Meckel Diverticulum 

A Meckel diverticulum is a vestigial remnant of the omphalomesenteric (vitellointestinal) duct. As a congenital anomaly, it is a true diverticulum that includes all 3 coats of the small intestine. Generally, a Meckel diverticulum ranges from 1-12cm in length and is found 45-90cm proximal to the ileocecal valve. It frequently contains heterotropic tissue; when it does, gastric mucosa accounts for 50%. (See the image below.)

Pluripotential cells line the omphalomesenteric duct; thus, gastric, colonic, duodenal, and pancreatic mucosa may be present. The diverticulum may or may not be attached to the umbilicus with a fibrous cord.

Autopsy records show that Meckel diverticulum occurs in about 2% of the general population. The male-to-female ratio of patients with symptomatic diverticula is 3:1, but it is 1:1 for patients with asymptomatic diverticula.

Human embryos initially have convex umbilical loops of primitive gut that communicate freely with the yolk sac through the omphalomesenteric duct. As development proceeds, the duct normally becomes occluded and disappears entirely by weeks 8-10 of gestation. The following anomalies are caused by the persistence of the omphalomesenteric duct:

• An outpouching diverticulum secondary to persistence of the proximal part of the vitelline duct (Meckel diverticulum), with or without a fibrous cord; Meckel diverticulum is the most common anomaly (see the image below.) A diverticulum connected to the umbilicus by a fibrous cord.
• Persistence and patency of the entire tract leading to a congenital umbilico-ileal fistula (see the image below)Umbilico-ileal fistula resulting from persistence of the entire intra-abdominal portion of the yolk stalk.
• Persistence of the duct near the umbilicus, forming an umbilical sinus (see the image below)Umbilical sinus resulting from the persistence of the yolk stalk near the umbilicus.
• Fluid-filled cysts (enterocystomas) located either intra-abdominally or just below the umbilical skin because of persistence of the middle portion of the duct (see the image below) Vitelline cysts at the umbilicus and in a fibrous remnant of the yolk stalk.
• Obliteration of the lumen of the duct but persistence of the duct, forming a fibrous cord

Although most commonly discovered as an incidental finding on laparotomy or laparoscopy, Meckel diverticulum can be associated with life-threatening disease states.^[1] Retrospective studies suggest that the onset and frequency of complications decrease during life. The risk of complications ranges from 4-25% in various studies. Complications manifest as the following:

• Ulceration
• Hemorrhage
• Small bowel obstruction
• Diverticulitis
• Perforation

In an excellent population-based study covering patient data over 42 years by Cullen et al, the lifetime risk of developing a complication that requires surgery was estimated to be 6.4%.^[2]

Hemorrhage

Hemorrhage is the most common complication, with an incidence of about 20-30% of all complications. It is more common in children younger than 2 years and in males. The patient complains of passing bright red blood in the stools. Bleeding may vary from minimal, recurrent episodes of hematochezia to massive, shock-producing hemorrhage.

The rate of bleeding can be assessed by the quantity of blood lost in the stools, the appearance of the material passed through the rectum, and the hemodynamic state. Hemorrhage from a Meckel diverticulum may or may not be associated with abdominal pain or tenderness. Patients may also present with weakness and anemia and may have a history of self-limiting episodes of intestinal bleeding.

Characteristics of hemorrhage based on the appearance of stools include the following:

• Bright red blood in the stools - Brisk hemorrhage
• Tarry stools - The bleeding is probably minor and associated with slow intestinal transit; tarry stools are commonly observed in patients with upper gastrointestinal (GI) bleeding, because transit through the bowel produces alteration of blood
• Currant jelly stools - Associated with copious mucus owing to ischemia of the bowel; are commonly observed in intussusception.
• Blood-streaked stools - A sign of fissure-in-ano

The gastric mucosa found in the diverticulum (shown below) may form a chronic ulcer and may also damage the adjacent ileal mucosa because of acid production. Ectopic gastric mucosa is found in about 50% of all Meckel diverticulum; in bleeding Meckel diverticulum, the incidence increases to 75%. Perforation may occur, and the patient then presents with an acute abdomen, often associated with air under the diaphragm, best visualized on an erect chest radiograph.

When a patient presents with painless lower GI bleeding, Meckel diverticulum should always be suspected. Panendoscopy helps to exclude disease in the upper GI and colorectal regions, the 2 most common sites of GI bleeding.

Intestinal obstruction

This is another frequent complication; it is observed in 20-25% of patients with symptomatic Meckel diverticulum. The diagnosis of bowel obstruction due to Meckel diverticulum may not be established preoperatively. At exploration, Meckel diverticulum may be identified as the cause of obstruction. (See the image below.)

