Abstract
Pancreatitis in cats has until recently been regarded as a chronic sub-clinical condition which is rarely of significance. However the findings of recent necropsy and clinical studies indicate that chronic pancreatitis is not always a benign condition and that acute pancreatitis is a potentially life-threatening condition that affects cats in Europe and the USA.
Pancreatitis has been categorised as acute, chronic active and chronic, with acute pancreatitis further subclassified as acute necrotizing and suppurative (Macy 1999, Hill & Van Winkle 1993). Infected necrosis has been occasionally documented. The correlation of histologic lesions to clinical disease requires further study — suppurative pancreatitis may be associated with more severe clinical signs such as hypothermia, shock and cachexia. Acute and chronic pancreatitis are likely to be involved in the development of exocrine pancreatic insufficiency and diabetes mellitus.
The etiology of most cases of acute pancreatitis is unclear. A small number of cases have been associated with trauma, Toxoplasma gondii, pancreatic and liver flukes, feline infectious peritonitis and lipodystrophy. An association between pancreatitis and organophosphate administration was suggested in one series. Ionized hypercalcaemia >1.8 mM precipitated pancreatitis in experimental cats. Dietary alterations may predispose to the development of pancreatitis in the cat.
While, pancreatitis has been diagnosed as the sole or predominant disease entity in cats at necropsy, accounting for one in 600 feline fatalities at the University of Pennsylvania (Hill & Van Winkle 1993), it has also been variably associated with diseases in other organs such as the liver (cholestasis, cholangiohepatitis, hydropic change, lipidosis), the kidney (mild to severe nephritis), the endocrine pancreas (diabetes mellitus), the lungs (pulmonary thrombosis), the intestine (ulceration, inflammation, lymphoma), effusions in the pleural and peritoneal cavity and subnormal serum concentrations of cobalamin (Hill & Van Winkle 1993, Akol et al 1993, Simpson et al 1994, Weiss et al 1996, Swift et al 2000, Simpson et al 2001, Gerhardt et al 2001). Whether these changes arise as a consequence of pancreatitis, or are associated with disease processes that cause pancreatitis, or are unrelated to pancreatitis is unclear at this time.
Despite postmortem studies firmly establishing pancreatitis as a clinically significant disease in cats the ante-mortem diagnosis of feline pancreatitis has been reported rarely (Simpson et al 1994, Swift et al 2000, Simpson et al 2001, Gerhardt et al 2001). This is not very surprising when one considers that cats with pancreatitis often present with a history of anorexia, lethargy, weight loss or vomiting and display clinicopathological findings such as elevated liver enzymes or hyperbilirubinemia that could easily be attributed to organ dysfunction in the absence of pancreatitis. Even cats with experimentally induced severe pancreatitis exhibit clinical signs and clinicopathological findings that are subtle and non-specific. The situation is further complicated by the observation that serum activities of amylase and lipase are often normal in cats with acute pancreatitis. Antemortem diagnosis currently relies on a high index of clinical suspicion, abdominal ultrasonography (varying hypoechogenicity), measurement of serum trypsin-like immunoreactivity (TLI) and surgical biopsy. The accuracy of this approach is somewhat controversial. TLI appears more sensitive than ultrasound, and was high in 33% to 86% of cats with gross/histologically confirmedpancreatitis (Swift et al 2000, Simpson et al 2001, Gerhardt et al 2001). The specificity of the TLI test could be impacted by azotemia, a complication known to increase TLI in other species, that was present in eight of 21 cats in one study (Gerhardt et al 2001. TLI concentrations may also be markedly and persistently elevated in cats suffering from inflammatory bowel disease or GI lymphoma that have normal pancreatic histology (Swift et al 2000, Simpson et al 2001). It should also be borne in mind that even if a diagnostic test such as TLI were 100% sensitive the low prevalence of pancreatitis would have a marked impact on the positive predictive value and diagnostic accuracy of the test. In this respect the combined application of serological tests and diagnostic imaging may offer better diagnostic accuracy than a single test, eg, the specificity of imaging combined with the sensitivity of TLI may be more accurate than TLI or imaging alone. The application of CE-CT to cats with pancreatitis is a novel aspect of the study of (Gerhardt et al) that held promise for improving the accuracy of non-invasive diagnosis.
Unfortunately the absence of visualisation of the pancreas in eight of 10 cats evaluated with CE-CT suggests that this imaging modality will not be as useful in evaluating cats with pancreatitis as it has been in humans. It seems fair at this time to caution the clinician against basing a diagnosis of acute pancreatitis solely on the results of non-invasive tests.
Given the spectrum of inter-current disease in cats with pancreatitis, a well performed exploratory laparotomy with biopsy of the pancreas, liver, intestines and mesenteric lymph nodes is often required to generate an accurate diagnosis.
The treatment of acute pancreatitis is symptomatic and supportive. Fluid therapy, prolonged anorexia, or feeding, were ineffective in combating pancreatitis in one large series (Hill & Van Winkle 1993). In another only one of five cats with pancreatitis and lipidosis survived (Akol et al 1993). Anorexia is a common finding and early enteral alimentation has enabled survival of some of our cats with pancreatitis. Surgery is indicated in cases of infected pancreatic necrosis, pancreatic abscesses and biliary obstruction. Transient euglycaemia and reduced insulin requirements has been observed after the removal of a pancreatic abscess. The prognosis for acute pancreatitis must always be considered guarded. Where extensive hepatic lipidosis is present or suppurative pancreatitis is diagnosed the prognosis is poor.