Meckel Diverticulum Surgery

The omphalomesenteric (vitelline) duct typically arises from a point about 60 cm proximal to the ileocecal valve in adults. The Meckel diverticulum is an antimesenteric structure but receives its blood supply from the mesentery of the ileum. Thus, a typical feeding vessel (vitelline artery, also described as the omphalomesenteric mesentery) may be identified. It crosses from the mesentery of the ileum, across the intestine itself, and along the length of the diverticulum. This feeding vessel must be individually clipped and divided during a laparoscopic Meckel diverticulectomy.

Meckel diverticula may contain ectopic tissue. The two most common types are gastric mucosa and pancreatic tissue. As many as 50% of all diverticula contain gastric mucosa, whereas 5% contain pancreatic tissue. Ectopic gastric mucosa results in secretion of acid onto adjacent ileal mucosa, causing ulceration and bleeding.

The pathophysiology varies, depending on the etiology of symptoms (see Presentation). A 16-year review of symptomatic Meckel diverticula in children revealed that 55.5% of patients had gastrointestinal (GI) bleeding, 14.2% had intestinal obstruction, 15.8% presented with peritonitis, and 14.2% had umbilical drainage.[3]  A study from Taiwan found that intestinal obstruction was the most common preoperative diagnosis in patients aged 0-10 years or older than 20 years, whereas acute appendicitis (acute abdominal pain) was the most common diagnosis in patients aged 11-20 years.[4]

Cases of malignancy arising from a Meckel diverticulum have been reported, but these are rare.[5]

The existence of a Meckel diverticulum or one of its variants is due to simple embryology. The yolk sac of the developing embryo is connected to the primitive gut by the yolk stalk or vitelline (ie, omphalomesenteric) duct. This structure typically regresses between weeks 5 and 7 of fetal life.

If this process of regression fails, various anomalies can occur. This spectrum of defects includes a Meckel diverticulum, a fibrous cord attaching the distal ileum to the abdominal wall, an umbilical-intestinal fistula, a mucosa-lined cyst, or an umbilical sinus. Various possible complications are associated with different omphalomesenteric remnants (see the image below).

Meckel diverticula are found in approximately 2% of the population. The prevalence of symptomatic Meckel diverticula is estimated to be 4-35% of the at-risk population, depending on the age group studied. More than 60% of patients who develop symptoms from this anomaly are aged 2 years or younger. A male preponderance has been noted.[6]

Meckel diverticulum may occur in pregnant women, in whom it can prove difficult to diagnose.[7]

Patients typically do not have further bleeding episodes once the Meckel diverticulum and ectopic gastric mucosa have been excised. Patients who require exploratory laparotomy for bowel obstruction are at risk for adhesive bowel obstruction in the future.

Painless bleeding

Lower gastrointestinal (GI) hemorrhage is the most common symptom in patients with a symptomatic Meckel diverticulum.[8] The mean age is 2 years, though this problem may occur in older children and even adults. The bleeding is typically painless; it can be massive and may require blood transfusion. Other causes of bleeding that may occur in this same age group include anal fissure, juvenile retention polyps, hemangiomas, peptic ulcer disease, inflammatory bowel disease, and primary hematologic disorders.

Bleeding is secondary to ulcerated ileal mucosa resulting from ectopic gastric mucosa that is contained within the Meckel diverticulum. The gastric mucosa secretes acid, which results in ulceration of the adjacent normal ileal mucosa. (See the images below.)

Bowel obstruction

In children, obstruction is the second most common symptom in patients with symptomatic Meckel diverticula and occurs in approximately 25% of symptomatic patients. Obstruction can be caused by several mechanisms. Volvulus of the small intestine may occur around a Meckel fibrous band attached to the umbilicus. Intussusception of the Meckel diverticulum may also result in intestinal obstruction. Incarceration of the diverticulum in a hernia, known as a Littre hernia, is a third cause of obstruction.

Another cause of bowel obstruction is entrapment of small bowel beneath the blood supply of the diverticulum, also known as a mesodiverticular band.

Meckel diverticulitis

Diverticulitis may occur in as many as 20% of patients with complications from a Meckel diverticulum. Meckel diverticulitis is commonly misdiagnosed as acute appendicitis. Inflammation of the diverticulum may be due to obstruction of the lumen, which is analogous to the pathophysiology of acute appendicitis. Progression of such inflammation may lead to perforation and peritonitis. The possibility of Meckel diverticulitis underscores the need to explore the distal small bowel in patients with suspected appendicitis when a normal appendix is found.

