Diseases of the Large Intestine, Pt. 2 Flashcards
How do SI and LI obstructions most commonly present? What are the 3 most common reasons to refer?
SI = reflux due to an accumulation of fluid in the stomach
LI = gassy abdominal distension - bloat
- high heart rate (dehydration and shock)
- reflux upon stomach tube placement
- serosanguinous abdominal fluid (dead bowel)
Why is acute diarrhea considered a snowball effect? What complications are associated?
it starts as a small incident but if it remains chronic, it leads to dehydration, electrolyte disturbances, and impaired cardiovascular function
sepsis, endotoxemia, immune compromise, superinfection, infarction, thrombosis, laminitis, coagulopathy, inflammation
What bacterial cause of acute diarrhea requires a culture along with PCR for diagnosis?
Salmonella
Where does equine coronavirus (ECoV) typically start? What signs are most common?
begins in the SI, causing necrosis and sloughing
anorexia, lethargy, fever > diarrhea, colic
What are 2 signs on bloodwork indicative of equine coronavirus (ECoV) infection? How is it diagnosed?
- leukopenia
- hyperammonemic encephalopathy
fecal PCR
What is the most frequence species of Salmonella to cause diarrhea in horses? What are 3 risk factors?
S. enterica serovar typhimurium
- stress - surgery, broodmare status
- carriers
- antibiotics
Why are salmonella infections especially important to prevent/maintain?
zoonotic and virulence potential
What is the most common sign of Salmonellosis in horses? What else is seen?
acute colitis - profuse, initially hemorrhagic diarrhea, occasional abdominal pain before the diarrhea breaks (not recommended to walk for relief!)
- fever, depression, dehydration
- tachycardia
- sepsis, endotoxemia: dark line over teeth
- CV shock
- vascular leak syndrome, coagulopathy
How is Salmonellosis diagnosed?
- culture: 3-5 fecal samples 12-24 hr apart with 5-10 g of feces on selective media or mucosal biopsy culture
- PCR screening
How is Salmonellosis treated? Prevented? What is indicative of a poor prognosis?
- fluid therapy with colloids or plasma
- Flunixine meglumine
- antimicrobials: Penicillin, Gentamycin, Enrofloxacin
- anticoagulants
> 10 days of diarrhea
biosecurity - cleaning, disinfection, isolation
What causes Potomac Horse Fever? When is infection most common?
Equine Monocytic Ehrlichiosis - Neorickettsia risticii infecting trematodes or aquatic insects (mayflies, caddisflies) ingested by horses (accidental host)
June-November in areas within 5 miles of river/water
What cells are infected with Potomac Horse Fever? How are horses in stables infected?
monocytes, macrophages, intestinal epithelium
aquatic insects (mayflies, caddisflies) find their way into horses’ water source
What are the 2 stages of PHF? What are the most common signs?
1st fever = 1-3 days following ingestion, typically unnoticed
2nd fever = 5-7 days later when organism moves from blood to colon
- diarrhea
- colic
- fever, anorexia, depression
- abortions
What is commonly the only sign of PHF in 30% of horses? How is it diagnosed?
laminitis
- fecal AND blood PCR (infection monocytes and macrophages!)
- serology (IFA): not considered diagnostic, indicates exposure
What 2 antimicrobials are recommended for treating PHF? What are 3 additional treatment strategies?
- oxytetracycline - q12h for 4 days, fever should resolve in 48h, diarrhea should resolve in 24-72h
- doxycycline - q12-24h, less effective due to decreased absorption
- fluids, plasma, colloids
- Flunixine meglumine
- vaccination in early Spring to mid Summer to decrease incidence - has unreliable efficacy due to multiple strains of N. risticii
What are the 2 main etiologies of Clostridial diarrhea?
- C. difficile - colitis in adults, Toxin A enterotoxin and Toxin B cytotoxin, risk increased with antimicrobial administration or hospitalization
- C. perfringens - occasional cause of colitis, types A-E based on exotoxin, risk based on age and environmental persistence
What are the major clinical signs of Clostridial diarrhea in foals and adults?
FOALS - hemorrhagic diarrhea, sepsis, gas/fluid-filled small intestine (intramural)
ADULTS - diarrhea, abdominal discomfort, fever, severe toxemic colitis
What are 4 diagnostics used for C. difficile diarrhea?
- culture with selective media - further testing needed to determine if isolates ar toxigenic
- antigen ELISA - initial
- Toxin A/B ELISA
- PCR for TcdA and TcdB - quick!
What are 4 diagnostics used for C. perfringens diarrhea?
- culture - shedding common in healthy horses!
- culture + PCR (toxin genes)
- toxin ELISA - enterotoxin only
- PCR
What are 4 treatments for Clostridial diarrhea?
- antimicrobials - Penicillin, Metronidazole, Vancomycin for resistance
- Saccharomyces boulardii (yeast) or probiotics to normalize flora
- GI protectants - di-tri-octahedral smectite powder (Biosponge)
- transfaunation with feces from a healthy or recently deceased horse through an NG tube
What is the most common cause of Cyathostomiasis? What is the most common sign? When is this most common?
(small Strongyles) - young horses with poor deworming history
poor body condition, usually no fever
October to April
What 3 conditions are seen with colitis-x? What are 3 possible causes?
acute colitis + endotoxemia + anaphylaxis
- anaphylaxis
- clostridiosis
- enteric bacteria
What is a common copathogen seen with Salmonella also found in clinically healthy horses?
