The Duodenal Aspirate Volume Does Not Correlate With the PEAK Bicarbonate Concentration During Secretin Stimulated Endoscopic Pancreas Function Testing. A Note of Caution for Secretin MRCP?

Abstract

Background. Abnormal exocrine function precedes most imaging changes of CP so stimulated pancreas function tests (PFT) are used as a surrogate for early diagnosis as histology is rarely obtained. Endoscopic PFT (ePFT) have shown promise as a less technically challenging PFT but may last one hour and require special equipment. Peak pancreas exocrine output takes at least 30 minutes to occur after secretagogue stimulation so we tested if a shorter endoscopic aspiration could differentiate patients with and without chronic pancreatitis. Methods. Synthetic secretin 0.2 μg/kg (ChiRhoClin,Inc.,Burtonsville,MD) was administered IV, and sedation started 30 minutes afterwards. After gastric fluid aspiration the endoscope was advanced to the major papilla and four continuous duodenal aspirations were done at 5 minute intervals, starting 35 minutes after secretin administration, collected in a sealed polyp trap on ice, and delivered to the laboratory. The first four samples were analyzed by an autoanalyzer (Corning 965, USA) calibrated to a bicarbonate of 80 mEq/L and compared to pH back titration. Variance between the methods was ±0.02 mEq/L so subsequent measurements were done with the auto-analyzer only. Peak bicarbonate concentration (PBC) >80 mEq/L during any collection is normal. ERCP and EUS were compared to ePFT and all three to a final diagnosis of CP which was established by considering history, imaging, histology and ePFT. Results. Twenty seven ePFT have been performed (16 females). Indications were suspected CP (17), abdominal pain (7), steatorrhea (2), idiopathic recurrent acute pancreatitis (1). Nine patients (pts) received a final diagnosis of CP and 18 no CP. 15 pts had ERCP (two had one, 9 pts had 2, 2 pts had 3 and 2 pts had 5). Seven pts had a normal pancreatogram. Cambridge class was I in one pt, II in 4 pts, III in 2 pts and IV in one pt. Two pts with Cambridge II and one with Cambridge III had normal PBC. 23 pts had EUS (21 had one, one pt had two, and one pt had 3). Ten pts had > 4 criteria for CP, and 6/10 pts had an abnormal ePFT. 13 pts had a normal EUS, and 11/13 had normal PBC (one pt had PBC 78.9 mEq/L). PBC was 80 mEq/ L in 17/18 pts without CP. The sensitivity and specificity of ePFT compared to ERCP and EUS and of all three compared to a final diagnosis of CP are in the tables. Conclusion. The ePFT was as good as EUS and ERCP in predicting CP. ePFT and EUS were non-statistically superior to ERCP in ruling out CP. The final diagnosis of CP was enhanced by combining numerous tests, but this proposed shorter ePFT requires less expertise, involves routine upper endoscopy, and may be more practical for regular use. More data is needed to determine how well it predicts early chronic pancreatitis, and if results decrease the ordering of other tests when CP is suspected. Comparison of ePFT to ERCP and EUS