Logical Approach to Diarrhoea in Dogs and Cats

Comprehensive practice flashcards covering the logical diagnostic approach, classification, aetiologies, and management of small, large, and mixed bowel diarrhoea in canine and feline patients.

Diarrhoea

An alteration in the normal pattern of defaecation characterized by soft, unformed stools, increased faecal water content, and/or an increased frequency of defaecation.

Problem-Based Approach Sequence for Diarrhoea

The clinical reasoning pathway comprising four sequential steps: 1) Define the problem, 2) Define the location, 3) Define the system, and 4) Define the lesion.

Clinical Mimics of Diarrhoea

Non-diarrhoeic conditions that owners frequently confuse with diarrhoea, specifically vaginal discharge, anal sac discharge, and tenesmus associated with constipation.

Acute vs Chronic Diarrhoea

The temporal classification where acute diarrhoea is typically managed symptomatically, whereas chronic diarrhoea requires systematic diagnostic investigation and represents a small proportion of general practice cases.

Small Bowel Diarrhoea

Diarrhoea originating from the small intestine, typically characterized by normal to slightly increased frequency, marked volume, melena, weight loss, vomiting, flatulence, and borborygmus.

Large Bowel Diarrhoea

Diarrhoea originating from the large intestine, typically characterized by markedly increased frequency of defaecation, reduced volume per movement, faecal mucus, haematochezia (fresh blood), and tenesmus without significant weight loss.

Tenesmus

Painful, ineffectual straining to defaecate, serving as a hallmark clinical sign of large bowel irritation or disease.

Secondary Gastrointestinal Disease

Extraintestinal systemic disorders that manifest with signs of small bowel diarrhoea, including hepatic disease, exocrine pancreatic insufficiency, pancreatitis, hyperthyroidism, hypoadrenocorticism (Addison's disease), and renal disease.

Acute Haemorrhagic Diarrhoea Syndrome (AHDS)

A condition (formerly called Haemorrhagic Gastroenteritis or HGE) presenting with sudden-onset vomiting and bloody diarrhoea, characterized by marked haemoconcentration ($\text{increased PCV}$) alongside normal or low total plasma protein, linked to a novel necrotising toxin from Type A Clostridium perfringens.

Visceral Larva Migrans

A zoonotic public health condition caused by human ingestion and tissue migration of roundworm larvae such as Toxocara.

Cutaneous Larva Migrans

A zoonotic skin condition resulting from skin penetration and larval migration of animal hookworms, predominantly Ancylostoma caninum.

Canine Dietary Allergens

The most common food allergens reported to trigger dietary hypersensitivity in dogs: beef, lamb, chicken, and wheat (gluten).

Feline Dietary Allergens

The most common food allergens reported to trigger dietary hypersensitivity in cats: fish, milk, and dairy products.

Cutaneous Manifestations of Food Hypersensitivity

Pruritic skin patterns associated with adverse food reactions: occurring on the feet and axillary region in dogs, and on the face and ears in cats.

Chronic Inflammatory Enteropathy (CIE)

The modern umbrella classification replacing idiopathic inflammatory bowel disease (IBD), subcategorized into diet-responsive, antibiotic-responsive, immunosuppressive-responsive, and non-responsive enteropathies.

Antibiotic-Responsive Enteropathy (ARE)

A small subcategory of chronic enteropathy typically presenting in young, large-breed dogs associated with gut dysbiosis, which may respond to antimicrobials (such as metronidazole or tylosin), probiotics, or increased dietary fibre.

Protein-Losing Enteropathy (PLE)

A clinical syndrome where severe, diffuse small intestinal disease leads to excessive leakage of serum proteins into the gut lumen, causing hypoproteinaemia and secondary complications like ascites, pleural effusion, peripheral oedema, and thromboembolism.

Granulomatous Colitis

A severe form of large bowel disease affecting Boxer dogs and French Bulldogs, caused by mucosal invasion by adherent-invasive Escherichia coli (AIEC).

Tritrichomonas foetus

A protozoal organism that acts as an important cause of chronic, intractable large bowel (and occasionally mixed bowel) diarrhoea in cats.

Giardia Trophozoite

A flagellated, pear-shaped protozoan parasite causing acute, chronic, or mixed bowel diarrhoea in dogs and cats, identifiable on fresh faecal smears.

Trichuris vulpis Ovum

A whipworm egg characterized by a thick, amber shell with symmetrical bipolar plugs, associated with canine large bowel diarrhoea.

Serum Trypsin-Like Immunoreactivity (TLI)

The definitive blood test used to rule in or rule out exocrine pancreatic insufficiency (EPI) in small animal patients with small bowel diarrhoea.

Serum Cobalamin (Vitamin B12)

An essential vitamin absorbed in the ileum; subnormal circulating concentrations serve as a negative prognostic indicator in CIE, indicate distal small bowel involvement or EPI, and cause steroid refractoriness if not supplemented.

Normal Small Intestinal Ultrasound Thickness

Ultrasonographic wall thickness thresholds defining normal bowel anatomy: duodenal wall $< 3\,\text{mm}$ and jejunal/ileal wall $< 2\,\text{mm}$.

Indications for Early Intestinal Biopsy

Clinical triggers to biopsy prior to completing exhaustive dietary or medical trials: hypoproteinaemia, severe intestinal wall thickening/loss of layering, pronounced weight loss, lethargy, hypercalcaemia, hypocobalaminaemia, or suspected neoplasia.