7.1.1: Approach to the horse with weight loss

Question 1

Mechanisms of weight loss

Answer 1

• 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

Question 2

True/false: gastric disease can cause post-prandial pain.

Answer 2

True
but only if the gastric disease is severe

Question 3

Which of the following might produce low grade, recurrent colic signs?
a) lead toxicity
b) abdominal adhesions
c) botulism

Answer 3

b) abdominal adhesions

Question 4

True/false: botulism in horses is uncommon in the UK compared to other countries, because here we don’t tend to feed horses silage.

Answer 4

True

Question 5

What are some possible diseases that could cause dysphagia?

Answer 5

• Pharyngeal/laryngeal dysfunction caused by guttural pouch disease or strangles
• Chronic grass sickness
• Toxicity e.g. lead toxicity
• Botulism

Question 6

How should you approach a case of weight loss?

Answer 6

• 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)

Question 7

If a horse has jaundice, what does this tell you?

Answer 7

Jaundice in horses indicates:
* Liver disease
* Several days of inappetance (horses have no gallbladder)

Question 8

When examining a horse with weight loss, you check for oedema. Why?

Answer 8

• Oedema is often connected to hypoalbuminaemia/suggests protein loss

Question 9

When might you see neutrophilia in horses?

Answer 9

Parasite infestations

Question 10

When might you see eosinophilia in horses?

Answer 10

• Somtimes in parasite infestations
• Generalised inflammation

Question 11

When assessing anaemia in horses, what should you take into account?

Answer 11

Different breeds have different reference ranges -> coldbloods naturally have lower PCV than TBs
e.g. 28-32% may be normal for a Cob/pony

Question 12

Normal PCV horse

Answer 12

37-42%

Question 13

What markers of inflammation could you assess in a horse?

Answer 13

• SAA - increases very quickly with inflammation
• Acute phase proteins
• Fibrinogen - increases about 48hrs after initiation of inflammation

Question 14

Why might low total protein be difficult to detect in some circumstances?

Answer 14

• Decreases in total protein may be masked by concurrent hypovolaemia e.g. with diarrhoea
• We may only notice when we rehydrate the horse

Question 15

Why might total protein be elevated?

Answer 15

• Hyperproteinaemia is usually due to hyperglobulinaemia

Question 16

What are the common causes of hypoalbuminaemia?

Answer 16

• 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

Question 17

What could cause hypoglobulinaemia?

Answer 17

GI loss

Question 18

What could cause hyperglobulinaemia?

Answer 18

• (Chronic) inflammatory disease inc. cyathostominosis
• Neoplasia

Question 19

What could cause hyperfibrinogenaemia?

Answer 19

• Infection
• Inflammation
• Neoplasia

Question 20

What is serum amyloid A?

Answer 20

An acute phase protein that increases very quickly with inflammation.

Question 21

Describe the test pictured here, referencing the expected normal results and those indicative of pathology
X axis - time (mins)
Y axis - glucose

Answer 21

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

Question 22

What does the green line indicate?

Answer 22

Complete malabsorption
There is no change in the level of glucose which means there is severe intestinal disease.

Question 23

What are the limitations of the oral glucose absorption test?

Answer 23

• 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

Question 24

What could we assess using intestinal ultrasonography?

Answer 24

• 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.

Question 25

Describe how to take a rectal biopsy, include which drugs you would give the horse

Answer 25

• 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.

Question 26

Rectal biopsy will provide a diagnosis in approximately what percentage of cases?
a) 10%
b) 25%
c) 50%
d) 75%

Answer 26

c) 50%
A normal biopsy result does not mean disease can be ruled out

Question 27

What are the advantages and disadvantages of laparotomy for diagnosis and in some cases treatment?

Answer 27

✅ 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.