Anal fissure, abscess and fistula
A fissure is a small tear in the skin of the anus, an abscess is a pocket of pus beside the anus, and a fistula is a channel that sometimes remains after an abscess. This page explains the symptoms of each, the treatments, and why a fistula usually needs surgery.
Three related problems
We have put three conditions together here because their symptoms are similar and they are linked. If you have pain, bleeding or discharge around the anus, you first need an examination to find out which one it is. Hemorrhoids, fissures, abscesses and other conditions can look alike.
Anal fissure
What is it?
A fissure is a small tear in the skin inside the anus. It affects women and men equally and can occur at any age; the NHS says it is more common between ages 15 and 40 and in children. ASCRS says about 85 to 90% of fissures are in the midline at the back of the anus and 10 to 15% at the front. A fissure in another place, or several fissures, or one without pain needs further investigation.
The cause is usually injury from a hard, dry stool, sometimes diarrhea. A cycle forms: pain makes the muscle spasm, pressure rises, blood flow falls, and the tear heals more slowly and hurts more.
Symptoms
- Sharp pain during a bowel movement that may last from a few minutes to several hours afterwards
- Bright red blood on the tissue paper or on the stool
- Fear of going to the toilet
ASCRS says a fissure is often mistaken for hemorrhoids, and this can delay diagnosis. A fissure does not cause colon cancer, but if symptoms persist or the bleeding has no clear cause, a colonoscopy may be needed.
Treatment
First, simple measures (for most acute fissures):
- 25 to 35 grams of fiber a day, a stool softener and enough water
- Warm sitz baths for 10 to 20 minutes, several times a day, especially after a bowel movement
- A local anesthetic such as lidocaine for pain
- Avoid opioid pain relief because it causes constipation
For a chronic fissure (usually longer than 8 to 12 weeks):
- Muscle-relaxing ointments: nitroglycerin (heals more than 50% of chronic fissures, but 20 to 30% of patients get headaches) and diltiazem or nifedipine (65 to 95% healing reported; headache up to 25%). ASCRS says recurrence after medicine is higher than after surgery, but there are fewer complications.
- Botulinum toxin (Botox) injection into the internal anal muscle: healing in about 50 to 80%, recurrence up to 40%; it can be repeated.
- Lateral internal sphincterotomy: a controlled cut of part of the internal muscle. ASCRS quotes success over 90% and very low recurrence in the hands of an experienced surgeon. The NHS also names a small cut in the muscle.
Complete healing with medicine or surgery can take 6 to 12 weeks. Acute pain after surgery usually eases within a few days, and most people return to work within a few days.
Risk
Both Botox and sphincterotomy can, in rare cases, affect control of gas or stool. If you have had incontinence, muscle injury or Crohn’s disease, another option such as an anal advancement flap may suit you better.
Preventing recurrence
Fissures often come back; keeping up fiber and good bowel habits matters.
Anal abscess
What is it?
An abscess is a cavity filled with pus near the anus or rectum. According to ASCRS, about 90% start from infection of small glands inside the anus.
Symptoms
- Pain, swelling and redness beside the anus, throbbing and sometimes with fever
- Pain when sitting and walking
- Sometimes nothing is visible and there is only deep pain or pressure
Anal pain with fever needs to be seen sooner (ASCRS).
Treatment
The standard treatment is surgical drainage, in the office under local anesthesia or in the operating room. Antibiotics alone are not enough, and for some patients (weak immunity, diabetes, spreading skin infection) they are needed in addition to drainage.
After drainage
ASCRS says about 40 to 50% of drained abscesses later become a fistula or come back. That is why follow-up is needed.
Anal fistula
What is it?
A fistula is a narrow channel between the inside of the anus and the skin around it. It usually remains after an abscess that has not healed completely. The NHS lists the less common causes as Crohn’s disease, diverticulitis and hidradenitis suppurativa.
Symptoms
- Foul-smelling, pus-like or sometimes bloody discharge from an opening beside the anus
- Pain, skin irritation
- Repeated abscesses
Assessment
Examination and sometimes a short endoscopy (proctoscopy). For a complex fistula or Crohn’s disease, an anal ultrasound, MRI or CT. ASCRS says pelvic MRI is up to 90% accurate in showing the track.
Treatment options
Because there is no medicine for it, surgery is usually needed. The main options named by ASCRS and the NHS:
- Fistulotomy: laying the channel open so it heals from the base. Success 92 to 97%, but cutting muscle carries a risk of incontinence.
- Seton drain: a thread left in the channel for several weeks (8 to 12 weeks or longer) to let the inflammation settle; sometimes it is the first stage and another procedure follows.
- Endoanal advancement flap: covering the inner opening with healthy tissue, for a complex fistula or high risk of incontinence. Recurrence up to 50% is quoted.
- LIFT: closing the channel between the two muscles without cutting muscle; success similar to the flap.
ASCRS does not name fistula plugs or glue in its text. The NHS says each method has its own benefits and risks and the surgeon will explain.
In Crohn’s disease
Fistulas are common in Crohn’s disease and ASCRS says the risk of incontinence is higher. The main treatment is medicine, and surgery is for infection and support.
Recovery
- Pain relief, fiber and water to prevent constipation; warm sitz baths
- Most operations are done as day cases; the NHS says many patients do not stay overnight in hospital
- Ask the surgeon about rest time and return to work; the sources give no fixed numbers
When to call
- Throbbing pain, swelling or redness beside the anus, especially with fever
- New or increased pus-like or bloody discharge
- After an operation: fever, more redness and discharge than expected, or being unable to pass urine
- A change in control of gas or stool
Shaking chills with a high fever, severe pain or heavy bleeding is an emergency: call 115 (Iran’s emergency number). Every patient’s treatment plan is different; ask your doctor about your own situation.
Frequently asked questions
Does a fissure heal by itself?
Often yes. The NHS says it usually heals without special treatment, and ASCRS says simple measures (25 to 35 grams of fiber a day, a stool softener, water, warm sitz baths for 10 to 20 minutes several times a day) heal more than half of acute fissures. If it has not improved after a few weeks or keeps returning, it becomes a chronic fissure and other treatment is needed.
Does an abscess heal with antibiotics?
Usually not. According to ASCRS the standard treatment is surgical drainage through a small cut beside the anus, sometimes under local anesthesia in the office. Antibiotics alone do not replace drainage, and routinely adding them in simple cases does not speed up healing. Antibiotics are advised for people with weak immunity, spreading skin infection or certain heart conditions.
Why does a fistula usually need an operation?
Because a fistula is a fixed channel from inside the anus to the skin, and ASCRS says there is no medicine that treats it. The NHS also says a fistula does not usually heal by itself and surgery is advised in most cases. Crohn's disease is an exception: the main treatment of the fistula is medicine, and surgery is mostly for infection or as an addition.
Can surgery for a fissure or fistula affect control of gas and stool?
There is a risk, although it is usually small, and procedures are chosen to protect the closing muscle. For fissures, ASCRS says both botulinum toxin injection and sphincterotomy can sometimes affect control of gas or stool, temporarily or longer. For fistulas, cutting part of the muscle carries a risk of incontinence, but a small amount can usually be cut safely. If you have had a difficult delivery, muscle injury, incontinence or Crohn's disease, tell the surgeon before the operation.
Does a fistula come back after surgery?
It can. ASCRS says a fistula can return even after it seems healed, and how often depends on the operation. For example, up to 50% is quoted for the advancement flap, and smoking, Crohn's disease and several earlier operations raise the risk of failure. No method is guaranteed.