Overview
Definition:
Lateral internal sphincterotomy (LIS) is a surgical procedure involving the division of a portion of the internal anal sphincter muscle
It is primarily indicated for the treatment of chronic anal fissures, a condition characterized by a tear in the anoderm, typically located in the posterior midline, that fails to heal.
Epidemiology:
Anal fissures are common, affecting an estimated 1 in 1000 individuals annually, with a slight female preponderance
Chronic fissures, defined as those persisting for more than 6-8 weeks, account for a significant proportion of anal fissure cases
They are seen across all age groups but are more prevalent in young to middle-aged adults.
Clinical Significance:
Chronic anal fissures cause significant pain, bleeding, and discomfort, leading to a reduced quality of life
The underlying pathophysiology involves a high resting anal tone and a localized lack of vascularity at the fissure site, which hinders healing
LIS addresses this by reducing the anal canal pressure, thereby promoting blood flow and allowing the fissure to granulate and heal
It is considered the gold standard surgical treatment for refractory chronic fissures.
Clinical Presentation
Symptoms:
Severe pain during and after defecation, often described as sharp or tearing
Bright red rectal bleeding, typically seen on toilet paper or the surface of the stool
A palpable skin tag (sentinel pile) at the external edge of the fissure may be present
Itching or irritation around the anus
A palpable bulge or lump in the anal area may indicate an associated abscess or fistula.
Signs:
Visualisation of a linear tear in the anoderm, usually in the posterior midline, with a sentinel pile at its distal end and a hypertrophied anal papilla at its proximal end
Digital rectal examination may elicit severe pain, limiting thorough assessment
A palpable induration or a palpable fistula tract might suggest complications.
Diagnostic Criteria:
The diagnosis of a chronic anal fissure is primarily clinical, based on the presence of a painful, linear tear in the anoderm that has persisted for at least 6-8 weeks
Key features supporting chronicity include induration of the fissure edges, a sentinel pile, and a hypertrophied anal papilla.
Diagnostic Approach
History Taking:
Detailed history of pain characteristics (onset, duration, severity, triggers)
Pattern of bleeding
Bowel habits (constipation, diarrhea)
Previous anal pathologies or surgeries
Any systemic diseases that might affect healing (e.g., inflammatory bowel disease, HIV)
Red flags include prolonged bleeding, fever, pus discharge, or significant weight loss, which may suggest malignancy or other complex pathologies.
Physical Examination:
Inspection of the perianal region for skin tags, fistulae, or external signs of infection
Gentle digital rectal examination to assess resting anal tone, identify the fissure (if tolerated), and check for masses
Anoscopy or proctoscopy may be necessary for precise visualisation if digital examination is not possible or inconclusive, ensuring adequate local anaesthesia if needed.
Investigations:
Generally, investigations are not required for a straightforward diagnosis of chronic anal fissure
However, if red flags are present or if inflammatory bowel disease is suspected, stool studies for infection or occult blood, colonoscopy to rule out underlying colonic pathology, or anoscopy to assess the fissure and anal canal in detail may be considered
Manometry can objectively assess resting anal pressure, though it is not routinely done pre-operatively.
Differential Diagnosis:
Other conditions that can mimic chronic anal fissures include: inflammatory bowel disease (Crohn's disease, ulcerative colitis), sexually transmitted infections (syphilis, herpes), tuberculosis, actinomycosis, anal cancer, and trauma
A history of constitutional symptoms, atypical fissure location, or non-healing despite appropriate treatment should raise suspicion for these differentials.
Management
Initial Management:
Conservative management is the first-line approach for acute fissures and may sometimes be attempted for chronic fissures
This includes dietary modifications (high-fiber diet, adequate fluid intake), stool softeners, topical agents (e.g., glyceryl trinitrate (GTN) ointment, calcium channel blockers), and sitz baths
The goal is to reduce anal canal pressure and promote healing.
