Anal Fistula Signs: 5 Common Symptoms and Early Diagnosis Methods

Anal fistula can start with just a painful, swollen area, discharge, or an abnormal small opening around the anus, but if left untreated, it can lead to infection and recurrence. According to medical literature, about 30–50% of anal abscess cases can progress to anal fistulas, so early recognition of signs of anal fistula is crucial for treatment.

In this article, Tiptory helps readers understand what an anal fistula is, common signs of an anal fistula, and how an anal fistula is diagnosed, from direct examination to imaging tests when necessary. By understanding their condition correctly, patients will know when to seek medical attention and what to prepare before a doctor diagnoses an anal fistula, instead of self-monitoring or prolonged home treatment.

Part 1: How to recognize anal fistula symptoms

Symptom 1: Recognizing pain from an anal fistula

Check for abnormal pain and swelling

• Anal fistula can cause pain, swelling, or irritation around the anus. Some people also feel discomfort in the genital area or perineum, which is the area between the anus and the genitals.

• Pain during bowel movements is a common sign of anal fistula that patients often notice, especially when the fistula or inflamed area is close to the anus. The pain may be more pronounced when stool passes through and irritates the affected area.

• If there is pain around the anus accompanied by swelling, discharge, pus, or the appearance of an abnormal small opening on the skin, the patient should see a doctor instead of trying to self-diagnose. These symptoms may be related to an anal fistula but can also occur with an anal abscess, anal fissure, or other conditions.

• Pain in the genital area during sexual intercourse may occur with some types of fistulas related to the vagina. This is not a specific sign of a fistula, so it needs to be evaluated by a doctor along with other symptoms.

Assess the severity and progression of pain

• When preparing for an anal fistula diagnosis, the patient should note the onset of pain, location of pain, severity of pain, and whether it increases during bowel movements.

• If the pain is prolonged, recurrent, or progressively worsening, especially if accompanied by fever, hot swelling around the anus, or pus discharge, specialized medical attention should be sought promptly. The doctor may examine the anal area and order additional imaging tests if necessary to identify the fistula tract.

• One should not rely solely on the sensation of pain to conclude that there is an anal fistula. The diagnosis of anal fistula requires a medical history, clinical examination, and in some cases, endoanal ultrasound or MRI may be needed to determine the location and course of the fistula.

Symptom 2: Recognizing discharge from an anal fistula

Check for abnormal bleeding or discharge

• Anal fistula can cause abnormal discharge or bleeding around the anus. The discharge may be recurrent and sometimes have a foul odor.

• Purulent discharge around the anus is a notable sign of anal fistula, especially if accompanied by swelling, pain, red skin, or the appearance of a small opening on the skin near the anus. However, these symptoms can also occur with abscesses or infections, so one should not self-diagnose based solely on discharge.

• When noticing discharge, the patient should pay attention to its color, odor, amount, and time of appearance. This information helps the doctor gather more data during examination and anal fistula diagnosis.

Note abnormal vaginal discharge

• With a rectovaginal fistula, the patient may notice abnormal vaginal discharge, which may contain pus or stool.

• Passing gas through the vagina is also an abnormal symptom that may suggest a communication between the rectum or bowel and the vagina. This symptom needs to be evaluated by a doctor, especially when it occurs with foul-smelling discharge or stool in the vaginal discharge.

When should you see a doctor?

• If perianal discharge is prolonged, purulent, foul-smelling, or recurrent, the patient should see a specialist to find the cause.

• Not all cases of discharge or bleeding are anal fistulas. The doctor will rely on symptoms, direct examination, and may order imaging tests to determine if a fistula is present and assess the location and extent of the damage.

Symptom 3: Recognizing abnormal urination

Note urinary tract problems

• Some types of urinary tract fistulas can create abnormal connections between the bladder and adjacent organs, causing many changes in urination. This is not a typical manifestation of an anal fistula, but it can occur in some complex fistula types.

• Urinary incontinence or leakage of urine from an abnormal location is a sign to pay attention to. For example, urine may escape through the vagina if a fistula exists between the bladder and the vagina.

• Recurrent urinary tract infections can also be associated with some types of fistulas. If infections repeat frequently without a clear cause, the doctor may need to check for the possibility of an abnormality in the urinary tract.

• Passing gas from the urethra during urination is an abnormal symptom. In some cases, this symptom can occur when there is an abnormal connection between the digestive tract and the urinary tract.

