7.1.1: Intestinal causes of weight loss including diagnosis and treatment Flashcards
What are some pathophysiological mechanisms of weight loss?
- Decreased dietary intake
- Increased rate of utilisation
- Loss of nutrients (malabsorption/maldigestion)
- Inadequate delivery to tissues
- Conditions that cause muscle wasting
What are some small intestinal causes of weight loss?
- Chronic inflammatory bowel disease (CIBD)
- Proliferative enteropathy
- Alimentary tract neoplasia
What are the 3 types of chronic inflammatory bowel disease?
- Granulomatous enteritis (GE)
- Eosinophilic enterocolitis (EE)
- Lymphocytic plasmocytic enterocolitis (LPE)
Cause, pathogenesis, incidence and signalment of granulomatous enteritis (GE)
- Cause: unknown, hypothetical response to intestinal bacteria
- Pathogenesis: lymphoid and macrophage infiltration into the lamina propria -> ileal villous atrophy
- Rare
- Any age, sex, or breed may be affected
Cause and signalment of eosinophilic enterocolitis
- Cause: unknown, speculated to be linked to nematode infestation (parasites inducing hypersensitivity reaction/containing factors that attract eosinophils)
- Signalment: any age and breed; TBs and standardbreds most commonly affected
Pathogenesis of eosinophilic enterocolitis
- Eosinophil infiltration into the intestinal mucosa
- Might see Multisystemic eosinophilic epitheliotropic disease (MEED), Diffuse eosinophilic enterocolitis (DEE), or Idiopathic focal eosinophilic enteritis/colitis (IFEE/IFEC)
Cause, pathogenesis and signalment of lymphocytic plasmocytis enterocolitis
- Cause: unknown, speculated to precede development of intestinal lymphoma
- Pathogenesis: there is lymphocyte and plasma cell infiltration into the lamina propria
- Signalment: can affect any age, sex and breed
Cause of proliferative enteropathy
- Causative agent: Lawsonia intracellularis
- Obligate intracellular bacterium
- Inhabits the cytoplasm of proliferative crypt epithelial cells
- Found in jejenum and ileum
Signalment and epidemiology of proliferative enteropathy
- Weanling foals 3-8 months old
- May be seen in individuals or outbreaks
- Uncommon in yearlings/adult horses
- Often seen in horses in close proximity to swine
Risk factors for proliferative enteropathy
- Overcrowding
- Feed changes
- Antibiotic usage
- Mixing and transportation
- Weaning
What are some large intestinal causes of weight loss?
- Parasite infestation
- Right dorsal colitis (RDC)
- Sand enteropathy
- Eosinophilic enterocolitis
Which groups of parasites can affect the large intestine?
- Large strongyles
- Small strongyles
What is an important and pathogenic large strongyle?
Strongylus vulgaris
Pathogenesis of large strongyles
- Migration of (4th stage) larvae through intestinal wall
- From the lumen through the mucosa and submucosa
- This affects the myoelectrical activity
- There is infiltration with inflammatory cells
- There is oedema and harmorrhage
- There is increased secretion and decreased absorption of nutrients from the lumen
Pathogenesis of small strongyles
- Migration of L4 through the mucosa of the large intestine
- The life cycle includes a period of hypobiosis
- Larvae emerge in response to an unknown stimulus
- Sudden emergency causes mucosal injury, ulceration, inflammatory reaction
- This affects motility patterns of the gut
What clinical signs can be caused by both large and small strongyles?
- Diarrhoea (increased secretion secondary to granulomatous inflammation, and disruption of the interstitium). Protein loss is often significant.
- Weight loss
- Colic
Cause and pathogenesis of Right Dorsal Colitis
Inflammation and ulceration of right dorsal colon is caused by NSAID use which inhibits prostaglandin production
* PGE2 and PGI2 prostaglandins are responsible for maintaining mucosal blood flow, increased secretion of mucus/H₂O, HCO₃⁻, and increased mucosal cell turnover and migration
True/false: right dorsal ulcerative colitis and right dorsal colitis are the same disease.
True.
What is a common cause of Right Dorsal Colitis?
- Phenylbutazone is a common cause
- Seen particularly in horses receiving inappropriately large doses of NSAIDs
- Some have underlying disorders
Clinical signs of Right Dorsal Colitis
- Intermittent colic
- Diarrhoea
- Weight loss
Cause and pathogenesis of sand enteropathy
- Horses live in sandy areas/paddocks and ingest sand over a period of time
- Intestinal contents and water continue to flow through the lumen but due to its weight sand accumulates in the ventral colon
- There is damage to the colonic mucosa/inflammation
- This leads to diarrhoea, weight loss, and in severe cases impaction leading to colic
Clinical signs of proliferative enteropathy
- (Seen in foals)
- Lethargy
- Anorexia
- Fever
- Peripheral oedema
- Weight loss
- Colic
- Diarrhoea
They didn’t teach us this.
Large strongyle egg
Small strongyle
Right dorsal colitis
Large strongyle larvae
What history questions are important in a horse with weight loss of a possible hepatic/intestinal cause?
