Ch.39 Rectum and Anus

Question 1

How long is the rectum in the adult horse?

Answer 1

30cm (12inches)

Question 2

How long is the anal canal in adult horses?

Answer 2

5cm (2inches)

Question 3

The internal anal sphincter is what sort of muscle?

Answer 3

Smooth

Question 4

The external anal sphincter is what sort of muscle?

Answer 4

Striated

Question 5

The levator ani muscle arises from where?

Answer 5

Ischiatic spine and sacrotuberal ligament

Question 6

What overcomes the tendency of the anus to prolapse during defecation?

Answer 6

Levator ani muscle

Question 7

What are the minimal measures required to prevent anal tears

Answer 7

Copious lubrication, sedation, adequate restraint

Question 8

Most rectal tears caused by rectal palpation occur due to what?

Answer 8

Rupture of the rectal wall as it contracts around the examiner’s hand not finger tips

Question 9

What horses are most prone to rectal tears?

Answer 9

Arabian, American miniature, mares, horses >9yo

Question 10

In what direction are IDIOPATHIC rectal tears orientated?

Answer 10

Transversely

Question 11

Grade 1 rectal tear

Answer 11

Only mucosa and submucosa

Question 12

Grade 2 rectal tear

Answer 12

Muscular layer only - Rare (2/89)

Causes mucosa and submucosa to prolapse through the muscle defect - creates site for fecal impaction

Question 13

Grade 3a rectal tear

Answer 13

All layers except serosa

Question 14

Grade 3b rectal tear

Answer 14

All layers except mesorectum and retroperitoneal tissue

Question 15

Grade 4 rectal tear

Answer 15

All layers (mucosa, submucosa, muscular, serosal)

Question 16

Most rectal tears occur where

Answer 16

Dorsally, 4-60cm from the anus and orientated parallel to the longitudinal axis

Question 17

The only cause which influences size of rectal tear is what?

Answer 17

Dystocia (25cm median)

Question 18

How long following a rectal tear will a horse show sings of shock and peritonitis

Answer 18

2 hours

Question 19

Initial first aid in tx of rectal tear

Answer 19

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

Question 20

What is used to pack a rectum with a grade 3 rectal tear?

Answer 20

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.

Question 21

How can a TIRL (Temporary Indwelling Rectal Liner) be fashioned?

Answer 21

Palpation sleeve minus hand glued to a 5cm diameter 7.5cm long rectal prolapse ring with holes through with Dacron loops are laced

Question 22

After how long will the TIRL (Temporary Indwelling Rectal Liner) be passed in faces

Answer 22

9-12 days

Question 23

Maintenance of a horse with a TIRL (Temporary Indwelling Rectal Liner)

Answer 23

Cross tie, oil, laxatives, soft feed

Question 24

Where can a loop colostomy be positioned on the abdomen?

Answer 24

1. High left flank
2. Low left flank
3. Ventral midline

Question 25

Reasons for a celiotomy to be performed to treat a rectal tear?

Answer 25

1. If colic preceded the tear 2. If intra-abdominal repair of the tear in considered feasible 3. To empty the large and small colons to reduce stress on the tear

Question 26

Why should a colostomy not be performed under GA

Answer 26

1. Muscle layers shift making accurate placement challenging 2. Expensive 3. Dehisence in rough recovery

Question 27

Where is the low flank colostomy placed

Answer 27

Left flank, at level of stifle fold - midway btw fold and costal arch

Question 28

What size and angle should the low flank incision be for a colostomy

Answer 28

8-10cm 20-30 degrees dorsad from cranial to caudal

Question 29

When performing a loop colostomy, the segment for the stoma must be how far from the rectum?

Answer 29

1 meter

Question 30

When performing a loop colostomy which end must most ventral

Answer 30

Orad

Question 31

What size incision should be made in the anti-mesenteric tenia of the colon to perform the stoma?

Answer 31

8cm - allowing the opening formed to be the same diameter as the small colon lumen

Question 32

In an end colostomy the aboard section os closed using what method

Answer 32

Parker-Kerr

Question 33

Complication of end colostomy

Answer 33

Aborad end may atrophy reducing its length and diameter by 50%

Question 34

How to avoid aborad atrophy in loop colostomy?

Answer 34

High volume water lavage starting 5-7 days post tear

Question 35

How long typically before a loop colostomy is reversed

Answer 35

6 weeks

Question 36

What is the main concern of a staples side to side anastomosis of the small colon post colostomy

Answer 36

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

Question 37

Preferred suture for transrectal closure of rectal tear

Answer 37

#5 Dacron w 6-8cm half circle cutting needle in the middle of the suture

Question 38

How long are rectal sutures typically left in place after a transrectal recta tear repair

Answer 38

12-14 days

Question 39

Prognosis for Grade 1 rectal tears w conservative management

Answer 39

93%

Question 40

Prognosis for Grade 3a/3b rectal tears w conservative management

Answer 40

70%/69%

Question 41

Type 1 rectal prolapse

Answer 41

Only the rectal mucosa and submucosa project through the anus

Question 42

Type 2 rectal prolapse

Answer 42

Complete prolapse of the full thickness of all or part of the rectal ampulla

Question 43

Type 3 rectal prolapse

Answer 43

Small colon intussuscept into the rectum in addition to Type 2 (complete full thickness of all or part of the rectal ampulla)

Question 44

Type 4 rectal prolapse

Answer 44

The peritoneal rectum and variable lengths of small colon form an intussusception through the anus.

Question 45

Most common type of rectal prolapse?

Answer 45

1 and 2

Question 46

Treating types 1 and 2 rectal prolapses

Answer 46

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

Question 47

When might a submucosal resection be indicated regarding rectal prolapse.

Answer 47

If prolapsed tissue is devitalised Recurring prolapse after conservative tx Horse continues to strain

Question 48

Why is the mucosa apposed in a submucosal resection when tx a rectal prolapse

Answer 48

Cover all denuded areas Prevent extensive granulation tissue Prevent scarring and stricture formation

Question 49

Prognosis for atresia ani

Answer 49

Good with sx intervention

Question 50

Prognosis for atresia coli

Answer 50

Poor

Question 51

What % of grey horses have melanoma

Answer 51

80% of grey horses over 15 years