Lifestyle modifications consisting of sitz baths, implementing a high fiber diet, increasing fluid intake, and the use of stool-bulking agents, have been shown to be safe and effective in promoting spontaneous healing in 90 % of patients with an acute anal fissure. For the remaining 10 % who progress to chronic fissure, treatments include those that are primarily medical (topical calcium channel blockers, nitroglycerin ointment, botulinum toxin injection) or surgical, typically lateral internal sphincterotomy.

A 2012 Cochrane review of 75 randomized clinical trials included over 5,000 patients with chronic fissures who were either treated with surgery or conventional medical therapies [1]. Nitroglycerine ointment was found to be marginally though significantly superior to placebo in achieving healing (48.9 % vs. 35.5 %, p < 0.0009). However, late recurrence developed in 50 % of these patients. Similar efficacy has been observed with topical calcium channel blockers and botulinum toxin injection. Such nonsurgical interventions lead to resolution of symptoms in up to 60 % of affected patients, making them worthwhile to attempt in patients with fissures of less than 12 months duration. The evidence supports the concept that they should typically be tried prior to surgery, given that they are safe and may be effective. Most surgeons do not advocate surgery as first-line therapy, primarily because of concerns related to incontinence.

However, it is well recognized that no medical therapies have enduring cure rates that are at all comparable to those associated with LIS (80–95 %, depending on the case series). Indeed, numerous studies have demonstrated the superiority of surgery in both the healing of and prevention of recurrence of chronic fissures [2–5]. The previously described Cochrane review of 75 RCTs found an odds-ratio of 0.11 (95 % CI 0.06–0.23) when comparing non-healing, defined as persistence or recurrence, at a median of 2 months in patients who underwent medical therapies compared to those who underwent any form of surgery for anal fissure [1].

A prospective randomized trial of 142 patients with anal fissure compared healing rates and defecatory pain following treatment with either LIS or anal dilation plus topical nifedipine [6]. 68.9 % of patients in the nifedipine group and 88.2 % of patients in the LIS group were healed by 8 weeks (p = 0.0077). Those who underwent LIS had significantly less pain with defecation at 3 and 7 days. A parallel, randomized controlled trial of 99 patients with chronic fissure found no significant difference in healing rates in patients with fissures of less than 12 months duration who underwent botulinum toxin injection with supplemental calcium channel blocker therapy compared to those who underwent LIS. However, in patients who had chronic fissures for more than 12 months, the healing rate was significantly higher in the LIS group (86 % vs 23 %, p < 0.001) [7].

Of all the medical therapies that are currently available, botulinum toxin injection has increasingly been used as first-line therapy for recalcitrant anal fissures, and nitroglycerine ointment may act in synergy with botulinum toxin [8]. Still, there is currently no consensus on the ideal dosage, precise location of injection (external vs internal sphincter), and number of injections of botulinum toxin needed to achieve optimal results. Higher doses do seem to correspond with higher healing rates and are just as safe as lower doses, though the recurrence rate remains higher than that following LIS (up to 42 %), making LIS a superior procedure for cure. Incontinence scores are higher in patients treated with LIS [8], however, incontinence to stool and flatus is also a potential complication of botulinum toxin injection, which occurs in up to 18 % of cases.

With the goal being to promote permanent cure while minimizing the likelihood of a disturbance in continence, some have advocated combined fissurectomy with botulinum toxin injection as a viable alternative to LIS. In a prospective nonrandomized study of 105 patients who underwent this procedure, 95 % of patients had resolution or improvement of symptoms at 12-weeks; 93 % had no complications; however 7 % developed postoperative incontinence to stool and/or flatus which proved to be transient (all patients had restored continence at 12 weeks) [9]. The authors argue that even though LIS remains the procedure with the highest cure and lowest recurrence rates, botulinum toxin injection with fissurectomy has similar efficacy and may be preferable given that it does not permanently alter the anal musculature, as LIS does. The latter consideration is important since muscular tone diminishes with aging (further increasing the probability of late incontinence) and LIS may distort planes for future anorectal surgeries that may become necessary. While other studies have demonstrated similar findings [10, 11], it remains difficult to make a broad recommendation on fissurectomy with botulinum toxin injection as an alternative to LIS due to a paucity of adequately-powered, prospective studies. Similarly, pneumatic dilation as a means to reduce the hypertonicity of the internal sphincter has also been explored as a nonsurgical means to healing. While the initial data seems promising with 94 % of patients reporting healing between 3 and 5 weeks, the few trials that have been reported are underpowered [12, 13].

