Chapter 39 - Rectum and Anus Flashcards
What is the approximate length of the rectum in an adult horse?
The rectum is approximately 30 cm long in an adult horse.
What factors influence the distance from the anus to the peritoneal reflection?
The distance from the anus to the peritoneal reflection is highly variable and is shorter in young horses and in horses with little body fat.
How is the peritoneal part of the rectum attached dorsally?
The peritoneal part of the rectum is attached dorsally by the mesorectum, which is a continuation of the mesocolon.
What forms the dilation in the retroperitoneal part of the rectum?
The retroperitoneal part of the rectum forms a dilation called the rectal ampulla, which has thick longitudinal muscle bundles.
What structures enclose the anal canal?
The anal canal is enclosed by the internal anal sphincter, a thickening of the circular smooth muscle, and the external anal sphincter, composed of striated muscle.
From where does the levator ani muscle arise, and what is its action?
The levator ani muscle arises from the ischiatic spine and sacrotuberal ligament. Its action overcomes the tendency of the anus to prolapse during defecation.
Why are rectal tears considered life-threatening injuries?
due to the risk of peritonitis and endotoxic shock. The risk of a malpractice claim against the veterinarian is influenced by the standard of care applied after the tear.
What are the minimal measures required to prevent iatrogenic rectal tears during examination?
Copious lubrication of the hand and forearm and adequate restraint of the horse, including sedation if necessary, are regarded as the minimal measures required to prevent iatrogenic rectal tears during examination.
What causes most rectal tears resulting from palpation per rectum?
Most rectal tears caused by palpation per rectum result from rupture of the rectal wall as it contracts around the examiner’s hand or forearm and not from penetration with the fingertips.
Which horse breeds, gender, and age groups are most prone to rectal tears?
Arabian horses, American Miniature Horses, mares, and horses older than 9 years are the breeds, gender, and age groups most prone to rectal tears.
How are rectal tears classified based on severity?
Rectal tears are classified into four grades based on severity:
grade I involves the mucosa and submucosa,
grade II involves the muscular layer
grade III involves all layers except the serosa (grade IIIa) or mesorectum and retroperitoneal tissues (grade IIIb),
grade IV involves all layers and allows fecal contamination of the peritoneal cavity.
a) Grade I: disruption of mucosa and submucosa, while muscularis andserosal layers remain intact.
Grade II: disruption of muscularis layers, while mucosa, submucosa and serosal layers remain intact.
Grade IIIa: disruption of mucosa, submucosa and muscularis layers while serosa remains intact
Grade IIIb: all 4 layers of the rectum
are disrupted dorsally into the mesocolon, but the mesocolon remains intact
Grade IV: all 4 layers are torn resulting in direct
communication between the rectal lumen and the peritoneal cavity
Where do most rectal tears involve the dorsal aspect of the rectum, and how are they oriented?
Most rectal tears involve the dorsal aspect of the rectum, **located 4 to 60 cm from the anus**, and are oriented parallel to the longitudinal axis.
The cause that appears to influence the size of the tear is ____(1w)
dystocia, with a median size of 25 cm in one study
What is the initial treatment for rectal tears, and why is early diagnosis essential?
Early diagnosis is essential for successful treatment and to avoid legal repercussions. Initial treatment includes (1) reduction of activity of the rectum,
(2) gentle removal of feces from the tear and rectum,
(3) treatment of septic shock and peritonitis, and
(4) administration of **epidural anesthesia **and packing of the rectum
What materials are used for rectal packing to prevent conversion of a grade III to a grade IV tear?
Rectal packing is done using a 7.5-cm stockinette filled with 0.25 kg of moistened rolled cotton, sprayed with povidone-iodine, and lubricated with surgical gel.
Which medications are administered for treatment of rectal tears?
