# Anorectal Disease: Hemorrhoids, Fissures, and Fistulae

## Anorectal Anatomy

The dentate (pectinate) line is the mucocutaneous junction that divides the anal canal into upper and lower halves. Above the dentate line, the canal is lined by columnar epithelium, receives visceral innervation (and is therefore insensitive to pain), and contains the internal hemorrhoidal plexus. Below the dentate line, squamous epithelium predominates, somatic innervation makes the area pain-sensitive, and the external hemorrhoidal plexus is located. The internal anal sphincter is composed of smooth muscle under involuntary control and is responsible for 70-80% of resting anal tone, while the external anal sphincter is skeletal muscle under voluntary control and is responsible for squeeze pressure. The anal cushions are three vascular cushions positioned at left lateral, right anterior, and right posterior locations.

## Hemorrhoidal Disease

### Classification

Internal hemorrhoids arise above the dentate line and are graded by severity.

| Grade | Description | Management |
|-------|-------------|------------|
| I | Bleed but do not prolapse | Conservative; office procedures |
| II | Prolapse with straining, reduce spontaneously | Office procedures (rubber band ligation) |
| III | Prolapse, require manual reduction | Office procedures or surgical |
| IV | Permanently prolapsed, cannot be reduced | Surgical (excisional hemorrhoidectomy) |

Grade I hemorrhoids bleed but do not prolapse. Grade II hemorrhoids prolapse with straining but reduce spontaneously. Grade III hemorrhoids prolapse and require manual reduction. Grade IV hemorrhoids are permanently prolapsed and cannot be reduced. External hemorrhoids arise below the dentate line and are covered by anoderm. Mixed hemorrhoids have both internal and external components.

### Presentation

Internal hemorrhoids typically present with painless bright red bleeding seen on toilet paper or dripping into the bowl, prolapse, mucous discharge, and pruritus. External hemorrhoids cause perianal swelling, discomfort, and difficulty with hygiene. A thrombosed external hemorrhoid presents with acute onset of severe perianal pain and a firm, tender, bluish mass.

### Conservative Management

First-line treatment includes fiber supplementation (25-35 g/day) and adequate hydration, sitz baths, and topical agents such as hydrocortisone and lidocaine. Patients should be advised to avoid straining and prolonged sitting on the toilet. Conservative measures are effective for Grade I and most Grade II hemorrhoids.

### Office-Based Procedures (Grade I-III Internal)

Rubber band ligation is the most effective office procedure and is placed above the dentate line. One or two sites are treated per session, with repeat sessions at 4-6 week intervals. Complications include pain (if the band is placed too close to the dentate line), bleeding at 7-10 days post-procedure, and rarely pelvic sepsis. Sclerotherapy involves injection of a sclerosing agent such as phenol in oil into the submucosa. Infrared coagulation is an option for Grade I-II hemorrhoids.

### Surgical Management

Excisional hemorrhoidectomy is indicated for Grade III-IV hemorrhoids, failed office procedures, significant external components, and thrombosed hemorrhoids. The Ferguson (closed) technique, which involves excision with primary closure of the wound, is most commonly performed in North America. The Milligan-Morgan (open) technique, which leaves wounds open, is more prevalent in the UK and Europe. It is essential to preserve adequate mucosal bridges between excision sites to prevent stenosis. Pain is the major postoperative issue, and multimodal analgesia with NSAIDs, acetaminophen, local anesthetics, and metronidazole is recommended.

Stapled hemorrhoidopexy (PPH/Longo procedure) uses a circular stapler to excise a ring of redundant mucosa above the dentate line. It produces less pain than excisional hemorrhoidectomy but has a higher recurrence rate and risks serious complications including rectal perforation, rectovaginal fistula, and chronic pain. Its popularity has declined.

Transanal hemorrhoidal dearterialization (THD/HAL-RAR) involves Doppler-guided ligation of hemorrhoidal arteries combined with mucopexy. It causes less pain and is used for Grade II-III disease but has moderate recurrence rates.

### Thrombosed External Hemorrhoid

A thrombosed external hemorrhoid should be excised (not simply incised and drained) within 48-72 hours of symptom onset. The procedure involves elliptical excision of the overlying skin and thrombus under local anesthesia. After 72 hours, when the pain is typically improving, conservative management with sitz baths, analgesics, and stool softeners is appropriate.

<image>Diagram of the anal canal showing internal and external hemorrhoidal plexuses, their relationship to the dentate line, and the grading system for internal hemorrhoids</image>

## Anal Fissure

### Pathophysiology

An anal fissure is a tear in the anoderm, located in the posterior midline in approximately 90% of cases. It is caused by passage of hard stool, which leads to internal anal sphincter spasm, ischemia, and impaired healing. Anterior fissures are more common in women, especially postpartum. An atypical location (lateral) should raise suspicion for Crohn's disease, HIV, syphilis, tuberculosis, or malignancy.

