There is a widespread misconception that vomiting in cats is normal. This belief is incorrectly reinforced by those who think that hair balls are often the cause, or that cats have sensitive stomachs or a tendency of being nervous eaters. In reality, vomiting is not normal in cats and warrants investigation — particularly if the animal has a history of vomiting more than 2 times per month or, certainly, if coupled with diarrhea and weight loss.
In addition to small bowel disease, there are several common diseases that can cause vomiting and/or diarrhea in cats including chronic kidney disease and hyperthyroidism. These, along with several others, can be ruled in or out by an initial evaluation that includes a thorough physical examination, bloodwork (CBC, Chemistry profile, T4, SDMA, Urinalysis) and fecal analysis. If a cause for vomiting and/or diarrhea is not pinpointed by those assessments, then the focus should turn to evaluating the GI tract.
Feline chronic small bowel disease primarily encompasses two conditions: chronic inflammatory enteropathy (CIE — previously termed inflammatory bowel disease or IBD) and gastrointestinal lymphoma, and they can be nearly identical in their clinical presentation. Cats with either condition may present with vomiting, weight loss, diarrhea, lethargy, or decreased appetite. Abdominal ultrasound is a valuable next step in the evaluation of patients for small bowel disease, commonly revealing intestinal thickening and lymphadenopathy. While ultrasound is highly effective at localizing disease to the GI tract, it cannot reliably distinguish CIE from lymphoma. Therefore, biopsy is required for definitive diagnosis.
There are two ways to obtain biopsies of the gastrointestinal tract – endoscopically and surgically. Endoscopic biopsies are minimally invasive but limited to superficial samples and restricted regions of the intestine, often missing segmental disease. Obtaining biopsies surgically allows for direct visualization and full-thickness sampling from multiple locations (and lymph nodes), but it is invasive and typically more costly. Submitting samples for histopathology is standard and we know that diagnostic disagreement can occur - what one pathologist calls "enteritis" (inflammatory disease) might be read as "lymphoma" (cancer) by another. Ancillary testing with PCR for antigen receptor rearrangement (PARR) and immunohistochemistry (IHC) significantly improves diagnostic accuracy when evaluating intestinal biospies and, when combined, these techniques greatly enhance diagnostic confidence. One study found that of cats who were initially diagnosed with CIE, approximately 45% were reclassified as lymphoma after IHC and PARR were added into the mix1.
As stated, abdominal ultrasound is very helpful for identifying intestinal thickening associated with both CIE and lymphoma but, if ultrasound and other variables do not strongly support a diagnosis of small bowel disease, one other important condition to consider is chronic pancreatitis. Clinically, cats with chronic pancreatitis can look identical to those with chronic inflammatory enteropathy and gastrointestinal lymphoma. Classic findings such as a scalloped pancreatic margin on abdominal ultrasound are well described but inconsistently observed, meaning a normal ultrasound does not exclude disease. Studies show only fair agreement between ultrasonographic findings and a histopathologic diagnosis of pancreatitis.
Pancreatitis is definitively diagnosed by taking a biopsy — but this is very rarely performed. Laboratory diagnostics can assist in making the diagnosis but they, too, are imperfect. Measurement of feline trypsin-like immunoreactivity (fTLI) is useful for ruling out exocrine pancreatic insufficiency but does not diagnose pancreatitis. For that purpose, feline pancreatic lipase immunoreactivity (fPLI) is the most sensitive and specific test available, with the Spec fPL assay being the most thoroughly validated. However, fPLI results must be interpreted cautiously. Values below 3.5 µg/L make pancreatitis unlikely, values between 3.5 and 5.3 µg/L are equivocal, and values above 5.3 µg/L suggest pancreatitis — but none are definitive. Notably, it's important to bear in mind that renal dysfunction can falsely elevate fPLI, as the marker is cleared by the kidneys. SNAP fPL testing provides a rapid binary result but lacks diagnostic precision. Ultimately, no single test confirms chronic pancreatitis — diagnosis relies on integrating clinical signs, laboratory data, imaging, and exclusion of other diseases.
Learn more about vomiting cats and treating feline CIE, lymphoma, and chronic pancreatitis.
References:
[1] Comprehensive comparison of upper and lower endoscopic small intestinal biopsy in cats wiht chronic enteropathy. J Vet Intern Med. 2021:35:190-198. doi: 10.1111/jvim.16000
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