What is it?
Pancreatic exocrine insufficiency (PEI) is the inability of the pancreas to produce and/or transport enough digestive enzymes to break down food in the intestine and allow its absorption. It may be due to problems arising in the pancreas itself or problems outside the pancreas. The most common cause is chronic pancreatitis as a result of long term pancreatic damage caused by a variety of conditions. Other causes of pancreatic insufficiency include cystic fibrosis, obstruction of the pancreatic duct system due to a tumour or a stricture, gastrointestinal tract and pancreatic surgical procedures, and rarely Shwachman-Diamond Syndrome (SDS), untreated coeliac disease or Crohn’s disease, and autoimmune pancreatitis. In children it is most frequently associated with cystic fibrosis and in adults it may follow chronic pancreatitis or repeated attacks of acute pancreatitis.
Pancreatic exocrine insufficiency usually results in symptoms of malabsorption, malnutrition, vitamin deficiencies, and weight loss (or reduced weight gain in children). The most common complaint is diarrhoea, which is frequently watery. It is due to fat malabsorption and is characterised by pale, fatty, foul-smelling, floating stools (steatorrhoea). Flatulence (wind), abdominal distension and cramps are also some of other symptoms. Adults with pancreatic insufficiency may also develop diabetes.
- Faecal pancreatic elastase-1. Elastase is a protein-cleaving enzyme produced in and secreted by the pancreas. It is resistant to degradation by other enzymes and so is excreted and can be measured in the stool. The amount of this enzyme is reduced in pancreatic insufficiency. The patient’s own (human) enzyme can be measured to assess pancreatic insufficiency even if they are receiving oral (animal) pancreatic supplements that include elastase.
- Serum Immunoreactive trypsin (IRT). Raised values show that there is obstruction of trypsinogen secretion by the pancreas into the intestine where it is normally converted to trypsin. It is used in many countries as a screening test for cystic fibrosis in newborn babies. Low serum values indicate failure of production in pancreatic disease.
- Faecal chymotrypsin. This is a stool test for an enzyme that digests food proteins. It is produced in the pancreas in an inactive form and then becomes activate when it enters the small intestine. Low values indicate pancreatic insufficiency.
The excretion of fat in the stools is increased in pancreatic insufficiency, but faecal fat is now very rarely measured in the UK, having been superseded by the enzyme tests described above.
In clinical practice, the diagnosis of pancreatic insufficiency is usually based on an assessment of the patient’s clinical state, self-report of bowel movements and weight loss in adults, or not gaining weight at the normal rate in children.
- Other blood tests to investigate malabsorption and malnutrition: Full blood count, serum ferritin, vitamin B12 and folate concentrations, prothrombin time, serum nutritional markers such as albumin, prealbumin, and retinol binding protein, serum electrolytes, total cholesterol, micronutrients such as zinc and selenium, lipid soluble vitamins.
- Trial of pancreatic enzyme replacement therapy (PERT) and symptom improvement also support the diagnosis of pancreatic insufficiency.
- ¹³C mixed-chain triglyceride breath test. This is a novel and accurate test. The patient ingests a small amount of ¹³C -marked triglycerides, together with butter on a piece of toasted bread, after an overnight fast. In a normal person with normal lipase enzyme activity, ¹³C triglycerides will be degraded in the intestinal lumen, and ¹³C -marked fatty acids will then be absorbed. These fatty acids will in turn be metabolized in the liver, and ¹³CO₂ can finally be measured in exhaled air. Patients with PEI have decreased lipase activity, which can be detected as a decreased recovery of ¹³CO₂ in exhaled air. Currently, there is no general agreement on the optimal design of the test and it is widely not available. This test also monitors and measures the success of PERT.
- Fasting plasma glucose testing as patients with chronic pancreatitis may have impaired glucose tolerance.
Non-laboratory tests
- Endoscopic retrograde cholangiopancreatography (ERCP): a flexible scope is passed through the nose and stomach into the common opening of the pancreatic and bile ducts in the small intestine. It is most often used when an obstruction, for example pancreatic carcinoma, is suspected.
- Endoscopic ultrasound scan (EUS) and computerized tomography (CT) are also used as other imaging techniques to detect abnormalities in the structure of pancreas and its duct system.
- Secretin test (not widely used): a tube is positioned in the duodenum to collect pancreatic secretion of enzymes and bicarbonate stimulated by intravenous (IV) secretin.
- Magnetic resonance imaging (MRI ) may be used to examine the structure of the pancreas and bile ducts.
- Secretin-stimulated magnetic resonance cholangiopancreatography is another imaging modality to measure pancreatic function.
Treatment involves dealing with the underlying condition, preventing further pancreatic damage and managing the symptoms. Medical therapy addresses the functional and nutritional deficiencies. To aid digestion patients may be given oral preparations of pancreatic enzymes as a supplement to make up for decreased production. This pancreatic enzyme replacement therapy (PERT) not only improves clinical status of the patient but also the quality of the life. Therefore, it is the mainstay of treatment for PEI. This is an oral preparation takes along with the meals. Involvement of a dietician to oversee dietary management is very important. This will improve energy and protein intake with adequate micronutrients. Today, no fat restriction is recommended and normal fat diet has been successfully used in combination with PERT. Small, frequent meals are usually better tolerated than large, high-caloric meals. Patients may be given vitamin supplements (especially fat-soluble vitamins A, D, E, and K because of impaired fat absorption). If the cause of the pancreatic insufficiency is chronic pancreatitis due to alcohol use, abstaining from alcohol is important in preventing further attacks. In chronic pancreatitis due to other causes, the treatment should be aimed at those. Patients with chronic pancreatitis should also be given adequate pain relief.