An anal fissure is a linear tear in the lining of the anal canal that usually becomes symptomatic because it exposes the internal anal sphincter and causes painful spasms in that muscle. An anal fissure is a common condition that significantly disturbs the quality of life of persons who experience it.
Most fissures are benign, primary, and idiopathic—that is, they are typical anal fissures. Atypical fissures are much less common and occur as a result of other conditions such as Crohn disease, immunosuppression (including human immunodeficiency virus), malignancy, syphilis, or tuberculosis, or they are drug induced (e.g., through the use of nicorandil). An atypical fissure is painless, not situated in the midline, multiple, or associated with a mass or a fistula-in-ano. Management of atypical fissures involves treating the underlying condition and is beyond the scope of this chapter.
Typical fissures can be arbitrarily classified into acute and chronic on the basis of duration of symptoms: chronic fissures have been present for more than 6 weeks. However, certain features are associated with chronic fissures, and the presence of one or more of these features is possibly a more accurate indicator of chronicity than the duration of symptoms alone.
Acute fissures are managed with a high-fiber diet, stool softeners, and topical local anesthetic ointment. They will not be discussed further. This chapter will focus on the clinical assessment, pathophysiologic features, and management of typical chronic anal fissures (CAFs).
The diagnosis of CAF can be suspected based on the patient’s history and confirmed with clinical examination. The patient usually reports having severe, sharp pain at defecation that persists for several minutes to hours afterward and then slowly subsides, with minimal discomfort experienced at other times of the day. CAF is often associated with a small amount of bright red blood on the toilet tissue. The patient often has a history of constipation and straining to defecate.
Upon examination, the following features of a CAF are observed:
A linear ulcer with a fibrotic rolled edge; the circular muscle fibers of the internal anal sphincter are visible at the base of the ulcer, and minimal granulation tissue is present.
A sentinel skin tag at the caudal (external) apex of the fissure.
A hypertrophied anal papilla at the internal apex.
CAF occurs in the midline and is usually posterior but may be anterior. Fissures away from the midline are atypical.
The caudal end of the fissure often can be seen upon gentle separation of the buttocks. Digital examination and proctoscopy will confirm the diagnosis but are unlikely to be tolerated because of anal spasm and pain. An anal block will allow anoscopy, but with the combination of a typical history and a “shy” anus, it is reasonable to begin empiric management and perform an examination at a later date when symptoms have improved. However, if the history is atypical, examination should be undertaken with use of an anesthetic.
Endoanal ultrasonography and manometry are not necessary in the initial workup but may be useful prior to considering more invasive treatment options if first-line conservative treatment fails.
Shearing forces created by passage of hard stool, childbirth, instrumentation of the anus, or anal intercourse leads to the development of a split in the anal canal mucosa. If this split exposes the internal anal sphincter, an acute fissure is present. There are probably two different mechanisms by which an acute fissure may progress to CAF.
High-Pressure Chronic Anal Fissure
Although the exact pathophysiology of CAF remains obscure, a baseline hypertonia of the internal anal sphincter appears to be the most important factor, particularly in posterior CAF. Patients with posterior CAF have been shown to have higher mean resting anal pressures than do control subjects. Whether the hypertonia is the cause of the CAF or a secondary phenomenon caused by pain is not clear. Nevertheless, treatment of internal sphincter hypertonia remains the focus of management and therefore must at least be central to the persistence of CAF. Sphincter hypertonia leads to reduced perfusion pressure of the anal canal, which is more pronounced posteriorly as a result of a relative paucity of small arterioles supplying the posterior anal canal. This phenomenon has been shown in anatomic studies of normal subjects. Reduction of anal pressure by either medical or surgical means is aimed at improving mucocutaneous blood flow, resulting in healing of the fissure.
Low- and Normal-Pressure Chronic Anal Fissure
Manometric studies have shown that up to 50% of patients with CAF do not have increased anal pressures. These patients are typically women with anterior midline CAF, which, in small studies, has been associated with vaginal delivery, external sphincter injury/dysfunction, rectocele, and rectoanal intussusception.
Until 20 years ago, surgery was the mainstay of treatment of CAF. Manual dilatation of the anus and internal anal sphincterotomy were the principal surgery therapies; however, increasing focus on permanent incontinence caused by surgery and the development of safer conservative treatments have led to a significant change in CAF management.
