Multi time point imaging for Pertechnetate scintigraphy of ectopic gastric mucosa in foregut and midgut duplication Cysts.

Introduction:

99mTc-Pertechnetate Scintigraphy is a well-established and time-tested investigation for the diagnosis of a meckel’s diverticulum with ectopic gastric mucosa. The classical teaching for interpretation includes a focal 99mTc pertechnetate uptake in the lesion which appears with the stomach and is of a similar intensity However, a few necessary variations in protocols can be helpful in determining ectopic gastric mucosae elsewhere, that is foregut duplication cysts that are intra-thoracic in location and midgut duplication cysts involving the small bowel. The aim of our study was to describe the scintigraphic patterns of 99m Tc-Pertechnetate uptake in patients who were referred to department of nuclear medicine for evaluating and diagnosing ectopic gastric mucosa in foregut and midgut duplication cysts and elaborating upon the incremental value of SPECT-CT for the same.

Methods: This hospital based, retrospective cum prospective research spans over a period of 8 years, where we enrolled pediatric patients (Age ranging from 15 days to 13 years), who were referred to us from the Pediatric Surgery department of our hospital from April 2014 to January 2022. Previous hospital medical records were analysed and subsequently a database was prepared which included the age, sex, clinical indication of a 99m Tc pertechnetate scan, the planar and SPECT-CT imaging findings. Post-Surgery histo-pathological reports were available for 18 patients. The recommended acquisition protocol for a meckel’s diverticulum with ectopic gastric mucosa includes anterior dynamic images for 30 minutes and static delayed images upto 60 minutes. However, we included early images where intestinal duplication cysts were visualized even before the visualization of stomach and delayed images upto 24 hours to visualize the minimal amount of ectopic gastric mucosa in thoracic duplication cysts. Also we included SPECT-CT in suspected duplication cysts to increase the sensitivity and specificity which is a tradeoff for small amount of additional radiation exposure.

Results: A total of 65 patients underwent Tc 99m Pertechnetate scan for suspected foregut or midgut duplication cysts. All were subjected to dynamic planar and delayed static images up to 24 hours or until focal uptake of radiotracer was noted which corroborated to the anatomical findings, whichever was earlier. Duplication cysts were localized in a total of 28 patients(18 thoracic duplication cysts and 10 small bowel duplications). 37 patients had no scintigraphic evidence of ectopic gastric mucosa. SPECT-CT was performed along with the planar study in 31 patients which confirmed the findings. Previously performed CT scans were used for anatomical correlation in the remaining ones. A total of 18 of 65 had histopathological diagnosis, out of which 12 were concordant with the scan findings and six patients showed discordance in histopathological diagnosis and scan findings.

Conclusions: Multi time point imaging is the key to diagnosing ectopic gastric mucosa of various sizes and in various locations. An abnormal radiotracer uptake in dynamic sequences, even before the appearance of the stomach in the region of the small bowel is indicative of intestinal duplication and delayed radiotracer visualization in the region of the thorax is characteristic of intrathoracic foregut duplication cyst.

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