Weight Loss Flashcards
What are the 4 broad mechanisms of weight loss?
Reduced intake
Reduced digestion, absorption or assimilation of nutrients
Increased losses
Increased requirements
List 3 reasons for reduced intake in a horse
Inappropriate feeding
Unable to obtain feed
Competition for feed
Dental issues
Dysphagia
Pain
(Gastric disease)
Which of the following isn’t a reason for reduced digestion or absorption of nutrients?
- Liver disease
- Malabsorption syndrome (e.g. intestines)
- Pregnancy
- Dental disorders
Pregnancy
Give 2 broad reasons for increased nutritional losses
Protein losing enteropathy (nephropathy rare)
Loss into a body cavity (peritonitis or pleuritis)
Which 2 of the following results in weight loss due to increased requirements?
- Neoplasia
- Dental disease
- Small intestinal disease
- Lactate
Neoplasia
Lactate
Also pregnancy, sepsis and other systemic disease
Out of dental disease and malnutrition, which the most common cause of weight loss in horses?
Dental disease - pain or poor function
Malnutrition is rarer but could occur if owners don’t match intake with requirements (pregnancy, lactation)
Dental disease can result in horses being unable to chew long, fibrous food. What does this predisposes horses to?
Impactions
A horse presents with anorexia, which you suspect is due to pain. What are your top differentials?
Gastric disease (severe post-prandial)
Intestinal disease
Adhesions (low grade colic)
Severe musculoskeletal pain (laminitis)
Visceral pain (pleural/peritoneal disease)
What clinical sign can be seen in chronic grass sickness, botulism and pharyngeal/laryngeal dysfunction?
Anorexia due to dysphagia
Also seen in toxicities, e.g. lead
Botulism now uncommon as silage rarely fed to horses
You have diagnosed a horse with weight loss due to malabsorption or a protein losing enteropathy. What other clinical sign may you see?
Chronic diarrhoea, due to either:
- Primary large colon dysfunction
- Different energy substrates to flora
Need extensive pathology to see this
True or False?
The 3 causes of malabsorption and protein losing enteropathies are:
- Parasitic disease (cyathostominosis)
- Idiopathic
- Infiltrative bowel disease (inflammation/neoplasia)
True
You are presented with a horse with weight loss and oedema. What is the most likely cause of the oedema?
Hypoalbuminaemia
What are the first things that you want to rule out when presented with a horse with weight loss?
Diet
Parasites
What things could you expect to find on a rectal examination of a horse with weight loss?
Abdominal mass
Neoplasia
Intestinal lesion
Worm larvae
What blood result areas (e.g. liver parameters) would you be most want to investigate when presented with a horse with weight loss?
Liver
Kidney
Inflammation (acute phase proteins)
Other than a blood test, what laboratory tests could be useful when investigating a horse with weight loss?
Abdominocentesis
Faecal worm egg count - remember tapeworm needs a blood test to diagnose
What could eosinophilia indicate on haematology?
Generalised inflammation
Parasitic infection (sometimes)
Name 2 acute inflammatory markers
Serum Amyloid A:
- Produced in the liver in response to cytokines
- Induces further cytokines
- Attracts neutrophils/mast cells
Fibrinogen:
- Produced in the liver in response to cytokines
- Increases 24-48 hours after stimulus
- Used in blood clots
What should you always remember when interpreting equine anaemia?
Breed-specific reference ranges of red blood cells
Why is it important to assess the horse’s hydration status before interpreting haematology and biochemistry results?
Hypovolaemia may mask total protein decreases
Which protein is normally responsible for hyperproteinaemia?
Globulin - hyperglobulinaemia
Give 4 causes of hypoalbuminaemia
Laboratory error (most likely)
GI loss
Renal loss (much less common than GI)
Effusions (peritoneal/pleural)
Liver disease (rare)
Give 2 causes of hypoglobulinaemia
GI loss
Renal loss (rare unless severe damage)
Which serum protein can be raised in chronic inflammatory disease (cyathostominosis) and neoplasia?
