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Anal Abscesses

Anorectal abscesses are infections that develop in and around the anus. They usually result in a swelling, constant pain, and sometimes fever. The pain is usually not relieved or made worse by BM. Anorectal abscesses, if left long enough will usually spontaneously drain pus through an opening that develops in the overlying skin. The drainage of pus from the infected cavity lessens or relieves the pain and swelling. In some patients, after spontaneous drainage, the abscess fully resolves without further incident. Sometimes, however, the abscess does not fully empty. In this situation the infection persists and continues to drain either on a daily or intermittent basis. Patients with an abscess that has spontaneously drained but persists need to see a surgeon and undergo an incision and drainage.

Ideally, before an abscess has the opportunity to drain spontaneously the patient is examined by a surgeon who, after making the diagnosis, will incise and drain the infection. Therefore, patients who develop constant pain in the area around the anus (with or without swelling or fever) should immediately see a general or colon and rectal surgeon. Before performing the drainage procedure the surgeon will obtain consent after explain the situation as well as the pros, cons, and possible complications of this minor surgery. The skin around the anus and abscess is cleaned and prepared after which a local anesthetic (lidocaine or similar agent) is injected into the skin surrounding the abscess. After the area has been numbed a needle is passed into the suspected abscess to confirm that the swelling contains pus. Next, a scalpel is used to drain the infection through a small incision made over the swelling. The surgeon then probes the area to make sure that all of the pus has been drained after which the cavity is irrigated and then lightly packed with gauze. A dressing is then placed over the area.

Sitz baths should be started after the first BM or about 24 hours after the drainage procedure if there has been no BM (see anorectal postoperative instructions). At the time of the first sitz bath, the packing in the abscess cavity is removed. After the bath a gauze dressing is used to cover the wound. Sitz baths should be carried out 2 to 3 times a day and after BM’s for the first 4 to 7 days. If needed, narcotic containing medications are taken for several days. The alternative is to take Tylenol or advil. It is a good idea to take a stool softener (docusate sodium, 100 mg pills, and 3times/day) during this time period in order to avoid constipation and difficult BM’s.

Antibiotics are not routinely given to abscess patients after surgical drainage. The exceptions to this policy are patients who have diabetes or have suppressed immune systems for other reasons (patients on steroids, transplant patients, etc.); these patients are given antibiotics for 5 to 7 days after abscess drainage.

Unfortunately, in between 33 and 66 % of abscess patients, after either spontaneous or surgical drainage, a fistula forms. Abscess patients, prior to undergoing incision and drainage, need to understand that a fistula may form.

Anal Fistulas

A fistula is a tube or tunnel between two structures. In the case of anal fistulas, the connection runs between the skin surrounding the anus and the anal canal. Anal fistulas have an external (on the skin) and an internal opening (in the anal canal). The causes of the vast majority of anal fistulas are anorectal abscesses. The symptoms associated with anal fistulas include: intermittent swelling and discharge, pain, bleeding, and a lump or small area of hardness next to the anus. The discharge may contain pus or blood and is most often noted between BM's. Because the fistula tract may become clogged or blocked, small abscesses can develop from time to time. These abscesses usually result in a painful swelling. Most often, after a few days, the abscess spontaneously drains through the external oal opening which usually relieves both the swelling and pain. With few exceptions (mainly fistulas due to Crohns Disease or Ulcerative Colitis), once a fistula has formed it remains. After learning that they have an anal fistula most patients, make the decision to undergo surgery with the hopes of curing this problem.


The path each fistula takes varies from patient to patient. Some fistulas tunnel beneath the skin alone, however, most runs through and across some of the anal sphincter muscle. The amount of muscle lying between the fistula tract and the skin surface is an important factor because the simplest and most effective way to get rid of a fistula is to surgically divide the skin, muscle, and other tissue down to the level of the fistula tract. This procedure, called a fistulotomy, is carried out after a thin wire-like metal probe is inserted through the external opening of the fistula and passed through the tract and out of the internal opening. The fistulotomy "unroofs" the tract and allows all of the infected material in the tract to be curetted and removed. The wound is left open to heal slowly over the course of 2-4 weeks. Of the treatment choices for anal fistulas (see below), fistulotomy has the highest success rate (over 90%).