### Classification

Acute fissures have been present for less than 6 weeks and appear as a superficial tear. Chronic fissures persist beyond 6-8 weeks and develop characteristic features: a sentinel pile (skin tag) externally, a hypertrophied anal papilla internally, and visible fibers of the internal anal sphincter at the base of the fissure.

### Conservative Management (First Line)

Conservative measures include fiber supplementation, stool softeners, and sitz baths. Topical nitroglycerin 0.2-0.4% relaxes the internal anal sphincter, though headache occurs in 20-30% of patients. Topical diltiazem 2% has similar efficacy with fewer side effects. The healing rate with medical therapy is 50-70%.

### Botulinum Toxin Injection

Botulinum toxin is a second-line option for patients who fail topical therapy. It is injected into the internal anal sphincter at a dose of 20-100 units, producing a chemical sphincterotomy effect lasting 2-3 months. The healing rate is 60-80%. Temporary incontinence to flatus occurs in 5-10%.

### Lateral Internal Sphincterotomy (LIS)

Lateral internal sphincterotomy is the gold standard surgical treatment for chronic anal fissure refractory to medical therapy. The procedure involves division of the internal anal sphincter from its distal end to the level of the dentate line, using either an open or closed technique. The healing rate exceeds 95%. The risk of minor incontinence to flatus is 5-10%, while significant fecal incontinence is rare at less than 1%. The procedure should be avoided in patients with prior obstetric injury, low resting pressures, or Crohn's disease. Anal manometry should be considered preoperatively in women and patients with continence concerns.

### Fissurectomy with Advancement Flap

Fissurectomy with a V-Y advancement flap is an alternative for patients at risk of incontinence, such as multiparous women or those with prior sphincter injury. The fissure is excised and the defect is covered with a flap, preserving sphincter integrity.

<image>Cross-sectional diagram of the anal canal showing a chronic posterior anal fissure with sentinel pile, hypertrophied anal papilla, and exposed internal anal sphincter fibers at the base</image>

## Anorectal Abscess

### Classification (by Location)

Perianal abscesses are the most common type (60%) and are superficial, adjacent to the anal verge. Ischiorectal abscesses lie deep to the external sphincter in the ischiorectal fossa. Intersphincteric abscesses are located between the internal and external sphincters. Supralevator abscesses sit above the levator ani muscle, are rare, and require imaging to define the anatomy.

### Management

Anorectal abscess is a surgical emergency requiring incision and drainage; antibiotics alone are insufficient. Adequate drainage with a cruciate or elliptical incision is essential. The cavity is packed loosely, and follow-up wound care is arranged. Antibiotics are indicated only in the setting of extensive cellulitis, immunosuppression, prosthetic valves or devices, or diabetes. A fistula develops after drainage in 30-50% of cases. MRI or endoanal ultrasound is useful for recurrent or complex abscesses and to define anatomy before surgery. Crohn's disease should always be considered in patients with recurrent or complex abscesses.

### Horseshoe Abscess

A horseshoe abscess communicates across the deep postanal space. It requires drainage of the deep postanal space with counter-drains placed in the ischiorectal fossae. The Hanley procedure involves unroofing of the deep postanal space.

## Anal Fistula

### Goodsall's Rule

Goodsall's rule provides a guide to fistula anatomy: anterior fistulae tend to follow a straight radial path to the anal canal, while posterior fistulae tend to curve to the posterior midline. This rule is useful but not always reliable.

### Parks Classification

| Parks Type | Frequency | Tract Course | Treatment |
|-----------|-----------|--------------|-----------|
| Intersphincteric | 45% | Between internal and external sphincters | Fistulotomy |
| Transsphincteric | 30% | Through both sphincters into ischiorectal fossa | Low: fistulotomy; High: seton/LIFT/flap |
| Suprasphincteric | 20% | Above puborectalis, descends through ischiorectal fossa | Seton, LIFT, advancement flap |
| Extrasphincteric | 5% | Outside sphincter complex entirely | Address underlying cause; complex repair |

The Parks classification describes four types of anal fistula based on their relationship to the sphincter complex. Intersphincteric fistulae are the most common (45%), with the tract running between the internal and external sphincters. Transsphincteric fistulae (30%) pass through both the internal and external sphincters into the ischiorectal fossa. Suprasphincteric fistulae (20%) extend above the puborectalis and descend through the ischiorectal fossa. Extrasphincteric fistulae (5%) run outside the sphincter complex entirely and are often secondary to Crohn's disease, trauma, or foreign body.

