Gavin A. Falk
Oliver S. Soldes
Presentation
An 18-month-old boy with an unremarkable past medical history presents to the emergency department (ED) with a 3-day history of episodic bright red bleeding per rectum. On examination, the child is quiet, tachycardiac, and normotensive. His abdomen is soft, nontender, and nondistended, without palpable masses. He does not seem to be in pain but appears pale and lethargic. He has not had any episodes of hematemesis. His distressed mother confirms that there is no family history of clotting disorders, inflammatory bowel disease, or polyposis syndromes. A nasogastric (NG) tube was placed and the aspirate is clear.
Differential Diagnosis
The causes of lower gastrointestinal (GI) bleeding in neonates (<30 days or age), infants (30 days to 1 year), children (1 to 12 years), and adolescents (>12–adults) are diverse and vary by age. Most causes in otherwise healthy children are self-limited. A child (1 to 12 years) who presents with bleeding per rectum has a differential diagnosis that includes anal fissures, Meckel’s diverticulum (MD), inflammatory bowel disease, intestinal polyps, and intestinal duplications. Uncommon causes of rectal bleeding include arteriovenous malformation, varices due to liver disease, and upper GI bleeding from peptic disease. In a young child (< 4 to 5 years), MD is the most common cause of clinically significant lower GI bleeding. Occasionally, the degree of hemorrhage is impressive and may require transfusion.
Workup
After a full physical examination and comprehensive history taking, the patient undergoes further evaluation in the ED with basic laboratory tests including a complete blood count, coagulation studies, and type and screen. His serum hemoglobin is reported as 11 g/dL, with a normal platelet count and BMP. His PT/INR and APTT are within normal limits. The patient undergoes a Technetium (Tc) 99m pertechnetate scan (“Meckel’s scan”), the diagnostic modality of choice to investigate for an MD with heterotopic gastric mucosa.
Discussion
Complications associated with MD are most readily understood in the context of the embryologic origin of these diverticula. MD is the most frequently encountered diverticulum of the small intestine (Figure 1). It is a true diverticulum containing all of the layers of the normal small intestinal wall. During the embryologic development of the midgut, the omphalomesenteric (vitelline) duct connects the yolk sac to the intestinal tract and usually obliterates by the seventh week of life. Arrest of the obliteration of the duct may lead to a number of omphalomesenteric anomalies, the most common of which is MD. The blood supply of the MD is derived from the paired vitelline arteries. The left vitelline artery involutes and the right artery (which also gives rise to the superior mesenteric artery) may persist and travel to the tip of the diverticulum. Incomplete involution of the duct and vitelline artery remnants, with failure to separate from the abdominal wall, may produce connections to the base of the umbilicus. These may give rise to draining ileoumbilical vitelline duct fistulas, vitelline duct cysts, blind-ending umbilical sinuses, and fibrous umbilicodiverticular bands, depending on the extent of involution
FIGURE 1 • The Meckel’s Diverticulum is delivered via the umbilicus when laparoscopically assisted extracorporeal diverticulectomy is performed.
The “rule of 2s” is often quoted as an aide-mémoire to the features of MD: The incidence is 2%; it is located within 2 ft of the ileocecal valve, is 2 in. in length, is usually symptomatic by 2 years of age, is two times as common in boys, and can contain two types of heterotopic mucosa. The heterotopic mucosa is most commonly gastric (80%) or pancreatic (5%) or both. The gastric mucosa is metabolically active and secretes hydrochloric acid. The pathogenesis of hemorrhage is thought to be ulceration of the ileum adjacent to the gastric mucosa (Figure 2).
FIGURE 2 • Meckel’s Diverticulum with heterotopic gastric mucosa. There is ulceration of the ileal mucosa adjacent to the heterotopic gastric mucosa.
Although MD is the most common cause of significant rectal bleeding in young children, intestinal obstruction is actually the most frequent presenting symptom of MD (30% obstructive vs. 27% hemorrhagic presentation). Fibrous umbilicodiverticular bands to the abdominal wall produce a point of fixation around which the midgut volvulus may occur. Mesodiverticular bands arising from vitelline artery remnants extending from the tip of the diverticulum to the mesentery may give rise to internal hernias. Heterotopic mucosa within the diverticula can act as a lead point for intussusception.
