What is anal fistula?

What is anal fistula? Many people don’t know much about it, but those who have suffered from anal fistula are very familiar with it. Anal fistula is actually a relatively common anal disease, which mostly occurs in male friends. People say that nine out of ten men have hemorrhoids, and anal fistula is an anorectal disease with a second highest incidence rate after hemorrhoids. It can be seen that anal fistula is also quite troublesome, and it is also quite painful during the onset, which is difficult to talk about.

During the onset of anal fistula, there will be a feeling of pins and needles, and many will be very painful, which is unbearable. It is so troublesome, so you need to pay more attention to all aspects during the onset. If you need to sit for a long time at work, try to put a thicker cushion on the stool. During the medication period, do not eat spicy food or drink alcohol. Let us understand what anal fistula is.

1 Causes

1. The existence of the internal opening. The primary infection source, such as anal sinusitis or anal gland infection, still exists. The intestinal contents can continue to enter the fistula from the internal opening and form a new fistula again. This is the key to the recurrence of anal fistula. When it comes to anal fistula, many unprofessional doctors often fail to find all the internal openings and simply eliminate the surface openings without solving the most critical internal opening, causing the anal fistula to recur again and again.

2. The anus cannot rest quietly, and the abscess cavity is not easy to adhere to. During defecation and urination, the anal sphincter contracts or the anal sphincter is stimulated by inflammation, causing the anal sphincter to be often in spasm.

3. Feces, intestinal fluid and gas in the intestinal cavity continue to enter the fistula, stimulating the wall of the tube, causing the connective tissue of the wall to proliferate and thicken, making the lumen difficult to close.

4. The abscess cavity is poorly drained, or the external opening is reduced, sometimes closed and sometimes ulcerated, and pus accumulates in the cavity, leading to recurrence of the abscess and rupture to form new branches or fistulas.

5. Most of the tubes pass through the anal sphincter at different heights. The contraction of the sphincter hinders the discharge of pus, resulting in poor drainage.

In addition, there are some diseases that are also the cause of anal fistula, such as tuberculosis, Crohn's disease, ulcerative colitis, etc.

6. The sacral curve of children has not yet formed, and the tension of the internal anal sphincter is relatively weak. Feces can easily directly press on the dentate line in the anal canal, causing abrasions of the anal sinus mucosa, making it easy for bacteria to invade and cause disease.

7. Children often suffer from diaper dermatitis, which irritates the skin around the anus, forming subcutaneous abscesses around the anus that communicate with the anal sinus and form anal fistulas.

8. The sebaceous glands of newborns secrete excessively, and the infection causes subcutaneous abscesses around the anus, which are connected to the anal sinuses and cause anal fistulas.

9. Newborns have incomplete physiological immune function and are prone to anal infection and anal fistula.

2 Clinical manifestations

1. The anal venous return is poor, local congestion often occurs, tissue malnutrition occurs, and healing is affected.

2. The fistula tract is tortuous or has sinuses or branches, resulting in poor drainage, pus retention, and repeated infections, making the fistula tract difficult to heal.

3. There is a certain pressure in the rectum, and rectal infected substances such as feces and gas can often enter the fistula from the internal opening, irritate the cavity wall, and be discharged from the external opening after secondary infection, which is also the cause of the fistula.

4. After the anorectal abscess ruptures, the pus is discharged, the abscess cavity gradually shrinks, the external rupture opening and incision also shrink, and the cavity wall forms a hard tubular wall of connective tissue hyperplasia, so it cannot close naturally.

5. Fistulas often pass between the anal sphincters. Since the sphincters are constantly contracting and relaxing, they compress the fistulas, affecting the discharge of pus, making it easy for pus to accumulate and become infected, making it difficult to heal.

6. When anorectal abscesses rupture or are incised, they are usually outside the anus, with pus flowing out of the external opening, but the primary infection is usually in the anal sinus. The anal sinus is the gateway for secondary infection, and repeated infection can form a fistula.

7. Abscesses caused by infections such as Mycobacterium tuberculosis, Actinomycetes, and Crohn's disease are difficult to heal on their own and form special anal fistulas.

Most anal fistulas are formed after an anorectal abscess ruptures or pus is drained after incision. The abscess gradually shrinks, but intestinal contents continue to enter the abscess cavity. During the healing and shrinking process, a tortuous cavity is often formed, which makes drainage poor and difficult to heal. After a long time, there is a lot of scar tissue around the cavity, forming a chronic infectious tract. It runs near the internal and external sphincters, and the skin of the external opening grows faster, often with pseudo-healing properties, causing repeated attacks. Most duct infections are purulent, and a few are tuberculous.

3. Diagnosis

1. Palpation

The fistula of a low-position anal fistula is a rope-like hard strip that can be felt under the skin, running from the external opening to the anus. When pressed with the fingers, pus will flow out of the external opening.

2. Observation

The visible external opening often forms a protrusion or depression on the skin around the anus or on the buttocks. The surrounding skin is irritated by pus and often peels and becomes red, and sometimes granulation tissue protrudes from the external opening. The surrounding skin is reddish purple, mostly tuberculous fistulas.