• Cloudy, discolored, or foul-smelling urine should also be noted, especially when accompanied by painful urination, frequent urination, lower abdominal pain, or fever.

What to do if these signs appear?

• One should not self-conclude that these are signs of an anal fistula because urinary symptoms can stem from urinary tract infections or many other medical conditions.

• If there is abnormal urine leakage, gas in the urine, recurrent urinary tract infections, or persistent foul-smelling urine, the patient should see a doctor to evaluate the cause.

• When diagnosing an anal fistula or other types of fistulas, the doctor will combine medical history, clinical examination, and necessary tests to determine the location and course of the fistula.

Symptom 4: Recognizing abnormal digestive symptoms

Note abdominal and pelvic pain

• Some types of gastrointestinal fistulas can cause pain in the abdomen or pelvis. The pain can be dull, persistent, or recurrent depending on the location and cause of the fistula formation.

• Abdominal or pelvic pain is not a specific sign of an anal fistula. However, if the symptom appears along with genital pain, abnormal discharge, or perianal symptoms, the patient should see a doctor to find the cause.

Monitor accompanying digestive symptoms

• Some people may experience nausea, diarrhea, or vomiting. These are common symptoms and can be related to many different gastrointestinal conditions, so they cannot be used in isolation to determine if a fistula is present.

• When diarrhea, nausea, or vomiting occur simultaneously with abdominal pain, pelvic pain, and abnormal discharge in the anus or genitals, the doctor may consider the possibility of a fistula or a related medical condition.

Do not self-diagnose based solely on symptoms

• Gastrointestinal symptoms are often insufficient for diagnosing an anal fistula. To determine the cause, the doctor needs to combine medical history, symptoms, anal examination, and necessary tests.

• If there is prolonged abdominal pain, severe vomiting, persistent diarrhea, fever, or pus discharge around the anus, the patient should see a doctor promptly. Correct evaluation of the cause helps differentiate anal fistula, anal abscess, and other gastrointestinal conditions, thereby choosing an appropriate treatment plan.

Symptom 5: Recognizing signs of infection

Monitor systemic symptoms

• Anal fistula can be associated with infection, especially when the fistula appears with an abscess or prolonged inflammation. In such cases, the body may exhibit non-specific symptoms.

• Fever is a symptom to note, especially when accompanied by pain, swelling, warmth, and redness around the anus, or discharge and pus. Fever can suggest an ongoing infection.

• Chills or shivering may occur as the body reacts to infection. If this symptom is accompanied by fever and perianal pain, the patient should seek prompt medical evaluation.

• Fatigue, malaise, or a general feeling of discomfort can also occur when the body is fighting inflammation or infection. However, these are non-specific symptoms and can be due to many other causes.

Combine symptoms for a more accurate assessment

• A single symptom is not enough to identify a sign of an anal fistula. The patient should pay attention to the combination of perianal pain, swelling, pus or abnormal discharge, and fever.

• If there is high fever, chills, rapidly increasing perianal pain or swelling, abundant pus discharge, or feeling very ill, medical attention should be sought promptly. These could be signs of an infection or abscess requiring treatment.

• When diagnosing an anal fistula, the doctor will evaluate both local symptoms and the systemic condition, then decide whether further tests or imaging are needed to identify the fistula.

Part 2: Steps for diagnosing anal fistula at a medical facility

Step 1: When to get checked for an anal fistula?

Schedule an appointment when a fistula is suspected

• If you notice any signs of an anal fistula such as pain or swelling around the anus, pus discharge, foul-smelling discharge, an abnormal opening on the skin, or recurring symptoms, you should proactively seek medical attention rather than waiting for the condition to resolve on its own.

• Untreated anal fistulas can lead to recurrent infections and affect surrounding tissues. Early examination helps the doctor identify the cause and assess the extent of the damage to determine an appropriate course of action.

Prepare information before the examination

• Record the symptoms you are experiencing: Onset, location of pain, severity of pain, swelling, discharge or pus, bleeding, and whether symptoms have changed over time.

• Provide medical history: Inform the doctor about any previous illnesses, procedures or surgeries related to the anorectal area, and current health issues.

• List current medications: Including prescription drugs, over-the-counter medications, vitamins, or supplements. This information helps the doctor make a comprehensive assessment before choosing a treatment method.

