Many cats suffer from inflammatory bowel disease (IBD), and it is common for this condition to go untreated for years. Vomiting and diarrhea are never normal, and cats who suffer from one of these signs on a regular basis should be evaluated—even vomiting due to hairballs is not normal. Although hairballs can irritate the stomach, most cats with normal gastrointestinal (GI) tracts will process these and pass them in feces.
Some cats with IBD show neither vomiting nor diarrhea and may only have weight loss symptoms despite a normal appetite. IBD can affect any segment of the GI tract and the clinical signs that ensue depend on what portion of the tract is affected. Vomiting happens when the stomach and the first part of the small intestine is affected while diarrhea results from the colon being involved. When only the middle part of the small intestine is affected it is possible to have weight loss without vomiting or diarrhea.
IBD is an inflammatory condition of the GI tract. There is a complicated relationship between the wall of the intestine, the immune system, the bacteria and other organisms living in the gut (the microbiome). The GI tract serves as both a barrier to invading pathogens (viruses, bacteria, parasites, fungi) and an absorptive organ for all the nutrients. When any part of the complicated relationship breaks down, inflammation can happen. In IBD the inflammatory response tends to be exaggerated and harmful.
A definitive diagnosis of IBD requires a biopsy, but a strong suspicion of the disease can be achieved after all the other common causes of vomiting and diarrhea have been ruled out. Intestinal parasitism and food allergies or intolerances can look like IBD but resolve with appropriate treatment or dietary modification.
Ruling out and treating these conditions is usually the first step in managing chronic vomiting or diarrhea. This usually involves a fecal sample and a trial of a food where the protein source is either new to the cat (has never tasted it before) or is hydrolyzed. Once these have been ruled out, more specific diagnostics are performed, which include specific fasted GI blood panels and ultrasound to look at the stomach, small intestine and colon.
In cats, it is common for IBD to be part of a broader syndrome with concurrent inflammation of the gallbladder and the pancreas, therefore bloodwork and ultrasound are aimed at ruling these out, too. Vitamin B12 deficiency is very common in IBD and this has to be ruled out and corrected before clinical signs can improve. The final step in diagnosis of IBD is a biopsy. This can be achieved through endoscopy or through direct biopsies obtained during exploratory surgery. Although this final step is ideal, some patients will be treated without a definitive confirmation if all the diagnostics point to IBD.
A significant disadvantage of not performing a biopsy is the risk of missing a more serious diagnosis of intestinal lymphoma (or other intestinal cancer). Intestinal lymphoma is unfortunately very common in cats and, just like IBD, tends to affect middle-aged to elderly cats.
Once a diagnosis has been obtained, treatment will depend on severity. Mild cases may respond to dietary modification and management of the microbiome (probiotics). More severe cases will often require the use of immune suppression with corticosteroids (prednisolone) or more powerful medications.
The prognosis for long term management is good in most cases, but lifelong therapy and dietary modification is usually needed. As with most diseases, early diagnosis and treatment usually result in the best outcome, so please make sure to mention any GI signs to your veterinarian. And always remember—normal cats should not vomit.