Globulin
What are 3 differentials for hyperfibrinogenaemia?
Infection
Inflammation
Neoplasia
Which test would you do to investigate small intestinal malabsorption syndromes?
Oral Glucose Absorption Test
Describe how to do an Oral Glucose Absorption Test
Starve the horse overnight
Give 1g/kg glucose solution via nasogastric tube
Collect blood samples into fluoride anticoagulant immediately after and then at regular intervals
Measure blood glucose levels and plot on a graph
How can you differentiate between horses with no, partial or complete malabsorption on an Oral Glucose Absorption Test?
No malabsorption = glucose increases by 90% in first 2 hours
Partial malabsorption = glucose increases slightly
Complete malabsorption = glucose doesn’t increase
How can you ensure the Oral Glucose Absorption Test is as accurate as possible?
Keep the horse calm - stress increases the insulin response
Ensure horse is properly starved - food delays and flattens the curve
State 3 problems with the Oral Glucose Absorption Test
Doesn’t only assess small intestinal function - small amount of glucose absorbed in large intestine (D-xylose absorption test more reliable)
Partial malabsorption gives variable results
Delayed flat curve - from delayed gastric emptying or poorly starved horses
What are you looking at during intestinal ultrasonography?
Wall thickness - 0.3cm for small intestine, 3-4mm for large colon
Lumen diameter
Motility
Anatomy
Which 2 regions are best to take GI biopsies from for a weight loss investigation?
Duodenum (transendoscopic)
Rectal mucosa (biopsy from 10am and 2pm position; needs extensive pathology to be diagnostic)
Which surgeries can you do to investigate weight loss in horses?
Midline exploratory celiotomy - GA
Flank laparotomy - standing sedation
Laparotomy - standing sedation
Expensive and requires significant time off (6 weeks box rest and 6 months rest)
How far inside the rectum should you go before taking a rectal mucosal biopsy?
20-30cm
Give flunixin meglumine to prevent horse straining
Submit for histology
How frequently does a rectal mucosal biopsy result in a diagnosis for weight loss?
50% cases
Give 3 advantages to doing a laparotomy to investigate weight loss
Multiple intestinal biopsies can be obtained
Whole intestinal tract can be examined
Segmental disease, e.g. focal eosinophilic IBD, can be resected and removed
Granulomatous enteritis, eosinophilic enterocolitis and lymphocytic-plasmacytic enterocolitis are all forms of which disease?
Chronic Inflammatory Bowel Disease - small intestine
Other than Chronic Inflammatory Bowel Disease, name 2 other small intestinal diseases which could cause weight loss
Proliferative Enteropathy
Alimentary Tract Neoplasia
What causes Equine Proliferative Enteropathy?
Lawsonia intracellularis
Infects enterocytes, particularly in the ileum, and causes proliferation of abnormal enterocytes
Intestinal mucosa is altered and the foal can’t absorb as many nutrients
Which cells infiltrate the lamina propria in Granulomatous Enteritis?
Lymphocytes
Macrophages
True or False?
Granulomatous Enteritis causes duodenal villous atrophy
False - causes ileal villous atrophy
What is the cause of Granulomatous Enteritis?
Unknown
Theorised inflammatory reaction to intestinal bacteria
Affects any age, sex or breed
Briefly describe the pathophysiology of Eosinophilic Enterocolitis
Eosinophil infiltration into the intestinal mucosa
Large numbers of eosinophils irritate and injure intestines
What are the 3 forms of Eosinophilic Enterocolitis?
Multisystemic Eosinophilic Epitheliotrophic Disease (MEED):
- Other organs involved
Diffuse Eosinophilic Enterocolitis (DEE):
- Affects all small and large intestine
Idiopathic Focal Eosinophilic Enteritis/Colitis (IFEE or IFEC):
- Segmental lesions in small or large intestines
Eosinophilic enterocolitis is caused by what?