What will the doctor do to diagnose?

• During the diagnosis of an anal fistula, the doctor usually begins by taking a medical history and examining the anorectal area to look for a fistula, swelling, pain, or signs of infection.

• Depending on the symptoms and the degree of suspicion, the doctor may order additional tests such as ultrasound, MRI, or other imaging tests to determine the course of the fistula, especially when the fistula is deep or difficult to observe with a conventional examination.

Step 2: Direct examination to find the fistula tract

Examine the external affected area

• When diagnosing an anal fistula, the doctor usually begins by observing the skin around the anus to look for a fistula opening, swelling, redness, discharge, or signs of infection.

• An anal fistula opening can sometimes be seen as an abnormal small opening on the skin near the anus. However, not all fistulas are clearly visible externally, especially when the fistula tract is deep.

Manual and specialized instrument examination

• The doctor may gently palpate the anal area to detect any abnormal masses, tender points, firm areas, or signs of inflammation. This is an important step to help assess the location of the lesion and guide the cause.

• In cases of suspected anal or rectal fistula, the doctor may perform a digital rectal examination with a gloved finger to check inside the rectum and look for abnormalities that cannot be detected by external observation.

• In some cases, the doctor may use an anoscope to directly visualize the inside of the anus and the lower part of the rectum. This method helps assess the mucosa and assists in identifying the location related to the fistula.

If a vaginal fistula is suspected

• When there are symptoms suggesting a vaginal fistula, the doctor may perform a pelvic examination and use a speculum to visualize the inside of the vagina, thereby looking for abnormal signs or suspected locations of the fistula.

Physical examination is not always sufficient

• The results of a direct examination can help the doctor recognize signs of an anal fistula, but not all fistulas can be fully identified by examination alone.

• If the fistula is deep, complex, or its course is not clearly defined, the doctor may order additional imaging diagnoses such as MRI or specialized ultrasound. Combining multiple methods helps diagnose an anal fistula more accurately and supports the selection of an appropriate treatment plan.

Step 3: Imaging diagnosis of fistula

Perform diagnostic imaging tests when necessary

• When a doctor suspects an anal fistula, imaging tests may be ordered to determine the location, direction, and complexity of the fistula tract. This step is especially helpful when the fistula opening is deep or cannot be fully identified through external examination.

• X-rays with contrast medium may be used to examine the rectum, urinary tract, or reproductive organs. The contrast medium helps highlight abnormal connections in the image. Depending on the area to be examined, the medium can be administered orally, by injection, or by enema as directed by the doctor.

• CT or MRI scans provide more detailed images of surrounding tissues and structures. In the diagnosis of anal fistula, pelvic MRI is often valuable in identifying the fistula tract and deep branches, thereby helping the doctor plan treatment.

• Anal or vaginal ultrasound may be chosen to examine fistulas in appropriate locations. This method uses ultrasound waves to create images inside the body and does not use X-rays.

Not everyone needs all tests

• The choice of anal fistula diagnostic method depends on symptoms, physical examination results, suspected location of the fistula, and medical history. The doctor will consider appropriate tests rather than performing all methods.

• If imaging is ordered, the patient should discuss with the doctor the purpose of the test, how it will be performed, and the use of contrast medium. This helps ensure a safe examination and provides the necessary information to accurately identify the fistula.

Step 4: When is a colonoscopy needed?

Colonoscopy when indicated by a doctor

• If the doctor suspects an anal fistula is related to Crohn's disease or another inflammatory bowel disease, a colonoscopy may be ordered to examine the inside of the colon and look for related lesions.

• Colonoscopy is performed using a flexible tube with a camera at the end, inserted through the anus into the colon. The images obtained help the doctor directly visualize the mucous membrane and detect abnormalities that cannot be seen during an external examination.

You may receive sedation

• Colonoscopy is often performed with sedation, which helps the patient relax and reduce discomfort during the procedure. The level of sedation and the method of administration may vary depending on the medical facility and the individual's condition.

• Before the colonoscopy, the patient needs to follow the doctor's instructions regarding fasting, bowel preparation, and medication use. Proper preparation helps the doctor see the colon more clearly and avoid having to repeat the test.

Colonoscopy is not a mandatory test for all cases

• Not everyone with signs of an anal fistula needs a colonoscopy. This test is usually considered when symptoms or medical history suggest inflammatory bowel disease like Crohn's.

