Gastroenterology and Hepatology Board Review: Pearls of Wisdom, Third Edition

Section IV SMALL INTESTINE

CHAPTER 20. Small Intestinal Congenital and Structural Abnormalities

Ashok Shah, MD and Rajiv Sharma, MD

Image What is the difference between true and false diverticula?

False diverticula do not include the muscularis propria in the sac wall.

Image True/False: Juxtapapillary diverticula have a strong association with gallstones.

True. Also known as extraluminal duodenal diverticula or periampullary diverticula, they occur within 2 cm of the ampulla of Vater.

Image True/False: Intraluminal duodenal diverticula are lined by duodenal mucosa on the inside and outside of the structure.

True. Also known as a windsock diverticulum, this is a single saccular structure that originates in the second portion of the duodenum. They may be connected to the entire circumference or only part of the duodenal wall.

Image Jejunal diverticula are associated with what disorders?

They are typically seen in disorders of small intestinal motility such as progressive systemic sclerosis and visceral myopathies and neuropathies.

Image True/False: Recurrent asymptomatic, nonsurgical pneumoperitoneum may be seen in jejunal diverticulosis?

True. The presence of free intraperitoneal gas usually warrants emergent surgery; however, some conditions such as jejunal diverticulosis and pneumatosis intestinalis may result in asymptomatic pneumoperitoneum and do not require surgical intervention.

Image A Meckel’s diverticulum is the remnant of what embryological structure?

The omphalomesenteric or vitelline duct.

Image True/False: A Meckel’s diverticulum occurs on the mesenteric border of the gut.

False. It occurs on the antimesenteric border.

Image True/False: The most common location for Meckel’s diverticulum is 10 cm from the ileocecal valve.

False. Most commonly they are 100 cm from the ileocecal valve.

Image Describe the “rule of two’s” as relates to Meckel’s diverticulum.

The rule of two’s best describes Meckel’s diverticulum. It occurs in 2% of the population with a male-to-female ratio of 2:1, is found within two feet of the ileocecal valve, is two inches long, and approximately 2% develop a complication over the course of their lives.

Image True/False: Heterotopic tissue is present in one-half of all Meckel’s diverticula.

True. The most common types are gastric mucosa, pancreatic tissue, or a combination of the two.

Image True/False: Detection of Meckel’s diverticula by technetium-99m pertechnetate radionucleotide scanning is dependent on the presence of gastric mucosa within the diverticula.

True. Technetium-99m pertechnetate scan is considered the standard method for preoperative diagnosis of Meckel’s diverticulum. It has a specificity of 95% and a sensitivity of 85%. Technetium-99m is taken up by the ectopic gastric mucosa and may be enhanced by blocking anion secretion from the mucosa with histamine type 2 receptor antagonists administered 24 to 48 hours before the scan.

Image What is the most common complication of a Meckel’s diverticulum in children? In adults?

In children, usually in infants and those younger than 5, gastrointestinal bleeding occurs most commonly. In adults, intestinal obstruction is more common.

Image What complications may result from a Meckel’s diverticulum in the adult population?

Complications include obstruction, bleeding, diverticulitis, perforation, and carcinoma.

Image True/False: Intestinal duplications are hypothesized to develop from aberrant recanalization of the gut during morphogenesis and share the same blood supply with the native intestine.

True.

Image True/False: Duplications of the gastrointestinal tract are located on the mesenteric border of the gut.

True.

Image True/False: The most common segment of the gut involved in intestinal duplication is the colon.

False. The ileum is the most common segment followed by the jejunum.

Image True/False: Intestinal duplication may range from single cystic structures that do not communicate with the native bowel to tubular structures that share the lumen with the native bowel.

True.

Image True/False: Gastric mucosa may line intestinal duplications.

True.

Image True/False: Intestinal atresia with occlusion of the gut lumen is a common cause of intestinal obstruction in the neonate.

True.

Image Duodenal atresia and stenosis are frequently associated with what congenital abnormalities?

Esophageal atresia, midgut malrotation, imperforate anus, annular pancreas, and Down’s syndrome.