Unknown cause
Possibly related to nematode infestation
Parasites can induce hypersensitivity reaction, and contain endogenous factors that attract eosinophils
Which horses are you most likely to see Eosinophilic Enterocolitis in?
Any age, sex or breed
Most likely in young Thoroughbreds and Standardbreds
Lymphocytic-Plasmacytic Enterocolitis involves which cells?
Lymphocytes and plasma cells - infiltrate the lamina propria
Unknown cause - may lead to intestinal lymphoma
Lawsonia intracellularis infects the cytoplasm of which cells?
Proliferative crypt epithelial cells in the jejunum and ileum
Obligate intracellular bacterium
Which horses are you most likely to see Proliferative Enteropathy in?
Weanling foals aged 3-8 months
Horses living near pigs
Individuals or outbreaks
Uncommon in yearlings and adult horses
Name 4 risk factors for Proliferative Enteropathy
Overcrowding
Feed changes
Antibiotic usage
Mixing and transportation
Weaning
Give 4 differentials for large intestinal causes of weight loss
Parasites
Right dorsal colitis
Sand enteropathy
Eosinophilic Enteritis
True or False?
It is more common for parasites to cause colic and diarrhoea than weight loss
True
Name 3 large strongyles
Strongylus vulgaris (bloodworm)
Strongylus edentatus
Strongylus equinus
Describe the pathophysiology of large strongyle infections
4th stage larvae migrate through intestinal wall
Migrate through the lumen to the mucosa and submucosa
Larvae affect myoelectrical activity
Inflammatory cells gather
Oedema and haemorrhage through the intestines
Increased secretion and decreased absorption result
Which larval stage of small strongyles migrate through the mucosa of the large intestine?
L4
Includes a period of hypobiosis before larval emergence after an unknown stimulus
What damage occurs when small strongyle larvae emerge from the large intestine?
Mucosal damage
Ulceration
Inflammatory reaction
True or False?
Cyathostomins are a group of small strongyles
True
What time of year are L4 larvae from small strongyles most likely to emerge?
Late winter or early spring
Results in “larval cyathostominosis” - can severely damage the gut wall (diarrhoea) and cause serious colic
Mortality rate as high as 50%
In Right Dorsal Colitis, which area of the large intestine is affected?
Right dorsal
Sometimes known as hindgut ulcers
Give 3 clinical signs of Right Dorsal Colitis
Weight loss
Diarrhoea
Lethargy
Recurring colic
What factors predispose a horse to getting Right Dorsal Colitis?
Prolonged NSAID use
(Also excessive grain intake, acidosis, stress and parasites)
Describe how NSAIDs can result in Right Dorsal Colitis
NSAIDs inhibit cyclo-oxygenase (COX) -1 and -2, which produce prostaglandins
Inhibition of prostaglandin production results in:
- Reduced mucosal blood flow
- Decreased secretion of mucus, H2O and HCO3-
- Decreased mucus cell turnover and migration
Results in epithelial surface damage, which leads to ulcer formation
Which of the following NSAIDs should you give to a horse prone to Right Dorsal Colitis?
1. Flunixin meglamine
2. Phenylbutazone
3. Ketoprofen
4. Firocoxib
Firocoxib - selective COX-2 inhibitor which only affects prostaglandins involved in inflammation
Phenylbutazone, Flunixin meglamine and Ketoprofen are all non-selective COX inhibitors (phenylbutazone is the worst)
Describe the pathogenesis of Sand Enteropathy
Horses living in sandy areas ingest sand with their food
This builds up over time and accumulates in the sacculations of the ventral colon
Damage of the colonic mucosa occurs
Diarrhoea, weight loss and sometimes impaction
You are presented with a horse with weight loss, which you suspect is due to hepatic disease. What are your top 4 differentials?
Theiler’s Disease/Serum Associated Hepatitis
Ragwort poisoning
Cholangiohepatitis
Cholelithiasis
How much of the liver needs to be damaged before clinical signs of hepatic failure are seen?
Over 75%
What are the 2 broad mechanisms behind weight loss due to hepatic disease?
