Sabiston Flashcards
anal Canal Lined By
The proximal anal canal is typically lined by columnar epithelium and the distal anus by squamous epithelium. The junction between the ectoderm and the endoderm, located at the midpoint of the anal canal, appears as an undulating demarcation referred to as the dentate line. Between the dentate line and the anal verge, the mucosa is lined by a modified squamous epithelium
Hemorrhoids Supply
- receive their blood supply from six hemorrhoidal arteries
- The venous drainage is provided by the superior, middle, and inferior hemorrhoidal vessels, allowing for communication between the portal and systemic circulations.
- These vessels form direct arteriovenous communications within the cushions, and for this reason, hemorrhoidal bleeding is arterial rather than venous in nature.
drainage above and below Dentate Line
Venous and lymphatic drainage above the dentate line flows into the internal iliac vessels;
below the dentate line, blood supply and drainage are provided by the inferior hemorrhoidal system.
Internal and External Sphincter
The internal anal sphincter
- autonomically innervated smooth muscle and contributes between 50% to 85% of the resting tone of the anal canal.
- Anatomically, the internal anal sphincter is a thickened continuation of the circular layer of the muscularis propria of the distal rectum and occupies the distal 2 to 4 cm of the anal canal.
The external anal sphincter
- composed of the pelvic floor muscles enveloping the distal rectum and anus.
- The puborectalis muscle, often referred to as the rectal sling, is one of the main muscles contributing to the external anal sphincter.
- It originates at the pubis, passes around the rectum posteriorly, and returns to the pubis. The external anal sphincter is unique because it can be controlled both by the autonomic nervous system and by voluntary contraction
Sphincters Nerve Supply
The internal anal sphincter
- sympathetic (L5) and parasympathetic (S2, S3, and S4) nerves.
The external anal sphincter
- the inferior rectal branch of the pudendal nerve (S2 and S3) and by the perineal branch of S4
Interuption of the nerves of sphincter
- unilateral interruption of the pudendal nerve will not result in external anal sphincter dysfunction, but the loss of bilateral S3 nerve roots (e.g., by surgical transection) will typically result in fecal incontinence.
- If the S1 through S3 nerve roots remain intact only on one side, the patient is still expected to maintain control of the anal sphincters
Which Nerve Transmit Sensation
The rectal branch of the pudendal nerve transmits anal sensation, and it is thought to play a role in maintenance of anal continence.
Organized nerve endings and Function
Meissner corpuscles (touch)
Krause bulbs (temperature sensation)
Golgi-Mazzoni bodies (pressure)
genital corpuscules (friction).
the most commonly used sclerosing agents for hemorrhoids
- the most commonly used sclerosing agents are 5% phenol in almond or vegetable oil and sodium tetradecyl sulfate.
- Injection is performed into the submucosa at the apex of a hemorrhoidal cushion, using approximately 1 ml of sclerosing agent.
- Sclerotherapy is appropriately offered to anticoagulated patients or those receiving antiplatelet therapy
Difference between open and Closed hemorrhoidectomy
- The most commonly used technique is the closed (Ferguson) hemorrhoidectomy
- This approach is associated with decreased postoperative pain, faster wound healing, and a reduced risk of postoperative bleeding compared to an open (Milligan-Morgan) hemorrhoidectomy
Tx of External Hemorrhoids
- Most patients will experience resolution of their symptoms within 72 hours after the onset of symptoms with conservative measures, such as sitz baths, application of lidocaine ointment and stool softeners.
- Acutely tender, thrombosed external hemorrhoids are often surgically removed when pain is excessive and/or fails to respond to expectant management.
- Thrombectomy with evacuation of clot is often performed in the emergency department setting; however, excision of the hemorrhoid is usually a far better option
Botulinum toxin (BT) for Fissure , Dose and Duration of effect
- Botulinum toxin (BT) can produce potent and sustained relaxation of anal sphincter by inducing temporary paralysis of the anal sphincter muscle.
