The relationship between gastric emptying and the postprandial exocrine pancreatic function measured by 11C-methionine PET-CT.

Background: As previously shown, pancreaticoduodenectomy (PD) results in accelerated gastric emptying and enhanced release of the incretin hormone GLP-1 which also constrains the exocrine pancreas for which the uptake of 11C-methionine is an established marker. To assess possible effects of PD on the exocrine function of the pancreatic remnant the postprandial uptake of 11C-methionine was measured by PET-CT in patients who have undergone PD and in healthy controls.

Subjects and methods: 18 tumor free survivors after PD and 10 healthy controls were given a mixed test meal. 1 g of paracetamol was ingested with the meal and the ensuing area under the plasma concentration curve of the first 30 minutes (paracetamol AUC30) adopted as measure of gastric emptying. Simultaneously 800 MBq of 11C-methionine were administered intravenously and the activity over the pancreas measured by PET-CT 30 minutes after injection.

Results: Gastric emptying was significantly slower in controls as compared to pancreatectomy subjects (p < 0.0001;Table1). The uptake of 11C-methionine in the pancreas was significantly higher (p < 0.0001) in controls as compared to the PD group.

Tab. 1

	PD	Control	p-value
Paracetamol AUC30	218 (61 – 587)µg/ml*min	44 (31 – 81)µg/ml*min	< 0.0001 *
Gastric emptying (Paracetamol AUC30 132) slow rapid	4/18 (22%) 14/18 (77%)	9/9 (100%) 0/9 (0%)	0.0002**
11C-methionine uptake (pancreas/spleen ratio at 30 min.)	1.8 (0.4 – 4.6)	6.9 (2.4 – 8.4)	< 0.0001*
*Wilcoxon-test **Fisher's exact test

Comment: The lower uptake of 11C-methionine in the PD group suggests an attenuated postprandial function of the exocrine pancreas. It is well known that gastric emptying is accelerated after PD and results in an exaggerated release of GLP-1. High postprandial concentrations of GLP-1 – triggered by rapid emptying – are conceivably the cause of the diminished tracer uptake of the exocrine pancreas. Further research should shed more light on the relationship between elevated GLP-1 concentrations and suppressed uptake of methionine by the pancreas.