Umbilical drainage

Drainage of succus entericus or feculent discharge is due to a patent omphalomesenteric duct, whereas clear drainage should prompt a search for a urachal remnant.

Umbilical mass or infection

Omphalomesenteric duct remnants may persist as an actual cystic structure, typically just beneath the umbilicus. This structure may be palpable upon physical examination or, if infected or ruptured, may lead to inflammatory changes in the umbilicus.

Perforation

Because a Meckel diverticulum may contain ectopic gastric mucosa, the bordering small intestine mucosa may ulcerate, which may cause actual perforation of the intestine. This leads to peritonitis and free intraperitoneal air, which can be seen on plain abdominal films. The intestine may also perforate if a closed-loop bowel obstruction is allowed to progress to bowel-wall necrosis.

A complete blood count (CBC) is helpful. In patients with a bleeding Meckel diverticulum, assessment of the hemoglobin level is critical. This helps guide transfusion therapy and should be repeated following transfusion to ensure that the hemoglobin level has adequately risen. This test is also important in the assessment of the patient with Meckel diverticulitis. An increased white blood cell (WBC) count and a left shift can support the diagnosis.

In patients with vomiting due to bowel obstruction, electrolyte abnormalities are common. Serum levels of sodium, potassium, chloride, carbon dioxide, blood urea nitrogen (BUN), and creatinine should be obtained. Studies are repeated as abnormalities are corrected.

Technetium-99m pertechnetate radioisotope scanning

Also known as the Meckel scan, this study is important for evaluating Meckel diverticula that contain ectopic gastric mucosa, which readily takes up the isotope.[9] A Foley catheter can be placed to drain the bladder and reduce signal intensity from this area. Because the false-negative result rate may approach 2%, pentagastrin (to stimulate uptake of the radioisotope), histamine blockers (to inhibit secretion of the pertechnetate once it is taken up), and glucagon (to inhibit peristalsis and thereby decrease washout of the pertechnetate) may be used to increase the sensitivity of the test. (See the image below.)

If the clinical index of suspicion for Meckel diverticulum is high but the Meckel scan is negative or equivocal, repeat scintigraphy may be useful.[10]

Several groups have reported that diagnostic laparoscopy should replace Meckel scanning in the assessment of patients with anemia who have lower gastrointestinal (GI) bleeding because it has a sensitivity of 60%.[11, 12]

Plain abdominal radiography

In patients with a Meckel diverticulum that causes bowel obstruction, plain radiography is needed and may reveal dilated bowel loops with air-fluid levels and a paucity of distal gas. In a protracted clinical course, perforation may occur, and free air may be seen on upright radiographs.

Ultrasonography

Many centers use ultrasonography (US) in the evaluation of abdominal pain. If the patient has Meckel diverticulitis, a thickened noncompressible tubular structure may be seen. These are many of the same criteria that are used to confirm the diagnosis of appendicitis by means of US. This modality is also helpful in assessing patients with persistent umbilical drainage. Structures such as fistulous tracts and persistent cysts may be readily identified by means of US.

Computed tomography

In many centers, abdominal-pelvic computed tomography (CT) is the radiologic test of choice if abdominal pain is present. In patients with Meckel diverticulitis, an inflammatory mass with peridiverticular stranding may be observed. Multidetector CT (MDCT) is helpful in cases of complicated Meckel diverticulum.[13]  A retrospective study (N = 76) by McDonald et al found CT to be relatively insensitive (0-29%) for prospective diagnosis of Meckel diverticulum in pediatric patients.[14]

Some patients have an unusual presentation and adjunctive assessment results that do not clearly lead to a particular diagnosis. In patients who have continued abdominal pain, laparoscopy may be useful. Laparoscopy has the advantage of being a minimally invasive approach to establishing the diagnosis of intra-abdominal pathology. Laparoscopy can also be the primary form of treatment in various disorders.

Double-balloon enteroscopy and capsule endoscopy are additional modalities that may aid in the diagnosis of a Meckel diverticulum prior to surgery.[15, 16, 17, 18]

A Meckel diverticulum is a true diverticulum, containing all four layers of the bowel wall. Ectopic tissue is frequently found within a Meckel diverticulum, most frequently gastric mucosa or pancreatic tissue. The remainder of the diverticulum lining is typical ileal mucosa.