Manual dilatation has been used for almost 200 years. A reduction in anal pressure is achieved by tearing the fibers of the internal sphincter by stretching after induction of general anesthesia. This stretching is traditionally performed with the surgeon’s fingers and is a relatively uncontrolled way of relieving sphincter spasm. Indeed, the disruption of the sphincter mechanism (especially that caused by an eight-finger dilatation) carries an unacceptable risk of permanent incontinence. In a 2011 Cochrane review that included seven studies of manual dilatation versus sphincterotomy, it was found that the risk of flatus incontinence or fecal seepage was as high as 27% in the dilatation group, with an odds ratio of 4.03 (95% confidence interval [CI], 2.04 to 7.46) when compared with sphincterotomy. In addition, dilatation is less effective for fissure healing compared with sphincterotomy, with an odds ratio of 1.55 (95% CI, 0.85 to 2.86) for persistence of the fissure, leading to the recommendation that use of manual dilatation to treat CAF in adults be abandoned.
Although internal sphincterotomy still has a role in the management of CAF, it also carries a significant risk of permanent incontinence and therefore is not the first-line option.
Topical creams containing glyceryl trinitrate (GTN) or calcium channel blockers in combination with a stool softener are now established as the first-line treatment for CAF. Therapy may be initiated by the primary care physician without the need for specialist assessment or an anesthetic and with no risk of permanent incontinence.
The most commonly used topical cream is GTN, which causes vasodilation and relaxation of the internal sphincter muscle via stimulation of guanylate cyclase and lowering of cytosolic calcium. A 0.2% cream is applied directly to the anoderm three times daily for 8 weeks. Symptoms may improve significantly after just 1 or 2 weeks, but the full course should be completed to achieve mucocutaneous healing. Although there is no risk of permanent incontinence, patients can be troubled by adverse effects such as headache (in up to 50% of cases) as a result of absorption of GTN into the systemic circulation. This adverse effect may lead to noncompliance because the headache can be severe and unresponsive to simple analgesics.
The efficacy of GTN cream was assessed in a 2012 Cochrane review. Healing rates of 48.9% for GTN versus 35.5% for placebo were found in a meta-analysis of 18 randomized controlled trials that included a total of 1315 patients. Although this result is statistically significant, it demonstrates that more than half of patients will have persistent CAF after treatment with GTN. The reasons for this lack of response to GTN are unclear but probably multiple. Noncompliance, whether as a result of headache or for other reasons, and tachyphylaxis are possible explanations. Another likely cause of recurrence is persistent hypertonia of the internal sphincter that makes the patient “fissure prone.” These patients may respond to treatment initially, only to quickly relapse once the resting anal pressure returns to normal at the conclusion of the treatment. Other patients may never exhibit a reduction in resting pressure despite treatment with GTN. It also has been demonstrated that patients with long-established CAF are less likely to respond to GTN. In a case series of 64 patients, the presence of a sentinel tag ( P <.035) and symptom duration of greater than 6 months ( P <.05) were found to be independent predictors of treatment failure. Various doses of GTN cream have been tested, ranging from 0.05% to 0.4%, but the dose has not been found to alter healing rates.
Calcium channel blockers also cause smooth muscle relaxation, thus lowering resting anal pressure. As with GTN, there is also a vasodilator effect, further contributing to improved mucocutaneous blood flow. Diltiazem and nifedipine have been studied using both oral and topical preparations. A 2% diltiazem cream is the most commonly used preparation and is applied topically in the same manner as GTN—three times daily for 8 weeks. A meta-analysis of seven randomized trials (including 481 patients) comparing topical diltiazem and topical GTN found an equal chance of healing (relative risk [RR] = 1.10, P < .36), although diltiazem was superior with regard to overall adverse effects (RR = 0.48, P <.01), headache (RR = 0.39, P <.0004), and recurrence of CAF (RR = 0.68, P <.006). Heterogeneity among the trials was significant. Nevertheless, this evidence supports the use of diltiazem before the use of GTN.
