Exam 4: Conditions of the Equine Large Intestines and Rectal Tears

what is the function of the large intestine and its relation to colic

• cecum functions in fluid resorption and initiation of microbial digestion

• large colon further functions in fluid resoprtion and digestion

• majority of large intestinal colics are caused by non-strangulating lesions

• overall improved prognosis for large intestinal lesions compared to small intestines

what are the common clinical signs of large intestinal colic

• abdominal pain

• decreased or absent borborygmi

• large intestinal gas distension

• tachycardia/tachypnea

• toxic/injected MM

• prolonged CRT

• dehydrated

• ± fever

how is NG intubation used in large colon colic

• should be performed on all horses displaying signs of colic

• >2L of net reflux abnormal

• reflux is uncommon in horses with primary large intestinal disease

• secondary simple obstruction of SI can occur, gastric impactions secondary

how is a rectal exam used for large colon colic

• ingesta in pelvic flexure, impaction?

• gas distension, cecum vs colon vs both

• nephrosplenic space

• tight colonic bands

• displaced large colon

what can be seen on transabdominal ultrasound

• spleen/kidney location

• colonic gas or fluid

• colon wall edema

• colonic vasculature

how might abdominocentesis present with large colon colic

• gas distention may prevent collection

• increased protein with non-strangulating obstruction could indicate need for surgical intervention

• increased lactate = strangulating lesion

how might bloodwork present with large colon colic

• results can be consistent with dehydration with colonic fluid shifts and SIRS/septic shock

• increased lactate with dehydration and strangulating lesion

what are the major cecal conditions

• cecal Tympany

• cecal impaction

• cecocecal intussusception

what is primary cecal tympany

• gas colic

• rapid gas distension due to high grain diet or lush pastures

• reduced cecal motility

what is secondary cecal tympany

• outflow obstruction due to impaction, displacement or torsion of the large colon

what is the etiology of cecal impaction

• dietary factors

• decreased exercise

• NSAIDs

• motility disturbances

• tapeworm

what are the clinical signs and and rectal presentation of cecal impaction

• low grade, intermittent pain

• acute onset severe pain

• signs consistent with GI perforation

• can occur without having any signs of colic prior to rupture

• rectal reveals doughy to firm impaction, severe cecal distention with gas and fluid

what is type 1 cecal impaction

• form, dry impaction of feed material

• fluid and gass usually pass over the impaction

• most common

what is type 2 cecal impaction

cecal dysfunction and fluid distention

soft ingesta and fluid filled cecum

what are the complications of cecal impaction

• compromised cecal wall, peritonitis from leakage

• perforation

• recurrence → unless has cecal motility dysfunction, not likely if management changes are made

how can you prevent recurrence of cecal impaction

• use caution in resuming feeding

• wait 2-4 days after impaction resolved, begin with small amounts of feed with increased water and decreased fiber

• clean, fresh water

• adequate exercise

• surgical → cecal bypass

what is the prognosis of cecal impaction

• 31% horses referred died <24hrs

• short term 81% medical, 95% surgical if recovered

• long term 95% medical, 89% surgical

what is the etiology of cecal intussusception

• unknown, suspected to be related to motility alterations

• parasites such as tapeworms and cyathostomes

• Salmonella a

what are the 3 forms of cecal intussusceptions

• acute - severe abdominal pain

• subacute-severe abdominal pain

• chronic wasting form- mild intermittent pain, fever, reduced fecal output, and chronic weight loss

how is cecal intussuceptions diagnosed

• can be difficult

• rectal exam for firm mass

• ultrasound

what are the major large colon conditions

• feed impactions

• sand impactions

• enteroliths

• displacements

• volvulus

what are the common locations of large colon impaction

• pelvic flexure extending into LVC and LDC

• transverse colon extending into RDC

what are predisposing factors to large colon impaction

• coarse feed

• poor dentition

• foreign materials or bedding

• motility disturbances

• parasites

• recent management changes

• surgery >1hr

• MSK pain, NSAIDs

what are the clinical signs and rectal exam for large colon impaction

• mild to marked intermittent pain, usually controllable with analgesics

• normal MM color

• HR 40-0

• mild dehydration

• decreased Broborygmi

• rectal showing doughy to firm impaction ± gas distension

what might diagnostics real for large colon impaction

• ultrasound showing presence of gas in the large intestine

• increased PCV and TP due to dehydration

• abdominal fluid usually WNL but may have increased TP and WBC if longstanding

how can large colon impactions be prevented?

