Rectum, anus, perineum surgery Flashcards
The rectum begins at…
and ends…?
the pelvic inlet and ends ventral to the second or third caudal vertebrae in the beginning of the anal canal.
Most of the rectum is within the peritoneal cavity. A short segment continues retroperitoneally before it joins the anal canal.
The retroperitoneal portion of the rectum lacks
a serosal layer, which can have implications for surgical healing.
Blood supply of the rectum and anus.
Dogs: cranial rectal artery
Cats: cranial, middle and caudal rectal arteries
The anal canal is…?
Length?
a continuation of the rectum to the anus and is only 1 to 2 cm long.
The anal canal is divided into
Three zones:
the columnar zone
the intermediate zone
the cutaneous zone
The columnar zone has
a series of longitudinal mucosal and submucosal ridges called anal columns.
The pockets between these columns are the anal sinuses, which extend caudally and end blindly.
Describe the anal sphincters.
The internal and external anal sphincter muscles surround the terminal rectum and anal canal to control defecation.
The internal anal sphincter is a caudal thickening of the circular smooth muscle lining the anal canal.
The external anal sphincter is a large, circumferential band of skeletal muscle chiefly responsible for fecal continence.
Describe the innervation of the internal anal sphincter muscle.
It is an involuntary smooth muscle that works with other muscles of defecation to prevent indiscriminate defecation.
It is innervated by the parasympathetic branches of the pelvic nerve, which are inhibitory.
Motor fibers from the hypogastric nerves are sympathetic to the internal anal sphincter.
The external anal sphincter is
a large, circumferential band of skeletal muscle chiefly responsible for fecal continence.
The only voluntary nerve supply to the external anal sphincter comes from
the caudal rectal branches of the pudendal nerves.
Indications for colorectal surgery: (5)
resection of masses or nonfunctional bowel and,
to repair rectal prolapse, perforation, or fistulae.
Perineal surgery is most often performed to treat (6)
perineal hernias,
perianal fistulae,
anal sac disease,
tumors, and
other traumatic or
congenital anomalies (e.g., atresia ani).
Preoperative Concerns for rectal and anal surgeries. (4)
Food should be withheld 12 hours before surgery in adult patients (4 to 8 hours in pediatric patients), but free access to water should be allowed.
Laxatives and warm water enemas should be given 24 hours before surgery.
The terminal rectum should be evacuated digitally after anesthetic induction but just before surgery in all patients.
Antibiotics for rectal and anal surgeries.
The risk of infection after colorectal surgery is high.
Systemic perioperative antibiotics effective against anaerobes and Gram-negative aerobes should be given.
Recommended ABs: second-generation cephalosporins (i.e., cefmetazole, cefoxitin, cefotetan) given at the time of induction.
Amikacin plus either ampicillin or clindamycin can be given intravenously at induction.
Suture Materials and Special Instruments for rectoanal surgeries.
Retractors (e.g., Gelpi) are recommended to aid in exposing the surgical field.
Doyen forceps may be needed to occlude or retract the intestine.
Metzenbaum (pic) and iris scissors are indicated for dissection.
For optimal healing, a monofilament, synthetic absorbable suture (e.g., polydioxanone, polyglyconate) and approximating suture patterns (i.e., simple interrupted, or simple continuous) should be used for rectoanal surgery.
Rectal prolapse (anal prolapse) is a protrusion or eversion of the rectal mucosa from the anus.
Rectal prolapse is principally associated with (4)
endoparasitism or enteritis in young animals, and tumors or perineal hernias in middle-aged and older animals.
What predisposes patients to rectal prolapse? (4)
Weakness of perirectal and perianal connective tissues or muscles,
uncoordinated peristaltic contractions, and
inflammation or edema of rectal mucous membranes predisposes patients to rectal prolapse.
Rectal prolapse treatment and prognosis depend on…
the cause, degree of prolapse, chronicity, and whether it is a recurrent prolapse.