Flunixin meglumine (1.1 mg/kg IV BID), sodium or potassium penicillin (22,000 IU/kg BW IV QID), gentamicin (6.6 mg/kg IV SID), and metronidazole (15 mg/kg PO QID) are administered for treatment.
Intravenous fluids are required to treat shock.
How can rectal tears be assessed and treated after initial first aid?
Rectal tears can be assessed through epidural anesthesia, xylazine (0.1-0.2 mg/kg), butorphanol tartrate (0.1 mg/kg IV), or butylscopolamine bromide (0.3 m/kg IV) slow, followed by lidocaine enema (12 mL of 2% lido in 50 mL tap water) or lidocaine jelly application.
Rectal tears are treated with appropriate antibiotics, and daily inspection and careful evacuation of the rectum may be sufficient for grade I and II tears.
Which grades require surgery?
Grade 1 & 2 tears RARELY require sx
*Grade 1 respond well to abx (TMPS),flunixin, mineral oil & dietary changes i.e. bran mashes,moistened pellets, or grass, to reduce fecal volume and soften the consistency
*Grade 3 can require sx BUT medical management can be successful (less ££)
Mair 2000 EVJ Supp –6/8 tx successfully with medical management grade 3b tearsALL developed septic peritonitis,3/6 developed rectal diverticulum in the tear – WITHOUT apparent C/S (onlymanually evacuate rectum if the tear becomes impacted)
*Full-thickness tears into retroperitoneal space maybe treated with manual evacuation of feces, abx, fecal softener, & packing with gauze soaked in antiseptic solution until defect fills with granulation tissue *
What are the repair techniques?
1.TEMPORARY INDWELLING RECTAL LINER
2.COLOSTOMY: LOOP COLOSTOMY
3.COLOSTOMY: END COLOSTOMY
4.COLOSTOMY REVERSAL
5.TEMPORARY VS PERMANENT COLOSTOMY
- LAPAROSCOPIC REPAIR
- DIRECT SUTRE
Faecal diversion procedures are 2 types of colostomy:
Loop - stoma in antimesenteric tenia of SC withouth completly transect the bowel
End colostomy - involves complete transection of SC
What is the purpose of bypass procedures in rectal tears, and how do they prevent complications?
Bypass procedures, such as Temporary Indwelling Rectal Liner (TIRL) and colostomy, divert feces away from grade III and grade IV rectal tears, preventing contamination, impaction, tear enlargement, and progression of peritonitis.
What is the procedure being performed?
Fig 8: Placement of an indwelling rectal liner in the distal small colon(a, b) with application of acircumferential ligature and simple interrupted retention sutures (c) and oversewing the circumferential ligature with an inverting continuous Lembert suture pattern (d).
How is a Temporary Indwelling Rectal Liner (TIRL) constructed, and what materials are used?
A temporary indwelling rectal liner can be assembled usinga plastic rectal prolapse ring (ProFix Tube), No. 5 Dacronsuture, a heavy plastic palpation sleeve or arthroscopiccamera sleeve (Video Camera Cover), a rubber band andcyanoacrylic glue (Super Glue).
To assemble a rectal liner, the plastic rectal ring must becut to a length of approximately 5–7.5 cm.
Small holes, 2 mmin diameter, are then drilled into the ring at one end of thecentral groove in a circumferential manner, approximately4 mm apart.
Dacron suture is threaded through the drill holesto act as an anchor for securing the rectal liner withinthe lumen of the small colon.
After removing the handportion of the sleeve, the wrist portion of the sleeve isfastened to the rectal ring using a rubber band and cyanoacrylic glue and is inverted after attachment toprotect intestinal mucosa from irritation by the plastic of therectal ring (Fig 6).The indwelling
Figure 7 - Placement of an indwellingrectal liner in the distal small colon.
