Abnormal Conditions of the Equine Large Intestine Flashcards
what comprises the “large” intestine?
cecum
large colon
small colon and rectum
what side of the horses body is the cecum on?
right side of the abdomen
what is the most common pathologic condition of the cecum?
cecal impaction
what are a large amount of fatalities from cecal impaction due to?
cecal rupture
How does hospitalization or surgery/general anesthesia within previous 5 days lead to cecal impaction?
NSAIDS and lack of exercise
what is important about clinical signs and cecal impaction?
clinical signs may be mild and underestimated
horse does not seem that painful but then cecum ruptures and horse dies
How do you diagnose a cecal impaction?
GI sounds decreased (borborygmi)
fecal production decreased
rectal palpation - tension in ventral cecal band, sacculations disappear, distended structure on right abdomen
where is the tension in a cecal impaction?
ventral cecal band
Are changes in peritoneal fluid an indicator of cecal deterioration?
not always
what are the two types of cecal impactions?
type 1 - mechanical obstruction
type 2 - cecal dysfunction
which cecal impaction can be indented with fingers, the walls do not feel thickened, and the cecum contains firm, dry, or doughy ingesta?
type 1 - mechanical obstruction
which cecal impaction does the cecum feel tightly distended with gas and ingesta of normal or fluid consistency?
type 2 - cecal dysfunction
How do you treat the two types of cecal impaction?
type 1 - medical treatment
type 2 - surgical treatment
why can a type 1 cecal impaction be managed medically?
ingesta can be softened to allow cecal contraction to empty cecal contents into right ventral colon
why does type 2 cecal impaction need to be managed surgically? (what needs to be done that is not done medically?)
decompression
typhlotomy and evacuation
cecal bypass (cecocolic anastomosis)
How is a type 1 cecal impaction managed medically?
withhold feed, IV fluids, oral laxatives via nasogastric tube (mineral oil, magnesium sulfate, DSS), psyllium, walked and limited controlled grazing to stimulate motility, analgesics
when should a cecal impaction be considered for surgery?
no improvement on rectal palpation during 24-36hr period
signs of systemic deterioration
increase in pain
cecum feels tight enough to rupture
what is the prognosis for cecal impaction?
57-90% survival for medical
29-90% survival for surgery
if surgery is an option refer it
Map out the pathway of the large colon
cecum > right ventral colon > sternal flexure > left ventral colon > pelvic flexure > left dorsal colon > diaphragmatic flexure > right dorsal colon
what are some abnormalities of the large colon?
tympany, impaction, sand impaction, enterolithiasis, displacement, volvulus
what are the two types of large colon displacement?
nephrosplenic entrapment/left dorsal displacement
right dorsal displacement
what is large colon tympany?
gas colic, spasmodic colic
results from excessive gas fermentation > distension and pain
what is the most commonly reported colic in horses?
large colon tympany
How is large colon tympany diagnosed?
acute pain +/- abdominal distension
rectal palpation reveals moderate to severe gas distension of large colon
what is a common challenge with large colon tympany?
hard to differentiate from more serious causes of abdominal pain
How is large colon tympany treated?
withhold food, analgesics
what does a lack of response to analgesics with large colon tympany indicate?
more serious problem
large colon volvulus primary differential diagnosis
what are the risk factors for large colon impaction?
windsucking, inc hours spent in stable, no parasite control, travel in previous 24hr, change in regular exercise program, previous colic, lameness, hospitalization, general anesthesia, medication (atropine, morphine)
How is a large colon impaction diagnosed?
pain, bloated, dec GI sounds, dec fecal production
what is the differential diagnoses for a large colon impaction?
large colon displacement +/- right dorsal colon impaction
List the most to least common location for the large colon to get impacted
pelvic flexure > right dorsal colon > transverse colon
How is a large colon impaction treated?
withhold feed, fluid thearpy, analgesic, cathartics (mineral oil)
what are the indications for referral and surgery in a large colon impaction?
uncontrollable pain, dec VC status, abnormal changes in peritoneal fluid (indicates bowel degeneration)
what is the prognosis for large colon impactions?
most respond well to medical therapy
surgical - can have rupture of colon, post-op diarrhea, incisional drainage, septic peritonitis
what are predispositions of large colon sand impaction?
insufficient roughage (fiber) in diet
access to sand (regional)
How many weeks after horses being exposed to sand have they been diagnosed with a sand impaction?
