Secretin-cholecystokinin test
Encyclopedia
The secretin-cholecystokinin test (secretin-CCK test) is a combination of the secretin test and the cholecystokinin
test and is used to assess the function of both the pancreas
and gall bladder. Cholecystokinin, a hormone secreted by the APUD cells
located in the proximal mucosa of the small intestine
is administered intravenously, this stimulates the pancreatic secretion of the digestive enzymes amylase
, trypsin
, and lipase
. These are measured by a catheter
placed in the duodenum
. Cholecystokinin also stimulates the flow of bile
and causes the gall bladder to contract and thus determine if the gall bladder is emptying properly. It also affects the esophageal sphincter and the sphincter of Oddi
by reducing contraction as well as increasing motility (movement) of the stomach and intestine.
The CCK test may be administered in conjunction with an ultrasound test to visually monitor gall bladder contraction. While the test is usually administered in a supine position Dr. William Smedley of Wilkes Barre, Pennsylvania has detected previously missed gallbladder abnormalities by administering the test in an erect position.
The concentration and output of bicarbonate
with the secretin-CCK test is similar to what has been observed with the standard secretin
test . The secretin-induced rapid flow of water results in lower and often unreliable enzyme concentrations. CCK also induces gallbladder
contraction and the release of bile
, which may further dilute enzyme concentrations. As a result, the quantification of total enzyme output (units/min) must be determined through continuous collection of duodenal fluid with or without the use of perfusion markers. Measurement of more than one enzyme (ie, amylase
, lipase
, and tryptase
) and bicarbonate may improve sensitivity since some patients may possess deficiencies of one parameter and not the others .
One study reviewed the relative diagnostic value of enzyme and bicarbonate concentrations compared with enzyme output in 363 secretin-CCK tests . The investigators also evaluated the requirement for perfusion markers to accurately quantify volume, and the validity of a shortened sampling time (first 20 minutes). Only 60 percent of volume was recovered with the duodenal aspiration tube, suggesting that marker perfusion to correct for distal loss of secretion is important to accurately quantify volume.
Using a trypsin
output <50 U/kg/h as the reference standard, measurement of enzyme concentration alone misclassified approximately 10 percent of patients. Use of a shortened collection time misclassified approximately 4 percent of patients. The authors concluded that this was an unacceptably high rate of misclassification and that the standard prolonged collection of fluid using a perfusion marker must be performed to accurately measure exocrine function.
Cholecystokinin
Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein...
test and is used to assess the function of both the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
and gall bladder. Cholecystokinin, a hormone secreted by the APUD cells
APUD cell
right|thumb|350px|Actions of the major digestive hormones secreted by APUD cellsAPUD cells constitute a group of apparently unrelated endocrine cells, which were named by the scientist A.G.E. Pearse, who developed the APUD concept in the early 60's. These cells share the common function of...
located in the proximal mucosa of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
is administered intravenously, this stimulates the pancreatic secretion of the digestive enzymes amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...
, trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
, and lipase
Lipase
A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...
. These are measured by a catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
placed in the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
. Cholecystokinin also stimulates the flow of bile
Bile
Bile or gall is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the process of digestion of lipids in the small intestine. In many species, bile is stored in the gallbladder and upon eating is discharged into the duodenum...
and causes the gall bladder to contract and thus determine if the gall bladder is emptying properly. It also affects the esophageal sphincter and the sphincter of Oddi
Sphincter of Oddi
The sphincter of ampulla or sphincter of Oddi is a muscular valve that controls the flow of digestive juices through the ampulla of Vater into the second part of the duodenum. It is named after Ruggero Oddi...
by reducing contraction as well as increasing motility (movement) of the stomach and intestine.
The CCK test may be administered in conjunction with an ultrasound test to visually monitor gall bladder contraction. While the test is usually administered in a supine position Dr. William Smedley of Wilkes Barre, Pennsylvania has detected previously missed gallbladder abnormalities by administering the test in an erect position.
The concentration and output of bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...
with the secretin-CCK test is similar to what has been observed with the standard secretin
Secretin
Secretin is a hormone that controls the secretions into the duodenum, and also separately, water homeostasis throughout the body. It is produced in the S cells of the duodenum in the crypts of Lieberkühn...
test . The secretin-induced rapid flow of water results in lower and often unreliable enzyme concentrations. CCK also induces gallbladder
Gallbladder
In vertebrates the gallbladder is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans the loss of the gallbladder is usually easily tolerated....
contraction and the release of bile
Bile
Bile or gall is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the process of digestion of lipids in the small intestine. In many species, bile is stored in the gallbladder and upon eating is discharged into the duodenum...
, which may further dilute enzyme concentrations. As a result, the quantification of total enzyme output (units/min) must be determined through continuous collection of duodenal fluid with or without the use of perfusion markers. Measurement of more than one enzyme (ie, amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...
, lipase
Lipase
A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...
, and tryptase
Tryptase
Tryptase is the most abundant secretory granule-derived serine proteinase contained in mast cells that has been used as a marker for mast cell activation. It is involved with allergenic response and is suspected to act as a mitogen for fibroblast lines...
) and bicarbonate may improve sensitivity since some patients may possess deficiencies of one parameter and not the others .
One study reviewed the relative diagnostic value of enzyme and bicarbonate concentrations compared with enzyme output in 363 secretin-CCK tests . The investigators also evaluated the requirement for perfusion markers to accurately quantify volume, and the validity of a shortened sampling time (first 20 minutes). Only 60 percent of volume was recovered with the duodenal aspiration tube, suggesting that marker perfusion to correct for distal loss of secretion is important to accurately quantify volume.
Using a trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
output <50 U/kg/h as the reference standard, measurement of enzyme concentration alone misclassified approximately 10 percent of patients. Use of a shortened collection time misclassified approximately 4 percent of patients. The authors concluded that this was an unacceptably high rate of misclassification and that the standard prolonged collection of fluid using a perfusion marker must be performed to accurately measure exocrine function.