Medical Management:
Topical GTN (0.2%-0.4%) ointment applied 2-3 times daily can improve blood flow and reduce anal sphincter tone, promoting healing in up to 50-70% of chronic fissures
Topical diltiazem (2%) or nifedipine (0.2%) ointments are alternatives with similar efficacy and potentially fewer side effects like headache
Botulinum toxin injection into the internal anal sphincter is another non-surgical option
These modalities aim to break the cycle of pain-spasm-ischaemia.
Surgical Management:
Lateral internal sphincterotomy (LIS) is the surgical treatment of choice for chronic anal fissures refractory to conservative management
The procedure involves a partial division of the internal anal sphincter muscle fibers, typically done laterally to minimize the risk of fecal incontinence
It is highly effective, with success rates exceeding 95%.
Surgical Management Procedure Steps:
The LIS procedure can be performed as an open or closed technique
In the open technique, a small incision is made over the fissure, the internal anal sphincter is identified, and a portion (usually 1/3 to 1/2) of its thickness is divided radially
In the closed technique, a small incision is made to expose the internal sphincter, the dividing cut is made, and the external wound is closed
The fissure itself may be excised (fissurectomy) if it is fibrotic or hypertrophied, or left to heal spontaneously after sphincterotomy
The choice of technique depends on surgeon preference and patient factors.
Postoperative Care:
Patients typically experience mild to moderate pain postoperatively, managed with analgesics
Stool softeners are recommended to prevent straining
Sitz baths are encouraged
Patients are usually advised to resume a normal diet, with emphasis on fiber and hydration
Most patients can return to normal activities within a few days to a week
Regular follow-up is recommended to monitor healing.
Complications
Early Complications:
Pain (usually transient and manageable)
Bleeding (mild to moderate, usually self-limiting)
Infection (rare)
Incomplete wound healing
Anal haematoma.
Late Complications:
Fecal incontinence (temporary or permanent, particularly with over-division of the sphincter or in patients with pre-existing sphincter dysfunction)
Anal stricture (rare)
Recurrence of fissure (rare if sphincterotomy is complete and underlying factors are addressed)
Formation of a fistula.
Prevention Strategies:
Meticulous surgical technique is crucial to minimize complications
Precise identification and controlled division of the internal sphincter are key to preventing incontinence
Careful assessment of the anal sphincter tone pre-operatively can identify patients at higher risk
Postoperative management focused on preventing straining and promoting healing is also important.
Prognosis
Factors Affecting Prognosis:
The main factor affecting prognosis is successful sphincterotomy leading to reduced anal pressure
Patient adherence to postoperative care, including stool management and wound care, also plays a role
Pre-existing sphincter damage or associated conditions like IBD can negatively impact outcomes.
Outcomes:
Lateral internal sphincterotomy offers excellent long-term outcomes for chronic anal fissures, with a high success rate (over 95%) in terms of fissure healing and pain relief
Most patients experience rapid improvement in symptoms after surgery
Recurrence rates are low.
Follow Up:
Routine follow-up appointments are typically scheduled at 2-4 weeks post-surgery to assess wound healing and symptom resolution
Further follow-up may be necessary for patients with complex histories or any persistent concerns
Long-term follow-up is generally not required for uncomplicated cases.
Key Points
Exam Focus:
LIS is the gold standard for chronic anal fissures refractory to conservative management
Key pathophysiology: high resting anal tone leading to ischaemia
Risks of LIS include faecal incontinence and recurrence.
Clinical Pearls:
Always consider conservative management first
Differentiate between acute and chronic fissures
The presence of a sentinel pile and hypertrophied anal papilla strongly suggests chronicity
Adequate pain control post-operatively is paramount for patient comfort and early mobilization.
Common Mistakes:
Performing LIS for acute fissures or fissures that are easily healing with conservative measures
Incomplete division of the internal sphincter, leading to recurrence
Over-division of the sphincter, causing incontinence
Failing to consider underlying conditions like IBD or malignancy in atypical presentations.