Aeromonas
How can NSAIDs affect the GIT? What 3 are the most common causes?
right dorsal colitis
- Phenylbutazone
- Flunixin meglumine
- Firocoxib
What are the 3 most common clinical signs seen with NSAID toxicity? How is it diagnosed?
- hypoproteinemia (hypoalbuminemia)
- diarrhea
- colitis
U/S can reveal edema of the right distal colon +/- SUCCEED fecal blood test
What are the 3 most common side effects of NSAIDs? What conditions in horses are typically treated with heavy NSAID doses?
- stomach ulcers
- right dorsal colitis
- kidney failure
laminitis and recurrent keratitis
When are oral fluids indicated for horses with acute diarrhea? What is commonly used?
if there is no reflux or pain
water + electrolyes (50% glucose, baking soda, KCl)
(make sure regular water is still available!)
What 3 IV fluids are used in horses with acute diarrhea?
- hypertonic saline - 2-4 mL/kg bolus followed by 10 L of crystalloids per L of hypertonic
- crystalloids - Plasma-Lyte, Normosol, LR + KCl
- colloids - plasma, hydroxyethyl starch (hetastarch, pentastarch)
What are 6 aspects to general therapy for acute diarrhea?
- treat endotoxemia with hyperimmune plasma, Flunixin megulmine (if no RDC), polymyxin, and pentoxyfylline
- prevent founder
- prevent thrombophlebitis
- slow IV vit B
- intestinal protectants
- nutrition
What specific treatment is recommended for Salmonellosis and Potomac Horse Fever?
antibiotics based on clinical signs and culture
oxytetracycline - the earlier the better, nephrotoxic in dehydrated horses
What specific treatment is recommended for antibiotic-associated C. difficile diarrhea? What else can be used?
Metronidazole
- di-tri-octahedral smectite (BioSponge)
- commercial plasma with Ab against C. diff
- transfaunation
What specific treatments are recommended for NSAID toxicity?
- plasma
- hetastarch
- sucralfate
- misoprostol (not used in pregnant mares)
What specific treatment is recommended for cyathostomiasis?
Moxidectin once with Dexamethasone
(Fenbendazole)
How does inflammation cause chronic diarrhea? What are 6 infectious causes?
morphological changes in the intestinal wall
- chronic salmonellosis
- chronic parasitism
- abscesses
- EPE
- R. equi
- Rotavirus
What are 3 non-infectious causes of chronic inflammatory diarrhea?
- cellular infiltrative disorders
- weanling foals - gastric ulceration or emptying dz
- NSAIDs
What is a non-inflammatory cause of chronic diarrhea? How long must diarrhea be occurring to be considered chronic?
abnormal fermentation of cellulose
> 1 month —> frustrating diagnosis, often remains undetermined despite extensive workup
Causes of chronic diarrhea in horses:
What is recommended for diagnosing chronic diarrhea?
- Hx, PE
- blood work: CBC, hypoproteinemia, hypoalbuminemia, biochemistry
- peritoneal fluid
- fecal tests
- absorption tests
- rectal mucosal biopsy
- U/S
- exploratory laparotomy
What treatments are recommended for chronic diarrhea? What is specifically recommended for cellulose maldigestion?
- hydration and nutrition
- inflammation
- antihelminthics + steroids
- GI protectants
- sulfasalazine
- tranfaunation
- cultured yogurt, brewers yeast, probiotics
iodochlorhydroxyquin
When should colic be referred?
- uncontrolled or recurring severe pain
- HR > 60
- abnormal rectal exam (not an impaction)
- reflux on nasogastric tube
- dehydration
- toxemia
- abnormal abdominal fluid
What pain management is recommended while a horse is being transported to a referral hospital?
<30 mins away = Xylazine IV
1-2 hr away = Detomidine IV
+ indwelling NG tube and IV fluids
Small intestinal issues:
Which of the following are common locations for impaction?
a. cecum
b. pelvic flexure
c. right dorsal colon
d. small colon
A, B, D
pelvic flexure - sudden housing change, lack of water
cecum - hospitalization, treatment
small colon - lack of water, infection
Which of the following is a typical site for colitis related to NSAIDs?
a. cecum
b. pelvic flexure
c. right dorsal colon
d. small colon
C
treatment with Phenylbutazone, Flunixin meglumine, or Firocoxib
U/S - edema of the right distal colon
A 16 y/o Warmblood gelding presents with…
- injected MM
- CRT of 3 seconds
- 68 bpm HR
- 20 bpm RR
- 100.5 F rectal temp
- increased gut sounds in all 4 quadrants
What is the % of dehydration? What amount of fluid is needed to correct it? What rate is recommended over 30 minutes?
8%
(assume 500 kg)
500kg x 0.08 = 40 L
10-20 mL/kg over 30 mins
500kg x (10mL/kg) = 5 L
What volume of IV fluids is required for most horses (500 kg) for maintenance?
40-60 mL/kg/day
500kg x (40-60 mL/kg/day) = 20-30 L/day
Each liter of hypertonic saline must be followed by at least how many liters of crystalloids?
a. 1 L
b. 5 L
c. 10 L
d. 20 L
D
What drugs are commonly used to prevent endotoxemia?
- Banamine
- Polymyxin
- Pentoxyfylline
