Meckel’s Diverticulum

Leor Arbel, MS-3

Background• Most prevalent congenital anomaly of the GI tract • True diverticula - contains all layers found in normal small intestine• Usually located in the ileum, within 100 cm of the ileocecal valve• ~60% contain heterotopic mucosa (gastric mucosa > pancreatic acini > Brunner’s

glands, pancreatic islets, colonic mucosa, etc)• Neoplasms, MC carcinoid tumors, are found in ~0.5-3% of symptomatic Meckel’s

diverticula• “Rule of 2’s” – useful (but crude) mnemonic

• 2% prevalence• 2:1 male dominance• 2 ft proximal to Ileocecal valve (in adults)• Half of symptomatic pts are < 2 y/o

Pathophysiology • In 8th wk of gestation, omphalomesenteric duct (aka vitelline duct) normally

obliterates, just before midgut returns to abdomen• Failure or incomplete vitelline duct obliteration results in a spectrum of

abnormalities, including omphalomesenteric fistulas and enterocysts (image on next slide)

• However, the MC abnormality associated with this is Meckel’s diverticulum• Remnant of the Left Vitelline Artery may persist, too, forming a

mesodiverticular band tethering the Meckel’s diverticulum to the mesentery of the ileum (image on next slide)

Pathophysiology cont’dLeft: Embryology diagram of vitelline duct incorporation into umbilical cord

Right: Abnormalities associated with failure of vitelline duct obliteration

Source: GI Embryology Flash Cards

Pathophysiology cont’dA. Meckel’s diverticulum

w/mesodiverticular bandB. Entrapment of intestine

by mesodiverticular band

Figure from Schwartz’s Principles of Surgery, 10e

Pathophysiology cont’d• May cause bleeding (classically painless rectal bleeding) - usually the result of

ileal mucosal ulceration that occurs adjacent to the acid-producing heterotopic gastric mucosa within the diverticulum

• May cause intestinal obstruction – a/w the following mechanisms:• Volvulus around fibrous band attaching diverticulum to umbilicus• Entrapment by a mesodiverticular band• Intussusception with the Meckel’s diverticulum serving as the lead point• Stricture formation due to chronic diverticulitis

• May also be contained within inguinal or femoral hernia sacs -- this is known as Littre’s Hernia• If it becomes incarcerated, it can also cause intestinal obstruction

Clinical Manifestations• Asymptomatic unless associated complications arise• Lifetime incidence of complications in pts with Meckel’s diverticula has been

estimated to be btwn 4-6%• It was previously thought that the risk of developing a complication decreases

with age – however, more recent data suggests that this is untrue and that the risk of developing Meckel’s related complications does NOT change with age! (Cullen et al)

• MC presentations a/w symptomatic Meckel’s diverticula are:• Bleeding MC presentation in pts < 18 y/o (> 50% of cases)• Intestinal Obstruction MC presentation in adults• Diverticulitis Presents w/a clinical picture that mimics acute appendicitis

Summary Slide: Complications a/w Meckel’s Diverticula

Source: Castleden (1970)

Diagnosis• Most are found incidentally (eg radiographic imaging, endoscopy, or during surgery)• For pts presenting with symptoms suggestive of Meckel’s diverticulum,

confirmatory imaging may be sought (but there are some challenges to keep in mind) • CT scans – sensitivity too low• Enteroclysis – 75% accuracy but usu N/A during acute presentations• Technetium-99m-pertechnetate scan (aka Meckel scan) – can be very helpful but this

test is only (+) when ectopic gastric mucosa (which can take up the tracer) is present. Also, while the accuracy of this scan is 90% in pediatric pts, it is < 50% in adults (images on next slide)

• Angiography – can localize site of bleed in pts presenting w/acute hemorrhage

Meckel’s Diverticulum Dx: 99mTc-Pertechnetate Scintigraphy

Meckel’s Diverticulum with ectopic gastric tissue. Image shows an abnormal focus of radiotracer uptake in the RLQ (arrow).

Figure from Schwartz’s Principles of Surgery, 10e

Tx of Symptomatic Meckel’s Diverticula• Surgical resection: Diverticulectomy + removal of associated

bands connecting diverticulum to abdominal wall or intestinal mesentery

• Additional surgical considerations:• If bleeding was the pt’s presentation, segmental resection of ileum that

includes both the diverticulum and the adjacent ileal ulcer should be performed

• Segmental ileal resection may also be needed if there is a tumor present, or if the base of the diverticulum is inflamed or perforated

Figure from Schwartz’s Principles of Surgery, 10e

Tx of Asymptomatic Meckel’s Diverticula• Unfortunately, mgmt. of asymptomatic (incidentally found) Meckel’s diverticula is less

straightforward – more controversy!• Until recently, recommendation was against PPx removal, given the relatively low

lifetime incidence of complications• However, more recently, there has been greater endorsement of PPx diverticulectomy.

Proponents argue that there is minimal morbidity a/w Meckel’s diverticulectomy and that the lifetime incidence of complications reported in the literature may be erroneously low.

• Still, others have advocated in favor of a more selective approach that recommends removal only in cases where the diverticula is attached by bands and or has a narrow base

• Minimal controlled data supporting/refuting any of these recommendations

References• Tavakkoli A, Ashley SW, Zinner MJ. Small Intestine. In: Brunicardi F, Andersen

DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE. eds. Schwartz's Principles of Surgery, 10e New York, NY: McGraw-Hill; 2015. http://accessmedicine.mhmedical.com.ezproxy.med.ucf.edu/content.aspx?bookid=980&sectionid=59610870. Accessed March 03, 2017.

• Cullen JJ, Kelly KA, Moir CR, et al. Surgical management of Meckel's diverticulum. An epidemiologic, population-based study. Ann Surg 1994;220:564-9.

• Castleden, W.M. (1970) Meckel's diverticulum in umblical hernia. Br. J. Surg., 57:932.