Anorectal Abscess and Fistula

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Anorectal Abscess and Fistula

DRG Category:348
Mean LOS:5.4 days
Description:SURGICAL: Anal and Stomal Procedures with CC
DRG Category:394
Mean LOS:4.4 days
Description:MEDICAL: Other Digestive System Diagnoses with CC

An anorectal abscess, sometimes called a perirectal abscess, is the formation of pus in the soft tissue that surrounds the anal canal or lower rectum. Perianal abscess is the most common form, affecting four out of five patients; ischiorectal (abscess in the ischiorectal fossa in the fatty tissue on either side of the rectum) and submucosal or high intermuscular abscesses account for most of the remaining cases of anorectal abscess. A rare form of anorectal abscess is called pelvirectal abscess, which extends deeply into pelvic regions from the rectum. In approximately half of the cases, fistulas develop without any way to predict them.

Anorectal abscesses can lead to anal fistulas, also known as fistula in ano. An anal fistula is the development of an abnormal tract or opening between the anal canal and the skin outside the anus. It should not be confused with an anal fissure, which is an elongated ulcer located just inside the anal orifice, caused by the traumatic passage of large, hard stools.


Perirectal abscesses are usually caused by an infection in an anal gland or the surrounding lymphoid tissue. Obstruction of anal crypts or sinuses occurs, leading to infection of the now static glandular secretions. Ultimately suppuration and abscess formation occurs within the anal gland. Lesions that can lead to anorectal abscesses and fistulas can be caused by infections of the anal fissure; infections through the anal gland; ruptured anal hematoma; prolapsed thrombosed internal hemorrhoids; and septic lesions in the pelvis, such as acute salpingitis, acute appendicitis, and diverticulitis. Ulcerative colitis and Crohn’s disease are systemic illnesses that can cause abscesses, and people who are immunosuppressed are more susceptible to abscesses. Patients who are at high risk are people with diabetes, those who engage in receptive anal sex, those who use cathartics habitually, and those with inflammatory bowel disease and immunosuppression. Other causes include constipation, chronic diarrhea, syphilis, tuberculosis, radiation exposure, and HIV infection.

Genetic considerations

No clear genetic contributions to susceptibility have been defined.

Gender, ethnic/racial, and life span considerations

The elderly are more prone to the condition because of their increased incidence of constipation, hemorrhoids, and diabetes mellitus. Women are more commonly affected by constipation than are men. An anorectal fistula is a rare diagnosis in children, but anorectal abscesses are common in infants and toddlers, particularly those still in diapers. Anal fistulas are complications of anorectal abscesses, which are more common in men than in women. For anatomical reasons, rectovaginal fistulas are found only in women. Ethnicity and race have no known effect on the risk of anorectal fistulas.

Global health considerations

No data are available.



Ask the patient to describe the kind of pain and the precise location. Determine if the pain is exacerbated by sitting or coughing. Ask if the patient has experienced rectal itching or pain with sitting, coughing, or defecating. Elicit a history of signs of infection such as fever, chills, nausea, vomiting, malaise, or myalgia. Ask the patient if she or he has experienced constipation, which is a common symptom because of the patient’s attempts to avoid pain by preventing defecation.

Physical examination

Inspect the patient’s anal region. Note any red or oval swelling close to the anus. Digital examination may reveal a tender induration that bulges into the anal canal in the case of ischiorectal abscess or a smooth swelling of the upper part of the anal canal or lower rectum in the case of submucous or high intermuscular abscess. Digital examination may reveal a tender mass high in the pelvis, even extending into one of the ischiorectal fossae if the patient has a pelvirectal abscess. Examination of a perianal abscess generally reveals no abnormalities. Examination may not be possible without anesthesia. Note any pruritic drainage or perianal irritation, which are signs of a fistula.