### Workup

Evaluation includes digital rectal examination and anoscopy. MRI of the pelvis is the gold standard for defining the anatomy of complex fistulae, with endoanal ultrasound as an alternative. Examination under anesthesia is often combined with definitive treatment.

### Surgical Management

#### Simple Fistula (Intersphincteric, Low Transsphincteric)

Fistulotomy, which involves laying open the tract, is the gold standard for simple fistulae, with a healing rate exceeding 90%. It is contraindicated when significant sphincter muscle is involved due to the risk of incontinence, and is considered safe for intersphincteric and low transsphincteric fistulae involving less than 30% of the sphincter.

#### Complex Fistula (High Transsphincteric, Suprasphincteric, Anterior in Women, Recurrent, Crohn's)

Seton placement is a key management tool. A cutting seton slowly cuts through the sphincter but is rarely used today due to incontinence risk. A draining or loose seton maintains drainage, controls sepsis, preserves the sphincter, and serves as a bridge to definitive repair. The LIFT procedure (Ligation of Intersphincteric Fistula Tract) involves an intersphincteric approach to ligate and divide the tract, with success rates of 60-80% and sphincter preservation. Endorectal advancement flap covers the internal opening with a mucosal or full-thickness rectal wall flap and has success rates of 50-80%, though it should be avoided in active Crohn's disease or proctitis. The bioprosthetic fistula plug has variable success rates of 30-60% and is declining in popularity. VAAFT (Video-Assisted Anal Fistula Treatment) uses fistuloscopy to visualize and cauterize the tract and is an emerging technique with limited long-term data. FiLaC (Fistula Laser Closure) uses laser energy to obliterate the fistula tract and is sphincter-sparing with moderate success rates.

<image>Parks classification diagram of anal fistulae showing intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric tracts in relation to the internal and external anal sphincter complex</image>

## Other Anorectal Conditions

### Pilonidal Disease

Pilonidal disease is a chronic infection of the natal cleft and is an acquired condition. Treatment ranges from incision and drainage for acute abscess to excision with primary closure, open healing, or flap closure. The cleft-lift (Bascom) procedure uses off-midline closure and has a low recurrence rate. The rhomboid (Limberg) flap is used for recurrent or complex disease.

### Perianal Condylomata (Anal Warts)

Perianal condylomata are caused by HPV, with types 6 and 11 being the most common. Treatment options include topical agents (imiquimod, podophyllin), electrocautery, and surgical excision. High-resolution anoscopy is recommended for patients with high-risk HPV types (16, 18) to screen for anal dysplasia and squamous cell carcinoma.

### Anal Cancer (Squamous Cell Carcinoma)

The primary treatment for anal squamous cell carcinoma is chemoradiation using the Nigro protocol (5-FU plus mitomycin C plus radiation). Surgery with abdominoperineal resection is reserved for residual or recurrent disease after chemoradiation. Risk factors include HPV infection, HIV, immunosuppression, and receptive anal intercourse.

## Clinical Pearls

Fistulotomy should never be performed when the amount of sphincter involved is uncertain; a seton should be placed first and definitive treatment planned with imaging. Lateral fissures are not typical anal fissures and should be biopsied to rule out Crohn's disease, malignancy, or infectious etiologies. Thrombosed external hemorrhoids should be excised (not incised and drained) within 48-72 hours for the best results. Crohn's disease should always be considered in patients with recurrent or complex anorectal abscesses and fistulae. Lateral internal sphincterotomy has a greater than 95% cure rate for chronic fissure but carries a small permanent risk of incontinence and should be reserved for patients who have failed medical therapy. Anorectal abscess requires surgical drainage, as antibiotics alone will not resolve a true abscess. Stapled hemorrhoidopexy has fallen out of favor due to rare but serious complications and higher recurrence rates.

## References
- Davis BR, et al. The American Society of Colon and Rectal Surgeons clinical practice guidelines for the management of hemorrhoids. Dis Colon Rectum. 2018;61(3):284-292.
- Stewart DB, et al. Clinical practice guideline for the management of anal fissures. Dis Colon Rectum. 2017;60(1):7-14.
- Vogel JD, et al. Clinical practice guideline for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula. Dis Colon Rectum. 2016;59(12):1117-1133.
- Parks AG, et al. A classification of fistula-in-ano. Br J Surg. 1976;63(1):1-12.
- Nelson RL, et al. Non-surgical therapy for anal fissure. Cochrane Database Syst Rev. 2012;(2):CD003431.