The downside of fistulotomy is that it requires division of a portion of the sphincter muscle in most patients. When muscle is cut there is a chance that sphincter function will be altered. Thankfully, most patients' sphincter control is not affected by the loss of small or even moderate amounts of muscle, however, a small number of patients will notice after fistulotomy that they have difficulty holding back flatus (gas) or, very rarely, liquid stool. The surgeon must determine, at surgery, how deep the fistula is (meaning how much of the anal sphincter would need to be cut if a fistulotomy was performed). If the fistula involves a large proportion of the sphincter muscle then the fistulotomy operation would not be done. Instead, the surgeon would perform one of the other fistula operations described below that either avoids or minimizes muscle division.

Cutting Seton

This method divides the sphincter muscle within the fistula tract over a period of 2 to 4 weeks instead of immediately in the operating room. It is believed by many surgeons that the chance of developing incontinence is much lower when the muscle is cut slowly over a long period of time. The cutting Seton method also gives the patient more control over the treatment because it is possible to remove the Seton at any time after surgery if the patient notices any symptoms of sphincter weakness. If the Seton is removed early then some of the sphincter muscle in the tract is preserved (as opposed to a fistulotomy in which the muscle in the tract is fully divided at once). A brief description of this method follows.

The first step is to identify the internal and external openings and to pass a probe through the tract. The tract is then cleaned with a curette. Next, the skin lining between the two openings is incised which exposes the underlying sphincter muscle. A thick suture or a thin rubber/plastic string (the Seton) is then passed through the fistula tract (after curetting and cleaning) and the two ends are tied together very tightly which places pressure on the muscle. As mentioned, the Seton divides the muscle contained within the fistula over a 2 to 4 weeks period. Patients tolerate cutting Setons well. In some cases the Seton may need to be tightened several weeks after surgery. This can usually be done in the office. Once the Seton has fully cut through the muscle the Seton will fall out of the anus usually during a BM.

The Risks of Fistula Surgery

Prior to the operation it is important that the patient understand the risks of fistula surgery. They must understand that in order to get rid of the fistula some of the sphincter muscle may need to be cut. If muscle is lost there is a small chance that symptoms of sphincter weakness may develop (most commonly incontinence of gas, soiling or staining of undergarments, and, rarely, incontinence of liquid stool). Fistulotomy is the most destructive method since it divides all the muscle that lies between the tract and the skin; however, it has the highest success rate. The alternate fistula approaches avoid simple division of the muscle in order to better preserve function. The success rate for all of these approaches, in regards to fully getting rid of the fistula, is notably lower than the success rate of fistulotomy. Therefore, there is a greater chance that the fistula will recur or persist if one of the alternate fistula treatment methods is used, yet, there is less risk of incontinence or staining. The patient must balance their desire to get rid of the fistula with the need to maintain and preserve anal muscle function.

After a full discussion of the various surgical approaches to anal fistulas the patient must tell the surgeon if they are willing to have some of their sphincter muscle cut in order to treat the fistula. If the answer is yes then the patient must be aware that the surgeon will choose the best fistula treatment method for them after a thorough examination under anesthesia has been performed at surgery. This means that the patient will give consent for a number of different methods, among which the surgeon will choose the single method he/she thinks will work best. If the patient is not willing to undergo any operation that may weaken the sphincter there are still several fistula operations that can be done to decrease symptoms. The consent that is signed should list the approaches that the patient has agreed to undergo as well as the possible side effects and complications.

Alternate Fistula Methods/Approaches that Avoid Cutting Sphincter Muscle

The goal of these methods is to eradicate or treat the fistula in a way that preserves anal function and limits or avoids muscle division. It is important to understand that the success rate for these methods is notably lower than for fistulotomy. What follows is a brief discussion of the following fistula operations: 1) fistula plug or fibrin glue methods and 2) non-cutting Seton.

