Laboratory Studies
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.
Imaging Studies
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.)
Test of choice for bleeding Meckel diverticulum is technetium-99m pertechnetate isotope scan (Meckel scan). It concentrates isotope in ectopic gastric mucosa, with sensitivity of 85% and specificity of 95%. In this scan, isotope is seen in stomach and bladder (normal), with radiotracer signal in midabdomen, suggesting presence of Meckel diverticulum with ectopic gastric mucosa. Image courtesy of Jaime Shalkow, MD.
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]
Procedures
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]
Histologic Findings
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]
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Diagram depicting possible complications associated with different omphalomesenteric remnants. Meckel diverticula are symptomatic in 4-35% of patients. Infants and young children are more likely to present with symptoms. (A) Meckel diverticulitis. These are true diverticula, which usually become inflamed from obstruction. (B) Meckel diverticula, which may contain ectopic gastric, pancreatic, or colonic mucosa. In gastric ectopic mucosa, acid secreted from parietal cells erodes adjacent intestinal mucosa, generating ulcers at base of diverticulum. (C) Omphalomesenteric (vitelline) duct, which connects primitive gut to yolk sac. It normally regresses between weeks 5 and 7 of fetal life. When failed regression results in fibrous band, midgut may volvulate around it. (D) Fibrous bands, which also produce abnormal peritoneal spaces through which internal hernia may result. (E) Omphalointestinal fistula. If patent connection persists between intestine and umbilicus, entity is recognized as omphalointestinal fistula. (F) Persistent fibrous cord with cyst. Failed regression of vitelline duct may also lead to umbilical polyps, umbilical sinus, or umbilical cyst. Image courtesy of Jaime Shalkow, MD.
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Test of choice for bleeding Meckel diverticulum is technetium-99m pertechnetate isotope scan (Meckel scan). It concentrates isotope in ectopic gastric mucosa, with sensitivity of 85% and specificity of 95%. In this scan, isotope is seen in stomach and bladder (normal), with radiotracer signal in midabdomen, suggesting presence of Meckel diverticulum with ectopic gastric mucosa. Image courtesy of Jaime Shalkow, MD.
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Newborn infant with persistent omphalomesenteric remnant, which is being resected to prevent obstruction and to close umbilical defect. Image courtesy of Kenneth Gow, MD, BSc, MSc, FRCSC, FACS, FAAP.
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Laparoscopic image courtesy of Charles L Snyder, MD.
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Large Meckel diverticulum on antimesenteric surface of terminal ileum. Image courtesy of Richard A Falcone, Jr, MD.
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Meckel diverticulum has been opened after resection, revealing ulcer and ectopic tissue, as indicated by forceps. Image courtesy of Richard A Falcone, Jr, MD.
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Resected Meckel diverticulum demonstrating ulcer.