• During the diagnosis of an anal fistula, the doctor may combine direct examination, imaging tests, and colonoscopy depending on the case. The goal is to find the cause, determine the extent of the damage, and choose the appropriate treatment plan.

Step 5: Blood tests when necessary

Perform blood tests as prescribed

• In some suspected cases of anal fistula, the doctor may request blood tests to assess inflammation, infection, or look for signs of an underlying related medical condition.

• Crohn's disease is one of the diseases that can be associated with fistula formation. When the patient has prolonged digestive symptoms or many other abnormal signs, blood tests can help the doctor assess the possibility of this inflammatory bowel disease.

Blood tests alone cannot diagnose an anal fistula

• Blood test results primarily provide supportive information, such as signs of inflammation or overall health status. An anal fistula cannot be confirmed based solely on blood tests.

• To diagnose an anal fistula, the doctor usually combines medical history, anal examination, and imaging methods when needed. If Crohn's disease or other inflammatory bowel disease is suspected, blood tests can help identify the underlying cause and guide further examination steps.

Discuss medical history and symptoms

• When seeing a doctor, the patient should report if they have prolonged abdominal pain, recurrent diarrhea, unintentional weight loss, perianal discharge, or recurrent anal fistula symptoms. This information helps the doctor make a more comprehensive assessment instead of focusing on a single symptom.

• If the doctor orders blood tests, the patient should follow the instructions and combine the results with other examinations to accurately determine the cause.

Step 6: Dye test to find a vaginal fistula

Perform a dye test when a vaginal fistula is suspected

• In cases of suspected vaginal fistula, the doctor may use a dye test to look for an abnormal connection between the vagina and the bladder or rectum. This method helps identify the location of the fistula based on the appearance of the dye at the abnormal site.

• Depending on the purpose of the examination, the dye can be taken orally or introduced into the bladder or rectum as directed. Afterward, the doctor may use a tampon placed in the vagina to check for the presence of the dye.

Double dye test helps find fistulas between the vagina and urinary tract

• A double dye test is often used when a fistula between the vagina and the urinary tract, especially the bladder, is suspected. The results can help the doctor determine the location of the abnormal connection.

• If dye appears on the tampon after being introduced into the urinary tract, the result may suggest a vesicovaginal fistula and needs further evaluation with appropriate methods.

Blue dye test helps detect fistulas between the rectum and vagina

• A blue dye test can be used to check for the presence of a fistula between the rectum and vagina. The dye is introduced into the rectum, then checked for its appearance in the vagina or on a tampon.

• If dye is detected in an abnormal location, the doctor may order additional imaging tests to accurately determine the location and path of the fistula.

Note on interpreting results

• The dye test primarily serves as a diagnostic aid and is not suitable for all cases of anal fistula. The choice of test depends on the suspected location and accompanying symptoms.

• When diagnosing an anal or pelvic fistula, the doctor may combine physical examination, imaging tests, and specialized tests to identify the fistula before choosing a treatment method.

Step 7: Perform additional tests when necessary

Perform additional tests as prescribed

• Not all cases of anal fistula require the same group of tests. Depending on the symptoms, medical history, and suspected location of the fistula, the doctor may order additional tests to find the cause or evaluate rectoanal function.

Intestinal tissue biopsy when Crohn's disease is suspected

• If the doctor suspects Crohn's disease is the cause related to the fistula, a bowel tissue biopsy may be ordered during colonoscopy. A small tissue sample is taken for microscopic examination to help assess the inflammatory condition.

• Biopsy is not directly intended to identify an anal fistula, but primarily helps find or assess underlying conditions that may be related to fistula formation.

Rectal and sphincter function tests

• Some tests may be performed to evaluate the muscle strength and function of the rectum and anal sphincter. The results help the doctor better understand the functional status of the rectoanal area.

• This assessment is especially useful when the patient has symptoms related to bowel control or when the doctor needs more information before choosing a treatment method.

Test selection based on individual cases

• During the diagnosis of an anal fistula, one should not self-request all tests. The doctor will choose the appropriate method based on symptoms and initial examination results.

• By combining clinical examination, imaging diagnostics, and specialized tests when necessary, the doctor can determine the cause, location, and complexity of the fistula, thereby developing an appropriate treatment plan.

Step 8: How to treat an anal fistula?

