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Diagnosing chronic small bowel disease in cats

Norsworthy GD, Estep JS, et al. Prevalence and underlying causes of histologic abnormalities in cats suspected to have chronic small bowel disease: 300 cases (2008-2013). J Am Vet Med Assoc. 2015 Sept 15;247(6):629-635.

Among clinical disease scenarios in middle-aged to older cats, chronic small bowel disease associated with vomiting, diarrhea, and weight loss is a common diagnostic challenge shared by veterinarians in practice. The primary causes of chronic small bowel disease are chronic enteritis or enteropathy (number one cause of chronic enteritis is inflammatory bowel disease [IBD]) and lymphoma. The underlying cause of IBD is unknown and diagnosis is often the result of ruling out other known causes of chronic enteritis. IBD can also be associated with inflammation of other nearby organs (pancreas and liver) leading to a disease complex called feline triaditis (chronic enteritis, pancreatitis, and non-suppurative cholangitis).

This study was a retrospective case series at a large feline exclusive practice evaluating the medical records of 300 client-owned cats suspected of having chronic small bowel disease. The median age of the 300 cats was 14 years of age with a slightly larger percentage of male cats versus female cats. The goals of the study were to determine of the prevalence of histologic abnormalities in cats suspected (based on clinical signs and ultrasonographic findings) of having chronic small bowel disease; determine the most common causes in affected cats; and compare methodologies for differentiation of the various underlying causes of the disorder. Veterinary practitioners prefer a less invasive approach to diagnosis. Because less invasive test methodologies evaluating changes in CBC, serum biochemistry analysis, serum activity of S-phase-specific protein TK-1 and histologic differentiation between chronic enteritis and EATL type 2 lymphoma (small cell) can be unclear or ambiguous, more specific information is needed to aid in reaching an accurate diagnosis.

Cats were included in the study if they had compatible clinical signs of vomiting ≥ 3 times/mo for at least 3 consecutive months, small bowel diarrhea of ≥ 3 weeks’ duration, and weight loss of ≥ 0.5 kg (1.1 lb) within the past 6 months. Along with compatible clinical signs, there needed to be ultrasonographic evidence of thickening of the small intestine (ie, intestinal wall thickness ≥ 0.30 in any location or ≥0.28 cm in ≥ 2 locations) and if full-thickness biopsy specimens had been collected from ≥ 3 small intestine sites considered likely abnormal as determined by gross examination of the entire small intestine during exploratory surgery. Biopsy specimens of the small intestine were evaluated by standard histologic methods along with immunohistochemical staining for CD3, CD79a, and CD20. In situations in which the diagnosis was ambiguous following these methods, the specimens were submitted to a university-based laboratory for PCR assay testing for antigen receptor rearrangement. Biopsy specimens were also collected of the pancreas and liver for histologic examination for comparison to the histopathologic results from the small intestine.

The results were significant in that chronic small bowel disease was diagnosed in 288 of the 300 (96%) cats. Of these numbers, the most common diagnoses were chronic enteritis in 150 cats and intestinal lymphoma in 124 cats. Segmental disease was found in 99 (33%) of the cats because ≥ 1 disease process was identified in the biopsy samples of the small intestine. A high percentage (249/300 [83%]) had ultrasonographic evidence of segmental thickening of the small intestine. The authors felt gross inspection of the entire small intestine is important to identify areas appropriately suited to collect the best biopsy specimens.  In addition, their data showed that serum TK activity, serum fPL concentration, serum cobalamin concentration, and results of preoperative CBC and serum biochemistry profiles cannot reliably be used to differentiate chronic enteritis from intestinal lymphoma in cats.

Cats over 14 years of age were 27% (81 cases) of the study cases undergoing exploratory laparotomy. All of the cats in this age group along with the remainder made a full recovery from surgery. The authors recommended some key factors for a good surgical outcome in geriatric cats. These are a preanesthetic workup, multiparameter anesthetic monitoring with special attention to maintaining core body temperature, a safe anesthetic protocol, and minimal surgery time.

To conclude, a high percentage of cats with compatible clinical signs of chronic small bowel disease and ultrasonographic evidence of thickening of the small intestine had histologic abnormalities. While full-thickness biopsy specimens were beneficial in differentiating between chronic enteritis and intestinal lymphoma, such differentiation was not possible with ultrasound examination of the intestines or clinicopathologic testing alone. (VT)

See also:
Jergens AE. Feline idiopathic inflammatory bowel disease: what we know and what remains to be unraveled. J Feline Med Surg. 2012 Jul; 14(7):445-458.