An anal fissure is a superficial tear in the skin distal to the dentate line and is a cause of frequent emergency room visits. In most cases, anal fissures are a result of hard stools and/or constipation, as well as injury. Anal fissures are common in both adults and children, and those with a history of constipation tend to have more frequent episodes of this condition. Anal fissures can be acute (lasting less than 6 weeks) or chronic (more than 6 weeks). The majority of anal fissures are considered primary/typical occurring at the posterior midline. A small percentage of these may occur at the anterior midline. Other locations (atypical/secondary fissures) can be caused by other underlying conditions that require further workup. The diagnosis of anal fissure is primarily clinical. Several treatment options exist, including medical management and surgical options.
Causes of anal fissures commonly include constipation, chronic diarrhea, sexually transmitted diseases, tuberculosis, inflammatory bowel disease, HIV, anal cancer, childbearing, prior anal surgery, and/or anal sexual intercourse. The majority of acute anal fissures is thought to be due to the passage of hard stools, sexually transmitted infection (STI), or anal injury due to penetration. Chronic anal fissure typically is a recurrence of an acute anal fissure and is thought to be also caused by the passage of hard stools against an elevated anal sphincter tone pressure, with symptoms lasting greater than 6 weeks. Underlying conditions such as inflammatory bowel disease, tuberculosis, HIV, anal cancer, and/or prior anal surgery are predisposing factors to both acute and chronic atypical anal fissures. Approximately 40% of patients who present with acute anal fissures progress to having chronic anal fissures.
Anal fissures present in any age group; however, they are mostly identified in the pediatric and middle-aged population. Gender is equally affected, and approximately 250,000 new cases are diagnosed each year in the United States.
The anoderm refers to the epithelial component of the anal canal. The location is inferior to the dentate line. It is a very sensitive area to microtrauma and can form a tear with repetitive trauma or increased pressure. Due to the high pressures in this area, it can result in a delayed healing secondary to ischemia. The tear sometimes can be deep enough to expose the sphincter muscle. Together with spasms of the sphincter, this creates severe pain with bowel movements, as well as some rectal bleeding. It is well known that the most common location of anal fissure is the posterior midline because this location receives less than half of perfusion in comparison to the rest of the anal canal. The perfusion of the anal canal has an inverse relationship to sphincter pressure. Other locations of anal fissures, such as lateral fissure are indicative of an underlying etiology (HIV, tuberculosis, Crohn's, ulcerative colitis, among others). The cause of this other location is not well known. Anterior fissures are rare and are associated with external sphincter injury and dysfunction.
Patients with acute anal fissures present with complaints of anal pain that is worse during defecation. At times, there is associated bleeding with bowel movements but usually not frank hemorrhage. Pain usually persists for hours after defecation. Often, acute anal fissures may be misdiagnosed as external or internal hemorrhoids. Therefore, a thorough physical exam should be performed to delineate between the two. Patients with chronic anal fissures will have a history of painful defecation with or without rectal bleeding that has been ongoing for several months to possibly years. Associated constipation is the most common factor involving chronic anal fissures and patients will provide a longstanding history of hard stools. Patients with underlying granulomatous diseases such as Crohn's disease, among others, will sometimes provide a history of chronic anal pain during defecation that is intermittent rather than constant over an extended period.
The physical exam of the patient with an anal fissure should involve the most comfortable position for the patient. Literature suggests the best position is the prone jackknife position, where the patient lies prone and the bed is folded so that the patient is flexed at the hips. The bed typically used to achieve this position is usually in an operating room or procedure room. Therefore, the best way to achieve this position in the acute care or office setting would be to have the patient bend over the exam table. Many times, however, an adequate physical exam can be achieved by having the patient in a lateral decubitus position. It is imperative that physical manipulation of the anus or rectum via digital exam should be kept to a minimum, and instrumentation such as anoscopy should never be used.
In the acute presentation, an anal fissure will appear as a superficial laceration, usually longitudinal extending proximally. Bleeding may or may not be present. The fissure and sometimes the entire anal sphincter may be extremely tender to palpation. In thin patients, this laceration is usually easily identified, however, in the obese patient it may not be as identifiable. In an obese patient, gently pressing on the anterior or posterior anal sphincter may reproduce the pain and a diagnosis can be made.
In the chronic anal fissure, there may be a tear large and deep enough to expose the muscular fibers of the anal sphincter. In addition, due to the repeated injury and healing cycle, the edges sometimes appear raised, and thickening of tissue at the distal ends of the tears may be present, which is called a sentinel pile. Granulation tissue may or may not be present depending on the chronicity and the stage of healing.
If the patient has chronic recurrent anal fissures, an examination under anesthesia is recommended to help diagnose the exact cause and sometimes treat the patient. Evaluation of both acute and chronic anal fissure initially involves determining if it is a primary or secondary anal fissure. As described earlier, a primary or typical anal fissure occurs in the posterior or anterior midline, and an atypical or secondary anal fissure occurs in any location other than a primary anal fissure. If an atypical or secondary anal fissure is encountered, conditions such as Crohn's disease should be immediately ruled out. It is to be noted that patients with Crohn's and/or other underlying conditions can have anal fissures located at the typical/primary locations.
