Clinical Reasoning in Veterinary Practice. Группа авторов

be reduced or less severe in patients fed a high‐fibre diet.

      8 If all the above fails or if the patient is hypoproteinaemic or significantly underweight or if neoplasia is suspected on physical examination or imaging, biopsy is indicated.Endoscopic biopsy is preferred if appropriate expertise and facilities are available.Whilst there are some limitations with this technique, surgical biopsy may be overly invasive for many cats and dogs with chronic diarrhoea.Exploratory laparotomy may be required:If endoscopic equipment and expertise are not availableDiagnostics have indicated that the disease is a focal lesion that may be unreachable with an endoscope, for example, a jejunal mass.If possible, consult a medicine specialist prior to biopsy if you are unsure.

      9 If biopsy is not an option for cost reasons or lack of access to appropriate facilities/expertise, following careful client discussion of the risks of misdiagnosis and inappropriate treatment…Treat with prednisolone 2‐3 mg/kg once daily and observe response.Large dogs should have no more than 40 mg/m2 once daily.If good response is seen, taper the prednisolone dose by 20–25% every 4 weeks.Consider a second immunosuppressive drug (e.g. azathioprine, ciclosporin, chlorambucil, mycophenolate or leflunomide) if steroid side effects are moderate to severe to allow more rapid tapering of prednisolone. Chlorambucil or ciclosporin are the most commonly used second‐line drugs in cats.

      Summary

      Acute and chronic diarrhoea are common clinical signs in small animal practice. Cats and dogs with mild chronic diarrhoea can usually undergo dietary or anthelmintic trials before costly investigation. Further investigation may be appropriate due to the severity of diarrhoea, concurrent clinical signs such as weight loss or a lack of response to therapeutic trials.

      Clinical pathology is frequently normal in dogs and cats with diarrhoea, but it is an important step during investigation to rule out non‐GI disorders.

      Intestinal biopsy is usually the final step during investigation of diarrhoea and is not necessary in many cases. Inflammatory change on intestinal biopsy is non‐specific and may be seen in FRE, ARD and IRE. Treatment trials are still required to differentiate between these causes.

      Key points

      As a result of reading this chapter you should be able to:

       Recognise the importance of differentiating small and large bowel diarrhoea

       Develop a rational approach to the investigation of small bowel diarrhoea

       Develop a rational approach to the investigation of large bowel diarrhoea

       Identify the causes of small bowel diarrhoea

       Identify the causes of large bowel diarrhoea

       Differentiate when symptomatic therapy vs. a diagnostic work‐up is indicated

       Understand how to perform a dietary trial properly.

      Questions for review

       Compare and contrast the characteristics of small and large bowel diarrhoea.

       List at least five causes of acute small bowel diarrhoea.

       List at least five causes of chronic small bowel diarrhoea.

       List at least five causes of large bowel diarrhoea.

       When is faecal bacterial culture indicated?

       How should a dietary trial should be performed?

       When is intestinal biopsy indicated in cases of chronic diarrhoea?

      Case example

      ‘Colin’ is a 10‐month‐old male neutered British shorthair cat. He presents with a 3‐month history of waxing and waning diarrhoea. He is otherwise lively and well, and his appetite is normal. Vomiting has not been observed. Diarrhoea is semi‐formed to liquid, passed frequently in small volumes, sometimes with tenesmus. Mucus and blood are occasionally seen.

      Colin is an indoor‐only cat and is up to date with routine vaccinations and parasite control. He is fed a commercial balanced diet suitable for his age. He was rehomed from a multi‐cat household, and his previous owner reported that some of the other cats had suffered with diarrhoea in the past.

      Physical examination is unremarkable. Colin is in good body condition and palpation of his abdomen is normal.

      Define the problem

      Colin has semi‐formed to liquid faeces passed in small volumes, frequently. This is compatible with diarrhoea, and this cannot be easily confused with anything else.

      Define the location

      When the problem is diarrhoea, we define the location first, as this helps us to confirm the affected body system. Colin has semi‐formed to liquid faeces, increased frequency of defaecation, small faecal volume, tenesmus, mucus and blood. These are all seen with large bowel diarrhoea.

      Define the system

      Colin has large bowel diarrhoea with no signs of small bowel diarrhoea (e.g. weight loss, appetite changes). It is therefore very likely that Colin has a primary GI cause of his diarrhoea.

      Define the lesion

      Large bowel diarrhoea in young cats is most commonly caused by parasitic or protozoal infection. Feline infectious peritonitis and food‐responsive enteropathy are other possible differentials in this age group. Neoplasia is less likely, although lymphoma can sometimes affect cats under a year of age.

      Case outcome

      Colin’s diarrhoea did not improve during a properly performed diet trial of a ‘novel’ protein‐source diet. His owners had a limited budget and were keen to perform a step‐by‐step investigation of his diarrhoea. Faecal testing was performed initially due to the increased chance of infectious diarrhoea at his age and also with the knowledge that he was originally from a multi‐cat household where other cats have had diarrhoea in the past.

      Faecal parasitology, Zn sulphate flotation for Giardia cysts and Tritrichomonas PCR were performed. Only the Tritrichomonas PCR was positive.

      Treatment was discussed with Colin’s owners. Some cats with Tritrichomonas infection do not require treatment if their diarrhoea is relatively mild as the disease usually resolves over time. However, resolution may take many months, and cats may continue to excrete the organism even once diarrhoea has resolved. Colin’s owners were keen to treat him, and he was given ronidazole at a dose of 25 mg/kg once daily for 2 weeks. His diarrhoea resolved and did not recur.

      Ronidazole should be used with caution and with informed owner consent as it may cause neurological and GI side effects. It is not licensed in most small animal markets and may not be readily available in formulations suitable for cats without the use of a licensed compounding pharmacy.