Image Acute pancreatitis occurring in an adult patient with a history of congenital duodenal atresia is most likely related to what condition?

Annular pancreas is a rare cause of acute pancreatitis in the setting of duodenal atresia.

Image True/False: The distribution of gut atresia can range from the esophagus to the rectum.

True.

Image What is the incidence of small bowel atresia?

1 in 3000 to 5000 live births.

Image True/False: Small intestinal atresia is more common in a woman who has had multiple pregnancies compared with a woman with a single pregnancy.

True.

Image Describe the four types of intestinal atresia.

Type I– diaphragm of mucosa and submucosa obstructs the lumen but the bowel wall and mesentery are intact.

Type II – two blind bowel ends connected by a fibrous cord.

Type IIIA – two blind bowel ends separated by a mesenteric gap.

Type IIIB – “apple peel” atresia—proximal small bowel atresia and absence of the distal superior mesenteric artery.

Type IV – “string of sausages”—multiple atretic regions throughout the small bowel.

Image Duodenal atresia is thought to develop at what gestational age?

Recanalization of the intestinal lumen from the solid cord stage occurs at 4 to 8 weeks of gestation.

Image True/False: Polyhydramnios is frequently associated with gastrointestinal atresia of the distal gut.

False. Proximal gut atresia is associated with polyhydramnios.

Image A double-bubble sign on abdominal radiograph or ultrasound in a neonate is classic for what type of intestinal atresia?

Duodenal atresia.

Image True/False: Common presenting signs of a proximal (duodenal or proximal jejunum) atresia include jaundice and bilious vomiting.

True. Distal atresias often present with abdominal distension.

Image What are the two major complications of gut malrotation?

Volvulus around the vascular pedicle and duodenal obstruction secondary to Ladd bands.

Image True/False: Ladd bands are peritoneal bands that pass from the cecum across the duodenum to the right upper quadrant or to the duodenum and form after malrotation of the gut.

True.

Image The Ladd procedure is undertaken for management of what condition?

Intestinal malrotation. The Ladd procedure involves division of the Ladd bands, if present, widening of the base of the mesentery by dividing any adhesions between the duodenum and cecum at the base of the mesentery, passing a tube through the duodenum to rule out any associated duodenal obstruction (in the newborn), appendectomy, and placing viable bowel in a position of nonrotation.

Image Describe the gut anatomy following nonrotation.

The small intestine (jejunum and ileum) lies on the right side of the abdomen and the colon is entirely on the left. The cecum lies in the left iliac fossa.

Image What is reversed rotation of the gut?

The gut rotates clockwise, instead of the normal 270-degree counterclockwise rotation, resulting in the colon entering the abdominal cavity first. The colon then takes a position posterior to the superior mesenteric artery and the duodenum. The small bowel mesentery passes in front of the transverse colon.

Image True/False: Less than half of midgut malrotations present in infancy.

False. Fifty percent to 80% present in infancy.

Image True/False: Biliary atresia and congenital heart disease are associated with gut malrotation.

True.

Image True/False: Omphaloceles are sac-covered abdominal viscera herniating through the umbilical ring.

True.

Image True/False: Gastroschisis is a small defect in the abdominal wall usually to the right of the closed umbilical ring through which there is massive evisceration of the intestines with direct exposure to amniotic fluid.

True. It requires immediate operation because a membrane does not cover the bowel.

Image What is the gestational age when gastroschisis or omphaloceles develop?

Between the fifth and tenth week of gestation.

Image True/False: An elevated alpha-fetoprotein level in maternal serum is associated with ventral fetal abdominal wall defects such as omphalocele and gastroschisis.

True.

Image True/False: Long-term morbidity and mortality of gastroschisis are high because of the high risk of necrotizing enterocolitis, bowel perforation, or necrosis and the need for prolonged parenteral nutrition complicating the course.

True.

Image True/False: Omphaloceles are associated with extraintestinal birth defects, whereas gastroschisis is rarely associated with other defects.

True.

