Meckel's Diverticulum in Adults: More Common Than You Think

Meckel's diverticulum is among the most common congenital defects of the gastrointestinal tract. Although often considered a disorder of childhood, it can also be diagnosed in adults. Meckel's diverticulum is often asymptomatic. When patients present with symptoms, diagnosis is complicated because the features are similar to those of many other gastrointestinal conditions, and traditional imaging studies often do not demonstrate an obvious abnormality. Management is evolving, and there is no consensus on the appropriate approach to treatment. This article discusses the pathophysiology, associated complications, and management options for this often-overlooked condition.

Rory L. Smoot, MD

Department of Surgery

Resident

Gregory J. Hanson, MD

Department of Internal Medicine

Consultant, Associate Professor of Surgery

Stephanie F. Donnelly, MD

Department of Surgery

Rochester, Minn

PRACTICE POINTS

• Features of symptomatic Meckel's diverticulum include melena, rebound tenderness, and right lower-quadrant pain.
• Most cases of Meckel's diverticulum are discovered incidentally during laparotomy procedures and the lesion may be safely removed.

Meckel's diverticulum, one of the most common congenital defects of the intestine, is found in approximately 2% to 3% of the general population.¹ The classic "rule of 2s" applies to this condition, suggesting that the lesion is located approximately 2 feet proximal to the ileocecal valve, is approximately 2 inches long, and is an important diagnosis to consider in children under 2 years of age who have gastrointestinal (GI) bleeding. Although some experts might dispute the gender distribution, evidence suggests that Meckel's diverticulum is also twice as common in men as in women, which is certainly true when considering symptomatic diverticula.

Pathophysiology

Meckel's diverticulum is a true diverticulum, containing all layers of the bowel wall, and unlike non-Meckelian small-bowel diverticula, it is located on the antimesenteric border of the bowel (Figure 1), specifically in the ileum.

Meckel's diverticulum represents a failure of the vitelline duct to completely obliterate during gestational weeks 5 to 7 in the process that separates the yolk sac from the developing embryo. The incomplete resolution of this embryologic structure can lead to the formation of several different defects, including an enteroumbilical fistula, a fibrous cord connecting the ileum to the umbilicus, an umbilical sinus, and a Meckel's diverticulum.² These defects can occur singly or in combination, with Meckel's diverticulum representing the majority of the defects.² Typically patients are asymptomatic, although Meckel's diverticula are associated with a variety of complications.

Complications

The rate of complications associated with Meckel's diverticula, which has implications for the removal of incidentally discovered diverticula, remains a subject of debate. Symptomatic Meckel's diverticula are more common in children³ but do occur in adults. Across all age-groups, complications are more common in men than in women, with a ratio of aproximately 2:1, but a ratio as high as 4:1 has been reported in some case series.^3-6

The literature reflects some disagreement regarding the magnitude and duration of risk for complications. A large population-based study of residents of Olmsted County, Minnesota, showed a 6.4% lifetime risk of complications in individuals with a Meckel's diverticulum.⁶ Earlier studies showed a lower lifetime risk of complications and suggested that the risk dropped to as low as zero as patients aged. Consequently, routine removal of an incidentally discovered Meckel's diverticulum was not recommended in the past. More recent studies, however, have not demonstrated any reduction in risk of complications over a person's lifetime.^4,6 Combined with a low rate of complications associated with the surgical treatment of an incidental diverticulum (2% in the population- based study already mentioned⁶), the higher lifelong rate of complications is used as the basis for the current recommendation that an incidentally discovered Meckel's diverticulum be removed.

Some case series specifically note a peak in complications from the condition itself (eg, bleeding, perforation) during the 4th and 5th decades of life, leading some experts to suggest that incidentally discovered diverticula need only be removed in male patients younger than 40 years or in those at higher risk of complications associated with clinical factors, such as the presence of ectopic mucosa or an anchoring fibrous connection.⁷

In studies that included a total of 352 patients with Meckel's diverticula, 20% to 60% had complications that led to symptoms.^3-7 Although most of the trials included children, one of these studies observed a similar incidence in adults.⁶

Hemorrhage appears to be a more common presentation in patients younger than 11 years.³ Although bleeding can be the presenting sign of a Meckel's diverticulum in adults, other causes of GI bleeding must be considered (Table). Bleeding associated with a Meckel's diverticulum has specific implications for surgical management.

Overall, the most frequent complications are hemorrhage and obstruction, followed by inflammation. Bowel obstruction accounted for 77% of complications in a study of 58 patients.⁴ Obstruction is of particular concern when a Meckel's diverticulum is tethered by a fibrous cord, since volvulus may occur.

Illustrative Case

A 78-year-old woman presents to the emergency department late at night complaining of significant abdominal pain along with abdominal "tightness" of approximately 24 hours' duration. The pain began while she was cleaning her house. She describes it as sharp, constant, and without radiation. She says that the pain was maximal at onset and was located throughout her abdomen but was possibly worse in the lower abdomen bilaterally. She had been experiencing fever and chills since shortly after the pain started.