Acute rectal prolapse is easily treated, but chronic disease may require resection.
Manual reduction and placement of a purse-string suture around the anus are recommended for
acute prolapses with minimal tissue damage and edema.
Treatment of acute prolapse with minimal tissue damage and edema?
Warm saline lavages, massage, and lubrication (e.g., with a water-soluble gel) should be applied to the everted tissue before digital reduction.
A purse-string suture tight enough to maintain prolapse reduction without interfering with passage of soft stool should be placed.
Rectal prolapse surgery positioning.
The patient should be positioned in sternal recumbency with the hind legs over the end of the table.
The pelvis should be elevated with padding and the tail secured over the back.
Place a probe into the rectal lumen to serve as a guide.
Rectal prolapse surgery procedure: Stay sutures.
Place a probe into the rectal lumen to serve as a guide.
Place three stay sutures (at the 12 o’clock, 5 o’clock, and 8 o’clock positions) through all layers of the prolapse just cranial to the proposed transection site.
These sutures should enter the rectal lumen with the needle being deflected by the probe before being passed through the rectal tissues again.
Rectal prolapse surgery procedure: suturing the transected site.
Transect the traumatized tissue in stages caudal to the stay sutures.
After each stage of the resection, anatomically appose the transected edges with simple interrupted sutures (e.g., 3-0 or 4-0 monofilament absorbable).
Space the sutures approximately 2 mm apart and 2 mm from the cut edge.
Inspect the anastomosis for gaps between sutures.
Remove the stay sutures, and gently replace the anastomotic site in the pelvic or anal canal.
Place a purse-string suture around the anus if postoperative tenesmus is expected.
In case of recurrence of rectal prolapse, ….
colonopexy can be performed.
Anal sac impaction is
an abnormal accumulation of anal sac secretions that occurs secondary to inflammation (anal sacculitis), infection (anal sac abscess), or obstruction of the duct.
Indications for anal sacculectomy.
Failure of medical therapy and suspicion of neoplasia are indications for anal sacculectomy.
If a draining tract persists after anal sac rupture, surgery should be delayed until inflammation is controlled.
Both anal sacs should be removed, even if only one is obviously involved.
Location of anal sacs (glands).
The anal sacs lie between the internal and external sphincter muscles on each side of the anus.
One anal sac lies on each side of the anus between the internal and external anal sphincters.
The anal sac is a cutaneous diverticulum lined by microscopic glands.
The ducts of the anal sacs open in the cutaneous zone at approximately 5 o’clock and 7 o’clock positions.
The duct opening are visible lateral to the anus in the normal contracted state.
Anal sacculectomy: closed technique.
Place a ligature around the duct at the mucocutaneous junction using 4-0 monofilament absorbable suture.
Excise the anal sac and duct, then inspect for completeness of removal.
Control hemorrhage with ligatures, electrocoagulation, or pressure.
Lavage the tissues thoroughly.
Appose subcutaneous tissues with 4-0 interrupted, monofilament absorbable sutures (polydioxanone, polyglyconate, or poliglecaprone 25),
and appose the skin with 3-0 or 4-0 monofilament non-absorbable (nylon, polypropylene, or polybutester) sutures.
Anal sacculectomy: closed technique.
Anal Sacculectomy: open technique.
Place a scissors blade or groove director into the duct of the anal sac.
Apply medial traction on the duct while incising through the skin, subcutaneous tissue, external anal sphincter, duct, and sac.
Continue the incision to the lateral extent of the anal sac.
Elevate the cut edge of the sac and use small Metzenbaum or iris scissors to dissect the sac free of its attachments to muscle and surrounding tissue.
Complete the procedure as for closed sacculectomy.
Anal Sacculectomy: open technique.
Perineal hernias occur when
the perineal muscles separate, allowing rectum, pelvic, and/or abdominal contents to displace perineal skin.