Fig 6: Assembly of a temporaryindwelling rectal liner by cutting oneend of a porcine rectal ring to alength of 5–7.5 cm and drillingadditional holes into the ring (a andb), threading the holes with No. 5Dacron suture (c), applying a rectalsleeve (after the hand has beenremoved) around the rectal ringand holding it in place with a rubberband (d), gluing the rectal sleeve tothe rectal ring with cyanoacrylicglue (e) and inverting the rectalsleeve over the rectal ring (f).
Once you have the indwelling rectal liner ready what is the procedure?
GA - DR - The indwelling rectal liner is manipulated into placethrough a ventral midline celiotomy after an assistant passesthe ring and sleeve through the anus and into the proximalportion of the rectum.
The surgeon manipulates the rectal ringintra-abdominally until it is in the most distal portion of the smallcolon orad to the rectal tear.
Using No. 3 chromic gut, acircumferential ligature is applied around the small colonat the level of the central grove of the rectal ring to constrictthe serosal surface.
4 equidistant simple interrupted retention sutures ofNo. 3 chromic gut are placed around thecircumference of the small colon, incorporatingthe circumferential ligature, the small colon wall and theDacron anchor sutures (Fig 7).
Serosal surface is apposed over the circumferential suture with 3-0 polydioxanonesuture in an inverting suture patterncontinuous Lembert pattern (Fig 8).
PF enterotomy
Flush and cleaning of the SC with hoose directed thorugh ring and liner from anus
What is the goal of the 4 equidistant sutures in TIRL?
*four retention sutures help maintain the ring in a coaxial relationship with thesmall colon so that it doesnot twist and obstruct the lumen
How does the circumferential suture function in TIRL, and when is it expected to cut through the rectal wall?
The circumferential suture in TIRL prevents passage of the ring and liner for approximately 9 to 12 days, allowing time for the apposed colon walls to heal. It is expected to cut through the rectal wall by this time.
What are the complications of this procedure? What can you do to prevent?
*tearing of the sleeve,
retraction of the sleeve into the rectum and uncovering the tear,
and formation of a rectoperitoneal fistula
*Mineral oil post op** – soften feces and prevent impactionat the prolapse ring
When do you perform direct suturing?
Because a grade III tear often progresses to a grade IV tear, direct suturing of these tears may be indicated
Direct suturing is very difficult if tears are notlocated close to the anus because visualisation of the tear isoften poor and manipulation of instruments within the rectummay be difficult because of limited surgical access
Repairs made by direct suturing are oftenperformed blindly.
Elongated instruments, such as the Deschamps needle and a rectal speculum have beendesigned specifically for repair of rectal tears, but may not beavailable in all referral hospitals because they are infrequently used and expensive.
Elevating the tail after caudal epiduralanaesthesia may aid in enlarging the anal orifice, improving access –> ballon of rectum allows better space for suture
A rectal tear that cannot be accessedthrough the anus might be repaired through an antimesentericenterotomy via a ventral midline celiotomy.
Figure 39-1. Impaction of feces into a grade IIIb rectal tear (a), causing progressive enlargement of the perirectal space and bacterial leakage across the peritoneum (b), swelling of the rectal wall (c), and small colon impaction (d). (From Freeman DE, Richardson DW, Tulleners EP, et al. Loop colostomy for management of rectal tears and small colon injuries in horses: 10 cases
Figure 39-2. Placement of a temporary indwelling rectal liner to divert feces from a rectal tear. The expanded view demonstrates the construction of the liner and the method of securing it in place. 1, Tear; 2, rectal liner; 3, rectal prolapse ring; 4, Dacron anchor suture; 5, circumferential suture; 6, retention suture; 7, interrupted Lembert suture.
Figure 39-3. (A) View through the transverse section of the abdomen shows the placement of the loop in the body wall. (B) Loop colostomy created with a double-incision technique with the high flank approach (broken lines) and placement of the stoma in a small low flank incision. The left opening (1) is the orad opening, and the right opening (2) is the aborad opening through which the aborad part of the small colon is flushed to prevent atrophy. (Redrawn from Freeman DE, Richardson DW, Tulleners EP, et al. Loop colostomy for management of rectal tears and small colon injuries in horses: 10 cases [
Suture should be long for direct repair of rectal tears why?