Physical examination demonstrates localized peritoneal signs. Laboratory studies reveal an elevated white blood cell count. A computed tomography (CT) scan, with contrast, of her abdomen and pelvis demonstrates inflammation extending into the mesentery of the midileum and what appears to be a diverticulum containing the contrast agent (Figure 2). The radiologist thinks the most likely cause is an inflamed Meckel's diverticulum. At surgery, a large Meckel's diverticulum is noted in the midileum, with a small perforation and localized abscess at the tip (Figure 3). Diverticulectomy is curative. Pathology of the specimen demonstrates a Meckel's diverticulum without ectopic tissue. The patient recovers uneventfully.

A Challenging Diagnosis

Signs and symptoms

Most cases of Meckel's diverticulum are discovered incidentally during laparotomy procedures. Symptomatic cases present a diagnostic challenge. Common presenting features in symptomatic patients include melena, rebound tenderness, and right lower-quadrant pain. In patients presenting with a symptomatic Meckel's diverticulum, the initial differential diagnosis is broad, because of the relative infrequency of this condition and the extensive overlap with other GI disorders. For example, in patients presenting with GI bleeding, other lesions must be considered first, such as bleeding ulcers or bleeding colonic diverticula, depending on the type of GI bleeding noted (eg, melena versus hematemesis versus bright-red blood from the rectum).

In patients presenting with peritoneal signs, colonic diverticulitis, appendicitis, or other hollow viscus perforation must be considered first.

Meckel's diverticulum should be suspected when the initial diagnostic workup has failed to demonstrate these abnormalities or has revealed abnormalities in an unsuspected location, such as a bleeding vessel located in the ileum seen on angiography or inflammation with or without free air located in the midileum seen on a CT scan.

Imaging studies

The difficulty with preoperative diagnosis in the symptomatic patient is not only the result of the variable presentation and overlap with other conditions but stems even more from the difficulty in identifying a Meckel's diverticulum on imaging studies.

In a study of 119 patients with a Meckel's diverticulum, 52 were symptomatic.⁷ In the 90% of these symptomatic patients who had an abdominal x-ray as part of their initial workup, none of the imaging studies suggested Meckel's diverticulum. The diagnosis was suspected based on imaging findings in only 1 of 14 symptomatic patients who underwent CT scanning, and this was based on the presence of a fecalith.⁷ Although other researchers have found CT to be relatively unhelpful for the diagnosis, it can sometimes suggest the diagnosis (as in our patient), especially in the setting of acute complications or the presence of a fecalith.^8,9

In the study of 119 patients, technetium Tc 99m (^99mTc) scan, also known as Meckel's scan, was positive in 3 of 4 patients.⁷ Although use of ^99mTc scan has demonstrated diagnostic accuracy, the false-negative rate can be high, especially in adults.¹⁰ In addition, detection of a Meckel's diverticulum depends on the presence of ectopic gastric tissue,¹⁰ and a focus of gastric mucosa at least 1 cm² in size is needed to identify Meckel's diverticulum with ^99mTc scanning.¹¹ An analysis of ^99mTc scanning in 2 adults with Meckel's diverticulum demonstrated a sensitivity of 62.5% and a specificity of 9%.¹⁰ This sensitivity level has been confirmed in other studies in children as well.¹² Although the patient population in the study of adults was obviously small, the results did correlate with surgical findings.¹⁰

Another problem is that the negative predictive value of the scan is decreased in patients with active bleeding. In a study of 235 children who were evaluated with a Meckel's scan, the negative predictive value decreased from 0.93 to 0.74 in patients with lower GI bleeding, suggesting that clinical suspicion may have more benefit than ^99mTc scanning, given the cost associated with a fairly high false-negative rate in the setting of lower GI bleeding.¹³

Gastric, pancreatic, and colonic mucosa have all been found in Meckel's diverticula. Gastric and pancreatic tissues are most often found, but only in about 25% of patients.^3,7 If ectopic tissue is present, sensitization can increase the detection on ^99mTc scanning.¹² Sensitization is based on either enhancing the gastric mucosal uptake of the marker with agents such as pentagastrin or decreasing the "washout" of the marker through the use of agents such as cimetidine or ranitidine HCl (Zantac). One study found that single-photon emission CT, combined with ^99mTc scanning, was useful for diagnosis in patients with equivocal or negative ^99mTc scans.¹⁴

Other imaging modalities that have been used to diagnose symptomatic Meckel's diverticulum include contrast studies, such as enteroclysis or angiography.¹⁵

Although the location of a Meckel's diverticulum rules out its diagnosis with routine upper or lower endoscopy, this condition could potentially be diagnosed by use of the newer technology of video capsule endoscopy, as has been demonstrated in early series and case reports.^16,17