Image True/False: Volvulus of the small bowel in the absence of preexisting defects is more common in Africa, the Middle East, and India because of the ingestion of bulky foods after periods of fasting.

True. Volvulus of the small bowel is rare in the United States without preexisting defects.

Image True/False: Intussusception is one of the most common causes of bowel obstruction in children under the age of 2.

True.

Image What is the cause and frequency of a pathologic lead point in pediatric intussusception?

Most are idiopathic. Approximately 8%–12% will have a structural abnormality such as a polyp, leiomyoma, or lymphoma. Benign lymphoid tissue has also been suggested as a potential lead point.

Image True/False: The classic triad of pain, a palpable sausage-shaped abdominal mass, and currant-jelly stool occurs in most children who present with intussusception.

False. This triad is seen in less than 15% of patients at the time of presentation.

Image True/False: Intussusception may complicate the course of Henoch–Schonlein purpura.

True. The vasculitic bowel may result in an intramural hematoma that acts as a lead point for intussusception.

Image True/False: Small bowel intussusception is a major cause of intestinal obstruction in adults in the Western world.

False. Approximately 5% of adult intestinal obstructions are caused by intussusception.

Image What is the frequency of a pathologic lead point in adult intussusception?

Approximately 90% of adult intussusceptions will have an identifiable cause such as a polyp, tumor, Meckel’s diverticulum, and celiac disease with flaccid bowel.

Image What is the most common bowel segment involved in cases of intussusception occurring in the pediatric population?

Ileocolic intussusception is the most common.

Image True/False: Reduction of an ileocolic intussusception in a stable pediatric patient should first be attempted by barium enema.

True. Pneumatic or hydrostatic (eg, barium) enema is often successful in reducing an intussusception in a child.

Image True/False: In adults with intussusception, the proper surgical management, in the absence of infarcted or gangrenous bowel, is manual reduction.

False. Since many lead points in the adult population are malignant, manual reduction is not recommended. Instead, bowel resection of the affected segment is recommended.

Image What clinical findings may be found in intestinal lymphangiectasia?

Steatosis, malabsorption, lymphocytopenia, hypogammaglobulinemia, protein-losing enteropathy, chylous ascites, chlyous pleural effusion, and peripheral edema.

Image What medical conditions may lead to secondary lymphangiectasia?

Abdominal/retroperitoneal carcinoma/lymphoma, retroperitoneal fibrosis, pancreatitis, tuberculosis, Crohn’s disease, celiac disease, systemic lupus erythematosus, and congestive heart failure.

Image Congenital lymphangiectasia is also referred to as what?

Milroy’s disease.

Image True/False: Wilkie syndrome is caused by compression of the third portion of duodenum by superior mesenteric artery.

True. Superior mesenteric artery syndrome is also known as both Wilkie syndrome and Cast syndrome.

Image Chronic postprandial abdominal pain and radiographic evidence of celiac artery compression should make one think of what diagnosis?

Median arcuate ligament syndrome (MALS). Also known as celiac artery compression syndrome, MALS is caused by abnormally low insertion of the median fibrous arcuate ligament and muscular diaphragmatic fiber resulting in luminal narrowing of the celiac trunk.

Image What is the traditional treatment of MALS?

Surgical division of the median arcuate ligament and complete celiac ganglionectomy.

Image How can a definite diagnosis of MALS be achieved?

Lateral aortography of the visceral aorta and its branches during inspiration and expiration.

• • • SUGGESTED READINGS • • •

Berrocal T, Lamas M, Gutieerrez J, Torres I, Prieto C, del Hoyo ML. Congenital anomalies of the small intestine, colon, and rectum. Radiographics. 1999 Sep–Oct;19(5):1219-1236.

Morikawa N, Kuroda T, Honna T, et al. A novel association of duodenal atresia, malrotation, segmental dilatation of the colon, and anorectal malformation. Pediatr Surg Int. 2009 Nov;25(11):1003-1005.

Vaos G, Misiakos EP. Congenital anomalies of the gastrointestinal tract diagnosed in adulthood–diagnosis and management. J Gastrointest Surg. 2010 May;14(5):916-925.