A fissure-in-ano is a small tear in the lining of the anal canal. It is common, and it causes disproportionate pain for its small size. This chapter explains fissure-in-ano in full. It covers presentation, examination, differential diagnosis, investigations, and management. This is the same pattern used for every disease chapter in this manual.
11.1 What Is a Fissure-in-Ano
A fissure is a linear tear in the skin of the anal canal, below the dentate line. This area is rich in pain-sensing nerves, as explained in Chapter 1. This is why a fissure causes sharp, severe pain. This differs from painless internal piles above the dentate line.
Most fissures occur in the posterior midline, at 6 o'clock, with the patient in the lithotomy position. A smaller number occur in the anterior midline, at 12 o'clock. Fissures away from the midline are unusual. They should raise suspicion of another cause, such as Crohn's disease, tuberculosis, or malignancy.
Fissures affect people of all ages. They are most common in young and middle-aged adults. They occur equally in men and women. A first episode often follows a period of constipation, or a single episode of passing a particularly hard stool.
11.2 Acute Versus Chronic Fissure
An acute fissure is recent, and looks like a simple, fresh tear. A chronic fissure has been present for six weeks or more. It develops certain features that mark it as chronic.
A sentinel pile — a small skin tag at the lower end of the fissure.
A hypertrophied anal papilla — a small, firm swelling at the upper end of the fissure, inside the anal canal.
Visible fibres of the internal sphincter, at the base of the fissure.
Raised, indurated edges to the tear. This differs from a simple, clean-edged cut.
This distinction matters greatly. An acute fissure usually responds well to conservative treatment. A chronic fissure often needs more active treatment. This is explained later in this chapter.
11.3 Why Fissures Persist: The Vicious Cycle
A fissure often becomes trapped in a self-sustaining cycle. Understanding this cycle explains why treatment is aimed at the internal sphincter.
A hard stool, or an episode of straining, first tears the anal lining.
The pain from this tear causes the internal sphincter to go into spasm.
This spasm raises the pressure inside the anal canal.
High pressure reduces blood flow to the area. This is especially true at the posterior midline. This area already has a relatively poor blood supply.
Poor blood flow slows healing, and the tear fails to close.
The unhealed tear causes more pain, more spasm, and the cycle repeats.
Every effective treatment for fissure works by breaking this cycle. Each one lowers the pressure in the internal sphincter, either temporarily or permanently. This lets the blood flow return, so healing can take place.
This is why treatment for fissure looks so different from treatment for a simple cut elsewhere on the body. A cut on the hand heals with rest and cleanliness alone. A fissure needs its underlying spasm addressed directly. Without this, it will not heal, no matter how much rest is given.
11.4 Presentation
Follow the history-taking method described in Chapter 2. Certain features are typical of fissure-in-ano.
Sharp, tearing pain during defecation. This is the hallmark symptom.
Burning pain that continues for minutes to hours after passing stool.
Bright red bleeding, usually a small streak on the stool or toilet paper, rather than heavy bleeding.
Fear of passing stool. Some patients delay defecation because of this fear. Delay can worsen constipation, and restart the cycle.
A history of hard stool, straining, or a recent change in bowel habit, just before the pain began.
Ask about the duration of symptoms. This helps to judge whether the fissure is likely to be acute or chronic, before examination even begins.
Also ask about the effect on daily life. Some patients avoid food, to avoid the pain of passing stool. Others become anxious about every bowel movement. This distress is real. It deserves acknowledgement, alongside the physical treatment plan.
11.5 Examination
Examination must be gentle, given the severe pain a fissure can cause. Follow the sequence from Chapter 3.
See Chapter 4 for the inspection method. Inspection usually shows the fissure directly. Gently part the buttocks, without forcing the anal margin open, to bring the tear into view.
A sentinel pile, or a visible tear with raised edges, points toward a chronic fissure.
Digital rectal examination is often deferred in a very painful, acute fissure. If attempted, do it with generous lubrication. Stop if the pain is too severe.
Proctoscopy is often not tolerated in the acute phase. It can be deferred until the fissure has begun to heal, unless another diagnosis needs urgent exclusion.
Never force an examination that is clearly causing severe pain. A gentle attempt, with honest documentation, is far better than causing unnecessary suffering. This approach is explained in Chapter 5.
11.6 Differential Diagnosis
Several conditions can mimic a fissure, or cause a fissure-like tear for a different reason.
