An anal fissure is an oval-shaped tear in the anus distal to the dentate line. Also known as fissures in ano, these are mostly found in the posterior midline but can also be found in the anterior midline. The initial inciting event is thought to be from the passage of hard stool through the anal canal. This is then propagated by an elevated internal sphincter tone [4].

The classic symptom is acute, sharp pain on defecation. Rectal bleeding can also be seen on toilet paper after defecation. The diagnosis can be confirmed with a gentle anal exam. Fissures will appear on the posterior or anterior anal canal. Acute fissures look like a tear, while chronic fissures can have edema, fibrosis, and exposed internal sphincter fibers. (For a full discussion of anal fissures, please see Chap. 5.)

When it can be tolerated, the first line of therapy for anal fissures is medical, with the goal of relaxing the internal anal sphincter. Nifedipine and nitroglycerin both can be applied topically. BOTOX^® (onabotulinumtoxinA) can be injected in the office setting. Stool should be kept soft with adequate hydration and fiber therapy. While 50 % of anal fissures will heal with medical therapy, others will require surgery. Lateral internal sphincterotomy had become the initial procedure of choice due to exceptional healing and low recurrence rates [5]. Second-line treatment for patients with normal sphincter tone can include fissurectomy with cutaneous flap. The fibrotic edges are excised down to normal anodermal tissue. Any skin tag or papilla is then excised. Sharp dissection is used without diathermy. Healthy perianal skin is then mobilized and advanced to fill the defect [6].

An anal fistula or fistula in ano is an abnormal tract or cavity connecting the skin with the anal canal or rectum. They are generally the result of a perianal abscess that fails to completely heal. Diagnosis is not always straightforward. Patients will usually have a history of an abscess that was drained either surgically or spontaneously. Often they will report purulent drainage and bleeding or pain on defecation, but sometimes they will only report chronic rectal pain. On exam, the external opening can usually be identified as perianal granulation tissue that expresses pus on palpation. Anoscopy or an exam under anesthesia is usually necessary to identify the internal opening. MRI is a useful tool for defining high fistulae. Treatment depends greatly on the anatomic location. (For a full discussion on anal fistulae please see Chap. 6.)

For patients with chronic anal pain, it is also important to consider the possibility of an unrecognized deep postanal space fistula after a horseshoe abscess, resulting in an internal sinus tract that does not rupture outside of skin. These fistulae are not easily recognized on physical exam. Signs include pain between the posterior anus and coccyx. They can frequently be confused with puborectalis spasm that also produces tenderness with posterior pressure. One way to differentiate between the two is that deep postanal fistulae hurt more with defecation, whereas puborectalis spasms sometimes improve with defecation. When unsure, endoanal US or MRI may help rule out deep unrecognized sepsis.

Anal stricture is an uncommon (but severely disabling) condition defined as narrowing of the anal canal (Fig. 11.3). Ninety percent of cases are the result of aggressive hemorrhoidectomy [7], but the condition may also be caused by any condition that leads to scarring of the anoderm: anal trauma, inflammatory bowel disease, chronic laxative abuse, radiation, and venereal disease.

Anal stricture produces an anatomic change to the anal canal which results in painful and/or difficult bowel movements and a marked decrease in quality of life. Patients will usually report painful or difficult bowel movements along with rectal bleeding or narrowing of stools. A history of hemorrhoidectomy, radiation therapy, or inflammatory bowel disease can usually be elicited. A digital rectal exam is usually sufficient to confirm the diagnosis, and anorectal manometry can provide an objective assessment of anorectal function. Patients with a mild stricture may achieve relief with fiber therapy, daily anal dilation, or sphincterotomy. For patients with more severe disease, treatment focuses on anoplasty with mucosal flaps or skin flaps [8, 9].

There are a number of possible flaps to employ. In patients with a short narrowing, a lateral mucosal advancement flap (Fig. 11.4a–c)—also known as a modified Martin’s anoplasty —could be considered. This procedure involves a longitudinal excision of scar tissue (Fig. 11.4a) followed by transverse undermining of the proximal rectal mucosa. Taking care to preserve vascular supply, the surgeon tailors the flap to have a wide base and to contain a few strands of the internal sphincter (Fig. 11.4b). If a functional component is present, an internal sphincterotomy is performed, though preferably not at the same spot as the flap. Once the flap is fully mobilized, it is advanced to the edge of the internal sphincter near the anal verge and secured in place with absorbable sutures (Fig. 11.4c). The external part of the wound is left open to minimize contracture. In properly selected patients, this simple intervention has a published success rate of 97 % [10].

A Y–V advancement flap (Fig. 11.5a–c) is another useful technique for addressing stenosis, though the technique is only effective when the surgeon needs to cover less than 25 % circumference of the anal canal (wider flaps tend to become necrotic) [11]. From the prone position, the surgeon makes a longitudinal incision over the area of stenosis. The incision is then extended on the perianal skin for 5–8 cm in either direction to form a V flap (Fig. 11.5a). The flap is incised down to the fatty subdermal tissue to ensure good blood supply (Fig. 11.5b). The flap is then advanced to the apex of the wound and sutured in place with absorbable sutures (Fig. 11.5c). Fiber supplementation and sitz baths are standard postoperative regimens. The Y–V flap has 90 % success rate in two published series [11, 12].