Management Choices

The debate about the need to remove an incidentally discovered Meckel's diverticulum still continues. The largest population-based study demonstrated a surgical complication rate of 7% for patients with a complicated Meckel's diverticulum, and a complication rate of only 2% over a 20-year period for incidental diverticulectomy, with the main complication typically being obstruction secondary to adhesions.⁶

Ultimately, the ability to remove the diverticulum safely is the deciding factor. Although studies have demonstrated low rates of operative morbidity and mortality associated with the removal of incidentally found diverticula,^4,6 risks remain. Deaths associated with the removal of Meckel's diverticulum have been reported, although usually in the setting of other complications, such as colectomies for GI bleeding.⁷ Many researchers believe it is safe to remove an incidentally discovered Meckel's diverticulum in the absence of any complicating conditions, such as diffuse inflammation or other absolute contraindications.^4,6,7 Contraindications to an incidental resection include patient instability, presence of ascites, or presence of gross contamination of the abdominal cavity by feces (in the setting of a perforated intestine).

Diverticulectomy or segmental resection

The treatment of a symptomatic Meckel's diverticulum is surgical and can range from diverticulectomy to segmental resection.² Diverticulectomy is adequate for the incidental Meckel's diverticulum or when diverticulitis presents at the tip of the diverticulum.

Segmental resection is recommended when the base is inflamed or if the patient presents with melena. This is because the site of bleeding is not typically in the diverticulum. Rather, it is located on the bowel wall adjacent to the opening of the diverticulum and is secondary to ulceration caused by secretions from ectopic gastric tissue in the Meckel's diverticulum.

Some experts have suggested that the morphologic characteristics of the diverticulum should be considered when deciding on the extent of resection, because there may be a difference in the risk of complications in short, broad-based diverticula compared with long, thin-based diverticula.¹⁸ The proposed explanation is that long, thin diverticula may increase the risk of volvulus, intussusception, or torsion, whereas short, broad-based diverticula can predispose to trapping of an enterolith, leading to inflammation, hemorrhage, or obstruction.¹⁸ There is also more ectopic tissue located at the inlet of a short diverticulum.

A recent study, which included adult patients, showed that whereas diverticulectomy was safe and effective for a long Meckel's diverticulum, a short diverticulum should be formally resected along with a portion of the small bowel so that any gastric mucosa could be completely removed.¹⁹ However, all these studies on complications and management of short or long diverticula are based on retrospective analyses, and further studies are needed, especially in adult patients.

Laparoscopy

Several reports have shown that laparoscopy is a safe and efficient way of localizing the lesion for the purpose of the removal of the Meckel's diverticulum.^20-23 In fact, some contend that laparoscopy also has a place in the diagnosis of a complicated Meckel's diverticulum, given the difficulties presented by other imaging studies, since it allows complete resection of the lesion during the same procedure.^20,21 This technique, however, is more invasive than traditional imaging studies and is therefore not included as an initial step in the diagnosis. (It would not be included in the workup of GI bleeding, which would be from the inside of the intestine.) The success of laparoscopy, however, depends on the ability to predict the necessary extent of resection (ie, simple diverticulectomy versus segmental resection) based on the external appearance of the diverticulum. Again, additional research is needed.

Conclusion

Meckel's diverticulum is a common condition that can present with serious complications, particularly in male patients. The most frequent complication is obstruction. The diagnosis of a complicated Meckel's diverticulum is difficult, in part because of variable success in localizing the lesion with diagnostic imaging, and in part because the features overlap those of many other conditions. The management of symptomatic diverticula is surgical. Some groups have reported success with laparoscopic resection, although further investigation is needed to determine how well the external appearance of the diverticulum correlates with the localization of ectopic tissue. Many experts believe that an incidentally discovered diverticulum should be removed if it can be done safely. Meckel's diverticulum should be included as part of the differential diagnosis in patients with abdominal complaints, regardless of age, especially when imaging studies do not indicate a specific disease process.

SELF-ASSESSMENT TEST

1. All these features are characteristic of Meckel's diverticulum, except:

• Approximately 2 inches in length
• Should be considered as a cause of GI bleeding in children younger than 2 years

2. Which of these is NOT a common complication of Meckel's diverticulum?

• Hemorrhage
• Bowel obstruction

3. All these statements about Meckel's diverticulum are true, except:

• Associated hemorrhage is usually caused by ulcers in the adjacent small bowel
• The ectopic mucosa in Meckel's diverticulum is usually colonic tissue

4. Diagnostic accuracy depends on the presence of ectopic tissue in Meckel's diverticulum for which of these imaging techniques?

• CT scan
• Enteroclysis

5. Which of these treatments is NOT appropriate for the stated Meckel's diverticulum type?

• Segmental resection for a Meckel's diverticulum with inflammation at the base
• Segmental resection for a patient who presents with melena

(Answers at end of reference list)

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Answers: 1. C; 2. A; 3. D; 4. C; 5. C