The secretin / cholecystokin-pancreozymin test may be used to assess pancreatic exocrine function. It is an invasive test and considerable skill is required to collect duodenal juice uncontaminated by gastric juice.
A double-lumen radio-opaque tube is passed following an overnight fast. One opening enables the collection of gastric secretions; the other, of duodenal secretions.
Three specimens of duodenal secretions are collected:
- basal secretion
- following intravenous secretin
- following intravenous CCK-PZ
The volume, pH, amylase and bicarbonate contents of all samples are measured.
In the normal person:
- secretin administration primarily stimulates bicarbonate secretion
- cholecystokinin primarily stimulates pancreatic enzyme secretion
In cases of exocrine panceatic failure, bicarbonate secretion is lost early and enzyme secretion lost later.
Abnormal results are obtained in chronic pancreatitis, enzymic activity and bicarbonate falling before there is any obvious reduction in the volume of juice.
In pancreatic carcinoma, results may also be abnormal. A marked feature is a low volume of juice especially when the tumour is at the head of the pancreas producing obstruction.
Secretin may cause a paradoxical increase in gastrin levels if the patient has a gastrinoma.