Meckel Diverticulum

Meckel diverticulum (MD) is a fetal abnormality which is formed as a result of a persistent vitelline (omphalomesenteric) duct in the fetus or neonate.

O35.8 Maternal care for other (suspected) fetal abnormality and damage

Meckel diverticulum (MD) is identified in approximately 2% of the general population.¹ Reports from autopsy and retrospective studies conclude that the prevalence of MD is between 0.3-2.9%.² The anomaly is seen twice as commonly in males as in females, with a ratio of 2:1.³ More than half of all symptomatic patients were under the age of 10 years and that the prevalence of symptomatic MD decreases with age.²

Meckel diverticulum is a true diverticulum, as it contains all 3 layers of the small bowel wall. The outpouching is usually located in the antimesenteric border of the ileum. Embryologically, it is caused by failure of closure of the omphalomesenteric (OMD) (also called vitelline) duct between the 5^th and 7^th week of gestation. This duct connects the yolk sac to the gut and provides nutrition to developing embryo until the placenta is established. Between the 5^th and 7^th week, the duct normally starts to obliterate and separate from the intestine. The persistence of the OMD results in various anatomic abnormalities, most commonly a diverticulum.⁴ Other anatomic abnormalities include omphalomesenteric cysts, omphalomesenteric fistulas which can drain through umbilicus, umbilical polyp or an omphalomesenteric fibrous band.⁵

Occasionally, an OMD is found to have ectopic tissues on microscopic evaluation. The embryological explanation for this finding is not completely known.

Meckel diverticula (MD) are located on the antimesenteric border of the ileum, typically 50-75 cm from the ileocecal valve. They typically measure between 1.5 cm x 0.5cm and 2 cm x 3 cm.³

The microscopic findings in children depends on whether the MD has been symptomatic or not. In asymptomatic children, only 18% of Meckel diverticula have evidence of histologically abnormal mucosa; 14% have ectopic tissue, and 4% have diverticulitis.⁶ In contrast, 45% of symptomatic patients have specimens which contain ectopic tissue, 25% have diverticulitis, 6% have enteroliths and 25% show no abnormality in resected MD specimens.⁶ The most common ectopic tissues include gastric (52%), pancreatic (5%) and carcinoid (2%) tissues; less commonly duodenal, lipoma, and leiomyosarcoma are identified.⁶ When children present with bleeding, 78% had a Meckel diverticulum lined with only with gastric mucosa.⁶

The prevalence of MD is increased in children with major malformations of the umbilicus, alimentary tract, nervous system or cardiovascular system.⁷

Patients with Meckel diverticulum can also have other forms of omphalomesenteric duct (OMD) remnants. An incompletely absorbed OMD can result in abnormalities including umbilico-ileal fistula (patent OMD), umbilical sinus, umbilical cyst, umbilical mucosal polyp, or a fibrous cord connecting the ileum to the umbilicus.⁸ They may also have a variety of urachal anomalies including a urachal sinus, patent urachus, or urachal cyst. 

Some of these malformations may not be identified on prenatal ultrasound.

Meckel diverticulum can be considered when an ovoid or tubular mass is identified in the midline⁹ or on the right side¹⁰ of the upper fetal abdomen above the fetal bladder. The mass typically contains low level echoes during the pregnancy and may be thought to be a prominent loop of bowel. The wall of the mass may develop a “layered” appearance which suggests GI origin.⁹ Some masses may appear globular and pedunculated.⁹ The mass will not demonstrate peristalsis, and when initially found, can be less than 1 cm in diameter. Some cases of Meckel diverticulum have demonstrated mild peristaltic movements in the third trimester¹¹ but the exaggerated peristaltic movements seen commonly with a bowel obstruction are not seen in cases of Meckel diverticulum. The mass can be demonstrated to be adjacent to the cord insertion site, and separate from the gallbladder, umbilical vessels and bladder. The anus should be identified.

In the third trimester, some cases of Meckel Diverticulum may become isoechoic to fetal bowel loops and difficult to find with ultrasound.

Intestinal (enteric) duplication cyst

Early small or large bowel obstruction or atresia

Segmental ileal dilatation

Focal area of bowel stenosis or atresia

Colonic pouch

Mesenteric cyst

Choledochal cyst

Displaced Ovarian cyst (female fetus)

Dilated appendix

Hirschsprung disease

Congenital chloridorrhea

Volvulus

Ileus

If Meckel diverticulum is suspected, a thorough search for additional abnormalities is suggested, with particular attention to the fetal abdomen, anus and umbilical cord.

Patients should have additional ultrasound examinations during pregnancy to assess fetal growth and fluid volume. The size and appearance of the fetal mass should be re-evaluated at each visit to ensure that the mass remains consistent with the diagnosis of a Meckel diverticulum. 

An advanced (targeted) anomaly scan should be performed.

Typically, aneuploidy screening is not suggested for fetuses with isolated bowel malformations. However, if additional abnormalities are suspected or the diagnosis is uncertain, invasive testing with karyotype/microarray can be considered to ensure normal chromosomes.