Suture used for direct repair of rectal tears should be longenough to allow knot tying outside the rectum, have lowmemory, resist stretching and resist faecal digestion.
Large-diameter suture should be used as small-diameter suturetends to cut through friable tissue edges
What type of suture is not recommend for direct repair?
Chromic gut is not recommended for direct repairs because ittends to stretch.
Simple interrupted or cruciate suture patternsare preferred over a simple continuous suture pattern becausecontinuous patterns tend to reduce luminal diameter(Freeman 2012).
What are the considerations in choosing the location for a loop colostomy, and why is a double-incision loop colostomy used as a standing procedure?
Loop colostomy locations can include left high flank, left low flank, or ventral midline incision.
A double-incision loop colostomy is used as a standing procedure to minimize:
(1) accurate placement ofthe stoma is difficult because muscle layers shift and landmarksbecome distorted in the recumbent horse compared with thestanding horse;
(2) it is expensive; and
(3) dehiscence ofthe stoma is a risk of rough anesthetic recovery
The loop-colostomy technique is preferred over theend-colostomy technique WHY?
*involves creating enterotomy incision stoma through antimesenteric taenia without resecting completly the SC
*EASIER and QUICKER to construct and reverse
Why is the loop colostomy technique preferred over the end colostomy, and what advantages does it offer?
The loop colostomy is preferred due to its ease of establishment, quick reversal, and prevention of fecal passage into the aboral end. Advantages include gravity assistance, complete fecal diversion, and access for daily flushing to prevent atrophy.
When should you decide to go for colostomy?
When the tear envolves more than 25% of the circumference of the rectum
Single-incision colostomy involves placing the stoma in the same incision used to explore the abdomen and prepare the colon loop, whereas a double incision colostomy involves a separate flank incision for the stoma
What does loop colostomy consist?
*The loop colostomy laces theopening to theoral and aboral segment ofcolon for daily flushing to prevent the atrophy of that segment.Failure to flushthe aborad segment causes atrophy
Where can you create the loop colostomy?
is created in a
- left high flank
- left low flank
- ventral midline incision with advantages and disadvantages.
When do you need to perform a ventral midline?
sx colic that preceded the tear, ifintraabdominal repair of the tear is considered feasible, or if the surgeonelects to empty the large and small colons to reduce stress on the colostomyand risk of impaction
*BUT COLOSTOMY IDEALLY NOT DONE UNDER GA
With single-incision colostomies, incorporation of the colostomy inthe abdominal closure weakens the body wall repair and makesthe ventrally placed stomas, such as the low flank and ventralmidline placements, prone to prolapse and herniation
Figure 39-4. Loop colostomy placed in the low flank by a double-incision technique as a standing procedure 2 days earlier. Congestion in the mucosal shelf separating the orad and aborad parts of the small colon is typical for this stage.
Figure 39-5. Loop colostomy placed in the low flank by a double-incision technique as a standing procedure, 60 days later (horse is not that shown in Figure 39-4). The stoma is mature and healed to the surrounding skin; the mucosal shelf is evident as a small bulge in its midpoint.
Describe the procedure
Dobule-incision loop colostomy
High flank to prepare the colon loop and guide it to separate low flank incision
Low flank incision midway between the flank fold and the costal arch at same level as the fold
Explain how you would construct the modified grid transverse flank laparo
The stoma is made in a segment of SC orad to rectal tear
At least 1 maway from the rectum
*Exteriorize the colon and SC isfolded to form a loop
*2 arms of the loop are sutured together 8 cmcontinuous Lembert pattern size 0 polydioxanone midway between the mesentericand antimesenteric teniae.
*As the suture line approaches the end loop it should be close to the mesocolon so that antimesenteric band is outermost
How do you perform bypass with double incision loop colostomy?