The V–Y anoplasty (Fig. 11.6a–c) can also be considered as an alternative to V–Y flaps. This flap is created by making a V-shaped incision within the anal canal to release the stenosis (Fig. 11.6a). A pedicled flap of skin and subcutaneous fat is then created by lifting the skin near the anus in the deep subcutaneous plane so as to preserve its blood supply (Fig. 11.6b). The skin is then closed behind the area to create the “Y” (Fig. 11.6c). V–Y anoplasty is used with positive results in severe low anal stenosis.

A diamond-shaped flap (Fig. 11.7a–c) is similar to the V–Y flap, but it allows for a larger segment of tissue to be moved into the anus while still closing the donor site. Scar tissue is incised within the anus (Fig. 11.7a) and then the skin, and the subcutaneous tissue in its proximity is mobilized on a diamond-shaped pedicle of skin and subcutaneous tissue (Fig. 11.7b). A diamond-shaped flap is pedicalized and advanced such that it covers the intra-anal portion of the defect. It is then sutured into place with absorbable sutures and the base closed primarily (Fig. 11.7c). A diamond flap is useful for strictures above the dentate line or strictures associated with mucosal ectropion [13].

The house flap is an excellent choice that has the dual advantages of a wide flap that increases the anal canal diameter and allows for primary closure of the donor flap (Fig. 11.8a–c). After an enema the day of surgery, a Hill-Ferguson retractor is used for exposure of the stricture. A longitudinal incision is made toward the perianal skin, from the dentate line to the area of stricture (Fig. 11.8a). Proximal and distal incisions are centered on the longitudinal incision such that the flap is designed in the shape of a house with the flat base near the anus (Fig. 11.8b). Care must be taken to preserve the subcutaneous vascular pedicle. Once the house-shaped skin, subcutaneous tissue is dissected, the flap is moved into the anus and sutured in place with absorbable sutures (Fig. 11.8c). High fiber diet is continued after the surgery, with some experts also advising sitz baths once wounds are noted to show some signs of unraveling—which they frequently do [9]. The house flap is a good choice if the stenosis is a long segment and extends all the way from the dentate line to the perianal skin.

A U flap is similar to the house flap except that the donor site is left open and allows to heal by secondary intention (Figs. 11.9a–c and 11.10a–d). This is considered when the perineal skin is woody and a longer incision with a primary closure is unlikely to hold. A U-shaped incision is planned in the adjacent perianal skin (Figs. 11.9a and 11.10a). The stenotic area is incised and a fissurectomy is performed if a patient has a concomitant unhealed chronic anal fissure (Fig. 11.10b). The flap is then raised, with attention to preserve the fatty subcutaneous tissue with wide mobilization to ensure good vascular supply (Figs. 11.9b and 11.10c). Finally, the flap is advanced and sutured in place with absorbable suture, and the donor side is covered with gauze (Figs. 11.9c and 11.10d).

Lastly, the rotational S flap (Fig. 11.11a–c) can be very helpful in patients presenting with a circumferential skin changes around the anus in association with mild anal stenosis. The flap is not very useful for significant stenosis, however. It involves a full-thickness S-shaped incision in the perineal skin with the size of the base equaling the length of the cut, starting from the dentate line (Fig. 11.11a). The flap is rotated and sutured to the normal mucosa (Fig. 11.11b), with the goal of bringing both wings of the S down to cover the anoderm and replace removed skin (Fig. 11.11c).

A number of other conditions should be considered when evaluating the patient with chronic anal pain. Most are identifiable with a careful rectal exam. Hemorrhoids are often assumed to be the cause of chronic pain, but are usually painless unless thrombosed. A fungal infection may create prolonged pain that is less severe than an abscess. A tumor, such as cancer, can produce progressively worsening pain. A rectal sexually transmitted disease, such as gonorrhea, chlamydia, or herpes, can cause pain and discharge. Proctitis , either primary or secondary to inflammatory bowel disease, is also a cause of anal pain. Another cryptic source of anorectal pain, commonly recognized on colonoscopy, is a solitary rectal ulcer (see Fig. 11.2). It is caused by obstructed defecation and paradoxical contractions of the puborectalis. It can sometimes coexist with levator ani syndrome (see further discussion later in this chapter). In female patients, endometriosis, vulvodynia, prolapse, and mesh erosion all can present with anal pain. In male patients, chronic prostatitis should be considered. Finally, dermatologic pathology, such as psoriasis or dermatitis, can cause itching and pain.

The so-called functional causes for anal pain are a diagnosis of exclusion. They may be considered only after all nonfunctional causes have first been ruled out and adequately managed (see Fig. 11.1). Again, as with any other medical condition, the evaluation of suspected nonfunctional causes of anal pain should start with a thorough history and a physical exam. It is not unusual to find situations where functional and nonfunctional causes of pain—occasionally with an acute or chronic component—may coexist, thus making the differentiation between these two pathways harder than it may seem.