Botulinum toxin A (BTX) is a neurotoxin produced by Clostridium botulinum. It acts on striated muscle by blocking acetylcholine release at the neuromuscular junction—hence its established role in the treatment of hypertonic skeletal muscle disorders and cosmetic medicine. Its action on smooth muscle such as the internal anal sphincter is less clear. In a study of animal subjects it was found that BTX causes a reduction in noradrenaline release from sympathetic nerves within the internal sphincter and possibly blocks acetylcholine release in the sympathetic relay ganglion in the vicinity of the muscle, thus reducing myogenic tone.
BTX injection is a minimally invasive option for the treatment of CAF with the aim of reducing resting anal pressure sufficiently to allow healing but only for a temporary period (2 to 4 months); consequently, any effect on continence is short-lived.
We inject BTX in the outpatient clinic after performing a local anesthetic anal block (10 mL of 0.5% bupivacaine and 10 mL of 1% lignocaine). When the procedure is combined with a fissurectomy (described in the next section), it is performed after induction of general anesthesia. A total of 20 to 40 units of Botox (Allergan, Parsippany, N.J.) or 100 to 200 units of Dysport (Galderma Laboratories, Lausanne, Switzerland) is mixed with saline solution and injected with a fine-bore (27-gauge) needle. We inject a divided dose directly into the internal sphincter on either side of the midline either anteriorly or posteriorly (depending on the location of the fissure). A number of alternative methods have been described, including unilateral injection, more than two injection sites, and injection into the external anal sphincter, without evidence to suggest that any one method is best. Given what we know about the mechanism of action of BTX, it seems logical to inject it either into the internal anal sphincter or intersphincteric space.
BTX injection is generally well tolerated, and adverse effects such as temporary incontinence, urgency, and perianal hematoma are infrequent. The major advantage of BTX is that it does not have the compliance issues associated with topical creams because a one-off injection is all that is required. Unfortunately, this does not translate into improved healing rates. In a Cochrane meta-analysis of six studies (including 334 patients), BTX was found to be equivalent to GTN, and therefore use of BTX as first-line therapy cannot be justified given its increased cost. However, evidence shows that BTX can be effective in patients who have not responded to initial management with GTN.
The presence of chronic fibrosis may be an important factor in patients who do not respond to medical therapy. Fissurectomy—that is, excision of the CAF complex (the hypertrophied anal papilla, sentinel tag, and fibrotic scar tissue), thus exposing the healthy underlying internal sphincter with freshened wound edges—treats the chronic fibrosis while sparing the sphincter. Fissurectomy alone was shown to result in excellent healing rates in a case series of 118 patients, but we believe it is most effective when used in conjunction with medical treatment of sphincter hypertonia. Thirty patients who had not responded to medical management (19 who were treated with GTN and 11 who were treated with GTN followed by BTX) underwent a fissurectomy in combination with a BTX injection. The healing rate was 93% at a median of 16.4 weeks follow-up, and even the patients who did not heal (n = 2) had significant symptomatic improvement. There were no cases of fecal incontinence and just two patients (7%) reported flatus incontinence, which, in both cases, resolved within 6 weeks.
Cutaneous Advancement Flap
After a fissurectomy has been performed, advancing a healthy flap of perianal skin into the defect appears to be a safe and effective treatment. It is certainly appropriate in persons with low- or normal-pressure fissures (who are less likely to have responded to medical treatment), but it is also a good option in persons with high-pressure CAF who may be at particular risk of incontinence upon undergoing a sphincterotomy, such as women, older persons, persons with pre-existing continence disturbance, and persons found to have a sphincter defect on ultrasound.
V-shaped incisions or rhomboid incisions are made with the furthest extent of the incision approximately 4 cm from the anal verge. The skin must be mobilized sufficiently to allow advancement of the flap into the anal canal without tension, while maintaining the vascular pedicle to the flap through the subcutaneous fat underneath. The flap is secured over the fissure using interrupted, rapidly absorbable, braided sutures.
In a series of 54 patients, a V-Y advancement flap led to immediate healing in 94% of subjects, and the healing rate was 85% with placement of a rhomboid advancement flap in a randomized trial of 40 patients in which this procedure was compared with sphincterotomy (100%, P = not significant). The median operating time in the group that received the flap was 10 minutes.
