All about... pancreatitis
The Exocrine Pancreas
The pancreas is a bi-lobed organ located in the cranial abdomen, and has both endocrine and exocrine functions; the acinar cells make up around 90% of the pancreas, and are responsible for the secretion of digestive enzymes into the duodenum. These digestive enzymes are released from the pancreas in inactivated forms called zymogens, until they reach the duodenum and are activated. This process protects the pancreas from damage associated with enzyme activation whilst still within the organ. A number of different enzymes are released, depending on the target source:
Trypsinogen – protein breakdown
Chymotrypsinogen – protein breakdown
Procarboxypeptidase – protein breakdown
Amlyase – carbohydrate breakdown
(Pancreatic) Lipase – fat breakdown
Cholesterol Esterase – fat breakdown
Phospholipase – fat breakdown
Pancreatic secretion is activated by several mechanisms, including the stomach filling, and by the presence of fat and/or protein within the intestinal lumen. This triggers the release of trypsinogen, which forms trypsin in the small intestine, and in turn activates the other digestive enzymes.
Pancreatitis
Pancreatitis is defined as inflammation of the pancreas; this can be acute or chronic, and the two often overlap. Acute pancreatitis occurs when trypsinogen is prematurely activated within the pancreas, causing further enzyme activation. This results in pancreatic autodigestion, severe inflammation of pancreatic tissue and peripancreatic fat necrosis. Systemic inflammatory response syndrome can result, with often significant systemic consequences.
Acute pancreatitis commonly affects middle-aged dogs and cats, with terrier breeds, miniature schnauzers and domestic shorthairs most commonly affected. The condition is likely multifactorial, and a number of factors have been reported, including:
Genetic factors e.g. breed
Consumption of a high-fat meal
Certain endocrinopathies in dogs
Cholangitis/inflammatory bowel disease in cats
Pancreatic duct obstruction
Pancreatic trauma
Ischaemia and reperfusion of the pancreas
Administration of certain medications e.g. L-asparaginase, azathioprine, furosemide
Idiopathic causes
Chronic pancreatitis is the continued inflammation of the pancreas and is characterised by destruction of pancreatic tissue. This can lead to progressive or permanent loss of pancreatic function. Typically, this is a rarer and less significant condition in dogs, however in cats, it is the most common form of pancreatitis seen.
Clinical Signs
Signs of canine acute pancreatitis vary according to disease severity, and include:
Anorexia
Abdominal pain
Vomiting
Haematochezia
Dehydration
Hypovolaemia
Pyrexia
Lethargy
+/- signs of SIRS/MODS
In cats, clinical signs are much milder, even if severe disease is present. Anorexia, lethargy and abdominal pain are reported in less than 50% of cats with pancreatitis, and even in cases of severe peritonitis, abdominal pain is typically not obviously identified.
In cases of chronic pancreatitis, dogs typically present with mild gastrointestinal signs, with episodes of anorexia, vomiting and mild haematochezia; abdominal pain is generally obvious after eating, but not otherwise. Dogs can also develop acute-on-chronic pancreatitis, showing signs of acute pancreatitis after a long period of subclinical disease.
Physical Examination
Examination aims to identify and assess the severity of any fluid losses, pain, or other cardiovascular instabilities present.
Increased skin tenting, mucosal dryness, and sunken eyes may be noted in the dehydrated patient, which may progress to tachycardia, reduced pulse quality, pale mucous membranes, reduced mentation and prolonged capillary refill time in patients with intravascular volume deficits.
Pyrexia may also be apparent on physical examination, and evidence of nausea, vomiting and/or diarrhoea may be apparent in addition to signs of dehydration (e.g. hypersalivation, lip-licking, wet mucous membranes and coat soiling).
In cases of chronic pancreatitis, mucous membranes may be icteric, and where systemic inflammation is present, mucous membranes may appear hyperaemic with a rapid capillary refill time. Abdominal palpation typically reveals abdominal pain in cases of acute disease, however in cases of chronic disease, or in cats, this may not be easily identified.
Diagnostics
Routine haematology and biochemistry analysis does not typically help with diagnosis of pancreatitis, but identifies concurrent disease, electrolyte disturbances requiring treatment, and allows assessment of organ function.
