Investigation of gastric carcinoid using the secretin test
Sagen Zac-Varghese, Radha Ramachandran, Niamh Martin, Karim Meeran
Mr. HS presented to his GP with tiredness and was found to be anaemic. This was investigated by endoscopy which revealed numerous sub-centimetre gastric polyps. These were resected and the histology found to be consistent with gastric carcinoid. Mr. HS also had a fasting gut hormone sample taken which demonstrated elevated levels of gastrin. The gastroenterologists referred this patient to the surgeons for a gastric resection.
At the same time this patient was referred to our endocrine services by his GP who had been sent the histology report. This patient went on to have imaging which revealed polyps limited within the stomach and no metastatic spread. In view of this finding and the lack of clinical symptoms it was felt likely that Mr. HS had type 1 gastric carcinoid that could be managed conservatively.
There are several types of gastric carcinoid. Types 1 and 2 are both associated with an elevated gastrin level. In type 1 gastric carcinoid the elevation is due to secondary hypergastrinaemia and in type 2 there is a primary cause for elevated gastrin levels e.g. gastrinoma or Zollinger Ellison syndrome. The importance in differentiating type 1 from 2 gastric carcinoid is to plan management. Type 1 gastric carcinoid can often be managed conservatively with endoscopic surveillance and polyp snaring whereas type 2 has a slightly higher malignant potential and therefore more aggressive management should be considered.
Secretin was the very first hormone to be identified by Bayliss in 1902. The secretin test has been around for a long time although is infrequently used. We used the secretin test in this case to differentiate type 1 from type 2 gastric carcinoid.
Mr. HS had an elevated baseline gastrin of 237 pmol/L (normal <40) with a rise to 304 pmol/L. This limited rise (< 100 pmol/L) adds evidence to a diagnosis of type 1 gastric carcinoid. On the basis of the clinical history, endoscopic appearance, imaging results and the secretin test Mr HS will continue to be conservatively managed with regular endoscopy and polyp resection.