Anatomy of the esophagus in the horse (skeletal vs. smooth muscle location)
first 2/3–skeletal
last 1/3–smooth
Why is it difficult to perform surgery on the esophagus
lacks a serosa which is important for closure
most common equine esophageal disease?
intraluminal feed impaction (choke)
2 most common locations for choke to occur
just distal to pharynx
thoracic inlet
What should be used when lavaging an esophageal impaction?
Water only!!
*NEVER mineral oil due to risk of aspiration
Most common complication associated with choke?
aspiration!
3 hormones/molecules that can stimulate parietal cells to produce H+
1) ACh
2) Gastrin (G-cells)
3) Histamine (ECL-cells)
Reflux is most commonly an indication of disease in which part of the GI tract?
Small intestine (stomach fills secondarily)
Which stomach disease is associated with aged, male horses?
Gastric SCC
3 forms of gastric ulcer disease in horses
1) primary squamous gastric ulcer disease
2) secondary squamous gastric ulcer disease
3) glandular gastric ulcer disease
Which form of EGUD is common to thoroughbreds in race training (and other performance horses)
Primary equine squamous gastric ulcer disease
Concerning NEONATAL foals with gastric ulcers
1) a common clinical sign
2) at a high risk for?
1) diarrhea
2) higher risk for perforation
Concerning WEANLING foals with EGUD:
1) more likely to get?
2) a common clinical sign
1) duodenal ulceration and stricture formation
2) diarrhea
3 goals of treating EGUD
reduce acid
promote healing
prevent recurrence
4 categories of drugs indicated in the Tx of EGUD
1) H2 antagonists
2) proton pump inhibitors
3) sucralfate
4) antacids
What type of diet modification should take place to prevent EGUD?
low carb diet, high fiber
small, frequent meals
*don’t let the stomach sit empty!!
4 COMMON clinical signs in horses with liver disease
weight loss
colic (mild)
fever
icterus
Top 4 differentials for a horse that presents with fever & colic
1) colitis
2) enteritis (anterior)
3) peritonitis
4) hepatitis
Most common reason horses become icteric/have high bilirubin?
Describe the pathophysiology
Anorexia
uptake protein for bilirubin, LIGANDIN, becomes downregulated so the liver cannot take up as much UNCONJUGATED bilirubin as normal
Two less common clinical signs of liver disease
Photosensitization
Hepatic encephalopathy
Photosensitzation occurs when the liver loses it’s ability to clear which substance?
Phylloerythrin (formed from chlorophyll by intestinal bacteria)
How can you differentiate hepatic encephalopathy from another neurological disease?
look for elevated GGT on bloodwork
Which two liver enzymes are liver-specific and can be considered sensitive indicators of disease
SDH (leakage)
GGT (inducible)
An increase in ____bilirubin of more than ___% can be considered specific for liver disease
DIRECT bilirubin (conjugated portion)
increase of 25% (or more)
What type of diet is indicated for hepatic insufficiency treatment?
low protein, high branch-chain AA, high carbohydrate
Cholangiohepatitis in horses is often secondary to?
a primary GI disease (anterior enteritis or ileus) that causes bile to sit in the intestine and be refluxed back into the common bile duct (taking bacteria with it)
3 differentials for icetrus in foals
1) sepsis
2) neonatal isoerytholysis
3) primary liver disease
Most common cause of liver disease in foals? Causative agent?
Tyzzer’s disease
Clostridium piliformis
3 common clinical signs of small intestinal colic in horses
1) SI distension (on US)
2) reflux
3) ileus
concerning anterior enteritis:
1) pain level
2) 2 PE findings
3) reflux present?
4) rectal findings
1) moderate–>become DEPRESSED when gastric pressure is relieved
2) fever, tachycardia
3) Yes; LARGE amount
4) distended, compressible SI
Most common complication associated with endotoxemia?
Laminits
Adhesions typically form within ______ following surgery (time frame)
3 months
Concerning endotoxemia:
1) which part of the bacterial wall is responsible
2) 2 ways/meds to neutralize the toxin
1) Lipid A moiety
2) hyperimmune plasma; polymixin B
* Polymixin B binds lipid A
A foal that fails to pass it’s meconium and colics in the first 24-48hrs of life may have? (name 2 things)
Intestinal agangliosis
Meconium impaction
Disease where the enteric nervous system fails to develop
intestinal agangliosis
Two etiologies commonly associated with ILEAL impaction
1) coast/bermuda hay (fine stemmed feed)
2) tapeworms
When viewing with US, how would an ileal impaction look different from anterior enteritis?