Consult your doctor to choose the appropriate method

• Treatment of anal fistula depends on the location, size, path of the fistula, degree of infection, and associated complications. There is no single method suitable for all patients.

• For complex cases or fistulas involving the urinary or reproductive organs, the doctor may collaborate or refer the patient to appropriate specialists such as urology, gynecology, or colorectal surgery.

Drainage of fluid or pus in case of infection

• If the fistula has accumulated fluid, pus, or is blocked, the doctor may use a small catheter for drainage. The goal is to allow fluid to escape and control the infection.

• If there is an infection, antibiotics may be used in appropriate cases. However, antibiotics do not always eliminate the fistula, and one should not self-medicate.

Surgical treatment of the fistula

• Anal fistula surgery is one of the important treatment methods for many persistent anal fistula cases. The doctor will choose the technique based on the path of the fistula and its relationship to the anal sphincter.

• For some fistulas between the anus and the external skin, the doctor may create a small opening in the skin and tissue above the fistula to help the fistula drain and heal from within.

Using materials to close the fistula

• In some selected cases, the doctor may use biological glue or specialized materials to seal or fill the fistula. This method aims to close the abnormal passage without needing to remove all surrounding tissue.

• The effectiveness of each method depends on the characteristics of the fistula and the specific condition of the patient. Therefore, treatment decisions should be made after a complete anal fistula diagnosis.

Treatment should address the cause and complications

• If an anal fistula is related to Crohn's disease or another underlying condition, controlling the underlying disease may also be an important part of the treatment plan.

• The patient should discuss with the doctor the location of the fistula, risk of recurrence, impact on the anal sphincter, recovery time, and possibility of needing surgery before choosing a treatment option.

• Do not self-puncture, squeeze, or attempt to close the fistula at home. These actions can damage tissue, impede drainage, and complicate the infection.

Part 3: Individuals susceptible to anal fistulas and their causes

Note 1: Inflammatory bowel disease can cause fistulas

Check for related inflammatory bowel disease

• Inflammatory bowel diseases such as Crohn's disease and ulcerative colitis can increase the risk of forming certain types of fistulas. Therefore, if signs of an anal fistula appear along with prolonged digestive symptoms, the patient should inform the doctor fully.

Recognize signs suggestive of inflammatory bowel disease

• Symptoms that may occur include:

  • Prolonged or recurrent diarrhea.

  • Abdominal pain or cramps.

  • Bloating, abdominal distension.

  • Bloody stools.

  • Fever.

  • Nausea.

  • Unexplained weight loss.

• Not all of these symptoms mean inflammatory bowel disease. However, when they appear along with pain, swelling, or discharge around the anus, the doctor may need to evaluate further to find an underlying condition related to the anal fistula.

Note on diverticulitis

• Diverticulitis occurs when small pouches that form in the colon wall become inflamed or infected. In some cases, this condition can lead to fistula formation.

• If previously diagnosed with diverticulitis or frequently experiencing abnormal digestive symptoms, the patient should provide this information during the examination. This is important data to help the doctor determine the cause and choose appropriate tests.

Report medical history when diagnosing a fistula

• If you have or suspect Crohn's disease, ulcerative colitis, or diverticulitis, proactively inform your doctor when signs of an anal fistula appear.

• During the diagnosis of an anal fistula, the doctor may combine medical history, physical examination, blood tests, endoscopy, and imaging diagnostics depending on the case. Identifying the underlying condition helps treatment not only focus on the fistula but also control the cause that could lead to recurrence.

Note 2: Difficult childbirth can cause fistulas

Note on obstetric history

• Anal fistulas and some types of pelvic fistulas can appear after difficult or complicated childbirth due to damage to tissues between the rectum, vagina, and anal area.

• Rectovaginal fistula is a type of fistula that can be related to birth trauma. Additionally, perianal injury after childbirth can also increase the risk of fistula formation in some cases.

Monitor postpartum recovery

• After childbirth, mothers should follow up with their obstetrician-gynecologist appointments to check if tears, stitches, or perineal injuries are healing properly.

• If persistent pain, swelling, foul-smelling discharge, pus, or an abnormal opening around the anus appears, it should be reported to the doctor. These could be signs of an anal fistula or infection that needs evaluation.

Pay special attention to signs of infection

• If you have recently given birth and experience fever, increasing pain, or unusual foul-smelling discharge, you should contact your obstetrician-gynecologist early for an examination.

