This child has presented with acute rectal bleeding. Examination reveals tachycardia and a delayed capillary refill time, but a normal blood pressure. These findings are suggestive of grade II hypovolemic shock. Thus, the first priority is resuscitation and stabilization (similar to any other emergency presentation). Once he is hemodynamically stable, the next step is to determine the cause of bleeding. The history yields several important clues in this regard - the first of which is the appearance of the blood. Upper gastrointestinal (GI) bleeding (i.e. duodenum and above) typically gives rise to malena, due to digestion of the blood in the small intestine. Bleeding from the terminal GI tract (i.e. from the sigmoid colon onwards) typically results in passage of bright red blood. Bleeding in-between these extremes (i.e. in the small bowel and proximal colon) typically results in passage of altered blood - which is dark red in color (as in this patient). In a child of 18 months, the small bowel and colonic pathologies which may potentially give rise to bleeding are Meckel's diverticulum, vascular malformations, colonic polyps and intussusception. In addition, bleeding disorders (such as acquired thrombocytopenias) may also result in bleeding into any part of the bowel. The second clue in the history is the nature of the stools. Dark red, jelly like stools are characteristically associated with intussusception, but may also occur in Meckel's diverticulum. Note that intussusception is very unlikely to cause this degree of bleeding, and there are no clinical findings suggestive of intestinal obstruction. While his full blood count shows a reduction in the hemoglobin level, this should not be used to guide management. as it does not reflect the severity of acute bleeding. In addition, his clotting profile and platelet counts are normal, virtually ruling out a bleeding disorder. As Meckel's diverticulum is the probable diagnosis, a Technetium 99m pertechnate scan (Meckel's scan) is probably the next best step - and in this patient demonstrates the presence of ectopic gastric tissue, clinching the diagnosis. Note that colonoscopy is of little diagnostic value during acute bleeding. Severe bleeding is an indication for surgery in these patients. After adqeuate resuscitation, he should be taken to the operating theatre for a Meckel diverticulectomy. As this is a clean-contaminated surgery, prophylactic antibiotics should be administered peri-operatively. An air enema would be indicated if he was diagnosed with intussusception.
Meckel's diverticulum is the most common congenital gastrointestinal anomaly, occurring in 2% of the population. There is an equal prevalence in both genders. In the developing embryo, the yolk sac is connected to the gut via the vitellointestinal duct. This structure regresses between the 5th to 8th weeks of life, as the placenta takes over the duties of the yolk sac. If regression fails partially or completely, various anomalies can occur - of which Meckel's diverticulum is one. Meckel's diverticulum occurs as a 3 to 5 cm long finger-like projection of the distal ileum along the antimesenteric border, around 30 to 45 cm proximal to the ileo-cecal valve. It possess all 3 layers of the intestinal wall, and often has an autonomous blood supply from the superior mesenteric artery. As the cells lining the vitellointestinal duct are pluripotent, Meckel's diverticula may contain ectopic gastric mucosa (~50% of cases), pancreatic mucosa or less often colonic or hepatobiliary tissue. The vast majority of patients remain asymptomatic throughout their lives. However, symptoms may develop if complications occur. Painless rectal bleeding (which may be massive) is the most common complication, accounting for between 20% to 30% of all presentations. It is more common in children less than 2 years of age. The underlying cause is believed to be ulceration of the diverticulum or adjacent intestinal mucosa due to acid secretion by the ectopic gastric mucosa. Intestinal obstruction accounts for between 20% to 25% of presentations and is more common in older children and adults. This may be due to intussusception (where the diverticulum acts as a lead point), volvulus, herniation, or entrapment of a loop of bowel through a defect in the diverticular mesentery. Similar to the appendix, Meckel's diverticulum is vulnerable to infection and obstruction, resulting in diverticulitis. In fact, the presentation may mimic that of acute appendicitis. In general, the likelihood of developing a complication ranges from 4% to 6%, with males affected 3 times more often than females. Most complications occur during the first 2 years of life, with the likelihood progressively decreasing with age. The diagnosis of Meckel's diverticulum is often tricky. First and foremost, a high index of clinical suspicion is necessary in any patient presenting with rectal bleeding or intestinal obstruction. Imaging studies are of variable use. The most sensitive modality is technetium-99m pertechnetate scanning, although this depends on uptake by heterotopic gastric mucosa. Arteriography is not always diagnostic because the arterial supply is not always abnormal. However, superior mesenteric arteriography may be of use in patients presenting with acute bleeding. Computed tomographic scans are often nonspecific but occasionally helpful. Contrast studies such as upper gastrointestinal series with small bowel follow-through are of limited value because the layers of barium-filled intestine will obstruct the view of the diverticulum. The diagnosis cannot be made with plain radiographs. Quite often, none of these imaging modalities are helpful and the diagnosis is made intra-operatively. The current standard of care is surgical resection of symptomatic Meckel's diverticula along with the ulcerated adjacent ileum. Note that diverculectomy is associated with early complications such as paralytic ileus, anastomotic leaks, intra-abdominal abscess formation and pulmonary embolism and late complications such as small bowel obstruction due to intestinal adhesions. It is a matter of controversy as to whether asymptomatic Meckel's diverticula should be removed, especially considering the morbidity associated with the diverticulectomy.