SI will be distended in both but with ileal impaction, the walls will NOT be thickened
Why is buscopan commonly used in treatment? (i.e. what’s is MOA)
it’s a muscarinic antagonist–stops spasming
Concerning inguinal/scrotal hernias:
1) which form is most common
2) differentiate where the intestine ends up with direct vs. indirect
1) indirect most common
2) indirect–ends up in vaginal tunic with the testicle
direct–ends up in SQ tissue of scrotum
Contrast acquired indirect inguinal hernias and congenital indirect inguinal hernias
Acquired: Adults, short nonreducible segment, strangulating
Congenital: foals, long reducible segment, NEVER strangulating (no colic)
For which 3 types of inguinal hernias is surgery required
1) adult-indirect
2) foals-direct
3) foals–ruptured indirect
4 boundaries of epiploic foramen
1) gastropancreatic fold
2) caudate lobe of liver
3) portal vein
4) caudal vena cava
An expected rectal finding with epiploic foramen entrapment
SI distension in RIGHT CRANIAL abdomen
Common signalment for mesenteric rents in the following locations:
1) duodenal/jejunal mesentery
2) gastrosplenic ligament
1) periparturient, multiparous mares
2) middle aged, QH geldings
Which segment of bowel is typically involved with pedunculated lipomas
jejunum
3 most common types of intussusception
1) ileocecal
2) jejunojejunal
3) jejunoileal
Concerning adhesions:
1) acute, clinical adhesions lead to?
2) chronic, subclinical adhesions lead to?
1) ileus (get reflux and SI distention); need Sx
2) mild to moderate recurrent colic; medical tx
Differentiate the types of pain associated with:
1) anterior enteritis
2) non-strangulating obstructions (i.e. ileal impaction)
3) strangulating obstructions
1) moderate/severe; become DULL after decompression
2) mild/moderate; INTERMITTENT
3) mod/severe; PERSISTENT
Which of the following would produce the most abnormal abdominocentesis:
1) anterior enteritis
2) non-strangulating obstructions (i.e. ileal impaction)
3) strangulating obstructions
3–strangulating obstruction
Most commonly reported colic in horses?
Large colon tympany (functional–spasmodic colic)
A common historical fact and clinical finding that would cause you to suspect right dorsal colitis
history of NSAID administration
hypoproteinemia/hypoalbuminemia
Concerning large colon impaction:
1) most common thing causing the impaction
2) 3 common sites for it to occur
1) dry/coarse ingesta
2) pelvic flexure, RDC, transverse colon
A common rectal finding with large colon impaction
doughy, indentible ingesta
Where is the incisions made for a large colon enterotomy?
pelvic flexure
Best method for detecting sand in the large colon?
radiographs
Common signalment for enterolithiasis
breed, diet, location
arabians, on alfala diet, in florida or Cal
With right dorsal displacement:
1) where is the colon
2) how is it oriented
3) where is the pelvic flexure
1) btwn cecum and body wall
2) oriented transversely
3) near diaphragm
Absence of pelvic flexure, taut transverse bands, and an slightly elevated GGT would be indicative of?
Right dorsal displacement
*GGT gets elevated bc RDC can kink off near major duodenal papillae
Exception for when you would do trocarization for decompression before surgery?
Large colon volvulus
Where is the colon located with left dorsal displacement?
nephrosplenic space (btwn kidney and spleen)
A disease where Phenylephrine is indicated and why
Left dorsal displacement
it’s an alpha-1 agonist that can be used to shrink the spleen (give more room for colon to get unstuck)
Concerning large colon volvulus:
1) most common site
2) direction of rotation
1) cecocolic fold
2) dorsal colon will rotate dorsomedial
A broodmare who recently gave birth presents for severe, uncontrollable colic; abdominocentesis reveals increased PCV but LOW TS…top ddx?
Large colon volvulus
2 most important taenia of the cecum?
Which taenia is palpable on rectal?
ileocecal fold (dorsal) & cecocolic fold (lateral) are most important
Ventral band is palpated on rectal
Most common disease of the cecum
cecal impaction
Differentiate:
1) Type 1 cecal impaction
2) type 2 cecal impaction
1) true impaction–feed filled
2) motility disorder–fluid
3 common risk factors associated with impactions
1) decreased water intake
2) decrease in exercise or stall rest due to injury (pain)
3) NSAID administration
A horse presents to you with reduced fecal output and on rectal palpation you feel firm, doughy ingesta in the right caudal abdomen.
You learn the horse has been on stall rest due to an injury and is also currently on an NSAID.
What is your top ddx?
cecal impaction
A mare who recently gave birth presents with a dull mentation and you note abrasions around the face, her MM are hyperemic
on rectal, your arm feels like it’s floating & the rectum is vacuum-packed to your arm;
Abdominocentesis contains plant material and intracellular bacteria… top ddx?
Cecal perforation/rupture
The most common disorder of the small colon
small colon impaction
Usual signalment (breed & time frame) and most common clinical sign of small colon impaction
miniature horses in fall and winter
small volume diarrhea
Primary concern in horses with small colon impaction?
Salmonella! (50% of cases shed the bacteria)
2 common sites of small colon obstruction
small colon
transverse colon
Most common cause of colic in neonates?
Meconium impaction
Which method of treatment is NOT indicated for meconium impaction
Surgery–foals will die if you go to surgery