• These symptoms are not enough to confirm an anal fistula, but early detection of postpartum injury or infection can help limit complications and facilitate timely treatment.

Provide complete history during diagnosis

• When performing an anal fistula diagnosis, tell your doctor the time of birth, method of delivery, any injuries or procedures during birth, and the recovery status afterward.

• Information about obstetric history helps the doctor assess whether rectoanal or pelvic injury is related to current symptoms, thereby choosing appropriate examination and testing methods.

Note 3: History of injury can cause fistulas

Check for history of pelvic trauma

• When diagnosing an anal fistula, the doctor may ask about a history of injury to the intestines, rectum, or pelvic area. Trauma to these areas can damage tissue and create conditions for abnormal communication.

• Causes may include trauma from accidents, pelvic injuries, or complications after surgery. Therefore, tell your doctor if you have had severe trauma or abdominal/pelvic surgery in the past.

Note on history of surgery and radiation therapy

• Some complex pelvic surgeries can damage adjacent tissues and increase the risk of fistula formation. A history of surgery such as hysterectomy or pelvic interventions is important information when evaluating signs of an anal fistula or pelvic fistula.

• Pelvic radiation therapy can also cause tissue damage and lead to fistulas after some time. Radiation-induced damage can sometimes appear late, so anyone who has had pelvic radiation therapy should inform their doctor even if treatment ended some time ago.

Check for possible infection or underlying conditions

• Some pelvic infections can be associated with fistula formation. Additionally, cancer or diseases causing tissue damage in the pelvic area can also be related factors.

• Some sexually transmitted diseases, such as chlamydia or HIV, can increase the risk of fistula-related complications in certain cases. If you have a history or risk of infection, you should discuss it openly with your doctor for appropriate assessment.

Provide a complete medical history during your examination

• Inform your doctor if you have ever had pelvic trauma, abdominal-pelvic surgery, radiation therapy, infection, or a medical condition affecting this area.

• This information helps your doctor make a more informed diagnosis of anal fistula, identify potential contributing factors, and select necessary tests. Do not disregard events that occurred long ago, as some fistulas can form or manifest after a significant period of time.

References

1. Dsouza R, Griner S, Mandava N. Anorectal Fistula. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026.
2. Gionchetti P, Dignass A, Danese S, et al. 3rd European Evidence-based Consensus on the Diagnosis and Management of Crohn’s Disease 2016: Part 2. Surgical Management and Special Situations. Journal of Crohn’s and Colitis. 2017;11(2):135–149.
3. Maaser C, Sturm A, Vavricka SR, et al. ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 1: Initial Diagnosis, Monitoring of Known IBD, Detection of Complications. Journal of Crohn’s and Colitis. 2019;13(2):144–164.
4. Panés J, Bouhnik Y, Reinisch W, et al. Imaging techniques for assessment of inflammatory bowel disease: Joint ECCO and ESGAR evidence-based consensus guidelines. Journal of Crohn’s and Colitis. 2013;7(7):556–585.
5. Van Assche G, Dignass A, Reinisch W, et al. The second European evidence-based Consensus on the diagnosis and management of Crohn’s disease: Special situations. Journal of Crohn’s and Colitis. 2010;4(1):63–101.
6. Schwartz DA, Wiersema MJ, Dudiak KM, et al. A comparison of endoscopic ultrasound, magnetic resonance imaging, and examination under anesthesia for evaluation of Crohn’s perianal fistulas. Gastroenterology. 2001;121(5):1064–1072.
7. Buchanan GN, Halligan S, Williams AB, et al. Effect of MRI on clinical outcome of recurrent fistula-in-ano. Lancet. 2002;360(9346):1661–1662.
8. Gecse KB, Bemelman W, Kamm MA, et al. A global consensus on the classification, diagnosis and multidisciplinary treatment of fistulising Crohn’s disease. Gut. 2014;63(9):1381–1392.
9. American Society of Colon and Rectal Surgeons. Clinical Practice Guidelines for the Management of Anorectal Abscess, Fistula-in-Ano, and Rectovaginal Fistula. Diseases of the Colon & Rectum.
10. World Gastroenterology Organisation. WGO Practice Guideline: Inflammatory Bowel Disease. Milwaukee, WI: World Gastroenterology Organisation.

Content edited by: Leigh Kennedy Ly.

Information consulted and verified by expert: Christopher Walker.