A. Baseline investigations

The history and clinical examination are particularly important as they may indicate systemic or metabolic disease, and may suggest specific dietary sensitivity. Weight loss may be indicative of malabsorption (pancreatic insufficiency or small intestinal disease) or protein-losing enteropathy, but may also be due to anorexia, vomiting or extra-gastrointestinal disease.

In animals that are losing weight and have a normal or increased appetite, it is important to consider pancreatic insufficiency and small intestinal disease once systemic diseases have been excluded – particularly hyperthyroidism in the cat – even if there is no vomiting or diarrhoea in the history.

Features of diarrhoea may help distinguish between small and large intestine disease:

Clinical SignsSmall IntestineLarge Intestine
volumeincreased > 3 timesincreased 1-3 times
frequency3-5 times/day>5 times
Weight losssometimesrare

Haematology and serum biochemistry help exclude systemic and metabolic diseases. Findings that may contribute to subsequent investigations of intestinal disease include eosinophilia, perhaps reflecting parasitism or eosinophilic gastroenteritis, neutrophilia in inflammatory disease (IBD), lymphopaenia in immunodeficiency, stress or lymphangiectasia, and panhypoproteinemia in protein-losing enteropathy. A regenerative microcytic anaemia may be indicative of chronic blood loss and Fe deficiency due to ulceration associated with parasites, IBD or neoplasia. Additional blood tests in cats include T4 to diagnose / exclude hyperthyroidism, and assay of FeLV and FIV status.

Faecal examination should focus on intestinal parasites (eg Giardia, coccidia, hookworms and whipworms) and potentially pathogenic bacteria (eg Salmonella, Campylobacter and pathogenic E.coli).

Abdominal imaging (ultrasonography and/or radiography) may be helpful if neoplasia or partial obstruction are suspected.

B. Specialised investigations

Serum trypsin-like immunoreactivity (cTLI in dogs, fTLI in cats) provides a sensitive and specific test for exocrine pancreatic insufficiency. These assays quantify trypsinogen that normally leaks from the pancreas into the blood, and hence provide an indirect assessment of functional pancreatic tissue. In animals with EPI, functional exocrine tissue is severely depleted and hence serum TLI concentrations are extremely low. These assays also detect trypsin specifically released during inflammation of the pancreas and can be used to detect pancreatitis in dogs and cats.

Serum folate and cobalamin (vitamin B12) provide useful information that can contribute to the diagnosis of small intestinal disease in dogs and cats, reduced concentrations being suggestive of damage to the sites for the normal absorption of these vitamins, or the presence of small intestinal bacterial overgrowth.

Investigation of intestinal permeability is a new and extremely sensitive technique to detect and manage small intestinal disease in dogs. This involves oral administration of a sugar solution containing lactulose and rhamnose, and the analysis of a single blood sample taken 2 hours later.

Visualisation and biopsy of the gastrointestinal tract for histopathology by endoscopy or at laparotomy may appear to be a definitive diagnostic step. However, frequently findings are negative or equivocal, particularly with suspected intestinal disease, and it is advisable generally to consider at least baseline investigations first to avoid an unnecessary procedure. In some cases, changes including inflammation, ulceration, and neoplasia may be described, but descriptions such as “inflammatory bowel disease” do not identify the underlying cause although they can direct an approach to treatment.