OVERVIEW: What every practitioner needs to know.
Are you sure your patient has Meckel diverticulum? What are the typical findings for this disease?
Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract. It is located on the antimesenteric border of the ileum and is a true intestinal diverticulum, containing all three layers of intestinal wall (Figure 1). Meckel diverticulum results from failure of obliteration of the omphalomesenteric duct. It carries its own blood supply from a remnant of the vitelline artery, also known as the omphalomesenteric artery, or occasionally from branches of the ileocolic artery.
An estimated 25%-33% of Meckel diverticula become symptomatic; the remainder are found incidentally during radiologic or surgical evaluation or at autopsy. Most symptoms develop during childhood and vary with patient age. Most patients (75%) with Meckel diverticulum present in the first 2 decades of life, with the majority presenting in the first 2 years.
Newborns and young infants typically present with intestinal obstruction manifesting as abdominal pain, distention, bilious vomiting, and/or constipation, most commonly due to a volvulus or internal hernia around a persistent fibrous cord between the diverticulum and the underside of the umbilicus. Other causes of intestinal obstruction associated with Meckel diverticulum include intussusception (Figure 2), luminal obstruction caused by an inverted diverticulum, a mesodiverticular band, an adhesive band, or from formation of a knot in a long diverticulum involving another viscus.
Slightly older infants and young children may present with painless, but significant, bleeding per rectum from peptic ulceration caused by ectopic, acid-secreting gastric tissue within the diverticulum. Bleeding can be massive, presenting as passage of bright red blood per rectum or less severe and occult, manifesting as guaiac-positive stools or chronic anemia. In cases of intussusception patients can present with the classic “currant jelly stools.”
Older children more commonly present with diverticulitis or free perforation, presenting as abdominal pain, fever, and vomiting, in a manner that is clinically indistinguishable from acute appendicitis.
Other less frequently encountered presentations include obstruction or perforation caused by an enterolith or foreign body in the diverticulum, regional enteritis, incarceration of the diverticulum in a hernia (Littre hernia), vesicodiverticular fistula, and rarely neoplastic obstruction. Symptoms in patients with Littre hernia are indolent, and the diagnosis should be considered in any patient with an atypical presentation of an incarcerated hernia.
Characteristics of Meckel diverticulum are often described by the rule of twos: it is located 2 feet proximal to the ileocecal valve, present in 2% of the population, usually presents by 2 years of age, it is twice as common in boys, and often contains two types of heterotopic mucosa (pancreatic and gastric).
Meckel diverticulum was first described in 1598 by the German surgeon Fabricius Hildanus. It was subsequently reported by Lavater in 1672 and by the Dutch anatomist Ruysch in 1701. It was named in 1809 by the German anatomist Johann Friedrich Meckel, who first identified its embryologic origin. Littre reported its presence in an inguinal hernia, and this finding is now called a Littre hernia. The presence of heterotopic pancreatic and gastric mucosa was identified by Zenker in 1861 and by Salzer in 1904.
What other disease/condition shares some of these symptoms?
Other intraabdominal pathologic conditions mimicking the various clinical presentations of Meckel diverticulum include acute appendicitis, inflammatory bowel disease, intestinal duplication cyst or solitary intestinal diverticulum, peptic ulcer disease, gastroenteritis, biliary colic, diverticulitis, or rarely cavitating malignancies of the gastrointestinal tract, such as lymphoma.
What caused this disease to develop at this time?
Meckel diverticulum is frequently asymptomatic. It is not clear why ectopic, acid-secreting mucosa suddenly results in ulceration and hemorrhage in some individuals and not in others. A role for Helicobacter pylori has been suggested in the pathogenesis of complications, but no convincing evidence has been found to date. Malignancy is rarely reported in association with Meckel diverticulum, the most common being carcinoid tumor. There is an increased incidence of Meckel diverticulum in patients with Crohn’s disease, reasons for which remain unclear.
What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?
Laboratory studies in cases of Meckel diverticulitis may reveal a high white blood cell count with neutrophilia and bandemia, with or without a positive stool guaiac test result. Metabolic acidosis with low serum bicarbonate (HCO3) may be seen in presentations with perforation and peritonitis.
Chronic presentations may include iron deficiency anemia and low ferritin levels due to ongoing blood loss or megaloblastic anemia due to vitamin B12 malabsorption, secondary to dilation and stasis in adjacent ileal loops, depending on the severity and chronicity of symptoms.
Would imaging studies be helpful? If so, which ones?
Meckel diverticulum can be difficult to diagnose, especially in the adolescent population. Radiologic evaluation should be tailored toward the age of the patient and clinical presentation. Angiography and sometimes red blood cell scintigraphy can be useful for localization of bleeding in a patient with lower gastrointestinal bleeding; however, neither study is specific for the diagnosis of Meckel diverticulum. More common approaches are as follows:
Scintigraphy: The diagnosis of a bleeding Meckel diverticulum may be made with a radiolabeled technetium scan, commonly referred to as Meckel scan, because of the high affinity of 99mTc-pertechnetate to the mucus-secreting gastric mucosa cells. A positive scan shows abnormal uptake of the isotope outside the stomach and urinary bladder (Figure 3). Pretreatment with substances such as pentagastrin, a histamine H2 inhibitor (e.g., cimetidine) or glucagon will enhance uptake of the radiotracer and should be used if there is strong clinical suspicion after a negative initial study result.
