Feline triaditis and pancreatitis: causes, diagnosis and treatment
Between 50 and 56% of cats with pancreatitis suffer from triaditis. We look at the possible causes of this condition, its diagnosis and the most appropriate treatment regimens based on the clinical signs.
Introduction
Pancreatitis in cats was previously considered a rare disease, but it is actually the most common disorder of the exocrine pancreas in cats. It can result in significant morbidity and mortality if appropriate treatment is not administered. Pancreatitis is usually accompanied by different diseases that affect other organs, although it has not yet been possible to determine whether these conditions are a direct consequence of the pancreatitis or due to the same pathological processes causing it.
Besides comorbidities such as diabetes, pulmonary thromboembolism and hepatic lipidosis, pancreatitis has also been associated with triaditis, inflammation of the pancreas, liver and small intestine. This inflammation affects between 50–56% of cats diagnosed with pancreatitis and 32–50% of those with cholangitis and inflammatory liver disease, as indicated in a study by Simpson at Cornell University(1).
Feline triaditis and pancreatitis: aetiology
Around 95% of cases of feline pancreatitis are considered idiopathic and no specific risk factors (age, sex, breed, weight, diet or medications) have been reported to date.(2)
A number of hypotheses have been proposed to clarify the aetiology of feline triaditis and pancreatitis, as explained by Carolina Arenas in her Webinar on diseases of the exocrine pancreas in cats. She mentions the association with biliary disorders, such as cholangitis and inflammatory bowel disease, as described in a study by Fragkou et al., which may derive from an immune system disorder.(3)
A number of parasitic (Toxoplasma gondii, Eurytrema procyonis, Amphimerus pseudofelineus) and viral agents (coronavirus, parvovirus, herpesvirus, calicivirus) are also believed to be involved. Some cases of feline triaditis and pancreatitis have also been linked to abdominal trauma, ischaemia, pancreatic tumours, obstruction of the pancreatic ducts, hypotension, acute hypercalcaemia, organophosphate poisoning and the use of certain medications.(2,3)
Given the complexity of the underlying pathophysiological mechanisms, these conditions are likely to be multicausal; that is, they are due to a heterogeneous group of conditions that trigger an inflammatory and immune response that ultimately affects the enteric bacteria.(2,3)
With regard to the pathophysiology, the pathogenesis of pancreatitis in both humans and cats is associated with the premature activation of pancreatic enzymes, such as trypsinogen, in pancreatic acinar cells followed by autodigestion. The trigger for this inflammatory process, however, remains unknown.(3)
Clinical signs
The physical examination and clinical signs associated with acute and chronic pancreatitis are nonspecific in cats. However, the clinical signs can help grade the severity of pancreatitis.
The most common clinical signs include lethargy, partial or total anorexia, vomiting, weight loss, diarrhoea and dyspnoea. Findings from the physical examination usually comprise dehydration, hypothermia and jaundice; there may also be abdominal pain, hyperthermia and organomegaly in the cranial abdomen.
Note that cats with pancreatitis do not usually have abdominal pain. This contrasts sharply with human medicine, in which abdominal pain is one of the characteristic clinical signs.
Diagnosis
Here is a brief summary of the main diagnostic tests:(3)
1. Abdominal X-ray: according to the latest ACVIM consensus statement, abdominal radiography is neither sufficiently sensitive nor specific for the diagnosis of pancreatitis. Loss of peritoneal detail in the cranial abdomen or a mass effect can be identified in cases of severe pancreatitis.
2. Abdominal ultrasound: abdominal ultrasound is still the most widely used imaging method. In cats with acute pancreatitis, the most common findings include an enlarged pancreas, hyperechoic mesentery and intra-abdominal free fluid. In chronic pancreatitis, common findings include a hyperechoic or mixed pattern, bile duct dilatation, enlarged pancreas and irregular borders. The use of CT and MRI has also been described, although they are not normally used as imaging methods for this condition.
