It is helpful to determine whether the clinical signs indicate large bowel or small bowel diarrhea as this may help focus your differential diagnoses list and diagnostic plan. For example, a patient with small bowel diarrhea is more likely to also have signs of systemic illness, whereas diseases that result in large bowel diarrhea are more likely to produce signs localized to the intestinal tract (e.g. ulcerative colitis).
Further questioning reveals that Tupper has not lost weight, but he sometimes has episodes of vomiting when the diarrhea occurs. The owners have not noticed blood or mucus in the stool, but they report it is watery and increased in volume. The current episode of diarrhea started about two days ago, and Tupper has not eaten since then.
Physical examination findings:
Your problem list for Tupper includes:
Based on his history, it appears that his primary problem is diarrhea, and you suspect that the vomiting, abdominal discomfort, and anorexia are related to the underlying cause. Given the chronicity of his signs and his age, a rational approach may be to start with a CBC and serum chemistry profile to look for metabolic problems (i.e. renal or hepatic disease) or abnormalities that may point to protein-losing enteropathy or hypoadrenocorticism. Because of Tupper’s discomfort on abdominal palpation, abdominal radiography would also be appropriate to check for evidence of organomegaly, a mass, obstruction, or pancreatic disease.
In any case of diarrhea, it is always a good idea to perform a direct fecal smear with saline to look for fungal or protozoal organisms, changes in bacterial ratios, or abundant inflammatory cells. Centrifugal fecal flotation should also be performed to rule out intestinal parasitism.