The tradeoff for the high efficacy of LIS is an increased risk for incontinence. After all, diminishing anal canal resting pressure is the primary mechanism by which surgery heals chronic anal fissures. Long-term manometric studies have established that preoperative resting anal pressure is high in patients with fissures and significantly declines following LIS. The sphincter tone and resting pressure gradually increase over a 12-month period, but they nevertheless remain elevated relative to normal controls without fissures. This makes incontinence in such patients possible, though still unlikely [14]. Retrospective studies have postulated that the likelihood of incontinence following LIS is unpredictable, though a history of vaginal delivery may increase this risk [15]. A recent systematic review of 22 studies including over 4500 patients who underwent LIS for chronic fissure showed an overall postoperative continence disturbance rate in 14 %, with a mean follow-up time of 24–124 months (flatus incontinence 9 %, soilage/seepage 6 %, and accidental defecation in 0.91 %) [16].

Still, most agree that the majority of incontinence following LIS is a transient phenomenon, and that the risk of this is far outweighed by the risk of failed, prolonged medical management with continuing distress of patients related to an unhealed symptomatic fissure. A retrospective cohort study of 38 patients who underwent LIS between 1998 and 2004 found that long-term symptomatic incontinence was reported by only two patients (5.6 %) [17]. The authors’ final recommendation is that patients with risk factors for the development of incontinence (preoperative incontinence, multiparous women) should arguably be treated with non-surgical therapies prior to LIS. Finally, there is speculation that incontinence may actually be a feature of the underlying condition itself, and is not solely a complication of surgical management [18].

The degree of sphincter division may proportionately dictate the likelihood of the development of postoperative incontinence. Numerous prospective studies have found that partial sphincterotomy, limited to division just beyond the fissure apex, correlates with a lower risk of postoperative incontinence than does complete sphincterotomy to the level of the dentate line [14–18]. In general, internal sphincterotomy to the level of the dentate line is associated with higher rates of healing as well as more rapid healing of chronic fissures, although it is associated with a higher risk for incontinence than is partial sphincterotomy [19]. A 2011 Cochrane review of 27 studies, including 2,056 patients, concluded that open and closed partial lateral sphincterotomy were equally efficacious and not different in terms of the risk of developing postoperative incontinence. The conclusion is that more data are needed to determine the effectiveness of alternate procedures such as posterior internal sphincterotomy, anterior levatorplasty, and bilateral internal sphincterotomy [20].

There has been recent interest in alternate surgical treatments for chronic fissures that do not carry as substantial a risk for even transient incontinence, as does LIS. Fissurectomy with advancement flap, particularly in patients without internal sphincter hypertonia, has been advocated as a promising option for such patients. One study of 26 patients with fissures refractory to medical therapy showed that fissurectomy with advancement flap led to complete healing by 30 days, and that the intensity of pain with defecation was substantially diminished. At 1 year, only three patients reported ongoing incontinence [21]. The obvious problem, of course, is that the etiology behind the large majority of chronic fissures is high internal sphincter tone. Fissurectomy with advancement flap does not address this, and therefore, most patients would conceivably neither benefit nor heal from such treatment.

Other prospective studies have suggested that what has been called “modified LIS” (partial sphincterotomy to the level of the fissure apex with dermal advancement flap) results in better healing and less postoperative discomfort than does isolated, conventional LIS to the dentate line. One such study of 32 patients found that modified sphincterotomy with a VY flap from perianal skin was associated with less postoperative defecatory pain and faster objective healing than was conventional LIS (p < 0.01) [22]. Similar findings have been reported by others [23, 24]. For obvious reasons, modified LIS carries less risk for postoperative incontinence than does conventional LIS. It may be useful and more appropriate in patients with preoperative incontinence or known risk factors for developing incontinence postoperatively (prior vaginal delivery, older age). There have been some low-powered studies suggesting that fissurectomy with advancement flap may be effective as a first line procedure in patients with chronic fissures, irrespective of anal sphincter tone [25, 26].