Specialties:
Colorectal and Anal Tumors (Conventional Open Surgery, Laparoscopic Minimally Invasive Surgery, Transanal Endoscopic Surgery); Benign Colorectal Diseases (Rectal Prolapse, Levator Ani Syndrome); Anal Disorders (LigaSure Hemorrhoidectomy, Laser Hemorrhoid Ablation, Anal Fistula Surgery); Colonoscopy; Endoscopic Polypectomy; Stoma Assessment and Management.

I. What Is an Anal Fissure?

Have you ever experienced severe pain during defecation—sharp, tearing, stabbing pain, as if fragments of glass were passing through your anus—and noticed bright red blood on the toilet paper when wiping? Although the intense pain may lessen after defecation, it can still persist for several minutes to several hours.

An anal fissure is a common anorectal diagnosis. It is a longitudinal tear of the anal canal that runs parallel to the anal folds and extends to the anal verge. Most anal fissures are caused by changes in bowel habits, such as constipation or diarrhea. Anal fissures are commonly associated with a hypertonic internal anal sphincter; however, other etiologies, including inflammatory bowel disease and malignancy, must be excluded. Acute anal fissures usually last less than six weeks and present as clean-based wounds, whereas chronic anal fissures generally persist for more than six weeks and are characterized by indurated edges, visible exposure of the internal anal sphincter, and the formation of surrounding anal skin tags. After excluding fissures caused by other etiologies, most acute anal fissures will heal spontaneously once normal bowel habits are restored.

According to current pathophysiological theories, failure of anal fissures to heal originates from excessive internal anal sphincter tone. The internal anal sphincter is composed of smooth muscle and is controlled by the autonomic nervous system. Increased resting tone within the anal canal impedes blood flow to the injured area, preventing healing. The posterior midline is inherently the area with the poorest perianal blood circulation, which explains why chronic anal fissures most commonly occur at this site. In addition, patients with chronic anal fissures have been found to have reduced nitric oxide synthase levels, resulting in decreased nitric oxide production and consequently increased resting anal canal tone.

II. How Can I Be Sure It Is an Anal Fissure?

The presence of an anal fissure can be confirmed through history taking and physical examination. After separating the buttocks, the fissure can often be visualized on inspection. In patients who excessively contract the anus due to pain, anoscopy may be required for assistance, and additional colonoscopic examination is not necessary. If the diagnosis cannot be confirmed through outpatient examination, or if the fissure is atypical (off the midline or with suspicious appearance), further investigations are necessary to exclude malignancy.

In selected cases, physicians may arrange high-resolution anorectal manometry (HRAM) to determine whether internal anal sphincter hypertonicity is present. Digital rectal examination alone in the outpatient setting cannot accurately distinguish a patient’s anal pressure status.

III. What Should Be Done for Anal Fissures?

■ Conservative Treatment

Most acute anal fissures (approximately 80%–90%) and some chronic fissures can heal with non-surgical treatment. The American Society of Colon and Rectal Surgeons (ASCRS) recommends that acute anal fissures do not require surgical treatment. Patients with anal fissures should first address abnormal bowel habits; therefore, increased fluid intake and dietary fiber are recommended. For pain related to the anal wound, warm sitz baths may be used to relax the internal anal sphincter, thereby reducing anal canal pressure and promoting healing, with more pronounced effects in patients with hypertonicity. A prospective randomized controlled trial demonstrated that patients who increased fiber intake and performed warm sitz baths twice daily had better symptom relief and wound healing at three weeks compared with those using topical steroids and anesthetics alone (components commonly found in over-the-counter hemorrhoid ointments). Furthermore, daily supplementation with 15 grams of unprocessed fiber significantly reduced the recurrence rate of anal fissures.

■ Topical Ointments

For patients who do not respond to the above treatments, topical nitrates or topical calcium channel blockers can also reduce resting anal canal tone, increase blood flow, and promote healing. However, neither of these medications is currently available on the Taiwanese market. Therefore, for patients with acute anal fissures, increasing fluid and fiber intake and performing warm sitz baths remain the mainstay of treatment, with hemorrhoid ointments used at most to alleviate wound pain. The ointments themselves do not promote wound healing.

■ Fissurectomy and Lateral Internal Sphincterotomy

When conservative treatment fails or when chronic anal fissures have developed ulcerative tissue with exposed sphincter muscle, surgical intervention is required. Currently, there are two standard surgical treatments, and surgeons will select the appropriate procedure based on individual patient conditions. The goal of fissurectomy is to debride the fissure wound, allowing healthy tissue to regenerate and heal the wound bed. In patients with high-tone anal fissures, lateral internal sphincterotomy is considered the gold standard surgical treatment for refractory anal fissures, with healing rates reaching 88%–100%. Incising the sphincter fibers reduces resting anal canal tone and thereby promotes healing. The most serious complication after sphincterotomy is incontinence, with a reported risk ranging from 2% to 5%. Other complications include bleeding, hematoma, wound infection, abscess formation, and fistula formation.

■ Anal Advancement Flap Surgery

For patients with low-tone anal fissures (commonly seen in women who have given birth), anal advancement flap surgery is the standard procedure with a high success rate. After debriding the base of the fissure down to healthy bleeding tissue, flap reconstruction is performed (such as V-Y advancement flaps, rhomboid flaps, etc.). Poor flap design may result in eversion of the rectal mucosa, leading to persistent mucous discharge; an undersized flap may result in poor flap viability.

■ Botulinum Toxin Injection

Botulinum toxin injection is currently not an officially approved indication, but it has been recognized in numerous studies and therefore must be entirely self-paid if performed. Botulinum toxin inhibits the release of acetylcholine from presynaptic nerve terminals, resulting in relaxation of striated muscle, with relatively less effect on smooth muscle. After dilution, the toxin is injected into the intersphincteric groove to reduce resting tone; however, the effect is not permanent. For patients who fail topical treatment but have risk factors for incontinence, and for whom sphincterotomy carries a higher risk of postoperative incontinence, botulinum toxin injection may be considered. Although temporary incontinence may still occur, it typically improves as the toxin effect diminishes over 2–3 months, thereby providing time for fissure healing. Because the injection process is extremely painful, the procedure must still be performed in the operating room under anesthesia.

IV. Do I Need Surgery?