- Signalment
- Length of weight loss
- Husbandry practices
- Environmental and pasture managament - type of pasture, size, grass coverage and species, weeds, trees
- If sharing pasture with other horses (how many?) or other animal species
- Diet: amount and frequency
- Worming history
- Dental care
- Episodes of diarrhoea/soft manure/inappetance/colic
Why might fibrinogen, SAA and globulins be elevated?
- Fibrinogen = marker of inflammation
- Serum amyloid A = an acute phase protein
- Acute phase proteins might be elevated esp in cases of parasitism/bacterial infections e.g. Lawsonia, Salmonella and in some neoplasia
Intestinal ultrasound: where would you assess the small intestine and what is an abnormal thickness?
- Assessed in the inguinal area and cranioventral abdomen, next to the R kidney
- Increased intestinal thickness is associated with reduced absorptive capacity
- Abnormal thickness small intestine >4mm
Intestinal ultrasound: where would you assess the large intestine and what is an abnormal thickness?
- Assess the right dorsal colon in the 11-13th ICS; also assess in the left ventral abdomen
- Increased intestinal thickness is associated with reduced absorptive capacity
- Abnormal thickness large intestine >6mm
True/false: we can image almost the entirety (90+%) of the small and large intestines using ultrasound.
False
* We can only image intestinal segments in close contact with the abdominal wall.
* We can see approx. 50% of the large intestine
* We can see approx. 30% of the small intestine
Why might we perform abdominocentesis in a horse with a suspected intestinal cause of weight loss?
- Abdominocentesis may not help us find out about inflammatory intestinal diseases but helps rule out other causes of weight loss e.g. peritonitis
- Assess colour, protein (abnormal >30g/L), lactate (abnormal >2.5 mmol/L)
True/false: in horses with intestinal lymphoma, you would expect to see elevated WBC in fluid obtained by abdominocentesis.
False
* Intestinal lymphomas/lymphosarcomas remain the most common abdominal neoplasia in the horse
* However these are rarely exfoliative so may not see cytology
Diagnosis of proliferative enteropathy
PCR
In chronic cases -> biopsy PCR and histo/silver staining
Diagnosis of chronic Salmonella
- PCR + enriched culture
- Don’t rule out if negative; may be intermittent shedding/need several samples
Diagnosis of sand enteropathy
- Abdominal radiography = gold standard
- Can perform abdominal ultrasound
- Faecal sedimentation test: low sensitivity (may yield false negatives) but is easy and cheap
What is the main diagnostic tool for detection of IBD in horses? What does diagnosis rely on?
Intestinal biopsies
* Diagnosis relies on samplying the right bit of intestine/disease being diffuse enough to be detected. Horses have 18m of small and 4m of large intestine.
1
2
3
4
5
Histology reaches diagnosis in what percentage of cases that undergo rectal biopsy?
50%
These are mainly cases of GE and MEED
Histology reaches diagnosis in what percentage of cases that undergo duodenal biopsies?
20%
These are mainly lymphocytic plasmocytic enteritis and eosinophilic enterocolitis
Which parts of the intestine can we obtain biopsies from?
Proximal part of small intestine (duodenum)
Distal rectum
When can we take full thickness biopsies?
- By laparoscopy/laparotomy (probably under GA)
- Full thickness biopsies are the gold standard
Treatment of IBD
- Prolonged corticosteroid therapy: dexamethasone IM for 2 weeks followed by prednisolone/dexamethasone PO for 3 weeks, then dexamethasone tapered for 6 weeks with half dose and every other day dosing
- Chemotherapeutic agents e.g. azathioprine, vincristine -> recommended for lymphosarcoma/refractory IBD
-
Resection and anastomosis: possible for localised idiopathic eosinopholoc enteritis
* Diet changes
What diet changes would you suggest for a horse with IBD?
- Need a highly digestible and well-balanced feed provided in small amounts throughout the day
- Add vegetable oils to diet (corn/sunflower/flaxseed)
- Prioritise a monodiet with fibre; limited/no commercial feeds -> minimise antigen exposure
- Frequent deworming to avoid parasites triggering inflammation. Even unproblematic parasite levels can be bad for horses with IBD.
Treatment of proliferative enteropathy
Antibiotics
* IV oxytetracycline for 1 week
* Then doxycycline PO
* OR macrolide + rifampicin (probably this is the less stewardship option)
* Continue antibiotic therapy for 2-3 weeks -> should get a rapid response clinically
Other
* Give NSAIDs (flunixin/phenylbutazone) if pyrexia
* IV fluids and plasma/colloids if profuse diarrhoea and severe hypovolaemia
* Do not give steroids!
Treatment of right dorsal colitis
- Withdraw NSAIDs
- Prostaglandin analogues e.g. misoprostol
Prostaglandin analogues should restore the action of prostaglanding and increase the vascular supply in the affected areas. Should also reduce neutrophilic infiltration of mucosal tissue.
Treatment of sand enteropathy
- Psyllium and MgSO4 by NG tube daily
- NSAIDs: flunixin
- Surgical emptying if refractory to medical therapy
- Provide enough roughage: hay/haylage
- Do not feed on the ground: use haynets, rubber mats, feeders