Various mechanisms of intestinal obstruction occur with Meckel diverticulum as a causative factor. Because the omphalomesenteric duct may be attached to the abdominal wall by a fibrotic band, a volvulus of the small bowel around the band may occur. The diverticulum may also form the lead point of an intussusception and cause obstruction. Infrequently, a tumor arising in the wall of the diverticulum may form the lead point for intussusception. When incarcerated in an inguinal hernia, a Meckel diverticulum is called Littré hernia.

Patients with intestinal obstruction due to Meckel diverticulum present with abdominal pain, vomiting, and obstipation. Radiography of the abdomen may indicate an ileus or frank stepladder air-fluid levels, as observed in dynamic intestinal obstruction.

In cases of intussusception, patients may also present with a palpable lump in the lower abdomen and currant jelly stools.

Diverticulitis

This condition develops in approximately 10-20% of patients with symptomatic Meckel diverticulum, occurring more often in the elderly population. Patients may present with symptoms of intermittent, crampy abdominal pain and tenderness in the periumbilical area. Perforation of the inflamed diverticulum leads to peritonitis.

Stasis in the diverticulum, especially in one with a narrow neck, causes inflammation and secondary infection leading to diverticulitis. Diverticular inflammation can lead to adhesions, which cause intestinal obstruction.

Umbilical anomalies

These occur in up to 10% of patients. The anomalies consist of fistulas, sinuses, cysts, and fibrous bands between the diverticulum and the umbilicus. A patient may present with a chronic discharging umbilical sinus superimposed by infection or excoriation of periumbilical skin. There may be a history of recurrent infection, sinus healing, or abdominal wall abscess formation. When a fistula is present, intestinal mucosa may be identified on the skin.

Cannulation and injection with radiographic contrast help to delineate the entire tract and aid in planning a surgical approach for cure. A discharging sinus should be approached surgically with a view toward correction. Exploratory laparotomy may be required.

When found at laparotomy, a fibrous band should be excised because of the risk of internal herniation and volvulus.

Neoplasm

This is the least commonly associated pathology and is reported in approximately 4-5% of complicated Meckel diverticulum cases. Of the various types of tumors reported, leiomyoma is the one that is most frequent found, followed by leiomyosarcoma, carcinoid tumor, and fibroma. One case of ectopic gastric adenocarcinoma has been reported. Lipoma and angioma have also been found.^{[3, 4]}

Other complications

Other reported complications in Meckel diverticulum are vesicodiverticular fistulas, "daughter" diverticula (formation of a diverticulum within a Meckel diverticulum), and formation of stones and phytobezoar in the Meckel diverticulum.

A diagnosis of symptomatic or complicated Meckel diverticulum is difficult to confirm on the basis of traditional history, physical examination, and laboratory testing. It is always considered as a differential diagnosis in cases of intestinal obstruction and intestinal hemorrhage. Painless, profuse hematochezia, especially in a child, should alert a clinician to the possibility of such a diagnosis and should prompt further investigation. Thus, in a child, the differential diagnosis for right lower quadrant pain includes appendicitis, acute mesenteric lymphadenitis, intussusception, or Meckel diverticulitis.

In an adult, Meckel diverticulum should be entertained in the diagnosis for lower GI bleeding, which would also include angiodysplasias, malignancy, arteriovenous malformations, and other causes.

Asymptomatic

Laparoscopy and laparotomy are the most frequent means by which an incidental diverticulum is found. Upper GI series with small bowel follow-through also detects a diverticulum. The diverticulum appears as a smooth, white, globular shadow on the antimesenteric border of the ileum, approximately 50cm proximal to the ileocecal valve.

Symptomatic

Technetium-99m-pertechnate radioisotope scanning

Diagnosis of a bleeding Meckel diverticulum is established by technetium-99m (^99m Tc) ̶ pertechnetate radioisotope scanning. This isotope, administered intravenously, is readily taken up by the gastric mucosa. Reportedly, 1.8 cm² of ectopic gastric mucosa in Meckel diverticulum is required for a positive result.

Pentagastrin, which has been known for several years to increase the acid production of ectopic gastric mucosa, enhances radioisotope uptake by the cells. Using a histamine-2 (H2) receptor blocker with pentagastrin provides a synergistic effect, since it blocks intraluminal release and promotes retention of the isotope. The value of^99m Tc-pertechnate scanning is more specific in children.

The incidence of false-negative results is high, especially in adults; therefore, a negative scan finding does not exclude a Meckel diverticulum. False-positive results are observed in patients with intussusception, volvulus, obstruction of the small intestine, acute appendicitis, carcinoid of the appendix, or carcinoma of the caecum. The use of pentagastrin and an H2 receptor blocker helps to minimize the number of false-negative results.

Approximately 30 images may be required (at 1min intervals) to demonstrate activity in the terminal ileum.

Angiography

Superior mesenteric angiography may be helpful in patients presenting with acute GI bleeding and is effective when blood loss exceeds 0.5mL/min.