A Meckel scan has a sensitivity of 85%, a specificity of 95%, and an accuracy of 90%. False-negative results have been reported with rapid intestinal transit time, mucosal ischemia, or necrosis or insufficient gastric mucosa. False-positive results may be seen in cases of intussusception, intestinal duplication, inflammatory bowel disease, arteriovenous malformation, and hydronephrosis.
Ultrasonography: Ultrasonography can be a useful adjunct in patients with a strong clinical suspicion after a negative Meckel scan, or in patients with nonbleeding presentations. Meckel diverticulitis may resemble appendicitis and appears as a cystic tubular structure with a thick irregular hyperechoic internal wall and a hypoechoic external wall. Inverted Meckel diverticulum gives a target-like appearance.
Computed tomography (CT): CT is rarely used as a primary imaging modality; most of the diagnoses made using CT are incidental. Findings suggestive of Meckel diverticulum include a blind-ending tubular structure communicating with the lumen of the small intestine, with or without soft tissue stranding or fluid in the adjacent mesenteric fat. One may see an intraluminal mass in the case of an inverted diverticulum.
Barium enema: Occasionally, a Meckel diverticulum can be diagnosed on contrast enema studies as an incidental finding. In this case, a Meckel diverticulum would be identified as a saccular, blind-ending pouch on the antimesenteric border of the ileum with a characteristic triradiate fold pattern at the junction of diverticulum and ileum. Filling defects within the diverticulum may represent enteroliths, fecoliths, or foreign bodies.
Double-balloon enteroscopy: A few cases of bleeding Meckel diverticulum diagnosed by double-balloon enteroscopy have been described in the literature when other diagnostic modalities were inconclusive.
If you are able to confirm that the patient has a Meckel diverticulum, what treatment should be initiated?
The treatment of choice for Meckel diverticulum is surgical resection, either by diverticulectomy or by segmental intestinal resection and anastomosis. Laparoscopy is our preferred operative approach (Figure 4). Fibrous bands are easily divided, allowing the entire small bowel to be examined.
If a diverticulum is present, it is usually located on the antimesenteric border of the distal ileum. Occasionally, the diverticulum may be folded over and kinked by a congenital band or an inflammatory adhesion. These bands or adhesions should be divided along with the vitelline vessels to expose the base of the diverticulum.
If the diverticulum has a narrow and intact base, it may be divided with an endoscopic stapler. If, however, the base of the diverticulum is wide or thickened (suggesting the presence of ectopic tissue) or if there is inflammation or ischemia involving the adjacent ileum, a minimally invasive intestinal resection should be carried out either in an intracorporeal or extracorporeal manner through an umbilical incision. Extracorporeal resection has the added advantage of avoiding potential intraperitoneal spillage and being able to palpate the lesion, especially in cases of a short diverticulum (<1.6 height-diameter ratio).
The transumbilical single trocar laparoscopic approach has been used for resection of Meckel diverticulum and is associated with fewer incisions and lower operative costs
What are the adverse effects associated with each treatment option?
The adverse effects of surgical management of Meckel diverticulum are not different from any other elective surgical intestinal resection.
Of more interest are complications that arise from unrecognized Meckel divertilum. The most common complications related to Meckel’s diverticulum are small bowel obstruction (23%-42%), hemorrhage from peptic ulceration (43%-80%), and diverticulitis (14%-24%).
What are the possible outcomes of Meckel diverticulum?
The reported prevalence of complications related to Meckel diverticulum in adult patients ranges from 26% to 53%, with an incidence of 4% to 16%. The lifetime risk of complications developing is 4% up to the age of 20 years, and the risk decreases with increasing age. Postoperative morbidity after incidental resection varies between 0% and 6%, with significantly increased morbidity after resection of a complicated Meckel diverticulum. Current mortality from Meckel diverticulum is reported as 0.001%.
What causes this disease and how frequent is it?
Meckel diverticulum is the most common anomaly associated with persistence of the omphalomesenteric duct. It is a sac-like remnant arising from the antimesenteric border of the distal ileum resulting from patency of the ileal end and fibrous obliteration of the umbilical end of the vitelline duct.
The omphalomesenteric (vitelline) duct is the embryonic communication between the yolk sac and the primitive gut during the initial weeks of fetal development. As the placental circulation develops, the duct regresses and usually disappears between the fifth and seventh weeks of gestation. Incomplete regression can lead to a spectrum of congenital anomalies, depending on which portion of the omphalomesenteric duct remains patent.
Meckel diverticulum has an estimated prevalence of 0.6% to 4% in the general population. There is no known sex predilection for Meckel diverticulum, although symptoms and complications are more common in male patients, with the male-female ratio being 3:1 for symptomatic patients.
Most (75%) patients with Meckel diverticulum present within the first 2 decades of life, with the majority presenting in the first 2 years. The incidence of heterotopic tissue has been reported to be 6% in asymptomatic diverticula and between 50% and 67% in symptomatic diverticula.
How do these pathogens/genes/exposures cause the disease?
It is not known how the disease is caused.
What is the evidence?
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- OVERVIEW: What every practitioner needs to know.
- Are you sure your patient has Meckel diverticulum? What are the typical findings for this disease?
- What other disease/condition shares some of these symptoms?
- What caused this disease to develop at this time?
- What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?
- Would imaging studies be helpful? If so, which ones?
- If you are able to confirm that the patient has a Meckel diverticulum, what treatment should be initiated?
- What are the adverse effects associated with each treatment option?
- What are the possible outcomes of Meckel diverticulum?
- What causes this disease and how frequent is it?
- How do these pathogens/genes/exposures cause the disease?