Perianal abscess or fistula — usually causes swelling and throbbing pain, rather than the sharp pain typical of a simple fissure.
Crohn's disease — can cause fissures that are large, multiple, or away from the midline. These fissures are often less painful than a typical fissure.
Tuberculosis — can cause an atypical, undermined ulcer in the anal canal, especially in areas where tuberculosis remains common.
Anal cancer — can present as a non-healing, irregular ulcer. It must always be considered in a fissure that does not fit the typical pattern.
Sexually transmitted infection — some infections can cause anal ulceration. Ask about a relevant history, with sensitivity.
Some fissures need biopsy, as described in Chapter 8. These include a fissure away from the midline, a fissure that does not heal with standard treatment, and a fissure with an unusual appearance.
Consider a patient with a fissure at 3 o'clock, rather than the usual 6 o'clock or 12 o'clock. This position alone should raise suspicion. Further assessment, including biopsy, is needed before assuming this is a simple fissure.
11.7 Investigations
Most fissures are diagnosed on history and examination alone. Investigation is reserved for specific situations.
Biopsy is taken from any atypical, non-midline, or non-healing fissure. This excludes Crohn's disease, tuberculosis, or malignancy.
Anorectal manometry is described in Chapter 8. It may be used before surgery in select cases. It assesses baseline sphincter pressure. This is especially useful if there is any concern about pre-existing weak continence.
Relevant blood tests, or further assessment, are added if Crohn's disease or another systemic cause is suspected.
11.8 Conservative Management
Conservative treatment is the correct first step for almost every acute fissure. It is also right for many chronic fissures.
A high-fibre diet, and plenty of fluids, to keep the stool soft.
A stool softener, if diet alone is not enough.
Warm sitz baths, several times a day, to ease sphincter spasm and pain.
Good anal hygiene. Avoid harsh soaps, or vigorous wiping. Both can worsen irritation.
These simple measures heal a large proportion of acute fissures within a few weeks. Give this a fair trial before moving to more active treatment.
Explain the vicious cycle to the patient, in simple words. A patient who understands why soft stool matters, and why straining must be avoided, is far more likely to follow the advice given. This understanding also reduces the fear that often builds up around each bowel movement.
11.9 Chemical Sphincterotomy
When simple conservative measures are not enough, chemical treatment is the next step. This aims to relax the internal sphincter without surgery.
Topical glyceryl trinitrate (GTN) ointment is applied to the anal margin. It relaxes the internal sphincter, and improves blood flow. Headache is a common side effect. Warn patients about this in advance.
Topical diltiazem is a calcium channel blocker. It works in a similar way. It is often better tolerated than GTN, with fewer headaches.
Botulinum toxin is injected directly into the internal sphincter. It gives a longer-lasting relaxation. It is useful when topical treatment has failed, or is not tolerated.
Chemical sphincterotomy heals a good proportion of chronic fissures, and avoids the risks of surgery. It should be tried before surgery is considered, in almost every patient without an urgent surgical indication.
A typical course of topical treatment lasts six to eight weeks. Warn the patient that improvement is often gradual, not immediate. Arrange a review visit at the end of this course. This visit judges whether healing is complete, partial, or absent.
11.10 Surgical Management
Surgery is reserved for chronic fissures that have failed an adequate trial of conservative and chemical treatment.
Lateral internal sphincterotomy is the standard surgical treatment. A controlled cut is made in the internal sphincter, away from the fissure itself. This is usually done at the 3 o'clock or 9 o'clock position. The cut permanently lowers the resting pressure in the anal canal. It breaks the vicious cycle, and allows the fissure to heal.
The author has developed a modification of this operation, called OPB-MOLIS, or Modified Open Lateral Internal Sphincterotomy. This technique is described in full in Chapter 29, together with outcomes from a large case series. In brief, it aims to give reliable relief of spasm and pain. It does this while protecting continence with a carefully judged, limited cut.
Whichever technique is used, the surgeon must judge the length of the cut carefully. Too small a cut may fail to relieve the spasm. Too large a cut raises the risk of incontinence. This judgement is one of the most important skills in fissure surgery.
Explain the procedure clearly before taking consent, following the approach described in Chapter 9. Most patients recover quickly, with relief of pain often noticed within days. Advise the patient to continue a high-fibre diet after surgery. This protects the result, and helps prevent a new fissure from forming.