Specific pancreatic enzyme assays include trypsin-like immunoreactivity (TLI), pancreatic lipase (PLi), amylase and lipase. In cats, amylase and lipase are of little diagnostic value, whereas in dogs, increases in both enzymes are typically seen. However, increases in amylase and lipase are not diagnostic for pancreatitis, since other organs in the body can also synthesise and secrete these enzymes.
PLi is a highly sensitive and moderately specific test for pancreatitis, and is currently the only reliable diagnostic test for feline pancreatitis. This test, unlike lipase alone, measures lipase which originates only from the pancreas.
Ultrasound is the primary imaging modality used in practice to evaluate the pancreas and peripancreatic fat, as well as other abdominal organs, and identifies the presence of peritoneal effusion. Abdominal radiography may be used, but often does not provide as much information compared with ultrasonography.
Treatment
There is no definitive treatment for pancreatitis; treatment is instead supportive, and aimed at reducing the clinical signs. Common treatments include intravenous fluid therapy, analgesia, anti-emetics +/- antibiotics in some cases.
Fluid Therapy
Pancreatitis patients often present with moderate-marked dehydration, electrolyte imbalances and metabolic acidosis or alkalosis. IVFT is therefore a staple of treatment. An appropriate fluid choice and rate should be selected for the individual patient, their acid/base and electrolyte status, and the type/degree of fluid losses present.
Analgesia
Acute pancreatitis is usually an extremely painful condition. All patients should be monitored closely for signs of pain, and their pain levels quantified using a validated pain assessment tool. Analgesia of some form should be given to all patients with pancreatitis, and should particularly always be administered to cats as their pain is hard to assess. Opioids are the main class of analgesic agent used in cases of pancreatitis, with full or partial mu-receptor agonists, such as methadone and buprenorphine, commonly used. Other analgesic agents may also be used in combination with opioids; non-steroidal anti-inflammatory drugs should, however, be avoided in pancreatitis patients.
Anti-emetics
Supportive treatment typically includes the administration of one or more anti-emetic agent/s. Drugs such as maropitant may also provide a degree of visceral analgesia which may be beneficial in the pancreatitis patient; in cases of severe nausea or ongoing vomiting, the use of additional antiemetics (which exert their effects on different receptors within the GI tract, in order to provide multimodal support) should be considered and discussed with the veterinary surgeon.
Nutrition
Early enteral nutrition is vitally important in the successful treatment of acute pancreatitis. Pancreatitis is a catabolic disease, and by providing enteral nutrition at an early stage, this process can be reversed.
Ideally, in dogs, a highly digestible, low-fat diet should be selected for administration. In cats, fat content is not considered as much of a concern, as their dietary fat requirements are naturally higher than dogs; cats should be fed a highly digestible diet with a moderate fat content.
Patients should have their bodyweight +/- body condition score measured at least daily and their resting energy requirement calculated each day, based on their admitted weight. Volumes fed should be weighed and measured, and volumes consumed recorded, in order to track the percentage RER consumed each day. Where RER consumption is below 80-85% for >3 days (from time of clinical signs, not time of presentation to the hospital), nutritional support with an appropriate feeding tube should be considered.
Monitoring
Patients with pancreatitis require close monitoring of vital parameters (at appropriate intervals based on the individual patient’s condition), hydration/perfusion parameters, signs of nausea and pain. The veterinary nurse plays a key role in monitoring these patients and providing day-to-day general nursing care, and is ideally suited to identify trends or changes in the patient’s condition at an early stage.
References
1. Cridge, H. and Sullivant, A. Canine and Feline Pancreatitis. Veterinary Ireland Journal 2018; 8: 367-372, http://www.veterinaryirelandjournal.com/images/pdf/small/sa_jun_2018.pdf.
2. Ettinger, S., Feldman, C., and Cole E. Textbook of Veterinary Internal Medicine. 8th ed. Missouri: Elsevier, 2016.
3. Merrill L. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell, 2012.
4. Nelson, R W. and Couto, C G. Small Animal Internal Medicine. 5th ed. Missouri: Elsevier Mosby, 2014.
5. Steiner, J. Pancreatitis in Small Animals. MSD Vet Manual, https://www.msdvetmanual.com/digestive-system/the-exocrine-pancreas/pancreatitis-in-small-animals, 2013.
