Diagnosis

If Meckel's diverticulum is suspected in a case of rectal bleeding (painless blood loss in a child somewhere around two years of age), a Meckel's scan (Technetium pertechnetate scinitgraphy) is ordered (Fig. 4.2). This nuclear imaging study involves intravenous injection of Tc-99m (Technetium pertechnetate) which concentrates within gastric mucosa. When seen on a nuclear medicine scan within the terminal ileum, this "bright spot" is diagnostic for Meckel's diverticulum.

Figure 4.2 Concentration of the Tc-99m (Technetium pertechnetate) in ectopic gastric mucosa, presumed to be within a Meckel`s diverticulum (arrow). Also note uptake in gastric mucosa of the stomach and excreted radionucleotide in the bladder.

Other agents may be used in conjunction with this test in an effort to increase its sensitivity and specificity. Three such agents are: (1) pentagastrin, which increases the uptake of Tc-99m by gastric cells; (2) H₂ blockers, which inhibit the excretion of Tc-99m by gastric cells; and (3) glucagon, which slows motility and prolongs retention of the Tc-99m in the Meckel's diverticulum. Additionally, a urinary catheter can be placed to drain the Tc99m from the bladder and facilitate visualization of the Meckel's diverticulum on the images. The test is 85% sensitive and 95% specific. False positives may occur in cases of intestinal obstruction/intussusception, bowel inflammation (i.e., Crohn's disease or ulcerative colitis), vascular malformations, ulcers, some tumors, enteric duplication and gastrogenic cysts. When high clinical suspicion exists despite a negative nuclear scan, laparoscopy may be indicated for definitive evaluation.