The anus is that part of the intestinal tract that passes through the muscular canal of the pelvis and the anal sphincters.
It is the final hole through which stool leaves the body.
In adults, the anus is 4 to 5 centimeters long. The lower half of the anal canal has sensitive nerve endings.
There are blood vessels under the lining, and in its middle portion there are numerous tiny anal glands.
Diseases and their causes
An anal fissure, also called an anorectal fissure, is a linear division or tear in the lining (“anoderm”) of the lower anal canal.
Most anal fissures occur when a large, hard stool overstretches the anal opening and tears the delicate anoderm.
Less commonly, anal fissures develop due to prolonged diarrhea, inflammatory bowel disease, or sexually transmitted diseases that affect the anorectal area.
Acute (short-term) anal fissures are usually superficial and shallow, but chronic (long-term) anal fissures can extend deeper through the anoderm to expose the underlying muscle surface.
Painful anal fissures can be a recurring problem in people who suffer from repeated episodes of constipation.
Fortunately, superficial fissures generally heal quickly with medical treatment, and most symptoms clear up within a few days to a couple of weeks.
An anal abscess is a painful, swollen collection of pus near the anus.
Most anal abscesses are unrelated to other health problems and arise spontaneously, for reasons that are not clear.
They originate in a small anal gland, which is enlarged to create a site of infection under the skin.
Generally, more than half of all anal abscesses occur in young adults between the ages of 20 and 40, and men are affected more often than women.
Most anal abscesses are found near the opening of the anus, but rarely can they occur deeper or higher in the anal canal, closer to the lower colon or pelvic organs.
An anal abscess sometimes drains on its own, although it is always safer for a doctor to evaluate the problem.
If the abscess does not drain on its own, the doctor may make an incision and drain the abscess. After draining an abscess, the pain usually improves immediately.
An anal abscess often turns into an anal fistula even with proper treatment.
An anal fistula is a narrow duct, which is the remnant of an old anal abscess after it has been drained.
It connects the middle portion of the anal canal (in the anal gland) to the surface of the skin. After an anal abscess has drained, either spontaneously or when drained by a doctor, an anal fistula will develop.
Sometimes the opening of the fistula on the surface of the skin constantly discharges pus or bloody fluid. In other cases, the fistula opening is temporarily closed, causing the old anal abscess to swell again like a painful pocket of pus.
Without treatment, an anal fistula can continue to ooze blood or pus for long periods of time.
Hemorrhoids are generally painless. However, at some point the blood vessels in a small hemorrhoid at the edge of the anal opening can clot (“thrombosis”).
This can be brought on by a period of constipation from diarrhea. When thrombosis occurs, the external hemorrhoid becomes swollen, hard, and painful, sometimes with bloody discharge.
When hemorrhoids are external and thrombosed, the body usually slowly reabsorbs the clot, and the pain and swelling will slowly subside over a period of days to a couple of weeks.
However, when it is very painful, the doctor can remove the clot.
Anal cancers that begin in the cells of the glands are called adenocarcinomas.
Anal cancers are often divided into 2 groups, which are sometimes treated differently:
- Cancers of the anal canal (above the anal rim).
- Cancers of the anal margin (below the anal margin).
The inner lining of the anal canal is the mucosa. Most anal cancers begin in the cells of the mucosa.
Sometimes anal cancers spread from one area to another, making it difficult to know exactly where they started.
Polyps are small, irregular, or fungal-like growths that form on or just below the mucosa. There are many types.
- Inflammatory polyps begin due to irritation caused by injury or infection.
- Lymphoid polyps are caused by an overgrowth of lymphatic tissue (which is part of the immune system). The lymphatic tissue under the anal lining (mucosa) is normal, but these overgrowths are not.
- Hypertrophied anal papillae are benign connective tissue growths that are covered by squamous cells. They are simply normal enlarged papillae, which are small folds of mucosa that meet at the dentate line. Hypertrophied anal papillae are also called fibroepithelial polyps.
Although all anal disorders cause some type of anal discomfort or pain, other symptoms vary, depending on the specific anal problem.
Symptoms can include:
- Pain in the anal area, often described as sharp, stabbing, or burning, and usually triggered by a bowel movement.