*Ideal as standingprocedure - allowsplacement of the colostomy in a small but secure incision in the ventralbody wal
l *Highflank incision - prepare colon loop, guide it intoa separate low flank incision, midway between the flank fold (just in front ofthe stifle) & the costal arch, and at the same level as the fold
*Fecal balls can drop away from thestoma without contacting and soiling the abdominal skin
*Lowflank incision (8-10 cm long) - extends throughall layers, with deep dissection guided by a hand through high flank incision- angled dorsad from cranial to caudalby 20-30 degrees *Small transverse incisions are madein muscles & fascia to eliminate constricting bands that could restrictfecal passage
Figure 39-8. (A) Deschamps needles, showing the rightandleft-handed configurations with 20-cm needles (right)and the 45-cm needle that is suitable for rectal tears (left).(B) Close view of the end of a Deschamps needle. Thethreaded eye near the pointed tip allows easy retrieval ofthe suture without the need for complete penetration bythe needle. Once the suture is grasped at the tip of theneedle, the instrument is rotated backward out of the tissueand can be rethreaded for the next bite.abcABCFigure 39-9. (A) Method of inserting the Deschamps needle into therectum and guiding it to the tear while protecting the tissues with theright hand. (B) The Deschamps needle grasps both sides of the tear andpulls the suture through it as well. (C) Suture placement for a grade IVtear. a, Serosa; b, muscularis; c, mucosa.
Figure 39-6. End-to-end anastomosis of the small colon with an interrupted Lembert pattern, using a 2-0 silk suture. The colostomy was reversed 21 days earlier, but the horse was euthanized because of laminitis.
Figure 39-7. Diagram showing the first bite of the nonvisual direct suturing technique being placed in the center of the caudal edge of the tear. The needle, held with the thumb and first two fingers, is inserted approximately 1.5 cm from the edge of the wound and guided into the defect subserosally by the second or third finger.
Figure 39-8. (A) Deschamps needles, showing the right- and left-handed configurations with 20-cm needles (right) and the 45-cm needle that is suitable for rectal tears (left). (B) Close view of the end of a Deschamps needle. The threaded eye near the pointed tip allows easy retrieval of the suture without the need for complete penetration by the needle. Once the suture is grasped at the tip of the needle, the instrument is rotated backward out of the tissue and can be rethreaded for the next bite.
Figure 39-9. (C) Suture placement for a grade IV tear. a, Serosa; b, muscularis; c, mucosa.
Figure 39-10. Type IV rectal prolapse in a postpartum mare.
Define the grade
Type I -Only rectal mucosa andsubmucosa are projected through the anus
Define the grade
Define the grade
Type IV : small colon prolapses through anus typical in dystocia of mares
Figure 39-12. Partially completed anastomosis retained in position outside the anus with crossed 14-gauge, 5.25-in-long Teflon catheters with the stylet in place. The mucosal closure has been completed on top and the visible sutures are full-thickness horizontal mattress sutures. This mare (the same one shown in Figure 39-10) made a complete recovery.\
describe procedure
igure 39-11. Treatment of a type IV rectal prolapse with intussusception of the aborad part of the small colon and peritoneal segment of the rectum. (A) The prolapsed tissues are resected as described and the healthy tissues anastomosed. (B) When the stabilizing cross-catheters or needles are released, the anastomosis assumes its position in the orad part of the rectum or in the abdomen. (From Edwards GB. Diseases and surgery of the small colon.
Figure 39-13. Atresia ani in a 5-day-old filly, with meconium staining of the perineum caused by defecation through a rectovaginal fistula.
Figure 39-14. (A) A large melanoma that deformed the anus and interfered with defecation. (B) The same horse after excision. Penrose drains are placed in the dead space created by the deep perirectal dissection required to remove the large masses completely. Small tumors were not removed so that sufficient skin remained for closure.
