Meckel's diverticulum may contain pancreatic and/or gastric tissue, resulting in inflammation and bleeding. Bleeding occurs downstream from the Meckel's due to the natural protective barrier of gastric mucosa in the diverticulum.
Terminal mesenteric vessels penetrate the circular muscle of the colon on the mesenteric sides of the taeneae. The resulting muscular defect allows mucosa and submucosa to protrude under pressure forming false diverticula in the majority of people over 40. Inspissated stool can erode the adjacent vessel causing bleeding, and can cause pressure necrosis of the diverticulum resulting in perforation. The majority (80%) of diverticular bleeds stop spontaneously, and are also subject to endoscopic control if necessary. Perforation may lead to longitudinal inflammation (diverticulitis), contained abscess, free perforation (usually a single diverticulum), and secondary perforation of an abscess.
The colonic peritoneal reflection (white line of Toldt) is the junction of the fusion plane between colonic mesentery and posterior parietal peritoneum. It is best identified by lifting the colon, causing the parietal peritoneum to fold on itself . The proper avascular plane to enter lies on the colonic side of the fold. The plane is best dissected bluntly with a moist sponge stick.