- Mild rectal bleeding, usually a small amount of bright red blood with a bowel movement or on toilet paper.
- Presence of a firm, tender mass or swelling in or around the anal area, which may become enlarged.
- Occasionally fever, chills.
- Persistent drainage of blood, pus, or foul-smelling mucus from the anal area.
- A firm and usually quite painful swelling at the anal opening.
- Discomfort or tightness in the anal area that interferes with bowel movements.
- Changes in bowel habits with unusual discharges from the anus.
Once the symptoms have been described, the doctor will ask questions about:
Bowel habits, especially any history of constipation.
Medical history, including any history of bleeding disorders, rectal bleeding episodes, inflammatory bowel disease, sexually transmitted diseases, or radiation therapy for cancer.
The use of prescription or over-the-counter medications that can increase the risk of bleeding.
If you have anal sex or if you have a history of anal trauma.
Next, your doctor will perform a physical exam of your abdomen, followed by an external exam of your anal area and a digital rectal exam.
Anal cancer can be found during a routine digital rectal exam or during a minor procedure, such as the removal of what is believed to be a hemorrhoid.
More invasive procedures, such as anoscopy, proctoscopy, or endorectal ultrasound, are also generally used for diagnosis.
If cancer is suspected, a biopsy should be done and the sample should be examined by a pathologist.
The staging study may include an abdominal and pelvic CT scan, a pelvic MRI to evaluate the pelvic lymph nodes, a chest X-ray, and liver function studies.
You may be able to prevent anal fissures by preventing constipation. To do this, soften your stool by gradually adding more fiber to your diet and drinking 6 to 8 glasses of water a day. Commercially available fiber supplement powders work well.
Although it is not always possible to prevent other types of anal disorders, you can lower your risk of these diseases by:
- Use gentle techniques to clean the anal area.
- Keep the anal area dry by changing your underwear frequently and avoiding moisture.
- Always use a condom if you have anal sex.
Never insert any foreign object into the rectum.
A doctor must diagnose anal disorders. Once the diagnosis is made, treatment may or may not involve surgery, depending on the specific disorder.
For an acute fissure, the doctor may recommend that you follow the suggestions to relieve constipation, he may also recommend that you apply a medicated ointment to the fissure and soak the anal area in warm water for 10 to 15 minutes several times a day (“bath seat”).
For chronic fissures, surgery can correct the problem in more than 90% of cases.
The doctor must open to drain the pus. This procedure is called an incision and drainage. This can usually be done as an outpatient procedure, especially if you are young and generally healthy, and your abscess is near the anal opening.
Surgery to undress the fistula line (“fistulotomy”) is the most effective therapy. The doctor opens the infected canal and removes the remains of the old anal abscess.
The wound is left open to heal from the bottom up. If the fistula is associated with Crohn’s disease, treatment is directed toward Crohn’s disease with anti-inflammatory drugs combined with an antibiotic.
Thrombosed external hemorrhoids
Usually this will slowly go away on its own. The process can be sped up by taking a fiber supplement to soften the stool, and also by taking frequent lukewarm baths (“sitz baths”).
If the hemorrhoid is unusually painful, the doctor may perform a limited operation under local anesthesia to remove the clotted hemorrhoid.
Anal cancer is mainly treated with a combination of chemotherapy and radiation. Surgery is generally reserved for patients who do not receive the above therapy.
Call your doctor right away when you have rectal bleeding or any bloody discharge from the anus. Even if you have been treated for a bleeding fissure in the past, it is always safer for your doctor to determine the best course of action.
This is especially true if you are over 40, when there is an increased risk of rectal bleeding from colorectal cancer and other serious digestive diseases.
Almost all acute fissures heal quickly with conservative treatment, and almost all chronic fistulas and fissures can be corrected with surgery.
Proper treatment of anal strictures will allow stool to pass easily and comfortably.
Most anal abscesses heal after being drained by a doctor. Some develop into anal fistulas.
If a fistula complicates the healing of an abscess, a fistulotomy will completely remove both the fistula and any remaining abscess in most patients.
Cancer prognosis is related to the stage at which it is diagnosed, the size of the tumor, and the presence of lymph node metastases.