A sphincterotomy is a procedure that involves cutting into a sphincter muscle to relieve a blockage or allow healing. The term applies to two very different procedures depending on which sphincter is involved: one targets the anal sphincter to treat painful anal fissures, and the other targets the sphincter at the opening of the bile duct to remove gallstones or treat other biliary problems. Both are common, well-studied procedures with high success rates.
Anal Sphincterotomy for Chronic Fissures
The most common reason for an anal sphincterotomy is a chronic anal fissure, a small tear in the lining of the anal canal that won’t heal on its own. Fissures become chronic when the internal anal sphincter muscle goes into spasm, reducing blood flow to the area and preventing the tissue from repairing itself. A lateral internal sphincterotomy (LIS) breaks that cycle by making a small cut into the internal sphincter muscle from the side, releasing the excess tension so blood can flow normally and the fissure can close.
Surgery is typically reserved for fissures that have persisted for six months or longer and haven’t responded to conservative treatments like topical medications, warm baths, or dietary changes. Signs that a fissure has become chronic include hardened edges around the tear, visible muscle fibers at the base of the wound, and the development of a small skin tag near the fissure.
The procedure can be done under local anesthesia or sedation. Your surgeon makes a small incision on the side of the anal canal, locates the internal sphincter muscle fibers, and cuts through a portion of the muscle directly beneath the fissure. The anal canal is only about 4 cm long, so this is a precise, targeted cut rather than a large operation.
How Well Anal Sphincterotomy Works
LIS has a healing rate of roughly 93 to 96 percent for chronic anal fissures, with most fissures closing within about three weeks after surgery. That makes it significantly more effective than alternatives like Botox injections into the sphincter muscle, which heal fissures in about 63 percent of cases and carry a higher recurrence rate. A meta-analysis of nearly 500 patients confirmed that surgical sphincterotomy was superior to Botox in both healing and long-term recurrence, though Botox had a lower risk of incontinence.
For patients whose fissures come back after a first sphincterotomy, a repeat procedure still works well, with one study reporting a recurrence rate of just 4 percent after a second surgery.
Risks of Anal Sphincterotomy
The main concern with LIS is its effect on bowel control, since you’re permanently cutting part of the muscle responsible for holding the anal canal closed. Up to 39 percent of patients experience some temporary change in continence in the weeks after surgery, most commonly difficulty controlling gas. These symptoms typically resolve within six to eight weeks.
Longer-term data from a high-volume surgical center found that about 25 percent of patients had some measurable change in continence within the first year. The vast majority of these cases were mild, limited to occasional difficulty controlling gas. Only 2 percent experienced any issues with liquid stool, and no patients in that study lost control of solid stool. Researchers noted that most of these mild cases did not meaningfully affect patients’ quality of life.
Biliary Sphincterotomy During ERCP
The other major type of sphincterotomy targets a completely different part of the body. At the point where the bile duct empties into the small intestine, there’s a small ring of muscle called the sphincter of Oddi. A biliary endoscopic sphincterotomy cuts this sphincter open to allow gallstones to pass, to place a stent in a narrowed bile duct, or to treat a condition where the sphincter itself isn’t opening properly.
This procedure is done during an ERCP (endoscopic retrograde cholangiopancreatography), where a flexible scope is passed through your mouth, down through your stomach, and into the upper part of the small intestine. Once the scope reaches the opening of the bile duct, a thin wire called a sphincterotome is threaded into the duct. The wire uses a brief electrical current to cut through the sphincter muscle in a controlled direction, widening the opening. The cut extends no further than where the bile duct meets the intestinal wall.
The indications for biliary sphincterotomy are broad. The most common is removing gallstones stuck in the bile duct. It’s also used to treat narrowing of the bile duct from scarring or tumors, to address bile leaks after gallbladder removal, and to manage sphincter of Oddi dysfunction, where the sphincter spasms and causes pain after eating.
Effectiveness for Sphincter of Oddi Dysfunction
Sphincter of Oddi dysfunction is categorized into types based on severity. For the most clear-cut cases (type I, where blood tests, imaging, and symptoms all point to the sphincter as the problem), sphincterotomy relieves symptoms in virtually all patients. One study of 17 patients with type I dysfunction found that every single one reported symptom relief over more than two years of follow-up, regardless of what their pressure measurements showed beforehand.
For less straightforward cases (type II), results are more variable. In patients whose pressure testing confirms the sphincter is too tight, sphincterotomy succeeds about 85 to 91 percent of the time, compared to only 25 to 38 percent improvement with a sham procedure. When pressure testing is normal, the benefit drops considerably, to roughly 42 to 50 percent. This has made type II treatment controversial, and practice varies widely between institutions.
Risks of Biliary Sphincterotomy
Complications occur in about 5 to 10 percent of ERCP procedures overall. The most common is pancreatitis, an inflammation of the pancreas that develops in roughly 2 to 4 percent of cases. This happens because the pancreatic duct shares the same opening as the bile duct, and the procedure can irritate or temporarily block it. Post-ERCP pancreatitis typically causes abdominal pain within 24 hours and requires at least a couple of days of hospital monitoring.
Several factors increase the risk of this complication. A difficult procedure requiring extra cutting techniques roughly triples the odds. Having sphincter of Oddi dysfunction, being female, or needing dye injected into the pancreatic duct also raise the risk. Other less common complications include bleeding from the cut site (about 1 percent) and a small perforation of the intestinal wall (under 1 percent). The overall mortality rate for ERCP is very low, under half a percent.
Preparing for the Procedure
For an anal sphincterotomy, preparation is straightforward. You’ll typically need to stop eating and drinking after midnight the night before. Depending on your surgeon’s preference, you may be asked to use an enema the morning of the procedure. A bowel prep with laxatives the day before is sometimes required but not always, since this is a relatively minor operation compared to larger colorectal surgeries.
For a biliary sphincterotomy done during ERCP, preparation centers on fasting. You’ll need an empty stomach, so nothing to eat or drink for several hours beforehand. You’ll receive sedation during the procedure, which means you’ll need someone to drive you home and should plan to rest for the remainder of the day. Your doctor will review any blood-thinning medications ahead of time, since both types of sphincterotomy carry some bleeding risk.
What Recovery Looks Like
After an anal sphincterotomy, most people go home the same day. Pain at the surgical site is common for the first few days but is typically manageable with over-the-counter pain relief and warm sitz baths. The fissure itself usually heals within about three weeks. Most people return to normal activities within a week or two, though strenuous exercise may need to wait a bit longer. You may notice some minor bleeding or drainage from the wound site during healing, which is normal.
Recovery from a biliary sphincterotomy is generally faster since there’s no external incision. You may have a sore throat from the scope and some bloating from the air used during the procedure. Most people can eat normally within a day and return to their usual routine within two to three days, assuming no complications develop. Your medical team will typically monitor you for a few hours after the procedure to watch for early signs of pancreatitis or bleeding before sending you home.