Approach to Chronic Vomiting and Diarrhoea in the Cat
World Small Animal Veterinary Association World Congress Proceedings, 2015
A. Harvey, BVSc, DSAM (Feline), DECVIM-CA, MRCVS, MANZCVS (Assoc)
Small Animal Specialist Hospital, Sydney, NSW, Australia

There are many fundamental points in clinical decision making, which apply to the approach of all clinical cases. The focus of this session will be on vomiting and diarrhea, using several case examples to illustrate important points in clinical decision making.

Before starting to think about an individual case, it is well worthwhile taking a moment to reflect on your approach to cases. We should all have a logical systematic approach to every case.

 How do you think logically through a case?

 How do you make diagnostic and therapeutic decisions?

 Do you have a systematic approach that would lead you to make the same decisions on a case whether you saw it Monday morning or Saturday afternoon, when you were feeling happy or sad?

 How do you gather and process the information and put it all together?

Broadly and simplistically speaking, there are two different ways of approaching a clinical case to reach a diagnosis:

 Problem solving; where a list of differential diagnoses are made for each clinical problem, with each differential gradually ruled in or out with diagnostic tests.

 Pattern recognition; where the pattern of the signalment, combination of clinical signs and other clinical findings, particularly fit with one differential diagnosis, and this differential is then focused on.

The best clinicians combine both ways of thinking and move back and forth between the two when 'working up' a case.

I like to always start with a complete list of differential diagnoses, of groups of diseases. And then assess the complete picture of signalment, history, physical examination, laboratory and imaging data to try to refine those differentials, and then move your thoughts from the more general to more specific diseases. If results of investigations don't fit with your top differentials, then move back to your differential diagnosis list and see what you may have missed.

Differential Diagnoses

Chronic vomiting differentials:

 Extra-intestinal

 Pancreatic disease - pancreatitis, EPI

 Renal disease

 Liver disease

 Hyperthyroidism

 Environmental factors

 Intestinal

 Infectious

 Helicobacter

 Inflammatory

 Diffuse (e.g., IBD)

 Focal; granuloma (e.g., FIP, eosinophilic sclerosing fibroplasia)

 Neoplastic

 Diffuse (e.g., LGAL)

 Focal (e.g., lymphoma, adenocarcinoma, mast cell tumour)

 Partial obstruction

 Foreign body

 Intussusception

 Extra-intestinal compression

Chronic diarrhea differential diagnoses:

 Extra-intestinal

 Pancreatic disease - pancreatitis, EPI

 Hyperthyroidism

 Environmental factors

 Intestinal

 Infectious

 Parasitic

 Protozoal

 Giardia

 Tritrichomonas

 Coccidial

 Isospora

 Cryptosporidia

 Bacterial

 Campylobacter

 Clostridia

 Viral

Syndromes involving FeLV, FIV, coronavirus

 Inflammatory

 Diffuse (e.g., IBD)

 Focal; granuloma (e.g., FIP, eosinophilic sclerosing fibroplasia)

 Neoplastic

 Diffuse (e.g., LGAL)

 Focal (e.g., lymphoma, adenocarcinoma, mast cell tumour)

 Partial obstruction

 Foreign body

 Intussusception

 Extra-intestinal compression

Assess the Clinical Picture

Signalment

 Young animals are more susceptible to dietary and infectious causes, and more likely to ingest foreign bodies

 Older animals are more susceptible to systemic disease and neoplasia

 Purebreds are more susceptible to some diseases like Tritrichomonas and FIP

History

 Previous clinical signs or diagnosed disorders

 Chronicity of signs

 Environmental conditions, including overcrowding and immune compromise increase the risk of infectious causes

 Other affected animals in the household

 Large or small intestinal diarrhoea

 Vomiting and diarrhoea or just one or the other

 Normal/increased/decreased appetite

 Presence of weight loss

Physical examination

 Demeanor

 Vital parameters

 Body condition

 Coat condition

 Hydration

 Presence of icterus

 Presence of goitre

 Abdominal discomfort

 Palpable abdominal abnormalities

At this stage, you should summarise the key features of the case. For example,

 Chronic large intestinal diarrhoea

 Otherwise well, no exam abnormalities

 Very young cat

 Pedigree

Use pattern recognition to then think which differential diagnoses are most likely - think about the clinical clues. What is most likely given:

 Signalment

 History

 Physical exam

Can you narrow down differentials & prioritise?

Next step: further investigation? Or treatment trial? What investigation or treatment?

In the above example, the key features would make infectious disease most likely. If we then move from the 'general' to the 'specific', most likely differential diagnoses would be Giardia and Tritrichomonas foetus. This would lead us to faecal testing for these organisms, and perhaps a trial treatment for Giardia and dietary trial pending results.

If further diagnostics are then performed, this step of evaluating the clinical clues in light of the whole clinical picture, before deciding on the next step, should be performed after each diagnostic.

What are the Next Diagnostic Options?

Further diagnostic options are similar for both chronic vomiting and diarrhoea, with the addition of faecal tests in cases of diarrhoea.

 Faecal parasitology

 Faecal culture

 Giardia

 ZnSO4 flotation

 ELISA

 PCR

 Tritrichomonas foetus

 Rectal swab wet prep

 Special culture

 PCR

 Haematology/biochemistry/T4

 B12/folate/TLI/fPL

 FeLV/FIV

 Abdominal radiographs

 Abdominal ultrasound

 Gastrointestinal biopsies

 Surgical vs. endoscopic

At each diagnostic test, think about what you are looking for before performing the test. For example, with abdominal ultrasound:

 Intestine - presence of a mass, wall thickness, loss of layering

 Liver - size, echogenicity, gall bladder contents and wall, bile duct diameter

 Pancreas - presence of irregular margin, increased size, hypoechogenicity, cavitary lesions, hyperechoic mesentery & peripancreatic fat, pancreatic duct dilation, ileus

 Mesenteric lymphadenopathy, free fluid

There are a couple of rules used in human medicine that can help to keep a logical approach when performing diagnostics:

 Simpson's rule = Only perform a test if the outcome of that test will change your management of the case

 Suttons's law = Always perform the test first that is most likely to give you the diagnosis

Both these rules emphasize the importance of thinking carefully before performing diagnostics, thinking about what differential diagnoses are most likely, and what the outcome of performing each diagnostic may be.

The final step is to think: "Does everything fit together?"

Are the signalment, history, clinical signs typical of what you are considering the most likely differential diagnosis?

If the outcome either of a treatment trial or diagnostic tests does not fit with your most likely differential diagnoses, then revisit your master list of differential diagnoses to see what you may have missed.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Andrea Harvey, BVSc, DSAM (Feline), DECVIM-CA, MRCVS, MANZCVS (Assoc)
Small Animal Specialist Hospital
Sydney, NSW, Australia


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