Lateral Internal Sphincterotomy
Lateral internal sphincterotomy (LIS) remains the single most effective treatment for CAF in terms of fissure healing (>90%). Sphincterotomy has been practiced for 200 years but was popularized by Eisenhammer in the 1950s. Eisenhammer divided the internal sphincter in the posterior midline at the base of the fissure, which resulted in significant postoperative pain, prolonged healing, and a “keyhole” deformity that was associated with poor continence. The technique of sphincterotomy was later refined by Notaras, who described lateral division of the internal sphincter, which results in fewer complications.
LIS can be performed in the lithotomy or prone jackknife position after induction of general, regional, or local anesthesia. Bowel preparation and antibiotic prophylaxis are not necessary. After preparing and draping the perianal region, a Pratt bivalve speculum or similar anal retractor is inserted into the anus and the intersphincteric groove is palpated. A short circumferential incision is made laterally at either 3 or 9 o’clock, and the internal sphincter is identified. Submucosal and intersphincteric planes are developed to isolate the internal sphincter, which may then be divided under direct vision. The caudal part of the internal sphincter is divided for a variable distance cranially, usually to the dentate line. The wound may be closed with fine absorbable interrupted sutures or may be left open. Routine postoperative care typically includes a stool-bulking agent and nonopiate analgesia.
A closed or subcutaneous sphincterotomy is a slight modification of the open procedure and leaves a tiny perianal wound. With a Pratt’s retractor or finger in the anal canal, a scalpel is inserted in a lateral position at the intersphincteric groove and advanced cephalad in either the submucosal or intersphincteric planes. The blade is then turned laterally (if submucosal) or medially (if intersphincteric) to divide the internal sphincter while feeling the characteristic “give” as the tension in the muscle is released. The blade is removed, hemostasis is achieved with pressure, and the wound is left open.
Risk of Incontinence
Although LIS certainly works in achieving CAF healing, incontinence rates of up to 30% have been reported. In a meta-analysis of 22 studies (including 4512 patients) that entailed use of open and closed LIS techniques and with a minimum follow-up of 2 years, an overall continence disturbance rate of 14% was reported. The following rates were reported: flatus incontinence, 9%; soilage/seepage, 6%; accidental defecation, 0.91%; incontinence to liquid stool, 0.67%; and incontinence to solid stool, 0.83%. Concerns regarding permanent incontinence after LIS are real and significant. Furthermore, evidence shows that delayed-onset incontinence may occur, analogous to the development of fecal incontinence many years after an obstetric injury.
A tailored sphincterotomy refers to various technical modifications aimed at reducing the risk of incontinence with LIS by dividing the minimum amount of internal sphincter required to achieve CAF healing. In 1997, Littlejohn and Newstead published a report on a series of 287 patients who underwent LIS that was tailored to stop at the internal apex of the fissure rather than going up to the dentate line as traditionally described. This method of tailored LIS is the most commonly reported and is what we recommend if LIS is to be undertaken. Littlejohn and Newstead reported excellent results: the rates of healing, flatus incontinence, minor soiling, and urgency were 99.65%, 1.4%, 0.35%, and 0.7%, respectively. These results have been supported by a subsequent randomized controlled trial using the same tailored LIS technique. Incontinence rates were 2.17% versus 10.86% in the traditional LIS group ( P = .039). Healing rates in the tailored LIS group were slightly lower (but not significantly so) and were still excellent (95.65%).
Treatment of Low/Normal Pressure Chronic Anal Fissure
Nineteen percent of men and 42% of women with CAF have low or normal resting anal pressures. Performing LIS in this group of patients would seem illogical, yet it is unclear how LIS can achieve overall healing rates of greater than 90% because most reports of LIS do not exclude this subgroup. Nevertheless, we do not recommend LIS for low- or normal-pressure CAF because these patients must be at a significant risk of incontinence with a surgical reduction in resting pressure of 25% (which is normally achieved with LIS).
Low- and normal-pressure CAFs appear to have different pathophysiologic features compared with high-pressure CAFs (as previously discussed). These patients are less likely to respond to topical smooth muscle relaxants and may even show an atypical contractile response of the internal sphincter to BTX. Fissurectomy with or without cutaneous advancement flap is the surgical treatment of choice for these patients. If this treatment fails, underlying anorectal dysfunction, such as rectocele and rectoanal intussusception, should be considered, and appropriate investigation and management should be undertaken. Successful treatment of CAF in highly selected patients has been reported with levatorplasty, stapled transanal rectal resection, and sacral neuromodulation.