Follow-up ultrasound examinations should be done periodically to ensure normal growth, fluid and to re-evaluate the fetal mass.

Consultation with neonatology and pediatric surgery may be helpful for the parents and caregivers alike. Delivery in a center with neonatal intensive care and support of pediatric radiology with pediatric surgical expertise is suggested.

Vaginal delivery at term is preferable; Cesarean delivery should be performed only for the usual obstetric reasons. The patient should be aware that neonatal imaging may change the diagnosis as intraabdominal masses may be difficult to fully evaluate in the antepartum period.  

Postnatal management of cases suspected to have Meckel diverticulum is difficult. If a MD is suspected the infant is not fed after birth. The diagnosis typically cannot be made on plain radiographs or ultrasound of the neonatal abdomen, and an upper GI series and barium enema may be helpful.³ Technetium 99 imaging can identify those MD which are lined by gastric mucosa. Occasionally, a CT scan can identify a MD, however, surgical exploration may be needed to identify and remove the mass.

Most neonates with MD are asymptomatic and the neonatal management of cases with suspected MD may be individualized. Some surgeons advocate the removal of MD because of the high risk of subsequent complications and the low risk associated with resection,³ while others prefer to resect only in selected cases or in cases which are suspected to have ectopic gastric mucosa.³

Neonates who are discharged from the hospital without surgical intervention should be watched for acute abdominal pain, lower GI bleeding, vomiting or abdominal distension, which should prompt evaluation.^11,12

Young children who become symptomatic typically present with symptoms of lower GI bleeding caused by ulceration or perforation of normal bowel due to acid secretion from ectopic tissues or from intestinal obstruction due to intussusception, segmental ileal dilation, or ileal volvulus.^11,13

For symptomatic patients, surgical exploration and removal of the mass is necessary. Depending on the size of the Meckel diverticulum, an open diverticulectomy, segmental bowel resection with re-anastomosis or simple resection anastomosis is performed.¹³ Diverticulotomy and segmental resection of the ileum is preferred to avoid restricting the intestinal lumen and to ensure that any ectopic tissue is removed and is preferred for cases which have a broad base.¹¹ For Meckel diverticula which are long and thin and which present without hemorrhage, simple resection is typically performed.² Recently, the laparoscopic approach has been found to be safe with minimal complication rates and shown to reduce length of stay and hospital costs.³

The long-term prognosis for patients with Meckel diverticulum is excellent after the lesion is completely resected. Rarely, a child will develop bowel obstruction due to intestinal adhesions.³

Recurrence of MD in siblings is quite rare and is thought to occur in only one of every 2500 families.¹⁵

1. ^{Sinha Ck, Fishman J, Clark SA. Neonatal Meckel’s diverticulum; spectrum of presentation. Pediatr Emerg Care 2009;25:348-9.}
2. ^{Hansen CC, Soreide K. Systematic review of epidemiology, presentation and management of Meckel’s diverticulum in the 21st century. Medicine (Baltimore) 2018;97:e12154.}
3. ^{Lin XK, Huang XZ, Bao XZ, et al. Clinical characteristics of Meckel diverticulum in children: A retrospective review of 15 year single-center experience. Medicine (Baltimore) 2017;96:e7660.}
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8. ^{DiSantis DJ, Siegel MJ, Katz ME. Simplified approach to umbilical remnant abnormalities. Radiographics 1991;11:59-66.}
9. ^{Lesieur E, Boubnova J, Hery G, et al. Prenatal imaging presentation of Meckel diverticulum. Diagn Interv Imaging 2017;98:569-70.}
10. ^{Della Chiaie L, Neuberger P. Early prenatal sonographic detection of an uncomplicated Meckel diverticulum. Ultrasound Obstet Gynecol 2007;30:790-91.}
11. ^{Huang CC, Lai MW Hwang FM, et al. Diverse presentations in pediatric Meckel’s diverticulum: a review of 100 cases. Pediatr Neonatol 2014;55:369-75.}
12. ^{Zani A, Eaton S, Rees CM et al. Incidentally detected Meckel diverticulum: to resect or not to resect? Ann Surg 2008; 247:276-81.}
13. ^{Rushford MP, Stys SJ, Latchaw LA et al. Prenatal sonographic detection of Meckel Diverticulum in utero with postnatal radiologic and surgical confirmation. J Ultrasound Med 2004;23:319-321.}
14. ^{Robinson J, Correa H, Brinkman AS, et al. Optimizing surgical resection of the bleeding Meckel diverticulum in children. J Pediatr Surg 2017;52:1610-1}
15. ^{Matsukuma Y, Matsuo Y, Sakaguchi M, et al. A case of siblings with Meckel’s diverticulum diagnosed before operation. Acta Paediatr Jpn 1994;36:291-3.}

Goswami S, Ranzini AC: Meckel Diverticulum, Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology, www.isuog.org, date of final edit

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