3. Clinical pathology:
- Blood chemistry, haematology and urinalysis: although these tests are nonspecific in the diagnosis of pancreatitis, they do help rule out other differential diagnoses and confirm any comorbidities or complications.
An elevated red blood cell count, which is secondary to dehydration, is a common finding in the haemogram. Inflammatory leukogram pattern is often noted in the white blood cell count.
The blood chemistry tends to reveal elevated pancreatic enzymes (ALT, AST) and total bilirubin levels due to biliary tree inflammation, biliary obstruction and/or hepatic lipidosis.
Creatinine, BUN and SDMA may be abnormally high due to dehydration and/or azotaemia. Electrolyte imbalances are another common finding, namely, hypokalaemia, hypochloraemia, hyponatraemia and hypocalcaemia.
- Pancreatic lipase: pancreatic acinar cells synthesise and secrete a series of active digestive enzymes that are released through the pancreatic duct into the small intestine. If there is inflammation, some of these enzymes reach the interstitial space and eventually enter the vascular system. Hence, testing for these enzymes or zymogens can theoretically serve as a diagnostic marker of acinar cell damage.
There are several commercial lipase tests available. ELISA assays for serum feline pancreatic lipase immunoreactivity (fPLI) currently offer the highest sensitivity and specificity, although it should be noted that the test has a higher sensitivity in cases of severe pancreatitis compared to mild ones.
A combination of ultrasound and fPLI is currently the gold standard diagnostic method.
4. Histopathology
- Cytology: is used to examine the specific point of aspiration, but the sample may not be representative of all the pancreatic tissue.
- Biopsy: for many years, a pancreas biopsy has been considered the gold standard for the antemortem diagnosis of pancreatitis. The sample can be collected using a surgical or laparoscopic technique. Multiple biopsy samples are recommended; if only one can be collected, it should be taken from the left lobe.
The histological characteristics of chronic pancreatitis in cats are lymphocytic or lymphoplasmacytic inflammation, fibrosis and pancreatic acinar atrophy. Acute pancreatitis can be either necrotising or suppurative, depending on whether the predominant trait is necrosis or neutrophilic infiltration.
Feline triaditis: treatment
The treatment of feline triaditis consists mainly of supportive measures. In dehydrated patients, which is common in pancreatitis due to vomiting, diarrhoea or not drinking enough water, intravenous fluid therapy should be administered to maintain general and pancreatic tissue perfusion and to prevent hypovolaemic shock.
An antiemetic should be used in case of vomiting, as dopaminergic antagonists are usually less effective. The use of 5-HT3 receptor antagonists, α2-adrenergic receptor antagonists and NK1 receptor antagonists are therefore recommended, as indicated in an article published by Xenoulis and Steiner (2009).3
The use of analgesics is recommended during an acute episode of pancreatitis, even if pain is not clinically observable, according to a study by Zoran. 5 Injectable and oral opioids, such as buprenorphine, are also options for consideration.
Studies have shown that corticosteroid therapy improves the prognosis for acute pancreatitis in humans and dogs. However, in the absence of studies in cats, the latest ACVIM consensus statement advises against their routine use. Nevertheless, corticosteroids should be considered in cats with comorbidities, such as chronic inflammatory enteropathy or sterile cholangitis.
Patients must also receive a suitable diet that provides all the protein required. Given that these animals often experience loss of appetite, appetite stimulants, such as mirtazapine and cyproheptadine, should be administered rather than forcing the patient to eat. Enteral feeding is recommended for cats with total anorexia. In general, there is no need to restrict fat intake, as noted in a study published in the journal In Practice (6), although highly digestible diets such as “gastrointestinal diets” are recommended.
Conclusions
Pancreatitis has been associated with triaditis, which is inflammation of the pancreas, liver and small intestine. The aetiology is multicausal and the clinical signs are usually nonspecific. A combination of abdominal ultrasound and serum feline pancreatic lipase immunoreactivity (fPLI) is the gold standard for diagnosis. Treatment is supportive and should be tailored to the clinical signs.
