The value of [14C]phenyl acetic dipalmitate (PADP) as a test for maldigestion

[14C]phenyl acetic dipalmitate (PADP) was prepared and evaluated in vitro and in vivo. Upon incubation with lipase it was hydrolyzed into phenyl acetic acid and monoglycerides. Phenyl acetic acid is not metabolized by the body and is quantitatively excreted in urine. When tested in rats there was no tissue deposition of the 14C label in any of the organs studied. There was also no evidence of absorption from the colon. The newly prepared compound was evaluated in 15 human volunteers and 24 patients with chronic pancreatitis and compared to fecal fat and D-xylose. Normal volunteers had a urinary excretion of 34.5 +/- 6.4% of the administered 14C label in 5 h. Both fecal fat and PADP were abnormal in 16 of 20 patients with chronic pancreatitis. They were both normal in two, while in two other patients fecal fat was normal and PADP abnormal. Both of the latter patients had clinical evidence of steatorrhea but reduced oral intake due to pain. D-xylose was abnormal in five patients presumably due to bacterial overgrowth. Our findings indicate that PADP is a simple, accurate and rapid test for pancreatic function; is not dependent on fat intake and may be run concomitantly with D-xylose.