Initial treatment of anal fissures is medical. Frequent Sitz baths, analgesics, stool softeners, and a high-fiber diet are recommended. Prevention of recurrence is the primary goal. Adequate fluid intake is also helpful in preventing the recurrence of anal fissures and is strongly encouraged. If conservative management with dietary changes and laxatives fail, other options can be used which include topical analgesics such as 2% lidocaine jelly, topical nifedipine, topical nitroglycerin, or a combination of topical nifedipine and lidocaine compounded by a pharmacy. Topical nifedipine works by reducing anal sphincter tone, which promotes blood flow and faster healing. Topical nitroglycerin acts as a vasodilator to encourage increased blood flow to the area of the fissure, increasing the rate of healing. While both have been shown to be effective treatments, topical nifedipine is regarded to be superior to topical nitroglycerin in 2 ways. First, nifedipine has been found to result in a higher healing rate compared to nitroglycerin. Second, it resulted in fewer side effects as nitroglycerin frequently causes headaches and hypotension. If patients use nitroglycerin, it is recommended that they apply the ointment in a seated position and refrain from standing too quickly. Patients should also be adviced to avoid medications such as sildenafil, tadalafil, and vardenafil while using nitroglycerin.
The chronic anal fissure (CAF), is typically more difficult to treat given recurrence and complications. Aside from using nitrates and calcium channel blockers, a third pharmacological method can be employed to prevent recurrence of CAF. Botulinum toxin (BTX) is generally considered safe and provides significant pain relief. Compared to nitrates and CCBs, BTX is superior and the most effective.
Conservative methods are likely to fail and have a higher failure rate in the chronic recurring anal fissure. In these situations, the gold standard is the lateral internal sphincterotomy (LIS). This surgical procedure treats CAF by preventing hypertonia of the internal sphincter. In a study conducted between 1984 and 1996, 96% of patients undergoing LIS had complete resolution of their CAF within 3 weeks. An open and closed technique can be used in this procedure, under either local or general anesthesia. It has been found that those undergoing LIS with local anesthesia have a higher rate of recurrence of CAF. In the open technique of LIS, an incision is made across the intersphincteric groove. Blunt dissection is then employed to separate the internal sphincter from the anal mucosa. Finally, the internal sphincter is divided with scissors. In the closed technique of LIS, a small incision is made at the intersphincteric groove, and a scalpel is inserted parallel to the internal sphincter. The scalpel is advanced along the intersphincteric groove, and the internal sphincter is then divided by rotating the scalpel toward it. The healing rate is found to be the same with either an open or closed approach.
Although LIS is nearly curative in all cases of CAF, it comes with complications that the healthcare provider should discuss with the patient before the procedure. Fecal incontinence (including uncontrolled flatus, mild stool soiling, and gross incontinence) is the major complication; it occurs in approximately 45% of patients in the immediate postoperative period with a higher likelihood in females (50% versus 30% in males.) Despite the high rate of incontinence, it is transient and usually resolves. Within 5 years of LIS, the rate of incontinence is substantially reduced to less than 10%, with a gross loss of solid stool being less than 1%. Recurrence of CAF in post-LIS patients is approximately 5%, in which conservative methods with pharmacological treatment cures approximately 75%.
Other acute complications from LIS surgery include excessive bleeding that is encountered more commonly during the open technique and may require suture ligation. Approximately 1% of patients undergoing the closed technique develop a perianal abscess, primarily because of the dead space created by the separation of the anal mucosa.
One long-term complication of sphincterotomy that is encountered more frequently in the repair of posterior CAFs is a keyhole deformity. A keyhole deformity is usually asymptomatic and is well tolerated by patients. In a study of over 600 patients undergoing internal sphincterotomy, only 15 developed a keyhole deformity, which was not associated with any anal incontinence, but went on to receive repair.
An anal fissure is a clinical diagnosis made essentially by physical exam alone and must be done to rule out other possible causes of rectal pain. Hemorrhoids are the most common finding in patients with rectal pain. However, only external hemorrhoids are painful, especially if they are thrombosed. Patients can also have perianal abscesses that cause pain on defecation and can bleed. Perianal abscesses can also form anal fistulas to a deeper site and can either bleed or have purulent drainage. Patients with STIs, inflammatory bowel disease, or TB can form perianal ulcerations. A rare condition, known as solitary rectal ulcer syndrome (SRUS) can also be encountered; however, this lesion has no known cause and is usually found by sigmoidoscopy several centimeters proximal to the anus itself.
Acute anal fissures in low-risk patients typically do well with conservative management and resolve within a few days to a few weeks. However, a percentage of these patients go on to develop CAF, which requires pharmacological treatment and/or surgical management. Over 90% of patients undergoing surgical management achieve cure within 3 to 4 weeks post-operatively.