Which radiopharmaceutical is used to localize a Meckel's diverticulum?

The radiopharmaceutical used to localize a Meckel's diverticulum is 99mTc-pertechnetate. This agent is particularly useful because it highlights gastric mucosa, which is sometimes ectopically present in Meckel's diverticulum. When 99mTc-pertechnetate is administered, it is taken up by the gastric mucosal cells, enabling the visualization of the diverticulum using a gamma camera during imaging.

This property of 99mTc-pertechnetate allows for effective detection of the diverticulum, as it can demonstrate areas where there is gastric tissue that may have been misplaced during development. This imaging technique becomes crucial when differentiating Meckel's diverticulum from other potential causes of gastrointestinal bleeding or abdominal pain in pediatric patients.

Other options like 131I and 111In-pentetate are not used for this specific localization purpose, as they target different processes or tissues. Similarly, 99mTc MAA is primarily employed in lung perfusion studies. Thus, 99mTc-pertechnetate remains the preferred choice for Meckel's diverticulum localization due to its specific uptake properties related to gastric mucosa.