in hindgut and foregut lesions.
Technetium-99m scintigraphy may be used as adjuvant imaging but is likely unnecessary in most cases.
The presence of a vertebral abnormality and a duplication is best investigated with MRI to evaluate communication with the spinal canal.
How do you differentiate pancreatic duplication cysts from pseudocysts?
Pancreatic duplications are the rarest type of GI duplication.
Commonly manifesting with abdominal pain that is often recurrent and chronic, they can easily be mistaken for a pancreatic pseudocyst.
What differentiates them from other alimentary duplications is that there is communication with the main or accessory pancreatic duct.
The cysts are similar to gastric duplications both grossly and microscopically, but they may or may not have attachment to the stomach.
They can be intrapancreatic or extrapancreatic, and may be combined with duplicated pancreatic tissue along an aberrant duct.
The location of ductal communication can be anywhere in the pancreas.
On exploration, there is often significant fibrosis, likely from chronic inflammation.
Intraoperative frozen section evaluation will differentiate a duplication from a pseudocyst based on the cyst wall cellularity.
Simple cyst resection is preferred, but the location may dictate a more complex resection.
What is the incidence of ectopic gastric mucosa among small bowel duplications?
The presence of ectopic gastric mucosa is found in 80% of tubular and 20% of cystic duplications.
Of note, these small bowel duplications can be mistaken for a Meckel diverticulum on technetium scanning.
Which of the following is true regarding alimentary tract duplications (ATDs)?
A incidence of 1 in 4500 births
B well-developed coat of smooth muscle
C intimate anatomical association with some portion of the gastrointestinal tract
D epithelial lining representing intestinal tract mucosa
E all of the above
E
Incidence of ATDs has been reported to be 1 in 4500 births with a male preponderance.
Three common findings as above are seen regardless of its location.
SPSE 1
The aetiopathogenesis of ATD includes
A partial or abortive twinning
B split notochord theory
C persistent embryonic diverticulum
D aberrant recanalisation of alimentary tract lumen
E all of above.
E
Multiple theories have been postulated, but no single theory can account for all known variants.
A persistent embryonic diverticulum from the developing alimentary tract was the first postulated theory. It was later postulated that duplications resulted from aberrant recanalisation of the alimentary tract lumen.
The coincidence of colonic and genitourinary tract duplications and similar findings in conjoined twins led to the partial twinning theory.
The association of enteric duplication and spinal anomalies led to the ‘split notochord theory’.
Several other environmental factors such as trauma and hypoxia have also been implicated.
This is supported by the presence of other anomalies like intestinal atresia, which may be induced by intrauterine vascular accidents.
SPSE 1
The most common location for ATD is:
A colonic
B rectal
C jejunoileal
D mediastinal
E thoracoabdominal.
C
ATDs can occur anywhere from oropharynx to anus.
Twenty percent occur in the chest and the remainder in the abdomen, with just 2% thoracoabdominal.
The various locations in decreasing order of frequency include jejunal and ileal (53%), mediastinal (18%), colonic (13%), gastric (7%), duodenal (6%), rectal (4%) and cervical (1%).
Between 10% and 20% of cases are multiple and presence of one such lesion, should warrant a search for others.
SPSE 1
