Chymotrypsin is detectable in the stool if the pancreas is functioning normally.

Chymotrypsin is an enzyme that digests protein in the small intestine. This test measures the amount of chymotrypsin in stool to help evaluate whether your pancreas is functioning properly.

Chymotrypsinogen, the inactive precursor of chymotrypsin, is produced in the pancreas and transported to the small intestine. In the small intestine, it is activated to form chymotrypsin. It is one of the enzymes responsible for breaking down the protein in food into smaller pieces, called peptides.

Individuals with pancreatic dysfunction may either have blocked pancreatic ducts or the cells that produce chymotrypsinogen may be damaged or destroyed. Such cell damage and duct blockage cause pancreatic insufficiency because the amount of enzymes transported to the small intestine is inadequate for proper food digestion. This is often seen in conditions such as chronic pancreatitis and sometimes pancreatic cancer.

Stool enzymes reflect the amount of proteolytic enzymes that the pancreas secretes into the intestine. As both pancreatic elastase (PE) and chymotrypsin are indicators of exocrine pancreatic function, the clinical indications for PE also apply to chymotrypsin. 

Potential symptoms:
- Loose, watery stools
- Undigested food in the stools
- Post-prandial abdominal pain
- Nausea or colicky abdominal pain
- Gastroesophageal reflux symptoms
- Bloating or food intolerance

Other conditions that have been scientifically proven to be associated with reduced chymotrypsin include:
- Diabetes
- Cystic Fibrosis
- Chronic pancreatitis
- Malabsorption

Differences between the markers pancreatic elastase (PE) and chymotrypsin:

While both chymotrypsin and PE are markers of exocrine pancreatic function, there are some distinct differences between the two tests. Chymotrypsin was the first non-invasive exocrine pancreatic test to be discovered and is a reflection of chymotrypsin activity in the pancreas. 

The more recently discovered PE reflects trypsin, chymotrypsin, amylase and lipase activity.

Both chymotrypsin and PE are highly accurate in distinguishing between pancreatic maldigestion and intestinal malabsorption (82% and 92%, respectively).

PE has been found to be more sensitive and specific than chymotrypsin.

In clinical studies, PE has been shown to correlate with the gold standard in pancreatic testing (secretin-pancreozymin test).

PE is not affected by bovine or porcine enzyme supplements, so patients do not have to discontinue therapy to assess baseline levels. 

Chymotrypsin is affected by exogenous supplementation which makes it an ideal tool to monitor dosing adequacy. 

When chymotrypsin values fall within the reference range in supplemented individuals, the clinician can be confident that an appropriate dosage of digestive enzymes is being administered. 

In summary, PE is a more accurate non-invasive marker to assess exocrine pancreatic function, and chymotrypsin is the preferred marker to monitor enzyme supplementation.

Exocrine pancreatic dysfunction can mimic the symptoms of other diseases and imbalances such as celiac disease, giardiasis and small bowel bacterial overgrowth.

Consider the following additional tests to determine the underlying etiology of imbalance:

- Celiac Panel
- Parasitology Profile
- Bacterial Overgrowth of the Small Intestine Breath Test
- Allergy Antibody Assessment

Potential causes for pancreatic insufficiency:

Pancreatic insufficiency can be caused by repeated bouts of acute pancreatitis or by chronic pancreatitis. It is less frequently but sometimes associated with pancreatic cancer. Other causes of insufficiency may include celiac disease, Crohn disease, autoimmune pancreatitis (immunoglobulin G4-related disease), Zollinger-Ellison syndrome, and some surgical procedures that can lead to a decrease in gastrointestinal or pancreatic function.

Additionally, people who are carriers of a mutation in the CFTR gene may have pancreatic insufficiency and experience the associated signs and symptoms.

In children, pancreatic insufficiency is most frequently associated with cystic fibrosis (CF) or Shwachman-Diamond Syndrome (SDS). SDS is the second most common cause of inherited pancreatic insufficiency, after CF. All those with SDS have some degree of pancreatic insufficiency beginning in infancy.

Pancreatic dysfunction typically leads to malabsorption, the severity of which is relative to the degree of exocrine pancreatic impairment. Assessment of absorptive markers (triglycerides, long chain fatty acids, cholesterol, and phospholipids) will provide valuable insight into the degree of malabsorption present.

Additional note: 

In general, chymotrypsin is nearly always present in the stool in measurable quantities in normal individuals. In those with exocrine pancreatic dysfunction, there is less activity. The exception is in patients with watery diarrhea. Levels may appear normal, however this is due to reduced proteolytic degradation from a rapid transit time, thus higher baseline levels.

References:

- Bockus Gastroenterology. Haubrich WS,Schaffner F, Berk JE (eds). Philadelphia, WB Saunders Co, 5th Ed, 1995 p 2844.
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