- A typical dose of 20 to 100 IU of BT will produce relaxation lasting approximately 3 months.
If the abscess cavity is larger than 5 cm, what would you do ?
- may consider placing counterincisions and bridge them with penrose drains. This technique avoids large gaping perineal wounds that may result in prolonged healing, scarring, and distortion of the perianal anatomy.
- An alternative to a wide incision and drainage is inserting a drainage catheter that can be left in place for several weeks
When to give Abx ?
patients with high-risk conditions such as immunosuppression, diabetes, extensive cellulitis, prosthetic devices, and high-risk cardiac, valvular, and related anatomical conditions
Why they need Follow Up
- Surgical follow-up is recommended because the abscess may recur in about 10% of patients
- development of a chronic fistula-in-ano occurs in up to 50% of patients.
Goodsall rule
- predict the course of the fistula track and location of the internal opening
- Fistulas with an external opening anterior to the anus typically track in a radial fashion directly into the anal canal
except for those located at a distance greater than 3 cm from the anal verge; this usually indicates an anterior extension of a horseshoe fistula originating posteriorly.
- Fistulas with an external opening posterior to the anus often track in a curvilinear fashion to a posterior midline internal opening.
Rectovaginal fistulas causes
may be the result of
- iatrogenic injury such as a stapled colorectal anastomosis that incorporates vaginal wall or occur as a result of a colorectal anastomotic leak complicated by an abscess that drains into the vagina.
- Crohn disease
- Diverticular disease
- Malignancies, particularly anal cancer,
- Radiation
rectovaginal fistula Tx
- Definitive surgical repair of a low rectovaginal fistula is typically recommended 3 to 6 months after onset to decrease the inflammation in surrounding tissues and enable a successful repair.
- A draining seton, antibiotics, or fecal diversion may be necessary depending on the size, location, and etiology of the fistula.
- Some fistulas may even close spontaneously during this time of expectant management.
- The most popular method of surgical repair is an endoanal sliding advancement flap. This repair involves excision of the fistula tract and closure of the rectal portion of the fistula with a vascularized mucosal flap
-A flap containing mucosa, submucosa, and circular muscle fibers is advanced to cover the anorectal side of the fistula
Antibiotics in PNS ?
Antibiotics may be an important adjunct in surgical treatment of pilonidal disease as bacterial colonization was found to range from 50% to 70%, with typical isolates including Staphylococcus aureus and anaerobes such as Bacteroides.
Chlamydial infection
present with perirectal abscesses, anal fissures, and fistula formation mimicking Crohn disease. Recommended treatment is with azithromycin 1 g orally in a single dose or doxycycline 100 mg orally twice a day for 7 days.
Fournier gangrene (FG)
FG is typically associated with a mixed flora, both aerobic and anaerobic.
Cultures from the wounds commonly show Klebsiella, streptococci, staphylococci, clostridia, Bacteroides, and corynebacteria.
FG Spread
- along the facial planes
- extend to involve the scrotum and penis and can spread through the anterior abdominal wall, up to the clavicles.
- Urogenital infections tend to extend posteriorly along Bucks and Dartos fascia up to the Colles fascia, but are limited from the anal margin by the attachment of the Colles fascia to the perineal body.
- In contrast, anorectal sources of infection usually involve the perianal skin.
- Regardless of the cause of FG, the testes are usually spared as the blood supply originates intraabdominally.
Most cases of anal dysplasia are caused by
HPV, particularly the HPV-16 subtype
Screening Anal Cancer ?
Screening of :
- HIV-positive
- HIV-negative MSM
- bisexual men
with Papanicolaou smear at 2- to 3-year intervals has been shown to be cost-effective with significant benefits on overall life-expectancy.
Other groups that can benefit from screening include all HIV-positive individuals irrespective of their sexual practices, immunosuppressed organ transplant patients, and women with a past history of cervical dysplasia or cancer.