Occasionally, a Meckel diverticulum may contain cancer. The tumors most likely to affect these diverticula are neuroendocrine tumors. These tumors are rare, but when present, they are often associated with nodal metastases and liver metastases. They are optimally managed with small-bowel resection with regional lymphadenectomy and debulking of liver metastases where feasible.[19]

Medical treatment has no role in the management of a Meckel diverticulum.

Indications for surgery

Indications for operative treatment depend on the patient's presentation, as follows.

Painless bleeding

Because initial bleeding from a Meckel diverticulum can be massive, it is essential that the patient be adequately resuscitated. This may require the transfusion of packed red blood cells (RBCs) to return the hematocrit level to approximately 30%. Two large-bore intravenous (IV) lines must be in place in case bleeding recurs, and crossmatched blood should be available.

If Meckel diverticulum bleeding is suspected, technetium-99m pertechnetate radioisotope scanning (see Workup) is the test of choice. This isotope is readily taken up by the ectopic gastric mucosa within the Meckel diverticulum. Once a positive result is obtained, the patient can be taken to the operating room for a Meckel diverticulectomy. False-negative results occur less than 2% of the time. The accuracy of such scanning may be increased with the use of pentagastrin, histamine blockers, and glucagon.

Bowel obstruction

Patients present with bowel obstruction due to volvulus, intussusception, a mesodiverticular band, or incarceration of the Meckel diverticulum in a hernia (though the presence of a Meckel diverticulum in a hernia does not actually increase the risk of incarceration).

Despite these different causes, the clinical presentation is bowel obstruction. Patients present with obstipation, crampy abdominal pain, and vomiting, which may be bilious. Plain abdominal radiographs reveal dilated loops of small bowel with air-fluid levels and a paucity of gas distally. This classic presentation of bowel obstruction is all that is necessary to warrant transporting the patient to the operating room for an urgent laparotomy.

Meckel diverticulitis

The presentation of Meckel diverticulitis may be indistinguishable from that of appendicitis. As with appendicitis, the course is progressive and may result in perforation, diffuse peritoneal contamination, and septic shock. Exploration is usually performed for suspected appendicitis; an inflamed Meckel diverticulum must be sought if a normal-appearing appendix is discovered.

Umbilical drainage

Drainage of succus entericus or feculent material indicates a persistent connection between the intestine and the umbilicus. Ultrasonography (US) or contrast studies may be used to confirm the diagnosis. An exploration can then be performed to resect the fistula.

Contraindications for surgery

Because many of the operations for omphalomesenteric remnants are used in emergency situations, surgery has relatively few contraindications. However, patients must be adequately prepared for surgery, even given short notice. In patients who are bleeding, the blood volume must be returned to acceptable levels, and adequate IV access must be obtained. In patients with bowel obstruction and repeated emesis, electrolyte abnormalities must be corrected while hydration is restored.

The indications for surgical intervention in Meckel diverticulum vary according to the patient's presentation. In all cases, patients should be adequately resuscitated, and prophylactic antibiotics should be administered.[20]

Procedure

Painless bleeding

Once a Meckel diverticulum has been diagnosed, laparotomy or laparoscopy can be used for resection. The goal is to resect the Meckel diverticulum, all ectopic gastric mucosa, and any ulcerated intestine to prevent recurrent bleeding.

A number of authors have maintained that laparoscopy is not adequate because it involves stapling the diverticulum at its junction with the ileum. Although most ectopic mucosa is at the tip of the diverticulum, this is not always the case. Furthermore, using laparoscopy may leave ulcerated ileum, which may bleed.

To avoid these problems, the author uses a technique of laparoscopic-assisted bowel resection. A large umbilical port is placed, and the Meckel diverticulum is identified, grasped, and brought up to this umbilical incision. The port is then removed as the Meckel diverticulum and ileum are brought up through the umbilical incision (the incision is widened as needed).

The author then resects the Meckel diverticulum and ileum with primary anastomosis. A wedge resection of the diverticulum with inspection of the ileal mucosa to look for ulceration can also be performed. This wedge can then be closed, avoiding a circumferential suture line.

