Ch.39 Rectum and Anus Flashcards
How long is the rectum in the adult horse?
30cm (12inches)
How long is the anal canal in adult horses?
5cm (2inches)
The internal anal sphincter is what sort of muscle?
Smooth
The external anal sphincter is what sort of muscle?
Striated
The levator ani muscle arises from where?
Ischiatic spine and sacrotuberal ligament
What overcomes the tendency of the anus to prolapse during defecation?
Levator ani muscle
What are the minimal measures required to prevent anal tears
Copious lubrication, sedation, adequate restraint
Most rectal tears caused by rectal palpation occur due to what?
Rupture of the rectal wall as it contracts around the examiner’s hand not finger tips
What horses are most prone to rectal tears?
Arabian, American miniature, mares, horses >9yo
In what direction are IDIOPATHIC rectal tears orientated?
Transversely
Grade 1 rectal tear
Only mucosa and submucosa
Grade 2 rectal tear
Muscular layer only - Rare (2/89)
Causes mucosa and submucosa to prolapse through the muscle defect - creates site for fecal impaction
Grade 3a rectal tear
All layers except serosa
Grade 3b rectal tear
All layers except mesorectum and retroperitoneal tissue
Grade 4 rectal tear
All layers (mucosa, submucosa, muscular, serosal)
Most rectal tears occur where
Dorsally, 4-60cm from the anus and orientated parallel to the longitudinal axis
The only cause which influences size of rectal tear is what?
Dystocia (25cm median)
How long following a rectal tear will a horse show sings of shock and peritonitis
2 hours
Initial first aid in tx of rectal tear
1 - Reduce activity of rectum - sedation/buscopan/epidural
2 - Gentle removal of feces
3 - Tx septic shock/peritonitis - flunixin, gent, k-pen, metro, IV fluids
4 - Epidural and pack rectum
What is used to pack a rectum with a grade 3 rectal tear?
3inch stockinette filled with 0.25kg of moistened rolled cotton sprayed with povidone - iodine and lubricated with surgical gel. Should fill the rectum without distention to a point 10cm cranial to the tear.
How can a TIRL (Temporary Indwelling Rectal Liner) be fashioned?
Palpation sleeve minus hand glued to a 5cm diameter 7.5cm long rectal prolapse ring with holes through with Dacron loops are laced
After how long will the TIRL (Temporary Indwelling Rectal Liner) be passed in faces
9-12 days
Maintenance of a horse with a TIRL (Temporary Indwelling Rectal Liner)
Cross tie, oil, laxatives, soft feed
Where can a loop colostomy be positioned on the abdomen?
- High left flank
- Low left flank
- Ventral midline
Reasons for a celiotomy to be performed to treat a rectal tear?
- If colic preceded the tear
- If intra-abdominal repair of the tear in considered feasible
- To empty the large and small colons to reduce stress on the tear
Why should a colostomy not be performed under GA
- Muscle layers shift making accurate placement challenging
- Expensive
- Dehisence in rough recovery
Where is the low flank colostomy placed
Left flank, at level of stifle fold - midway btw fold and costal arch
What size and angle should the low flank incision be for a colostomy
8-10cm
20-30 degrees dorsad from cranial to caudal
When performing a loop colostomy, the segment for the stoma must be how far from the rectum?
1 meter
When performing a loop colostomy which end must most ventral
Orad
What size incision should be made in the anti-mesenteric tenia of the colon to perform the stoma?
8cm - allowing the opening formed to be the same diameter as the small colon lumen
In an end colostomy the aboard section os closed using what method
Parker-Kerr
Complication of end colostomy
Aborad end may atrophy reducing its length and diameter by 50%
How to avoid aborad atrophy in loop colostomy?
High volume water lavage starting 5-7 days post tear
How long typically before a loop colostomy is reversed
6 weeks
What is the main concern of a staples side to side anastomosis of the small colon post colostomy
It transects all the circular muscle fibres along the length of the stoma by necessity - with no circular mm contraction intestinal contents cannot be expelled into the narrow lumen - increase risk of impaction
Preferred suture for transrectal closure of rectal tear
5 Dacron w 6-8cm half circle cutting needle in the middle of the suture
How long are rectal sutures typically left in place after a transrectal recta tear repair
12-14 days
Prognosis for Grade 1 rectal tears w conservative management
93%
Prognosis for Grade 3a/3b rectal tears w conservative management
70%/69%
Type 1 rectal prolapse
Only the rectal mucosa and submucosa project through the anus
Type 2 rectal prolapse
Complete prolapse of the full thickness of all or part of the rectal ampulla
Type 3 rectal prolapse
Small colon intussuscept into the rectum in addition to Type 2 (complete full thickness of all or part of the rectal ampulla)
Type 4 rectal prolapse
The peritoneal rectum and variable lengths of small colon form an intussusception through the anus.
Most common type of rectal prolapse?
1 and 2
Treating types 1 and 2 rectal prolapses
Decrease edema/irritation - glycerine, sugar, lidocaine jelly, lidocaine enema
Epidural
Umbilical tape - purse string - open every 2-4 hours (2 days)
Hold off feed 24hrs
Then laxative diet - 10 days
When might a submucosal resection be indicated regarding rectal prolapse.
If prolapsed tissue is devitalised
Recurring prolapse after conservative tx
Horse continues to strain
Why is the mucosa apposed in a submucosal resection when tx a rectal prolapse
Cover all denuded areas
Prevent extensive granulation tissue
Prevent scarring and stricture formation
Prognosis for atresia ani
Good with sx intervention
Prognosis for atresia coli
Poor
What % of grey horses have melanoma
80% of grey horses over 15 years
