Clinical Presentation

Pathophysiology

Meckel's diverticulum is a true diverticulum, consisting of mucosal, submucosal and muscularis propria layers. As a result of the pluripotential cells lining the vitelline duct, the presence of ectopic mucosa is common in Meckel's diverticula (over 60%). Approximately 50% will contain ectopic gastric mucosa. These comprise 75% of symptomatic Meckel's diverticula. Pancreatic tissue is contained in 5%, while an additional 5% will contain both gastric and pancreatic mucosa. Although studies have demonstrated the presence of Helicobacter pylori within Meckel's diverticula, there is no evidence of a correlation between colonization and symptomatology or ulceration. This is in contrast to similar pathology in the stomach and duodenum.

Symptomatic Meckel's diverticula present in a variety of ways. The three most common are rectal bleeding (40%), obstruction (35%) and diverticulitis (17%). Other presentations include umbilical fistulae, presence within an inguinal hernia (Littre's hernia) or internal hernias.

Patients with rectal bleeding present with episodic, painless and sometimes severe bleeding. They often require transfusion. Bleeding is a result of ulceration from exposure to gastric acid secreted by parietal cells in the ectopic gastric mucosa. Histologically this ulceration usually occurs at the border between the ectopic and normal ileal mucosa and very rarely on ileal mucosa more remote from the diverticulum. In less severe cases, children may present with melena and mild anemia.

Obstruction is usually due to intussusception (about 50% of those cases that present with obstructive symptoms) with the Meckel's diverticulum serving as the lead point. Patients present with classic signs of obstruction including vomiting, abdominal pain, distension and often a palpable abdominal mass. Other causes of obstruction associated with a Meckel's diverticulum include volvulus, internal herniation, inguinal herniation (Littre's hernia) and kinking of the bowel at the diverticulum.

Meckel's diverticulitis usually occurs prior to 10 years of age and is very similar to appendicitis in presentation. In other words, pain, mildly elevated white blood count, nausea and anorexia appear in association with right lower quadrant pain. As such, it is often diagnosed during an appendectomy. The location of this pain can be more variable with Meckel's diverticulum as the position of the diverticulum within the abdomen is less fixed than that of the appendix. Additionally, free air in the abdomen is much more common in perforated Meckel's diverticula secondary to its lack of retroperitoneal attachments and free-floating position in the abdomen.

Meckel's diverticula can also be associated with malignancy, the most common being carcinoid tumors. Other documented neoplasms include adenocarcinoma, leiomyoma and lymphoma.

Дата добавления: 2014-10-15