3-8 weeks
How is sand impaction diagnosed?
clinical signs similar to large colon impaction
sand auscultated in ventral abdomen
observation of sand/gravel in feces
abdominal radiography
How is a large colon sand impaction treated medically?
remove horse from access to sand, rehydrate, laxatives (magnesium sulfate, psyllium, mineral oil)
How is a sand impaction treated surgically?
san evacuated through pelvic flexure enterotomy
what do you do if you suspect/diagnose a large colon displacement?
refer
what can happen with the right dorsal colon during a sand impaction surgery?
predisposed to rupture
what is the prognosis for a large colon sand impaction?
good long-term survival
most common complication is post-op diarrhea
How can sand impaction be prevented?
feed off ground, provide additional roughage, psyllium
What are the ways the large colon can get displaced?
-large colon lacks mesenteric attachment to body wall
-pelvic flexure pacemaker
-diet too high in soluble carbohydrates (excessive fermentation and gas distension)
what is a pelvic flexure pacemaker?
contraction of longitudinal muscle layers shorten length of left colons and move pelvic flexure forward diaphragm, followed by caudal movement towards pelvis during relaxation
what is a nephrosplenic entrapment?
left dorsal and left ventral colon migrate lateral to spleen in dorsal direction until entrapped in nephrosplenic space
Is a nephrosplenic entrapment strangulating or non-strangulating?
non-strangulating
what is a nephrosplenic entrapment also called?
left dorsal displacement
How is a left dorsal displacement diagnosed?
transabdominal ultrasound- gas-filled colon dorsal to spleen overs left kidney
rectal palpation
what is the medical treatment for a left dorsal displacement?
what is the surgical treatment for a nephrosplenic entrapment?
what is the pathology?
large colon left dorsal displacement
what is a right dorsal displacement?
retropulsive movement of pelvic flexure with subsequent migration craniad
large colon located between cecum and body wall
what is the pathology?
right dorsal displacement
what does the success of a large colon volvulus treatment rely on?
rapid referral and prompt surgical intervention
where are large colon volvulus more prevalant?
higher prevalence in areas with a high broodmare concentration (parturition risk factor)
How is a large colon volvulus treated?
SURGERY - stabilize preop
what is the prognosis of a large colon volvulus?
mortality rates between 56 to 65%
what is the small colon a continuation of?
transverse colon
what is the small colon suspended by?
long mesocolon
what does the anti mesenteric border of the small colon contain?
longitudinal teniae
What are some abnormal conditions of the small colon?
Simple obstructions (fecal impaction, enterolithiasis, fecaliths, phytobezoars, trichobezoars, meconium)
Vascular lesions
(intramural hematoma, mesocolic rupture, nonstrangulating infarction)
Strangulation lesions(strangulating lipomas, intussusception)
what are the risk factors for enterolithiasis?
feeding alfalfa hay
How are enterolithiasis diagnosed?
acute severe luminal obstruction (severe pain), intermittent mild signs of colic, right dorsal colon discomfort, abdominal distension
How are enterolithiasis treated?
large - surgical
small - pass on their own
what is the prognosis of enterolithiasis?
excellent if there is no local necrosis and in a location where it can be excised
what is the risk of malpractice claim determined by in a rectal tear?
standard of care applied after the tear and the circumstances that led it its occurence
what should be done to avoid rectal tears?
copious lubrication and adequate restraint (sedation if necessary)
How can you tell the rectum tore?
sudden release of pressure, direct palpation of abdominal organs, large amount of blood on sleeve/glove, hemorrhagic feces
what do you do once you’ve confirmed a rectal tear?
assess its severity
inform owner
apply appropriate treatment, including referral
contract liability insurance
How are rectal tears treated?
reduction of rectal activity (IV sedation, caudal epidural, lidocaine enema, Buscopan), gentle fecal removal, treatment of septic shock and peritonitis, refferal
What causes a rectal prolapse?
tenesmus from diarrhea, dystocia, intestinal parasitism, colic, rectal tumor
How are rectal prolapses treated?
