Approach to the horse with weight loss Flashcards
Why is weight loss important?
▪Common clinical challenge
– Potentially involving multiple body systems
– Multiple potential causes
– Often a specific diagnosis is not reached
▪ Emotive
– Weight loss or neglect?
Mechanisms of Weight Loss
Reduced intake
▪Inappropriate feeding, unable to obtain feed, competition for feed,
dental disorders, dysphagia, pain, (gastric disease - has to be quite severe to cause significant weight loss as they usually maintain a decent appetite)
Reduced digestion, absorption or assimilation of nutrients
▪Dental disorders, malabsorption syndromes
▪Liver disease
Increased losses
▪Protein losing enteropathy (or nephropathy, but kidney dz in horses is very rare) ▪Sequestration to body cavity (peritonitis or pleuritis)
Increased requirements
▪Pregnancy, lactate, sepsis, neoplasia, other systemic disease
Reduced intake due to malnutrition
Malnutrition
▪Uncommon in most horses presenting to veterinary surgeons (by
owners)
▪Consider failure to match requirements to intake (pregnancy, lactation)
Reduced intake due to dental disease
▪Dental pain, poor dental function
Reduced intake - causes of anorexia
Pain
▪Gastric disease – post prandial pain (only if severe)
▪Intestinal pain
▪Adhesions – low grade recurrent colic
▪Visceral pain – pleural/peritoneal disease
▪Severe musculoskeletal pain (e.g. laminitis)
Dysphagia
▪Pharyngeal/laryngeal dysfunction (guttural pouch disease)
▪Chronic grass sickness
▪Toxicity - e.g. lead
▪ Botulism - uncommon as don’t tend to feed silage to horses in the UK
Intestinal disease
Malabsorption and protein losing enteropathies
▪Complex range of conditions which lead to reduced energy
uptake
– Parasitic disease – cyathostominosis, (large strongyles)
– Idiopathic
– Infiltrative bowel disease -> inflammation or neoplastic infiltrates
▪May also cause chronic diarrhoea
– Primary large colon dysfunction
– Abnormal energy substrates to hind gut flora
– Requires extensive pathology
Clinical approach
History
▪Rule out obvious causes
▪Diet, parasites
Clinical Examination
▪BCS – genuine weight loss
▪ Oedema
▪ Fever
▪Oral/dental examination
▪Jaundice (extremely rare clinical sign)
Rectal examination
Laboratory Testing
Targeted
▪Liver, renal, inflammation (acute phase proteins)
If the first set of bloods don’t give you a diagnosis, repeating the same tests more than once more rarely will
▪Reference ranges are calculated to include 95% of the normal population – i.e. in any given horse, 1 in 20 results will be “abnormal”
Abdominocentesis
Faecal worm egg count
- good to rule it out
- Tapeworms don’t produce the same type of eggs so it’s more difficult to assess their burden
Hematology and Biochemistry
▪ Often non-specific signs ▪ Increased WBC
▪ Neutrophilia
– Horses generally have neutrophilia associated with parasite infection, cf other species & eosinophilia
▪ Eosinophilia
– Sometimes seen in parasite infestation
– Generalised inflammation
▪ Anaemia
– Often ‘anaemia of chronic disease’ i.e. mild
– Breed specific reference ranges
-> Cold blooded horses e.g. cobs, ponies, will have naturally lower PCV than e.g. TBs
▪ Acute inflammatory markers
– SAA
– Fibrinogen
-> SAA much more acute
-> Lag with fibrinogen ~48h after initiation of inflammation
▪ Liver enzymes
Interpretation of serum proteins - total protein
▪Decreases may be masked by concurrent hypovolaemia ▪Hyperproteinaemia usually due to hyperglobulinaemia
Interpretation of serum proteins - Hypoalbuminaemia
▪ Extremely rare and assume it’s a lab error until proven otherwise
▪GI loss far more common than renal
▪Effusions – peritoneal/pleural
▪Liver disease – rarely a cause
-> End stage liver disease exception for cause of hypoalbuminaemia - cirrhosis, marked reduction in liver function
