A child with maroon-colored stool that is otherwise well appears to potentially have a Meckel's diverticulum. What type of tissue is predominantly found within the diverticulum?

Meckel's diverticulum is a common congenital anomaly of the gastrointestinal tract, resulting from the incomplete obliteration of the omphalomesenteric duct. This diverticulum often contains ectopic tissue that can lead to complications such as gastrointestinal bleeding, which is often indicated by maroon-colored stools.

In the case of Meckel's diverticulum, it is most commonly associated with heterotopic gastric tissue. This means that gastric tissue, which normally belongs in the stomach, is found inappropriately located within the diverticulum. This ectopic gastric tissue can secrete acid, which can lead to ulceration of the adjacent intestinal mucosa, resulting in bleeding.

The presence of heterotopic gastric tissue is crucial to understanding the pathology associated with Meckel's diverticulum because this tissue can cause significant clinical manifestations, including the characteristic maroon-colored stool due to gastrointestinal bleeding. While intestinal epithelium is typically found in the diverticulum, the predominance of heterotopic gastric tissue is what distinguishes Meckel's diverticulum in many cases, especially when evaluating potential symptoms and their causes.