Fistula plug methods attempt to eradicate the fistula by tightly filling the fistula tract with a “plug” made up of a material or substance that is slowly absorbed by the body. The fistula tract is first identified and the internal opening located. Next a probe is passed along the tract after which the tract is scraped and cleaned with a curette inserted through the external opening and then irrigated. The sterile plug is then pulled into the tract through the internal opening. Once the plug has been properly positioned several sutures are placed to anchor the plug and to close the internal opening of the fistula. No muscle is cut with this method, thus, there should be no loss of function. The success rate of the plug method in most surgeon’s hands is, at best, 50 %. In some failed cases the plug becomes dislodged from the tract. In other patients the fistula returns after a symptom free period that may last several months. If this method fails the patient has the option of undergoing one of the other fistula methods.

The use of Fibrin glue or other injectable substance is a similar approach because the goal is to completely fill the fistula tract after it has been scraped and cleaned. This method, also, leaves the sphincter muscles intact. The success rate for fibrin glue is, unfortunately, also in the 50 % range, at best. If this method fails the patient has the option of undergoing one of the other fistula operations.

The safest method, from the viewpoint of anal sphincter preservation is the “Non-cutting Seton”. The goal of this method is not to get rid of the fistula but to eliminate the worst symptoms caused by the fistula. Untreated, fistulas usually develop intermittent blockages along the fistula tract. These blockages lead to a small abscess, swelling, and pain. Usually, days later, the fistula opens up again and some pus or fluid drains out from the external opening. This cycle tends to repeat itself at regular intervals in most fistula patients. When the non-cutting Seton method is used a thin soft rubber/plastic string is passed through the fistula tract (after curetting and cleaning) and the two ends are tied together forming a very loose loop. The external part of the loop protrudes an inch or two from the anal area. The non-cutting Seton does not cut or destroy any of the anal sphincters. The Seton is left in place, ideally, for months and usually is very well tolerated. The Seton, by holding the fistula tract open, prevents small abscesses from forming and also allows the fistula tract to develop a lining. A small amount of drainage is expected daily both with the Seton in place and after the Seton has been removed. Although the fistula is not eradicated with this method, the worst symptoms should be eliminated. This method is most often used in patients who have fistulas that involve a large part of the anal sphincter or in those who at high risk for developing incontinence. It is also used for fistula patients who are not willing to take a chance that weakness may develop.

Sphincter Function Preserving Fistula Treatment Methods

The goal of these methods is to eradicate or treat the fistula in a way that preserves anal function and limits muscle division. It is important to understand that the success rate for these methods is lower than for fistulotomy. What follows is a brief discussion of the following fistula operations: 1) anorectal advancement flap, and 2) L.I.F.T procedure.

The anorectal advancement flap method preserves the external anal muscle, the most important part of the sphincter, which minimizes the chances of major anal control problems. A “U” shaped flap of anal skin, rectal lining, and a portion of the internal anal muscle is made around the internal opening of the fistula. Next, a piece of the free end of the flap, including the internal opening of the fistula, is excised after which the flap is pulled downward and sewn to the outer edge and sides of the wound. This covers over and closes off the internal opening altogether. The outer part of the fistula tract is left in place after it has been cleaned out with a curette. The success rate of this approach, in most surgeons’ hands, is between 50 and 65 %.

The L.I.F.T. procedure occludes and closes the fistula with a suture placed around the tract between the internal and the external sphincter muscle. This approach preserves the anal sphincter muscles and does not cut open or remove the fistula tract. The fistula tract is first cleaned with a curette in order to place the suture the surgeon must carefully dissect between the internal and external muscles to expose the part of the fistula tract that runs between these 2 muscles. This method cannot be done if the fistula tract is not mature. The success rate for this approach has been reported to be in the 65-75 % range although others have noted worse results.

What Our Patient’s Say…

Our family wishes to express our heartfelt appreciation for the kindness, excellent care and wisdom our mother, Jean Broussard, received during her hospitalization.

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