Trypsin activity in stool and duodenal aspirate of neonates for differential diagnosis of intestinal obstruction.

The diagnosis of a non-surgical cause of delayed passage of meconium in a neonate may be challenging to the pediatric surgeon. The usefulness of determining trypsin activity (TA) in stool and duodenal aspirate for the diagnosis of cystic fibrosis (CF) and the existence of an entity called transient deficiency of trypsin (TTD) was assessed in 49 neonates over a 14-month period. TA was determined by a gelatin liquefaction technique. An absence of TA was considered if gelatin liquefaction was seen at a dilution of less than 1:100. Neonates with negative activity in both samples were started on supplementary pancreatic enzymes (pancreatin) for 1 month. TA was retested in the stool after stopping pancreatin for 1 week. Neonates with a return of TA were considered to have TTD; those who showed persistent TA deficiency at re-evaluation were investigated for CF by sweat iontophoresis. Twenty-one neonates had negative TA (in 1 only stool was tested); 13 could be re-evaluated (4 died, 4 were lost to follow-up). Nine were found to have TTD as a stool or duodenal sample showed the presence of TA; 3 of 4 patients with persistent negative TA were confirmed to have CF. One patient with normal sweat chloride is awaiting genetic studies. Determination of TA by gelatin liquefaction is a simple, rapid, inexpensive, and reliable (sensitivity 100%, negative predictive value 100%) means to differentiate non-surgical causes of intestinal obstruction such as neonatal and postoperative TTD and CF.