Symptomatic Meckel diverticulum

Absolute indications for resection in Meckel diverticulum are hemorrhage, intestinal obstruction, diverticulitis, and umbilico-ileal fistulas.^[5]

Incidentally discovered Meckel diverticulum

Incidental discovery of Meckel diverticulum at laparoscopy or laparotomy requires a decision whether to resect. Most surgeons generally do not resect a Meckel diverticulum with a wide mouth. On the other hand, a diverticulum with a narrow neck, which may obstruct or twist, can be easily resected at the neck without the need for segmental resection. A diverticulum deemed to be abnormal because of inflammation, thickening, or intramural pathology should be resected, with a decision for local or segmental resection based on the pathology.^[4]

In 1976, Soltero and Bill reported that the lifetime risk of complications from Meckel diverticulum is 4.2%, with the risk decreasing with age.^[6] Their data indicated that 800 asymptomatic diverticula would have to be removed to save the life of 1 patient. On that basis, they opposed surgical excision.

Miltiadis et al stated that resection of incidentally found Meckel diverticulum protected patients from future surgery caused by complications of Meckel diverticulum. This strategy could help to reduce morbidity and mortality, especially in elderly patients.

Cullen et al reported that prophylactic diverticulectomy is warranted to eliminate the possibility of future deaths.^[2] As a result, they advocated diverticulectomy for asymptomatic disease even in the older age group.

Overall, selected cases of incidentally discovered diverticulum in adults and most asymptomatic diverticulum found in children may be removed. Resection is recommended in the following cases:

• Patients younger than 40 years
• Diverticula longer than 2cm
• Diverticula with narrow necks
• Diverticula with fibrous bands
• Suspected ectopic gastric tissue
• Inflamed, thickened diverticula

Removal of a healthy diverticulum in the presence of peritonitis, Crohn disease, ulcerative colitis, or any other complication that would militate against resection is not advised.

Surgical dissection and excision depend on the evident pathology. In asymptomatic Meckel diverticulum, excision is generally performed if the neck of the diverticulum is narrow or if stasis is present. Tangential excision with suture closure of the base is performed. In complicated cases, the diverticulum must be resected. (See the image below.)

Four possible surgical procedures are as follows:

• Diverticulectomy with suture closure of the base
• Wedge resection of the intestinal wall containing the diverticulum with suture closure
• Segmental resection of the intestine, including the diverticulum, and end-to-end anastomosis
• Division of the fibrous band with or without diverticulectomy

The preoperative, intraoperative, and postoperative management of Meckel diverticulum follows the general principles of abdominal surgery and includes the use of perioperative antibiotics. Surgical considerations also include the following:

• Hemorrhage - In cases of hemorrhage, wedge or segmental resection ensures adequate excision of the part containing gastric and ulcerated ileal mucosa
• Intestinal obstruction - In cases of intestinal obstruction, the viability of the bowel wall delineates the extent of excision
• Segmental resection - This is advised in children with broad-based diverticula in whom the risk of ileal stenosis is greater if diverticulectomy or wedge resection is performed
• Umbilical sinus and fistula - These may require excision of the umbilicus
• Meckel diverticulitis - Because Meckel diverticulitis often mimics appendicitis, examine the distal ileum for diverticulitis when the appendix is discovered to be normal during exploration for suspected appendicitis

Surgical principles include ensuring adequate blood supply to the resectional margins, recognition of bowel viability, suture line tension, and potential for intestinal stenosis due to narrowing.

Hand-sewn technique versus stapling

All procedures are carried out either by hand-sewn technique or by stapling, depending on the preference of the surgeon. Stapling enables faster resection of a Meckel diverticulum without opening the bowel's lumen, avoiding potentially septic and postoperative complications. Meckel diverticulum, which fits well into the stapling device, is easy to remove and has a low complication rate, especially when it has been found incidentally.

Laparoscopic management

Laparoscopic techniques are increasingly being used for Meckel diverticulectomy and intestinal resection. With advancements in technology, therapeutic interventions, such as intracorporeal resection or laparoscopic-assisted extracorporeal resection, can easily be performed. Currently, laparoscopic management of Meckel diverticulum is limited to symptoms of abdominal pain and GI bleeding. For symptoms of obstruction, diagnostic laparoscopy is not recommended because of difficulties in establishing pneumoperitoneum.^[7]

The issue of managing a Meckel diverticulum in an asymptomatic patient is controversial. The risk of postoperative complications following excision of an incidental diverticulum is as much as 8%.

Symptomatic patients have a 10-12% incidence of early postoperative complications, such as ileus, suture line or intestinal anastomotic leak, intra-abdominal abscess, and pulmonary embolism.

Late postoperative complications occur in 6-8% of patients and consist of small bowel obstruction due to intestinal adhesions. The reported mortality rate for surgery in symptomatic patients is 2-5%.

In incidental diverticulectomy for asymptomatic disease, the morbidity rate is 2%, the late postoperative complication rate is 2%, and the mortality rate is 1%.