2. Laparotomy performed in a 4-year-old Caucasian girl with abdominal pain reveals a blind pouch connected to the ileum. The pouch is removed; under microscopy, it demonstrates pancreatic acini in the mucosa. The latter finding would be best described as which of the following?
A) Hypoplasia
B) Hyperplasia
C) Metaplasia
D) Dysplasia
E) Ectopy
Explanation
Correct Answer E. Ectopy
Meckel diverticulum is the most common congenital anomaly of the small intestine, being present in 2% of the population. It forms due to incomplete obliteration of the omphalomesenteric duct that connects the midgut lumen and yolk sac cavity early in fetal life. Meckel diverticulum is connected to the ileum, and is located approximately 2 feet proximal to the ileocecal valve.
A variety of tissues have been found in Meckel diverticulum, including gastric, pancreatic, colonic, jejunal, duodenal and endometrial. The most common of these is gastric tissue, which is significant because gastric epithelium produces acid that can cause ulceration of adjacent tissues and lower GI bleeding. Meckel diverticulum most often presents with painless melena. The diverticulum may also become inflamed and simulate the clinical presentation of acute appendicitis.
Gastric, pancreatic, and other types of mucosa found in Meckel diverticulum are examples of ectopy (also called heterotopy). “Ectopy” is a term that identifies microscopically and functionally normal cells/tissues found in an abnormal location due to embryonic maldevelopment.
Educational Objectives
A number of ectopic tissues are found in Meckel diverticulum-most commonly, gastric epithelium. Gastric mucosa is present in 80% of cases of symptomatic Meckel diverticulum. Gastric acid production leads to ulceration and subsequent bleeding.