-> But in this case there would usually be many other signs (other than low protein/albumin) that there’s severe liver dz
Interpretation of serum proteins - Hypoglobulinaemia
▪GI loss
▪Could also occur due to severe kidney damage/loss
Interpretation of serum proteins - Hyperglobulinaemia
▪(Chronic) inflammatory disease (including cyathostominosis)
▪ Neoplasia
Interpretation of serum proteins - Hyperfibrinogenaemia
▪ Infection
▪ Inflammation
▪ Neoplasia
Interpretation of serum proteins (acute phase proteins)
Serum amyloid A
Serum Protein Electrophoresis ▪Sensitivity 45%, Specificity 63%
alpha
▪ infection, inflammation, neoplasia (acute phase proteins)
beta
▪ parasitism, chronic infection, neoplasia (C reactive protein)
▪ gamma - polyclonal
▪ chronic infection, abscesses, neoplasia
monoclonal
▪ tumours of the reticuloendothelial system
Oral Glucose Absorption Test
▪With-hold food overnight
▪1g/kg in a 10-20% solution administered by nasogastric tube
▪Keep horse calm
▪Looking for partial or complete malabsorption
Normal
– looking for the blood glucose to double, or increase by 80%, in the last 90mins-2h
Problems with the oral glucose absorption test
▪Does not only assess small intestinal function
–Small amount of glucose absorbed in large intestine
– D-xylose absorption test more reliable
-> Expensive
-> Not available
▪Partial malabsorption (25-80%)
▪Delayed flat curve
– Delayed gastric emptying -> less of a dramatic upwards spike in the curve
– Poorly starved
– Food in the stomach delays glucose exit from the stomach
What to look for on intestinal US
▪Wall thickness
– SI wall should be ~3mm thick
– Large colon should be ~3-4mm thick
▪Lumen diameter
– Although normally look at this for colic cases rather than weight loss cases
▪ Motility
▪ Anatomy
GI Biopsies
▪ Duodenal biopsy (transendoscopic)
– only get the surface, so no deep pathology will be found
▪ Rectal mucosal biopsy
Rectal mucosal biopsy
▪Uterine biopsy forceps
▪Relies on extensive pathology
▪Rectal eosinophils very common
– Eosinophiliic proctitis
▪Easy to perform
▪20 - 30 cm inside rectum
– still recto-peritoneal i.e. not in the peritoneal cavity, therefore risk of seeding infection into the peritoneum are much lower
▪Small piece of mucosa from 10-2 o’clock position
▪Submit for histology NSAID
– Flunixin meglumine
– Give as causes irritation in the area and don’t want the horse to strain
Surgery for biopsies
▪Midline exploratory celiotomy
▪Flank laparotomy
▪ Laparoscopy
▪Expensive and require significant time off
Laparotomy
▪Multiple intestinal biopsies can be obtained
▪Whole intestinal tract can be examined
▪Segmental disease such as focal eosinophilic IBD
can be resected and removed
Common causes of weight loss
- inadequate nutrition
- dental problems
- parasitic
- IBD
- liver disease
Less common causes of weight loss
- peritonitis
- chronic grass sickness
- neoplasia
Initial diagnostic approach
- PE
- haematology and biochemistry
- US exam
- peritoneal fluid analysis
- OGAT
- assessment to response to non-specific therapy
Further diagnostic options
- laparoscopy
- laparotomy
(scintigraphy)
Why can IBD cause malabsorption?
- thickening -> increases the barrier between the intestinal lumen and the blood, so nutrients have further to travel to be absorbed into the blood.
Most common intestinal neoplasia
- lymphoma
What does oedema often follow?
- hypoalbuminaemia
An example of a GI condition where the horse may be pyrexic
- colitis
Why can jaundice potentially be a sign of weight loss
- can be an indication of liver disease or that it hasn’t eaten for several days
- No bile duct so no storage of bile, if become inappetent they can become jaundice, e.g. 3d of inappetence.
Why do an abdominocentesis?
- looking for evidence of neoplastic cells, inflammation, infection, peritonitis (protein in there)