• dental care

• dietary management using small frequent feedings of good quality roughage, minimize feeding of grain

• ensure water intake

• appropriate exercise

• deny access to sand

• bulk laxative in diet

• appropriate anthelmintics

wha are the potential complications and prognosis of large colon impaction

• recurrent colic

• colonic rupture

• thromophlebitis

• diarrhea

  • overall prognosis is good, 40% have at least 1 recurrent episode

what is the etiology of sand impaction

• short of non-existent grass

• insufficient roughage in diet

• feed on ground with sandy soil

• sand in stalls or paddocks

• geographic area

what are the clinical signs of sand impaction

• intermittent, mild to severe pain

• ± diarrhea

• HR variable 40-60

• may have toxic MM

• ± dehydration

• abdominal auscultation, may hear sand pouring

• sand in feces

how does sand impaction present on diagnostics

• rectal = firm impacted viscous, may not feel due to gas distention

• US- small hyperechoic particles may be seen

• Rads may see sand

• abdominal fluid- WNL to mild increase in TP and WBC, be careful that ventral colon can be heavy with sand and enterocentesis can occur

what is the prognosis of sand impaction

• good to excellent in most cases, but poor if colon ruptures

how can sand impaction be prevented

• feed off the ground

• maintain good quality pasture

• use bulk laxative
  -psyllium hydrophilic muciloid
  -bran in intermittent feedings

• do not use sand in stalls or paddocks

what is enterilithiasis

• mineral concretions that form in the colon, usually found around a nidus

• precipitation of minerals

• magnesium, ammonium, phosphate

• age >4yrs, alfalfa hay feeding

what are the common locations of enterolithiasis

• right dorsal colon

• transverse colon

• small colon

what are the clinical signs of enterolithiasis

• history of intermittent abdominal pain with mild to moderate discomfort

• hr 40-60

• may have diarrhea

• rectal exam has variable findings, from normal to being able to palpate the enterolith

what is the treatment and prognosis of enteroliths

• surgery necessary to remove via enterotomy, presence of polyhedron shaped stone indicates >1

  • good prognosis unless necrosis of the bowel wall occurs at site

what are the kinds of large bowel displacements

• right dorsal displacement

• left dorsal displacement

• pelvic flexure retroflexion

what are predisposing factors for large colon displacement

• large colon is highly mobile

• motility disturbances

• parasites

• large breed horse

• recent foaling

describe right dorsal colon displacement

colon moves into a position between the cecum ad body wall

what are the signs of right colon displacement

• variable pain and hr

• lab findings typically WNL ± increased GGT

• large colon gas distention, taut bands coursing horizontally or diagonally across abdomen

what is the prognosis of right colon displacement

• usually good with appropriate and timely surgical intervention

describe left dorsal displacement

• aka nephrosplenic entrapment

• left colon moves dorsally and becomes entrapped between spleen and left kidney and hangs over the NS ligament

• simple obstruction develops

what are typical findings of left dorsal displacement

• mild to moderate pain, variable HR

• lab typically WNL

• gastric impactions may occur secondary

• rectal shows large colon gas distention, taut and coursing toward nephrosplenic space, LC within the nephrosplenic space

  • cannot ultrasound left kidney

what is large colon volvulus

• twisting of colon around its long axis

• >270 results in lumen and vascular occlusion = strangulation

what is the etiology and risk factors of large colon volvulus

• exact cause unknown

• alterations in GI motility

• changes in VFA content

• electrolyte abnormalities

• broodmare, <100days post partum increases risk

what are the clinical signs of large colon volvulus

• varies with magnitude, as <180 signs similar to displacement but >270 more severe

• HR 40-100

• MM pale to purple

• dehydration occurs rapidly

• extreme abdominal distention

how does large colon volvulus present on rectal exam

• tight distended large colon

• colon may felt transversing the abdomen horizontally in the pelvic inlet

• colon wall thickening

• may be too painful or too distended to palpate

how does large colon volvulus present on ultrasound or abdominocentesis

• colon wall edema, vessel dilation (right side)