Anorexia
Abnormal metabolism
Other than weight loss, what clinical signs may suggest hepatic disease in a horse?
Colic
Diarrhoea
Ascites
Due to hepatic swelling, portal hypertension, altered microflora and abnormal bile acids
What is hepatic encephalopathy?
Syndrome of neurologic problems due to poor liver function resulting in increased blood toxin levels
What clinical signs would make you suspect hepatic encephalopathy?
Depression
Lethargy
Head pressing
Circling
Aimless walking
Ataxia
Dysphagia
Pica
Behavioural changes
Stupor/Seizures/Coma
Name one GI-derived neurotoxin
NH3 (ammonia)
True or False?
Increased cytokines, increased BBB permeability and altered benzodiazepine synthesis are all involved in hepatic encephalopathy?
True
Also increased neurosteroid synthesis and manganese
You have a horse with Theiler’s Disease (hepatitis). What are the 3 most likely causes?
History of being given an equine blood production (transfusion) - most likely
Equine parvovirus-hepatitis - association
Equine hepacivirus - can’t be ruled out as causative
Give 3 clinical signs of Theiler’s disease (hepatitis)
Lethargy
Anorexia
Jaundice
Hepatic encephalopathy
Which alkaloid is involved in ragwort poisoning?
Pyrrolizidine alkaloid toxicity
A horse presents with lethargy, jaundice, photosensitisation, diarrhoea and weight loss. The owner mentions that the horse was accidentally given access to hay containing ragwort 12 months ago. Could this be the cause of this horse’s clinical signs?
Yes - technically clinical signs can occur after 1-12 months after ingestion
What is the most common source of ragwort poisoning in horses?
Contaminated feed, especially pellets
Which organisms are frequently involved in Cholangiohepatitis?
Salmonella spp.
Klebsiella spp.
E. coli
Ascending bacterial infection likely from the intestines
Can also be as part of sepsis from systemic spread
Are you more likely to see weight loss in horses with acute or chronic Cholangiohepatitis?
Chronic disease results in:
- Liver fibrosis = weight loss
Acute disease results in:
- Inflammation/infection = fever
- Biliary obstruction/hepatic enlargement = colic
- Biliary obstruction = jaundice + photosensitivity
What is the name given to stone formation in the biliary ducts of the liver?
Cholelithiasis
Unknown cause, but bacterial infection likely involved
You have a horse with inflammatory bowel disease. What 3 treatment options are available?
Prolonged corticosteroid therapy:
- Dexamethasone +/- prednisolone for 3-5 weeks, then taper
Chemotherapeutic agents:
- Azathioprine, vincristine, etc. (lymphosarcoma)
Resection and anastomosis:
- If localised idiopathic eosinophilic enteritis
Why might you treat a horse with inflammatory bowel disease with IM dexamethasone before oral prednisolone?
Bypasses intestinal malabsorption
What dietary modifications can you recommend for a horse with inflammatory bowel disease?
Increase fibre intake to minimise small intestine function
Add vegetable oils into diet (reduce VFAs)
Avoid/Minimise commercial feeds to try and reduce antigens
A horse with inflammatory bowel disease is being treated with dexamethasone and dietary modifications. What else can you do to reduce the likelihood of recurrence?
Frequent deworming - parasites which don’t normally trigger inflammation can do if the bowel isn’t normal
You have a horse with proliferative enteropathy. Which antibiotic will you choose to treat her?
Tetracyclines - IV oxytetracycline BID for 1 week, then oral doxycycline BID
Macrolide and rifampin SID
The owner of a horse with proliferative enteropathy has asked you to give steroids to reduce pyrexia as part of the treatment plan. What do you respond?
Don’t give steroids - bacterial infection
NSAIDs if pyrexia
A horse you are treating for proliferative enteropathy has profuse diarrhoea and severe hypoalbuminaemia. What additional treatment can you provide?
IV fluids
Plasma/Colloids
You have diagnosed a horse with Right Dorsal Colitis. How are you going to treat him?