3. Digital rectal examination

A small hard lump with a central depression can often be felt at the back of the anal canal, near the dentate line, with slight tenderness. This is the primary internal opening.

4. Determine the location of the inner opening

The location of the internal opening can be determined by pathological examination and bacterial culture, judging the location of the internal opening from the medical history, iodized oil radiography, anoscopy, judging the location of the internal opening based on the distance between the external opening and the anus, staining examination, probe examination and palpation to help understand the location of the internal opening.

4 Treatment

1. Fistulotomy

It is a method of completely cutting open the fistula and relying on the growth of granulation tissue to heal the wound. It is suitable for low-position anal fistula because the fistula is deep below the external sphincter. After the incision, only the subcutaneous and superficial parts of the external sphincter are damaged, and postoperative anal incontinence will not occur. The operation is performed under caudal anesthesia or local anesthesia. The patient is in the lateral position or lithotomy position. First, methylene blue solution is injected from the external opening to determine the position of the internal opening. Then a probe is inserted from the external opening into the gall duct to understand the course of the fistula and its relationship with the sphincter.

The surgical steps of anal fistula incision:

(1) Correctly explore the internal opening. The operation of finding the internal opening is the same as that of the hanging thread therapy. After finding the internal opening, pull the probe out of the anus. If the fistula is bent or has branches, the probe cannot enter the internal opening. Inject a small amount of 1% methylene blue solution from the external opening to determine the location of the internal opening. Then use a slotted probe to explore from the external opening, gradually cut the tract open, and explore until the internal opening is found. If the internal opening cannot be found after careful exploration, the anal sinus suspected of having a lesion can be treated as the internal opening.

(2) Open the fistula tract and fully remove the marginal tissue. After the fistula tract is opened, check for branches. If found, they should also be opened. After the fistula is completely incised, the rotten granulation tissue will be scraped clean. Generally, there is no need to remove the entire fistula to avoid excessive wound size. Finally, trim the wound edges to make it into a "V" shape with a small bottom and a large mouth, so that the deep part of the wound can heal first.

(3) During the anal sphincterotomy, the relationship between the position of the probe and the anorectal ring should be carefully understood. If the probe enters below the anorectal ring, although the fistula and most of the external sphincter and the corresponding internal sphincter are completely cut open, anal incontinence will not occur because the puborectalis muscle is preserved. If the probe enters the rectum above the anorectal ring (such as suprasphincteric anal fistula and extrasphincteric anal fistula), fistula incision should not be performed, and hanging thread therapy or hanging thread staged surgery should be performed. In the first stage, the fistula tract below the ring is incised or removed, and the fistula tract above the ring is hung with a thick silk thread and tied tightly. The second stage of surgery is to wait until most of the external wounds have healed and the anorectal ring has been adhered and fixed, and then the anorectal ring is cut open along the hanging line. After the fistula is opened, the granulation tissue on the wall can be scraped off with a curette and generally does not need to be removed to reduce bleeding and avoid damaging the sphincter on the posterior wall. The excised fistula tissue should be sent for pathological examination.

(4) Wound treatment: Change the dressing once a day, preferably after defecation. Gradually reduce the amount of dressing in the wound until the wound in the anal canal heals. Performing a digital rectal examination every few days can dilate the anal canal and prevent bridge-shaped adhesions and false healing.

2. Hanging Thread Therapy

It is a method of slowly cutting open the anal fistula by using the mechanical compression of a rubber band or corrosive thread. It is suitable for simple anal fistulas with low or high internal and external openings within 3 to 5 cm from the anus, or as an auxiliary treatment for incision and resection of complex anal fistulas. The ligated muscle tissue suffers from blood circulation obstruction, gradually necrotizes and disconnects, but the fibrosis caused by the inflammatory response causes the severed muscle to adhere to the surrounding tissue. The muscle will not contract too much and will gradually heal, thus preventing anal incontinence caused by the retraction of the severed anorectal ring. The operation is performed under caudal anesthesia or local anesthesia, and the probe is inserted from the external opening. Follow the direction of the fistula and pass it out from the inner opening. Tie a sterilized rubber band or thick silk thread on the probe at the inner opening. Guide it through the entire fistula, cut the skin between the inner and outer openings, and then tie the hanging thread tightly.

SFT technology, that is, a fully computerized anorectal disease diagnosis and treatment system that combines examination and treatment, is mainly used in minimally invasive treatment of anal fistula and perianal abscess. The lesion site is displayed on the computer screen with clear images and accurate diagnosis. At the same time, the images can be frozen, stored, replayed, enlarged for analysis, measured and calculated, and can be compared before and after treatment.

Everyone has a basic understanding of what anal fistula is. Many friends who have this disease find it difficult to talk about it and are embarrassed to go to the hospital. If you have many similar symptoms, it is best to seek medical attention as soon as possible and receive early treatment to avoid serious illness and bring more inconvenience to your life.