The laparoscopic-assisted approach was found to be safe and effective in a series of 20 children with complicated Meckel diverticulum over a 10-year period.[21]  A subsequent study of 14 children with complicated Meckel diverticulum over a 15-year period also found laparoscopy to be safe and effective.[22]

A retrospective study that used data from the National Surgical Quality Improvement Program-Pediatric (NSQIP-Ped) to compare laparoscopic treatment (n = 73) of Meckel diverticulum with open surgical treatment (n = 75) found a high (27.4%) rate of conversion from laparoscopy to laparotomy but noted that the two approaches had equivalent outcomes.[23]

Another study using NSQIP-Ped data to compare open and laparoscopic resection of Meckel diverticulum found that laparoscopic resection was associated with a shorter length of stay than open resection, a comparable complication rate, and a similar operating time.[2] Laparoscopic procedures converted to open ones, as compared with purely open procedures, were associated with an increase in operating time but no increases in length of stay or morbidity.

Bowel obstruction

Laparotomy is the procedure of choice for bowel obstruction. It typically involves a midline or transverse incision, which is cosmetically superior in children.

If the volvulus is around a fibrous Meckel band, the bowel must be untwisted and observed after the band is divided. Frankly necrotic intestine must be resected.

Another cause of bowel obstruction is an intussuscepted Meckel diverticulum. The Meckel diverticulum sags into the bowel lumen and then serves as a lead point and allows telescoping of the small intestine into first the distal ileum and then the large intestine. Attempts to reduce such a mass are sometimes difficult. Typically, the intussuscepted mass must be resected, and primary anastomosis must be performed.

A third cause of bowel obstruction is an incarcerated hernia that contains a Meckel diverticulum, also called a Littre hernia.[24] The hernia is reduced, and the Meckel diverticulum is resected.

For a mesodiverticular band, the small bowel is reduced, and the diverticulum and its blood supply are resected.

Meckel diverticulitis

The surgical approach is similar to the one used in acute appendicitis. Open or laparoscopic surgery can be used, and the diverticulum is divided at its base. The closure is performed perpendicular to the axis of the intestine to avoid any narrowing of the ileum. If perforation has occurred, the abdomen is copiously irrigated after resection of the diverticulum has been completed.

Umbilical drainage

A periumbilical incision is made, and the abdomen is entered. The fistulous tract is identified and removed. After its connection with the ileum is divided, the enterotomy is closed with interrupted absorbable sutures in one or two layers (according to the surgeon's preference).

Surgical controversies

There are two major controversies surrounding surgical treatment of Meckel diverticulum. The first involves the use of laparoscopy. Laparoscopy for diagnosis or excision of an inflamed diverticulum is not controversial. However, questions arise when laparoscopy is used in the setting of a bleeding Meckel diverticulum. Some have advocated routinely using laparoscopy in this situation.

Opponents of this view, however, argue that because the base of the diverticulum and the ileum cannot be palpated, ectopic mucosa could be left behind. Some surgeons routinely send the diverticulum for frozen-section examination of the margin to determine that no ectopic mucosa remains. Others argue that ulcerated areas of the ileum remain, and, thus, the patient is still at risk for bleeding episodes in the immediate postoperative period. No randomized controlled studies have been performed to answer these questions.

The other major controversy involves what to do with a Meckel diverticulum when it is discovered during an exploration for other reasons. The argument weighs the probability for future complications from a currently asymptomatic Meckel diverticulum against the potential morbidity of incidental Meckel diverticulectomy.

If a thickening appears to be present upon palpation, the diverticulum may contain ectopic mucosa. These patients are at greater risk for complications, and resection is warranted. Likewise, if the diverticulum has a narrow base, the likelihood of luminal obstruction and diverticulitis may be higher, and resection is appropriate. In most other cases, the diverticulum may be left in situ.

A population-based study indicated an increasing lifetime risk of operation for Meckel diverticulum-related complications and suggested removing an incidentally detected Meckel diverticulum, regardless of age.[25]

Postoperative care depends on the type of procedure performed. Patients with a relatively minor procedure such as diverticulectomy for diverticulitis or umbilical exploration for persistent fistula can resume a regular diet soon after surgery. Those with bowel obstruction or peritoneal contamination must wait until bowel function has returned to resume a regular diet.

Complications are rare but may include the following:

• Bleeding
• Infection
• Wound dehiscence
• Intra-abdominal abscess formation

A standard postoperative follow-up visit 7-10 days after surgery is recommended. If no problems are reported, no further tests or additional visits are required.