Remove NSAIDs
Prostaglandin analogues, e.g. Misoprostol BID
Which of the following isn’t a good treatment option for a horse with Chronic Sand Enteropathy?
1. Dexamethasone BID for 2 weeks
2. Psyllium and MgSO4 by NG tube
3. Surgical emptying
4. Hay, haylage or alfalfa mix
Dexamethasone - should give NSAIDs BID instead
Also prevent horse from eating on the ground - rubber mats, feeders, hay nets
You have a horse with liver disease. Which of the following isn’t used to support the liver?
1. Milk thistle extracts (silymarin)
2. Vitamin A
3. N-acetylcysteine
4. S-adenosylmethionine
Vitamin A
Should use vitamin E instead
How does Silymarin in milk thistle support the liver?
Inhibits hepatic fibrosis
Encourages hepatocyte regeneration
Anti-oxidant
True or False?
Increasing levels of fat and protein in the diet supports the liver by reducing the level of metabolic work it has
False - decreasing levels of dietary fat and protein does this
How does Vitamin E support the liver?
Reduces blood glucagon levels (so increases insulin levels)
Helps detoxification pathways
Are diets high in alfalfa, legumes and carbohydrates good for horses with liver disease?
High levels of carbohydrates are helpful, but care if obese
High levels of alfalfa and legumes are bad as contain heaps of protein
Should include low protein foods, e.g. beet pulp, cracked corn, bran (care hyperphosphataemia)
An injection of which vitamin can help support the diseased liver?
Vitamin B, especially in acute disease
Pyrrolizidine alkaloid toxicity causes irreversible liver damage. Which diagnostic test can you do to establish long term prognosis?
Liver biopsy
Which 2 antifibrotic agents can you use to treat a horse with pyrrolizidine alkaloid toxicity?
Steroids - dexamethasone or prednisolone for several weeks and then tapered off
Colchicine - disrupts tubulin, which downregulates the innate immune system; extremely toxic if overdosed
Which antibiotics could you use in a horse with cholangiohepatitis?
Broad spectrum with good gram -ve cover and anaerobes
Potentiated sulphonamides
Fluoroquinolones - enrofloxacin
Cephalosporins
+/- Metronidazole
Which sample would you take to do an antibiotic culture and sensitivity test for a horse with cholangiohepatitis?
Liver biopsy
How long should you give antibiotics to a horse with cholangiohepatitis?
Until 2-4 weeks after liver enzymes have returned to normal and no pyrexia present
Which antibiotics should you give a horse with cholelithiasis?
Broad spectrum with good gram -ve cover and anaerobes
Potentiated sulphonamides
Fluoroquinolones - enrofloxacin
Cephalosporins
+/- Metronidazole
Dimethyl sulphoxide - may help dissolve sludge and stones
Which history questions are important when investigating a horse with weight loss?
Age and activity
Perceived length of weight loss
Diet - amount and frequency
Worming history
Dental care
Episodes of diarrhoea, soft manure, inappetence, colic, etc.
Type of pasture - size, vegetation species
Sharing pasture with other horses or species
In which body areas is muscle wastage most notable?
Head muscles
Cervical muscles
Epaxial muscles (around the spine)
Other than muscle wastage, what things will you specifically look for on clinical exam of a horse with weight loss?
Oedema - ventrally or distal limbs
Faecal staining on hindquarters - type and quality of faeces, sand, gravel, long fibre, parasites
Heart rate
Abnormal lung sounds
GI motility
Dental exam
What is the ideal body condition score for the pet horse, breeding mare and breeding stallion on the 1-9 scale?
Pet horse: 4-6
Breeding mare: 6-7
Breeding stallion: 5-6
Performance horses are normally 4-5
What are you analysing when doing a liver ultrasound?
Sharpness of edges
Echogenicity
Masses
Gas-shadowing structures
Right and left lobes
Where can you find the small and large intestines when doing ultrasonography?
Small intestine: inguinal area in the cranioventral abdomen
Large intestine: left ventral abdomen
How much of the small and large intestine will you be able to see on ultrasound?