Inflammation related to the heterotopic mucosa may produce Meckel’s diverticulitis, which may be confused with acute appendicitis and may rarely lead to perforation with peritonitis and abscess formation. Enteroliths within the diverticula and incarceration of an MD within an inguinal hernia (Littre’s hernia) may also rarely occur.
Diagnosis and Treatment
Given the varied presentation of patients with MD, several different diagnostic modalities may be used in an attempt to arrive at the diagnosis. The correct diagnosis of MD is made more often in children presenting with bleeding versus other symptoms.
Tc 99m nuclear scan is the most accurate way to detect the heterotopic gastric mucosa frequently found in MD. The usefulness of the Tc 99m Meckel’s scan derives from the finding that approximately 95% of diverticula excised for bleeding contain gastric mucosa. The patient is injected intravenously with Tc 99m pertechnetate and a nuclear scan is performed. This isotope is selectively taken up by gastric mucosa and, if present, produces a positive scan (Figure 3A,B). Scintigraphy has a sensitivity of 85%, specificity of 95%, and accuracy of 90% in children. Pentagastrin stimulation, H2 histamine blockers, and glucagon may enhance the accuracy of the scan. Angiography is infrequently used due to its invasive nature and because it is useful only if there is brisk active bleeding. Tagged red cells scans are less sensitive and specific than Meckel’s scans and are seldom used.
FIGURE 3 • A, B Meckel’s scan demonstrating heterotopic gastric mucosa. Heterotopic gastric mucosa within a MD with uptake of radiotracer. There is also uptake in the mucosa of the stomach and the bladder. Courtesy of Sankaran Shrikanthan, MD.
Management of the Symptomatic MD
When the cause for presentation is hemorrhage, bleeding related to a MD is often episodic and surgery can usually be briefly delayed until the patient is stabilized and diagnostic evaluation can be performed. Intravenous hydration and volume resuscitation are a first step in management. Infrequently, a blood transfusion may be required. A NG tube should be inserted early in the evaluation to help rule out an upper GI source and confirm lower GI bleeding. A Meckel’s scan should be obtained and, if positive, proceed to operation without delay. A child with an unexplained source of lower GI bleeding may require exploratory operative intervention (preferably laparoscopy) even if the nuclear scan is negative.
Management of an Incidentally Found MD
It is not definitely clear from the medical literature how a surgeon should proceed when they find an MD incidentally. The vast majority of incidentally discovered Meckel’s diverticula will remain asymptomatic, especially if it has been asymptomatic into adulthood. The lifetime complications from Meckel’s diverticula are estimated as 4% to 6%. An incidentally discovered Meckel’s diverticula should be palpated. If there is an area of palpable thickening thought to be heterotopic mucosa, resection is usually indicated. In younger children, it can be argued that an incidentally found MD should be removed given the child’s greater lifetime risk of developing complications. Asymptomatic incidentally discovered MD should generally only be resected under optimal conditions, in the absence of peritonitis and shock, because of the limited benefits and the small risk of suture line leak and peritonitis.
Surgical Approach
Surgical resection is the treatment of choice for symptomatic MD, and the approach is dependent on the patient’s presentation and clinical condition (Table 1). Preoperative intravenous antibiotics are administered. The operation for bleeding or intussuscepted MD can be performed either as an open, laparoscopic, or laparoscopic-assisted procedure with extracorporeal resection. In slender children, the diverticulum is readily externalized by minimally enlarging the umbilical trocar incision, allowing palpation, examination, and excision of the diverticulum by conventional technique while conferring the benefits of a small abdominal incision. An initial minimally invasive approach is usually possible in children.
TABLE 1. Key Technical Steps and Potential Pitfalls in Resection of MD
Regardless of approach, the first step is to inspect and assess the diverticulum. There is often a large mesenteric vessel, which extends to the tip of the diverticulum that should be ligated. Resection of the MD can then be achieved either by diverticulectomy or segmental bowel resection and primary anastomosis by stapled or hand-sewn techniques. Open resection is generally performed via a transverse right lower-quadrant incision. An incidental appendectomy is generally performed when this incision is used, to eliminate the diagnosis of appendicitis in the evaluation of abdominal pain later in life.