11.11 Anal Canal Stenosis and Fissure Recurrence
A chronic fissure is often accompanied by some degree of anal canal narrowing. This narrowing is caused by long-standing spasm and scarring. The author grades this narrowing using a simple system. It is assessed under spinal anaesthesia, or general anaesthesia with muscle relaxants. Calibrated anal dilators are used. This system is called the OPB Grading of Anal Canal Stenosis. It applies to stenosis from any cause, not only fissure. It is described in full in Chapter 18, together with its general use and management.
For fissure surgery specifically, the author has observed a link. This link is between the calibre achieved after unilateral MOLIS, and the chance of recurrence. When a 27 mm dilator still passes tightly after a unilateral MOLIS, the chance of recurrence appears considerably higher. When a 30 mm dilator passes freely after the same procedure, the chance of recurrence appears close to nil. This fits the vicious cycle explained earlier in this chapter. A tight calibre suggests the spasm has not been adequately released. This can restart the cycle of poor blood flow and non-healing.
For higher-grade stenosis, a unilateral MOLIS is unlikely to give an adequate calibre. In these cases, the author has begun using a bilateral MOLIS. This means dividing the internal sphincter at two separate sites. Results have been good so far. Bilateral sphincterotomy needs extra caution, since it divides more sphincter muscle overall. To protect continence, only the lower one-third of the internal sphincter should be divided on each side. Bilateral MOLIS, and its results in severe stenosis, are described further in Chapter 30.
These observations are the author's own, drawn from ongoing practice. They are not yet supported by a formal published series. A structured case series would strengthen this finding. It should record the stenosis grade, the post-operative calibre, and confirmed recurrence. The 333-case MOLIS series has already done this for continence outcomes.
11.12 Special Situations
Fissure in pregnancy — conservative treatment is preferred wherever possible. Pregnancy-related fissure often improves after delivery. Many topical treatments are also used cautiously in pregnancy.
Fissure in Crohn's disease — treatment focuses on controlling the underlying bowel disease. Surgery is used cautiously, since healing can be poor, and the risk of a non-healing wound is higher.
Anterior fissure — less common than posterior fissure. It is sometimes associated with a weaker sphincter, particularly in women after childbirth. Sphincterotomy is used with extra caution here.
Recurrent fissure after previous sphincterotomy — needs careful reassessment. Consider an alternative diagnosis, before planning a repeat procedure.
11.13 Preventing Recurrence
A fissure can return, even after successful healing. Prevention lowers this risk considerably.
Maintain a high-fibre diet permanently, not only while the fissure is active.
Keep up good fluid intake every day.
Avoid straining, and avoid delaying the urge to pass stool.
Treat constipation early, rather than waiting for symptoms to build up again.
Share this advice with every patient who has had a fissure, even after full healing. A patient who understands the vicious cycle is well placed to prevent it from starting again.
11.14 Complications of Treatment
Every treatment for fissure carries some risk. This should be explained clearly to the patient.
Headache, with topical GTN treatment.
Temporary or, rarely, permanent difficulty controlling flatus or stool, after sphincterotomy.
Bleeding or infection at the surgical site, though this is uncommon.
Delayed healing, or a non-healing wound, especially if an underlying cause such as Crohn's disease was not recognised beforehand.
A patient who understands these risks in advance is better prepared. They are also more likely to report a problem early, if one occurs.
11.15 Common Mistakes to Avoid
Moving to surgery before a fair trial of conservative and chemical treatment.
Missing a non-midline or atypical fissure, and treating it as a standard fissure without further assessment.
Cutting too much, or too little, of the internal sphincter during surgery.
Forcing digital rectal examination in a patient with severe, acute pain.
Failing to warn the patient about headache with GTN treatment, leading to unnecessary alarm or early discontinuation.
11.16 Recording and Follow-Up
Record the position of the fissure on the clock face, whether it is acute or chronic, and the treatment plan chosen. For example: "Chronic fissure at 6 o'clock, with sentinel pile. Plan: topical diltiazem for eight weeks, given first presentation." Arrange a follow-up visit to check healing, and to plan further treatment if needed.
11.17 Why This Chapter Matters
A fissure is a small tear, but it can cause severe, disproportionate suffering. Understanding the vicious cycle of spasm and poor blood flow explains every treatment used, from simple dietary advice to surgery. A staged approach moves from conservative treatment, to chemical sphincterotomy, to surgery only when needed. This gives each patient the safest path to relief. The next chapter turns to fistula-in-ano, a condition closely related to fissure, but needing a very different approach to management.