Anal Fistula

Abstract

A perianal abscess is caused by inflammation due to bacterial infection of the anal gland, which is located in the anal crypts along the dentate line, and is formed by tunneling under the skin of the anus. An anal fistula is formed when pus is discharged from an opening of the abscess to the skin (Fig. 42.1). The symptoms are more common in breastfed male infants aged less than 6 months. Abscesses and external fistulae (secondary openings) are more likely to be located to the side of the anus (at 3 and 9 o’clock). Abscess symptoms rapidly improve and are relieved by incision and drainage, but symptoms are likely to recur after some time. However, an anal fistula in infants generally resolves before 1 year of age. When the fistula is palpable and the symptoms recur, even at 1 year of age or older, radical surgery for the anal fistula is indicated.

The figures in this chapter are reprinted with permission from Standard Pediatric Operative Surgery (in Japanese), Medical View Co., Ltd., 2013, with the exception of occasional newly added figures that may appear.

1 Preoperative Management

1.1 Incision of a Perianal Abscess

There are no special preoperative preparatory procedures, other than verifying the last feeding time to prevent vomiting associated with crying. In general, we perform the procedures during hospitalization to confirm postoperative hemostasis and provide instructions for sitz baths and anal cleansing to parents (Fig. 42.1).

Fig. 42.1

Anatomy of rectum/anus and perianal abscess and anal fistula

1.2 Radical Surgery for Anal Fistula

If there are atypical symptoms, the fistula location and surrounding area should be evaluated by fistulography in advance. The patients should not be fed after breakfast on the day before surgery and should be administered a 50 % glycerin enema according to body weight (2 mL × weight in kg) in the afternoon and evening on the same day to promote defecation.

2 Operations

2.1 Incision of a Perianal Abscess

A scalpel is inserted into the dome of the abscess, and an approximate 5-mm incision is made in parallel to the anal folds and spread radially under local anesthesia. The tip of a mosquito clamp is inserted into the abscess, and purulent discharge is promoted. The abscess cavity is filled with ribbon gauze.

2.2 Radical Surgery for Anal Fistula

The procedures are performed in the lithotomy position under general anesthesia (if a fistula is located in the ventral region, the procedure can be performed in the jackknife position). Approximately 2 mL of indigo carmine is transferred to a 3-mL needleless syringe and injected into a secondary opening or forcefully instilled into the fistula to check for flow from a primary opening (Fig. 42.2) (use of an intravenous catheter trocar may allow excess leakage from the side of the trocar, with insufficient pressure). After confirmation of the location of the primary opening, a probe or mosquito clamp is inserted from the secondary opening to the primary opening to open the fistula (Fig. 42.3). Then, the primary opening is completely excised, and necrotic and diseased granulation tissue in the fistula is also excised. The margin is trimmed to make the open wound suitable for drainage, and complete hemostasis is performed using electrocautery (Fig. 42.4). Square gauze with Xylocaine^® Jelly is then packed into the open wound.

Fig. 42.2

Check the internal fistula (primary opening) by injecting the dye into the external fistula (secondary opening). (a) Directly inject the dye into the secondary opening using a needleless syringe. (b) Check the drainage of the dye from the primary opening

Fig. 42.3

Opening of the fistula

Fig. 42.4

Complete removal of the fistula and open wound formation

A complex anal fistula in an older toddler should be treated by sphincter splitting fistulotomy or fistulectomy, as in radical surgery for anal fistulas in adult patients. It is important to completely remove primary openings (multiple anal crypts adjacent to the primary opening may sometimes be removed).

3 Important Points of Postoperative Management

3.1 Incision of a Perianal Abscess

If ribbon gauze spontaneously falls out, it is not necessary to repack the wound after completion of hemostasis. The ribbon gauze should be removed the next day if it remains in the site. Sitz baths and anal cleansing in lukewarm water from postoperative day 1 are recommended. The incision is likely to close at an early stage, and the parents should be instructed in a method for drainage of pus at home. If the patient has fever, oral antibiotics are administered for a few days (as antibiotic administration may cause diarrhea, it is not always necessary if there is adequate purulent drainage).

3.2 Radical Surgery for Anal Fistula

If split gauze in the wound spontaneously falls out, it is not necessary to repack the wound after completion of hemostasis. The gauze should be removed the next day if it remains in the site. Water intake is allowed a few hours after surgery, and food intake is restarted the next morning. Antibiotics are routinely administered intravenously for three doses: immediately before surgery, the evening on the day of surgery, and in the morning on the day after surgery. Wound cleansing with lukewarm water is started from postoperative day 1, and instructions for the method of sitz baths and wound cleansing are given to the parents. The patient can be discharged from the hospital when sufficient oral intake, smooth defecation, and excellent wound healing are confirmed (in general, 3–4 days after the surgery). The parents provide sitz baths and wound cleansing for the patient after discharge, and the wound healing process is followed up in the outpatient department. When the wound size has decreased, an anal digital examination is performed in the outpatient department. Bougienage is also performed as appropriate, to prevent closure of the deeper aspect of the open wound, and appropriate wound closure and epithelialization are promoted.