How to determine whether it is anal fistula, symptoms and signs need to be understood

Anal fistula has a high incidence rate among men. Whether it is anal fistula can be diagnosed through the symptoms of this disease. The most common manifestation is repeated pus discharge. The skin around the anus is sometimes irritated and itchy. It is necessary to check and confirm the disease in time for surgical treatment.

1. Symptoms and signs Anal fistula is often caused by the spontaneous rupture of perianal abscesses or the failure of the wound to heal after incision and drainage. The clinical manifestations are repeated discharge of a small amount of pus from the outer opening of the fistula, which contaminates the underwear; sometimes the pus irritates the skin around the anus and causes itching. If the external opening is temporarily closed and pus accumulates, there will be local pain, redness and swelling. The closed external opening may be ruptured again, or another new external opening may be ruptured nearby. Repeated attacks may form multiple external openings that communicate with each other (Figure 3). If the fistula drainage is smooth, there will be no local pain, only slight swelling and discomfort, which the patient usually does not mind.

Examination: The external opening is a papillary protrusion or a bulge of granulation tissue, and a small amount of pus flows out when pressed. Low-position anal fistula often has only one external opening. If the fistula is shallow, a hard cord can be felt under the skin, leading from the external opening to the anal canal (Figure 4). High anal fistulas are often located deep and the fistula tract is difficult to feel, but there are often multiple external openings. Due to the irritation of secretions, the skin around the anus often thickens and becomes red.

If there are external openings on both sides of the anal canal, it should be considered a "horse-shoe-shaped" anal fistula. This is a special type of transsphincteric anal fistula, also a high-positioned curved anal fistula. The fistula surrounds the anal canal and extends from one side of the ischiorectal fossa to the other side, forming a semi-circular shape, like a horseshoe, hence the name. There is an internal opening near the dentate line, and there can be multiple external openings, scattered on the left and right sides of the anus, with many branches spreading around. Horseshoe anal fistula can be divided into two types: anterior horseshoe and posterior horseshoe. The latter is more common because the tissue at the back of the anal canal is looser than that at the front, allowing the infection to spread easily.

2. Distribution pattern of fistula openings The distribution of the external and internal openings of anal fistulas has a certain regularity. Goodsall (1900) once proposed: draw a horizontal line at the midpoint of the anus. If the external opening of the anal fistula is in front of this line, the fistula tract often runs in a straight line into the anal canal, and the internal opening is located at the corresponding position of the external opening; if the external opening is behind the horizontal line, the fistula tract often has a curved shape, and the internal opening is mostly in the middle of the back of the anal canal. This is generally called Goodsall's law (Figure 5). Most anal fistulas conform to the above rules, but there are exceptions. For example, the high-positioned horseshoe-shaped anal fistula in the front may be curved, and the low-positioned perianal abscess in the back may be straight. Clinically, it has been observed that the straightness and curvature of anal fistula are not only related to its location in the front or back of the anal canal, but also to its high or low position and the distance of its external opening from the anal margin. Cirocco (1992) conducted a retrospective analysis on a group of anal fistula cases to test the accuracy of Goodsall's rule in predicting the course of anal fistula. He believed that the rule was quite accurate in predicting the course of anal fistulas with posterior external openings, especially in female patients, 97% of whom had internal openings located in the posterior median anal recess. However, the prediction of anal fistulas with an anterior external opening was inaccurate, with only 49% having radial fistulas that met the rule. This was because Goodsall did not realize that 9% of anterior anal fistulas also originated from the anterior median anal recess.