exam 3 - the stomach Flashcards
what is the basic structure and function of the equine stomach?
single chambered, compound stomach with 2 types of tissues lining it
fxn as a reservoir - relatively small compared to the rest of the GIT
what 2 types of tissue line the equine stomach?
what is the demarcation btwn them?
squamous epithelial tissue and glandular epithelial lining
margo plicatus btwn the 2 regions
what types of digestion occur in the stomach?
mechanical and enzymatic digestion
t/f
HCl is produced intermittently in the equine stomach, during feeding times
false
HCl is produced constantly
what important functions does HCl have in the stomach?
- disinfection
- microbial digestion
what is the function of Ghrelin?
and Leptin?
opposing action
Ghrelin: stimulates eating in the brain
Leptin: suppresses appetite
t/f
there is a pH gradient/stratification w/in the equine stomach
true
what is the relative pH of the top versus the bottom of the stomach?
top = less acidic [squamous epithelial lining] bottom = more acidic
where is HCl secreted from?
by what mechanism of action?
sec from parietal cells
via proton pump action
what is the proton pump that secretes HCl stimulated by?
- histamine
- gastrin
- acetylcholine
- prostaglandins
what effect does gastrin have on histamine?
what causes elevation of gastrin?
gastrin stimulates histamine release
gastrin is elevated by cortisol
what is the main inhibitor of HCl prduction?
somatostatin
what is EGUS?
what % of adult horses are affected?
equine gastric ulcer syndrome
common: 60-90% of adult horses
what populations of horses have a higher predisposition of EGUS?
- race and show training horses
- common in hospitalized horses
- common in horses affected with colic
t/f
EGUS is a common primary cause of colic
false
umcommon primary cause of colic
what are common consequences of colic?
being held NPO
stress
drugs
what are 3 types of EGUS?
- 1* squamous ulceration [MC]
- 1* glandular ‘ulceration’ [2nd MC]
- 2* squamous ulceration
what causes 1* squamous ulceration?
- excessive exposure to HCl corrodes the lining => bile acids may play a facilitatory role
what causes 1* glandular ulceration?
breakdown of bicarbonate-rich mucus layer
may be a role of bacT also
what causes 2* squamous ulceration?
pyloric outflow obstruction => excessive exposure to HCl
what is ESGD?
EGGD?
equine squamous gastric dz
equine glandular gastric dz
t/f
horses often have both ESGD and EGGD as a part of EGUS
false
most horses have 1 or the other - NOT both
what are the mechanisms that lead to squamous epithelial injury?
minimally protected
HCl exposure from the fundus
what risk factors contribute to the development of squamous epithelial injury?
- VFAs produced in the stomach of horses assoc with inc ulcer severity
- pepsin maybe
- bile salts maybe
what effects might bile have on the squamous cell epithelium?
- detergent action can ‘enable’ H+ to gain access to intercellular squamous epithelial cellular attachments
- bile may enter stomach during fasting => enterogastric reflux
what are the components of the glandular epithelial protection apparatus?
- bicarbonate rich layer of mucus
- growth factors [epidermal growth factor]
- epithelial restitution [stimulated replication]
- blood flow (NO)
- PGe2
- peristalsis
- saliva production [buffer to acids]
what is the pH in the bicarbonate rich layer of mucus near the glandular epithelium?
7
risk factors for EGUS?
low forage ration intense/inc exercise high concentration ration regular / prolonged transport intermittent fasting [being fed BID] mgmt / housing change water deprivaiton weaning protracted stable accommodation stress
approximately what % of horses at pasture have EGUS?
why?
11%
b/c continuous flow of saliva -> bicarbonate -> growth factors
what effects does stabiling a horse have on chances for developing EGUS?
INCREASED chances of EGUS
d/t stress and acid mobility [altered eating habits]
what effect does NPO for 24 hours have on horse GIT?
gastric pH drops to less than 2
squamous ulceration occurs w/in 96 hours
BID feeding gives horse ___% chance of developing EGUS
TID feeding gives a horse ___%
BID = 75%
TID = 58%
unavailability of water inc chances of EGUS by ___ times
3
why do rations with low roughage content contribute to EGUS?
- VFAs play a role [high NSC (non structural carbohydrate) rations]
- low dietary fiber [cellulose]
what effect does high intensity exercise have on EGUS?
- dec pH to less than 4
- inc intra abdominal pressure
- pushes acidic fluid onto squamous epithelium
t/f
NSAIDs are commonly linked to EGUS
false
ulcers NOT commonly linked to routine NSAID asministration
t/f
uremia d/t kidney dz can inc risk of developing EGUS
true
c/s of EGUS?
- may be sub clin and NO signs
- behavioral signs
- poor performance
- wt loss
- poor haircoat
- bruxism [grinding teeth]
what behavioral changes may occur with EGUS?