When the patient presents with acute hemorrhage, it is safest to perform a wedge resection of the diverticulum and adjacent area of ileal ulceration is usually performed. The ileal mucosa should be visually inspected to identify and control the sight(s) of bleeding. The closure is generally performed transversely by hand-sewn technique in young children but may be stapled if the base of the diverticulum is narrow and the bowel lumen is large enough to avoid narrowing. A segmental ileal resection is indicated if there is evidence of intestinal ischemia, extensive inflammation, irreducible intussusception, the base of the diverticulum is very wide, or there is palpable ectopic tissue near the diverticular opening. Ileal mucosa with significant ulceration and bleeding opposite the diverticulum (on the mesenteric side) usually requires segmental resection. In cases where diagnostic testing has failed to make a definitive diagnosis, an exploratory laparoscopy is a safe way to proceed to localize the lesion.
Pitfalls associated with resection of a bleeding MD include failure to control hemorrhage from areas of adjacent ulceration if the diverticulum is excised with a stapler without opening the ileum and inspection of the mucosa. Longitudinal closure and simple wedge excision (diverticulectomy) of a wide-based diverticulum may create a stenosis. Leaks from suture or staple lines may occur and offset the limited benefits of excision of asymptomatic MD especially in acutely ill elderly patients, who are unlikely to develop complications of the MD late in life. Caution should be observed in placement of the primary laparoscopic trocar in cases where attachment to the umbilical abdominal wall is suspected (volvulus, draining ileoumbilical vitelline duct fistulas, vitelline duct cyst, or sinuses). A nonumbilical site for the primary trocar may be selected in these cases.
Postoperative Management
Postoperative care following Meckel’s diverticulectomy or segmental resections consists of conventional care for small bowel surgery with supportive care consisting primarily of intravenous fluids, 1 or 2 doses of postoperative antibiotics, a brief period of nothing by mouth (NPO), and sometimes NG suction (segmental resections) until any ileus resolved. If a simple wedge resection or diverticulectomy is performed with laparoscopic or laparoscopically assisted extracorporeal technique, an NG tube is usually not needed and clear liquids may be initiated the following day.
Case Conclusion
The patient undergoes successful laparoscopicassisted Meckel’s diverticulectomy with wedge resection. At follow-up in the outpatient clinic 3 weeks later, the child was well, with no further bleeding, and a benign abdominal examination. Pathologic analysis of the surgical specimen confirms a gastric mucosa containing MD with ulceration. Further follow-up is unnecessary.
TAKE HOME POINTS
· MD is the most common cause of clinically significant rectal bleeding in young children (<4 to 5 years). Bleeding may be impressive and require transfusion.
· With the exception of tachycardia, hypotension, and pallor, the physical exam in patients with MD is often normal. The NG aspirate is usually clear.
· MD often presents with episodic painless rectal bleeding, but obstructive symptoms are more common (with volvulus, internal hernia, or intussusception). An acute abdomen (diverticulitis and perforation), or umbilical fistulas/cysts/sinuses may occur.
· A positive Meckel’s nuclear scan is diagnostic in the child with significant lower GI bleeding and is the test of choice.
· Wedge resection of the diverticulum and adjacent ulceration with direct inspection of the ileal mucosa is safest in MD presenting with hemorrhage. A laparoscopically assisted extracorporeal approach is usually possible in the slender child.
· Segmental resection may be necessary to control hemorrhage from extensive ulceration, ulceration opposite the diverticulum, for ischemia, or when narrowing of the ileal lumen will result from diverticulectomy.
SUGGESTED READINGS
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Dassinger MS. Meckel’s diverticulum. In: Mattei, P ed. Fundamentals of Pediatric Surgery. 1st ed. New York, NY: Springer, 2011.
Ruscher KA, Fisher JN, Hughes CD, et al. National trends in the surgical management of Meckel’s diverticulum. J Pediatr Surg. 2011;46:893–896.
St. Vil D, Brandt ML, Panis S, et al. Meckel’s diverticulum in children: a 20-year review. J Pediatr Surg. 1991;11:1289–1292.
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