Perineal hernia occurs when pelvic diaphragm muscles fail to support the rectal wall, allowing persistent rectal distention and impaired defecation.
The pelvic diaphragm is stronger in female dogs than in males.
Conditions that cause straining and may predispose to perineal herniation.
Perineal herniation may be unilateral or bilateral.
Most herniations occur between what muscles?
the levator ani, external anal sphincter, and internal obturator muscles (caudal hernia).
Hernial contents are surrounded by a thin layer of perineal fascia (hernial sac), subcutaneous tissue, and skin.
The hernial sac may contain pelvic or retroperitoneal fat, serous fluid, a deviated or dilated rectum, a rectal diverticulum, prostate, urinary bladder, or small intestine.
Organs displaced into the hernia may become obstructed and strangulated.
The pelvic diaphragm is composed of
the paired medial coccygeal and levator ani muscles.
The sacrotuberous ligament in the dog is…?
And in cats…?
a fibrous band running from the transverse process of the last sacral and first caudal vertebrae to the lateral angle of the ischiatic tuberosity rostral to the pelvic diaphragm.
Cats do not have a sacrotuberous ligament
The sciatic nerve lies
just cranial and lateral to the sacrotuberous ligament.
Approach to herniorrhaghy.
An incision is made over the hernia beginning near the tail base and extending just ventral to a point midway between the ischial tuberosity and the pubis.
The incision is curved outward slightly so that it midpoint is directed away from anus.
Herniorrhaphy procedure in general.
Incise the subcutaneous tissue and hernial sac. Identify and reduce the hernial contents by dissecting subcutaneous and fibrous attachments.
Biopsy any abnormal structures within the hernia (e.g., prostate, masses).
Maintain hernial reduction by packing the defect with a moistened, tagged sponge.
Identify the muscles involved in the hernia, the internal pudendal artery and vein, the pudendal nerve, the caudal rectal vessels and nerve, and the sacrotuberous ligament.
Traditional Herniorrhaphy procedure.
Preplace simple interrupted 0 or 2-0 monofilament sutures using a large, curved needle.
Begin suture placement between the external anal sphincter and the levator ani, coccygeus, or both muscles. Space sutures less than 1 cm apart.
As placement progresses ventrally and laterally, incorporate the sacrotuberous ligament for a secure repair if necessary.
To avoid entrapping the sciatic nerve, place sutures through rather than around the sacrotuberous ligament.
Direct ventral sutures between the external anal sphincter and the internal obturator muscle. Be cognizant of the pudendal vessels and nerves at all times to avoid traumatizing these structures.
Tie sutures beginning dorsally and progressing ventrally. Close the subcutaneous tissues in an interrupted or continuous appositional pattern with 3-0 or 4-0 monofilament absorbable suture and close the skin in an appositional interrupted pattern with nonabsorbable suture.
Internal Obturator Transposition Herniorrhaphy procedure.
Incise the fascia and periosteum along the caudal border of the ischium and origin of the internal obturator muscle.
Using a periosteal elevator, elevate the periosteum and internal obturator muscle from the ischium.
Transpose dorsomedially or roll up the muscle into the defect to allow apposition between the coccygeus, levator ani, and external anal sphincter.
Transect the internal obturator tendon of insertion, if necessary, to get adequate coverage of the defect.
Closing the musculature and skin after Internal Obturator Transposition Herniorrhaphy -procedure.
Take care to avoid transection of the caudal gluteal vessels and perineal nerve.
Preplace simple interrupted sutures as with the traditional technique. Begin by apposing the combined levator ani and coccygeus muscles with the external anal sphincter muscle dorsally.
Then place sutures between the internal obturator and external anal sphincter medially and the levator ani and coccygeus muscles laterally.
Whats this?
Internal Obturator Transposition Herniorrhaphy
Mesh for Herniorrhaphy
Try to avoid though, it can cause foreign body reactions.