- abnormal / dec appetite **
- slow eating **
- girthing pain or stretching
- abnormal attitude / personality
- uncharacteristic protracted recumbency
dx of EGUS based on:
Hx
c/s
gastric endoscopy
trial Tx and response
complications commonly assoc w EGUS?
aspiration pneumonia reflux esophagitis peritonitis blood loss hypoproteinemia cholangiohepatitis gastrorrhexis
when does EGUS and reflux esophagitis occur?
2* to what?
c/s?
prognosis?
- 2* to gastric outflow obstruction: severe acid reflux erosive ulceration
- c/s: dysphagia, ptyalism, wt loss, inappetence, lethargy
- more severe ulceration at gastric aspect
- unfavorable prognosis
- indicator of severe dz
what abnormalities may be seen on blood work for EGUS?
presence of inflammation
t/f
a fecal occult blood test is helpful in Dx of EGUS?
false
is unhelpful
what is the typical protocol for gastro-esophageal endoscopy?
- NPO at least 15 hours
- restraint - twitch, stocks, experienced assistants, tranquilization
- pass line NG tube
- gastruc infufflation and deflation
EGUS Tx and Px?
risk reduction and pharmaceuticals
prognosis of EGUS?
- squamous ulceration tends to heal better than glandular ulcers
- extensive squamous ulcers heal better than deeper focal ulcers
what is essential to follow up of EGUS treatment?
ENDOSCOPY
how to reduce risks of EGUS?
- mirrors in stables and during transport - horse feels less lonely - dec stress
- provide plenty of water - promotes salivary flow
- use haying nets to promote smaller feedings and foraging behavior
- dec risk factors for stereotypical behavior
- alfalfa for forage
- offer small forage feeding 30 mins prior to exercise
why is alfalfa a good feed for an EGUS animal?
has high Ca - neutralizing effect on gastric acid
what is the drug of choice for EGUS?
Tx dose? Px dose?
Omeprazole
gastro gard to Tx: 4 mg/kg PO SID
ulcer gard to Px: 1 mg/kg PO SID
4 wk duration
what is mechanism of omeprazole?
must be absorbed into circulation from duodenum / SI - circulates back and works systemically on gastric mucosa
what is the mechanism of action of Ranitidine for Tx of EGUS?
histamine inhibitor
how does sucralfate work?
promotes PGe2 production
most helpful in glaudular ulcers
t/f
antacids are effective Tx for EGUS
false
right idea but you would need very large amounts to be effective
how commonly is Sx a Tx option for EGUS?
rarely
what role do oils have in Tx of EGUS?
corn oil or rapeseed oil
promote PGe2 prod
help gastric glanduular dz
EGGD is easier or more difficult to resolve than ESGD?
why?
more difficult
b/c does not respond as well to fast and simple Tx with omeprazole
needs longer term Tx
how common is gastric neoplasia in horses?
RARE
what types of neoplasia occur in equine stomach?
gastric squamous cell carcinoma
lymphosarcoma
leiomyoma
common presentation for gastric squamous cell carcinoma?
- old horse
- wretched halitosis
- weight loss and inappetance d/t pain upon eating
- colic: post prandial
- episodes of choke
dx of gastric squamous cell carcinoma?
enodscopy
u/s of cavities
analysis of peritoneal fluid
what is behavior typical of gastric squamous cell carcinoma?
- may only involve the stomach
- may spread to involve abdominal vescera and ascites
- may spread to invade chest
why might a horse with gastric squamous cell carcinoma experience inc respiratory rate and effort?
if tumor has metastasized to the chest
puts pressure on diaphragm
what causes a 1* gastric distension disorder to occur?
ingestion of fermentable food => food impaction [simple grain ingestion]
what causes a 2* gastric distension disorder to occur?
small intestinal obstruction
what might cause a gastric / pyloric outflow obstruction?
ulceration
neoplasia
what is a phytobezoar?
clinical significance?
hair ball
horses will eat whole persimmons and get a large mass of “persimmon-bezoar” in their stomach
in the event of a gastric distension disorder, what MUST be done?
if this is not done, the patient will die.
STOMACH TUBE
necessary to relieve fluid accumulation
what occurs if a horse consumes too many persimmons?
foreign body mass in stomach
outflow obstruction and colic
spontaneous reflux common
consider location and time of year for Dx / case presentation
dx persimmon problem?
geographic location and season first
endoscopy
exploratory coeliotomy
tx for persimmon-boezer?
Sx
anecdotal - coca cola - questionable
t/f
gastric impaction may be primary OR 2* d/t hepatic dz
true
what is gastric impaction?
- outflow obstruction
- risk of rupture
predisposing factors to gastric impaction?
dental
gastritis
ulceration
dx of gastric impaction?
difficulty passing NG tube
x ray evidence
what is gastrorrhexis?
caused by?
gastric rupture
may be spontaneous or idiopathic
2* to weakness in wall or to distension
potentially but invariably fatal
