Norm of Secretin Test for Pancreatic Function
|Bicarbonate||74–121 mEq/L||74–121 mmol/L|
|Lipase||<1.5 U/mL||<415 IU/L|
Usage of Secretin Test for Pancreatic Function
Assessment of exocrine secretory ability of the pancreas for carcinoma, ductal obstruction, or chronic pancreatitis.
Description of Secretin Test for Pancreatic Function
Secretin is a polypeptide secreted by the duodenal mucosa and the upper jejunum in response to gastric acidity. Some of its actions are to stimulate pancreatic enzyme secretion and bicarbonate pancreatic juice production. This test allows an assessment of pancreatic endocrine function by assessing duodenal contents for volume and bicarbonate, amylase, lipase, and trypsin levels before and after pancreatic stimulation by secretin. In chronic pancreatitis and cystic fibrosis, all values are low because of pancreatic tissue destruction. In early stages of obstructive pancreatic cancer, volume may be low, with other values normal. In pancreatic pseudocyst, bicarbonate level may be decreased, with other values normal. This test is usually followed by magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasound (EUS), or spiral computed tomography (spiral CT) and is replacing endoscopic retrograde cholangiopancreatography for confirming diagnosis of chronic pancreatitis.
Professional Considerations of Secretin Test for Pancreatic Function
Consent form IS required.
Allergic reaction to secretin. Complications of nasogastric tube insertion include bleeding, dysrhythmias, esophageal perforation, laryngospasm, and decreased mean po2.
Positive reaction to secretin skin testing.
- Obtain a double-lumen orogastric tube, pH paper, secretin, and two aspiration syringes or mechanical suction.
- Perform secretin skin testing to assess for allergy to the foreign protein. Inject 0.1 mL intradermally and observe 30 minutes for development of a wheal at the injection site.
- Establish intravenous access.
- See Client and Family Teaching.
- Just before beginning the procedure, take a “time out” to verify the correct client, procedure, and site.
- An orogastric tube is passed into the duodenum to the ligament of Treitz. Placement is assessed by analysis of the pH of secretions. Gastric pH is acidic, whereas duodenal secretions are alkaline.
- The gastric (proximal) lumen is continuously aspirated to prevent acidic gastric secretions from contaminating duodenal contents.
- All the duodenal fluid is aspirated from the distal portion of the lumen and placed into a sterile container. The container is labeled with the date, time, and specimen source and sent to the laboratory for baseline volume and bicarbonate and amylase measurement.
- Secretin, 1–2 U/kg of body weight, is administered intravenously.
- All fluid is aspirated from the distal lumen every 20 minutes and analyzed for volume and bicarbonate, amylase, and lipase levels, as for the baseline sample.
- Test may be followed by MRCP, EUS, or spiral CT.
- Remove the orogastric tube.
Client and Family Teaching
- This test is one of several used to screen for pancreatic cancer or pancreatitis.
- A nasogastric tube will be inserted through your nose into your stomach. Insertion may be uncomfortable and cause a pressurelike feeling or cause you to gag and cough. You will be asked to take sips of water and swallow to make tube insertion easier.
Factors That Affect Results
- Failure to insert the tube fully into the duodenum causes unreliable results.
- There is a 5.1% chance of false-positive results and a 5.2% chance of false-negative results.
- This test is somewhat out of favor because duodenal intubation is unpopular, and pancreatic disease is usually far advanced before exocrine function is appreciably reduced.
- This test is of little help in distinguishing chronic pancreatitis from advanced pancreatic cancer.
- Pancreozymin may be used in place of secretin for pancreatic stimulation, but it is more expensive.