7.1.1: Approach to the horse with weight loss Flashcards
Mechanisms of weight loss
- Reduced intake e.g. inappropriate feeding, dental disorders, pain
- Reduced digestion/absorption e.g. dental disorders, liver disease
- Increased losses e.g PLE/PLN, sequestration to body cavity (peritonitis, pleuritis; often effusions are high protein)
- Increased requirements e.g. pregnancy, lactation, sepsis, neoplasia, other systemic disease
True/false: gastric disease can cause post-prandial pain.
True
but only if the gastric disease is severe
Which of the following might produce low grade, recurrent colic signs?
a) lead toxicity
b) abdominal adhesions
c) botulism
b) abdominal adhesions
True/false: botulism in horses is uncommon in the UK compared to other countries, because here we don’t tend to feed horses silage.
True
What are some possible diseases that could cause dysphagia?
- Pharyngeal/laryngeal dysfunction caused by guttural pouch disease or strangles
- Chronic grass sickness
- Toxicity e.g. lead toxicity
- Botulism
How should you approach a case of weight loss?
- Take a history and rule out obvious causes e.g. inappropriate diet, parasites
- Clinical exam: check if weight loss/muscle disease, check for oedema, fever, jaundice, oral/dental exam
- Rectal exam: check for abdominal mass, neoplasia, chronic intestinal lesion, some parasites (may see larvae on glove when remove)
If a horse has jaundice, what does this tell you?
Jaundice in horses indicates:
* Liver disease
* Several days of inappetance (horses have no gallbladder)
When examining a horse with weight loss, you check for oedema. Why?
- Oedema is often connected to hypoalbuminaemia/suggests protein loss
When might you see neutrophilia in horses?
Parasite infestations
When might you see eosinophilia in horses?
- Somtimes in parasite infestations
- Generalised inflammation
When assessing anaemia in horses, what should you take into account?
Different breeds have different reference ranges -> coldbloods naturally have lower PCV than TBs
e.g. 28-32% may be normal for a Cob/pony
Normal PCV horse
37-42%
What markers of inflammation could you assess in a horse?
- SAA - increases very quickly with inflammation
- Acute phase proteins
- Fibrinogen - increases about 48hrs after initiation of inflammation
Why might low total protein be difficult to detect in some circumstances?
- Decreases in total protein may be masked by concurrent hypovolaemia e.g. with diarrhoea
- We may only notice when we rehydrate the horse
Why might total protein be elevated?
- Hyperproteinaemia is usually due to hyperglobulinaemia
What are the common causes of hypoalbuminaemia?
- GI loss is far more common than renal (i.e. PLE > PLN)
- Effusions cause loss of protein into pleural cavity/peritoneal cavity
- Liver disease can cause hypoalbuminaemia, but this is rarely the case unless end-stage/v severe liver disease
What could cause hypoglobulinaemia?
GI loss
What could cause hyperglobulinaemia?
- (Chronic) inflammatory disease inc. cyathostominosis
- Neoplasia
What could cause hyperfibrinogenaemia?
- Infection
- Inflammation
- Neoplasia
What is serum amyloid A?
An acute phase protein that increases very quickly with inflammation.
Describe the test pictured here, referencing the expected normal results and those indicative of pathology
X axis - time (mins)
Y axis - glucose
Oral glucose absorption test
* Withhold food overnight
* 1g/kg in a 10-20% solution of glucose/dextrose given by NG tube
* Keep horse calm -> stress can impair result
* Expect glucose to double/increase by 90% in 2 hrs, then decrease as insulin starts to take effect
* Depending on the degree of intestinal dysfunction, may see partial or complete malabsorption
What does the green line indicate?
Complete malabsorption
There is no change in the level of glucose which means there is severe intestinal disease.
What are the limitations of the oral glucose absorption test?
- Does not only assess small intestinal function; small amount of glucose absorbed in the large intestine
- Starving the horse delays gastric emptying, however the slower the glucose trickles into the small intestine, the flatter the curve (sometimes this can be confusing)
- Poorly starving the horse affects the results
- D-xylose absorption test is more reliable but expensive and not widely available
What could we assess using intestinal ultrasonography?
- Wall thickness
- Lumen diameter (this is more typically done in colic than weight loss cases)
- Motility
- Anatomy
Left image shows marked thickening of small intestine.
Right image shows thickening of right dorsal colon - this is right dorsal colitis secondary to NSAID administration.
Describe how to take a rectal biopsy, include which drugs you would give the horse
- Use same instrument as for mare uterine biopsy
- 20-30cm inside rectum - no further, we want to stay outside the peritoneal cavity as this means the risk of seeding infection to peritoneum much less
- Pull mucosa away from the wall (you can’t take full thickness biopsies here) at 10-2 o’clock position
- Submit for histology
- Drugs: provide NSAIDs to prevent irritation and horse straining. Don’t usually need to give antibiotics.
Rectal biopsy will provide a diagnosis in approximately what percentage of cases?
a) 10%
b) 25%
c) 50%
d) 75%
c) 50%
A normal biopsy result does not mean disease can be ruled out
What are the advantages and disadvantages of laparotomy for diagnosis and in some cases treatment?
✅ Multiple intestinal biopsies can be obtained
✅ Whole intestinal tract can be examined
✅ Segmental disease e.g. focal eosinophilic IBD can be resected and removed
❌ GA (midline) or standing sedation (flank or laparoscopically)
❌ Requires much time off: 4-6 weeks box rest, 6 months before working again if midline
Very useful diagnostically but hard to convince owners to do.