30% of small intestine
50% of large intestine
What is the aim of doing a rectal examination for a horse with weight loss?
Find masses, impactions, strictures and mesenteric lymphadenopathies
Take faecal samples
What is the normal gross appearance of peritoneal fluid collected via abdominocentesis?
Turbid
Serosanguinous
Green-dark
How can you measure protein levels in peritoneal fluid? What are the normal values?
Use a refractometer
Abnormal if >30g/L, which would indicate inflammation or infection
Peritoneal fluid normal lactate levels are <2.5mmol/L. What might cause them to rise?
Intestinal ischaemia - peritoneal lactate levels are double systemic
Bacterial infection
<5000 white blood cells/ul in peritoneal fluid is normal. What might you see if there was a bacterial infection?
Likely infection if >10000 cells/ul
>90% neutrophils
Degenerative neutrophils due to bacterial toxins (large, swollen nucleus, vacuolated cytoplasm)
Intra and extracellular bacteria
Abdominal glucose >2.8mmol/L
What is the most common abdominal neoplasia in the horse?
Intestinal lymphoma/lymphosarcoma
Which organisms involved in weight loss can be found on histopathology and culture/PCR of an intestinal biopsy?
Lawsonia intracellularis
Salmonella
Out of Multisystemic Eosinophilic Disease, Granulomatous Enteritis and Lymphocytic-Plasmacytic Enterocolitis, which 2 are most likely to be found on a rectal biopsy?
Granulomatous Enteritis
Multisystemic Eosinophilic Disease
Still only find 50% cases
Which area of the large intestine would you biopsy to look for Lymphocytic-Plasmacytic Enterocolitis and Eosinophilic Enteritis?
Duodenum
Finds only 20% of cases
Full thickness intestinal biopsies are used to find which causes of equine weight loss?
Eosinophilic Enteritis
Lymphoma
Grass sickness (ileum)
Which of the following causes of inflammatory bowel disease would have a normal Oral Glucose Absorption Test?
1. Multisystemic Eosinophilic Epitheliotropic Disease
2. Granulomatous Enteritis
3. Intestinal Lymphoma
4. Lymphocytic Enterocolitis
Multisystemic Eosinophilic Disease
Focal Eosinophilic Enteritis can have a normal or abnormal Oral Glucose Absorption Test
Which 2 of the following would you see anaemia on haematology and biochemistry?
1. Lymphocytic enterocolitis
2. Intestinal lymphoma
3. Granulomatous enteritis
4. Focal eosinophilic enteritis
Granulomatous enteritis
Intestinal lymphoma
Will also see anaemia in Multisystemic Eosinophilic Epitheliotropic Disease
What diagnostic test could you do to help determine Ascarid burden in weaning and yearling horses?
Ultrasound
How can you diagnose Proliferative Enteropathy?
Faecal PCR for Lawsonia intracellularis
How could you diagnose Salmonella in a horse with weight loss?
PCR and enriched culture from a faecal sample
What is the best diagnostic test for sand enteropathy?
Radiography
Also ultrasound and a sedimentation test, but that has low sensitivity
Where are AST and ALT enzymes found in the liver?
AST is hepatocellular (lots produced in muscles, as well as red blood cells and kidneys)
ALP is in the biliary ducts (20% produced from bone)
What is the main cause of increased bilirubin on biochemistry analysis?
Anorexia
True or False?
Bile acids are liver specific
True
Which intercostal spaces would you use to find the liver on ultrasound?
Left: 7-9th intercostal space
Right: 6-17th intercostal space
Other than pyrrolizidine, what 2 main toxins cause liver damage?
Mycotoxins - severe hepatic necrosis
Iron supplements - hepatic necrosis, haemochromatosis
True or False?
A bacterial culture can be done on liver biopsies to test for Clostridium piliforme, which causes cholangiohepatitis
True - foals 1 week - 2 months
Also virus PCR can be done for Equine Parvovirus-Hepatitis