• may be too distended to collect fluid without risk of enterocentesis

what is the prognosis for large colon volvulus

• guarded to poor

• depended upon duration prior to surgical correction

• improved prognosis if diagnosed and treated quickly, up to 80%

what are the most common small colon conditions

• impactions

• fecaliths/enteroliths

• strangulating lipomas

• mesenteric rents

what are the risk factors and predilections of small colon impactions

• poor dentition

• poor hay quality

• lack of water

• parasites

• submucosal edema

• motility problems

• older horses and yearlings, miniature horses, ponies, Arabians, fall and winter

what are the clinical signs of small colon impaction

• abdominal pain that is initially mild with slow progression

• straining to defecate, intermittent cramping

• infrequent diarrhea

• history of decreased manure production

• gross abdominal distension may be present

• fever

how might small colon impactions present on diagnostics

• bloodwork- leukopenia is not uncommon, dehydration

• rectal exam- impaction at the small colon, gas distention of the large colon, rough rectal mucosa

• occasional gastric reflux, with severe distension

• abdominocentesis usually WNL

what are the indications for surgery with small colon impactions, prognosis and complications

• increasing abdominal pain

• increasing abdominal distension

• abnormal abdominocentesis

• deteriorating CV

• presence of refllux

• prognosis generally good

• complications include re-impaction, diarrhea, Salmonella

what is the presenting complaint with small colon fecaliths or enteroliths

• miniature and young horses

• straining to defecate may have infrequent diarrhea, history of no recent manure production, gross abdominal distension

how does small colon enterolith present on diagnostics

• abnormal abdominocentesis suggestive of small colon wall compromise

• abdominal Rads low yield

• surgery is indicated

what are the differentials for small colon strangulating

• mesenteric rents

• pedunculated lipoma

• intussusception

• volvulus

• clinical findings similar to non-strangulating lesion except abnormal abdominocentesis and perhaps level of pain

what are the causes of rectal tears

• iatrogenic during rectal palpation or transrectal ultrasound

• dystocia

• enema administration

• breeding accident

• passage of fecalith/enterolith

• idiopathic in aged geldings

what are the signalment risk factors for rectal tears

• arabians and minis

• older horses

• mares due to more frequent palpation and breeding/foaling

• stallions/geldings due to lack of palpation

what is the etiology of rectal tears

• failure of the rectal wall to relax during rectal palpation

• weakening of rectal musculature

• trauma to the rectal mucosa

• 10-2o clock, 15-20cm oral to sphincter

how are rectal tears diagnosed

• history

• sudden decrease in pressure around an examiners arm during the examination

• blood on palpation sleeve, though could be mucosal irritation only

• palpable defect

• rectal scoping

what grade rectal tear

grade 1- through mucosa and submucosal only

what grade rectal tear

grade 2- torn muscularis with intact mucosa and submucosal

what grade rectal tear

grade 3a, serosa only intact layer

what grade rectal tear

grade 3b, mesocolon only intact layer

what grade rectal tear

grade 4, entrance to peritoneal cavity

how are rectal tears prevented

• well restrained- handler on lead, twitch, in stocks

• sedation- alpha-2 adrenergic gonist like xylazine, butorphanol

• n-butylscopolammonium bromide that decreases peristaltic waves

• lidocaine per rectum

• generously lubricated rectal sleeve

• remove feces before exam

• do not move forward while horse is straining

how should liability be handled for rectal tears

• cause of malpractice claims

• not required to inform client of risk, but doing so can protect

• inform owner → provide appropriate emergency treatment → offer referral → maintain detailed records including client communication → notify professional liability insurance

• vets should not admit liability

what are potential sequelae of rectal tears

• periana fistula

• dissecting cellulitis

• formation of rectal diverticulum with grade 2

• rectal stricture

• septic peritonitis with grade 4 → tachycardia, ileus, pyrexia hyperhidrosis, reluctance to move, colic, pain on rectal palp

what is the prognosis for rectal tears

• 1= good

• 2= considered incidental

• 3= fair to guarded

• 4= poor to grave