amounts of undigested fat are present. A yellow‐green coloration is common and due to malabsorbed bile salts.
Diarrhoea can be due to primary disorders of the small bowel and/or large bowel or due to other systemic, secondary GI disorders such as hepatic disease, exocrine pancreatic insufficiency, pancreatitis, hyperthyroidism or hypoadrenocorticism. As discussed earlier, large bowel diarrhoea is almost always due to primary GI disease, whereas small bowel diarrhoea may occur with either primary or secondary GI disease.
Severe systemic diseases such as sepsis and uraemia can cause large bowel diarrhoea, but this will be a very minor clinical sign in relation to the patient’s other systemic clinical signs. Thus, secondary disorders are not usually likely differentials when considering the work‐up of a patient whose primary problem is large bowel diarrhoea.
Diarrhoea due to primary GI disease is more common than diarrhoea due to secondary GI disease. In animals with secondary GI disease, with the exception of exocrine pancreatic insufficiency and some dogs with hypoadrenocorticism, diarrhoea is not usually the primary presenting complaint.
The following tables summarise the causes of acute and chronic small and large bowel diarrhoea (Tables 4.2–4.4).
Table 4.2 Causes of acute small bowel diarrhoea in dogs and cats.
| Cause | Examples | Comments |
|---|---|---|
| Diet related | Overeating (especially puppies)Dietary changeSpoiled foodDietary indiscretion | Including change to food that causes allergy/hypersensitivity. |
| Parasites/protozoa | ParasitesMost commonly ascarids (Toxocara and Toxascaris spp., also hookworms Ancylostoma and Uncinaria spp.) Protozoa Giardia spp.Coccidia, for example Cystisospora spp. (formerly called Isospora)Cryptosporidium spp. | Zinc sulphate flotation is a sensitive test for Giardia cysts, provided three faecal samples collected over 5 days are examined (∼95% sensitive).The ELISA test can identify Giardia antigen in faeces. The test is reported to be about 90% sensitive and is probably more sensitive than performing zinc sulphate flotation examination on a single faecal sample.Faecal IFA and PCR are also available.A negative result does not necessarily exclude Giardia infection, and some clinicians will treat with metronidazole or fenbendazole regardless and proceed with further investigations only if the diarrhoea persists. |
| Infection (bacterial/viral) | Viral enteritisParvovirus/panleukopeniaCoronavirusDistemperFeline immunodeficiency virus (FIV)/Feline leukaemia virus (FeLV)Other viruses (e.g. adenovirus, norovirus, torovirus)Bacterial enteritisCampylobacter spp.Salmonella spp.E. coliClostridium spp. | Microbial culture of faeces is often unrewarding due to the abundant normal flora in the gut and the predominance of anaerobes.E. coli is frequently, and Salmonella is sometimes, isolated from faeces of normal animals, and therefore their presence does not necessarily imply that they are the cause of the diarrhoea. Campylobacter spp. and Clostridium spp. are also found in animals with and without diarrhoea, which makes interpretation of results quite difficult.Clostridium perfringens and Clostridium difficile have equal prevalence in dogs with and without diarrhoea. However, there is a correlation between the presence of diarrhoea and the detection of toxins that are produced by these bacteria, although enterotoxin can also be found in healthy dogs.Identification of an overgrowth of Clostridia or Clostridial spores on faecal smears means nothing diagnostically and will occur in many situations when gut flora is disturbed by a variety of GI disorders. |
| Toxins | ToxinsLeadOrganophosphatesPlants *Ingestion of many toxins can cause acute diarrhoea sometimes in combination with other systemic signs | Plants that may cause diarrhoea if ingested (as well as other clinical signs) include:Lily of the valleyDaffodil bulbsAloe veraAsparagus fernChrysanthemumsCyclamens. |
| Unknown | Acute haemorrhagic diarrhoea syndrome (AHDS) | Previously called haemorrhagic gastroenteritis (HGE). This is a syndrome causing acute onset of vomiting and bloody diarrhoea.Characteristically the patient will have significant haemoconcentration (increased packed cell volume [PCV]) with a normal or low plasma protein due to protein loss into the bowel. It is typically described in small breed dogs but any size/breed can be affected.It is now believed that the cause may be novel necrotising toxin produced by Type A Clostridia perfringens.However, antimicrobial therapy does not improve outcome unless the patient is septic. |
| Secondary GI disease | Acute pancreatitisSevere systemic disease | See previous comments regarding presence of other clinical signs. |
Table
