Assessment of exocrine pancreatic function in children and adolescents with direct and indirect testing

Abstract

The exocrine pancreas plays an important role in digestion. Understanding of the physiology and regulation of exocrine function provides insight into disease processes and basis of functional testing. Specifically, exocrine pancreatic insufficiency (EPI) can cause maldigestion and thus a proper assessment of exocrine pancreatic function is important. There are indirect and direct methods for evaluating pancreatic function. Indirect methods are varied and include stool, serum, urine, and breath tests. Fecal elastase is a commonly used indirect test today. Direct methods involve stimulated release of pancreatic fluid that is collected from the duodenum and analyzed for enzyme activity. The most used direct test today is the endoscopic pancreatic function test. Indirect pancreatic function testing is limited in identifying cases of mild to moderate EPI, and as such in these cases, direct testing has higher sensitivity and specificity in diagnosing EPI. This review provides a comprehensive guide to indirect and direct pancreatic function tests as well as an in-depth look at exocrine pancreatic function including anatomy, physiology, and regulatory mechanisms.

Keywords: acinar cells; direct pancreatic function test; duct cells; exocrine function; indirect pancreatic function test; pancreas.

Figure 1

Picture of the collection catheter passed through endoscope working channel (A); the tip of catheter is seen in the duodenum close to the ampulla of vater (B).

Figure 2

Ductal function assessment with bicarbonate concentration from prolonged ePFT with fluid collection up to 45 min. (A) Normal tests with the bicarbonate concentration is above 80 mmol/L. (B) Abnormal tests in patients with genetic abnormalities in three patients when the bicarbonate never reached the 80 mmol/L [adapted from Horvath, K. et al. (125)].

Figure 3

This flowchart shows the optimal time of fluid collection for acinar and ductal function after IV push administration of secretin [modified from Engjom, T. et al. (134)].