On inspection, the external opening of the fistula is usually visible as a red elevation of granulation tissue with purulent or serosanguinous drainage on compression. Palpate the tract, noting that there is a hardened cordlike structure. Note that superficial perianal abscesses are not uncommon in infants and toddlers who are still in diapers. The abscess appears as a swollen, red, tender mass at the edge of the anus. Infants are often fussy but may have no other symptoms.


Patients with perirectal abscesses and fistulas may delay seeking treatment because of embarrassment relating to the location, the odor, or the sight of the lesion. Provide privacy and foster dignity when interacting with these patients. Inform the patient of every step of the procedure. Provide comfort during the examination.

Diagnostic highlights

TestNormal ResultAbnormality With ConditionExplanation
White blood cell (WBC) countAdult males and females 4,500–11,000/mLElevatedInfection and inflammation may elevate the WBC count

Other Tests: Barium studies, sigmoidoscopy, colonoscopy, cultures of exudate

Primary nursing diagnosis


Pain (acute) related to inflammation of the perirectal area


Comfort level; Pain control behavior; Pain level; Wound healing


Pain management; Medication administration; Positioning; Teaching: Prescribed medication

Planning and implementation


For anal fissures, use the WASH regimen: Warm-water shower or sitz bath after bowel movement; Analgesics; Stool softeners; High-fiber diet. Note that most uncomplicated fissures resolve in 2 to 4 weeks with supportive care, but chronic fissures may require surgical treatment.

The abscess is incised and drained surgically. For patients with fistulas, fistulotomies are performed to destroy the internal opening (infective source) and establish adequate drainage. The wound is then allowed to heal by secondary intention. Frequently, this procedure requires incision of sphincter fibers. Fistulectomy may be necessary, which involves the excision of the entire fistulous tract.

Encourage the patient to urinate but avoid catheterization and the use of suppositories. Postoperatively, a bulk laxative or stool softener is often prescribed on the day of the surgery. Intramuscular injections of analgesics are given to control pain. Assess the perirectal area hourly for bleeding for the first 12 to 24 hours postoperatively. When open fistula wounds are left, as in a fistulotomy, the anal canal may be packed lightly with oxidized cellulose.

Encourage the patient to drink clear liquids after any nausea has passed. Once clear liquids have been taken without nausea or vomiting, remove the intravenous fluids and encourage the patient to begin to drink a full liquid diet the day after surgery. From there, the patient can progress to a regular diet by the third day after surgery. The most common complications are incontinence (if sphincter fibers were incised during surgery) and hemorrhage.

Pharmacologic highlights

Medication or Drug ClassDosageDescriptionRationale
AntibioticsVaries by drugAntibiotics to cover gastrointestinal infections: ampicillin plus aminoglycosides plus either clindamycin or metronidazole; cefoxitin or cefotetan alone; aminoglycoside and cefoxitinProvide antimicrobials directed against bowel flora, particularly in people who are immunosuppressed


Immediately following the procedure and before the patient enters the postanesthesia care unit, place a dry, sterile dressing on the surgical site. Provide sitz baths twice a day for comfort and cleanliness and place a plastic inflatable doughnut on a chair or bed to ease the pain of sitting. As soon as the patient tolerates activity, encourage ambulation to limit postoperative complications.

patient teaching.
Teach the patient how to keep the perianal area clean; teach the female patient to wipe the perianal area from front to back after a bowel movement in order to prevent genitourinary infection. Teach the patient about the need for a high-fiber diet that helps prevent hard stools and constipation. Explain how constipation can lead to straining that increases pressure at the incision site. Unless the patient is on fluid restriction, encourage him or her to drink at least 3 L of fluid a day.

Evidence-Based Practice and Health Policy

Wei, P., Keller, J.J., Kuo, L., & Lin, H. (2013). Increased risk of diabetes following perianal abscess: A population-based follow-up study. International Journal of Colorectal Disease, 28(2), 235–240.

  • Diabetic patients are at an increased risk for developing anorectal abscesses; however, the risk for developing diabetes post anorectal abscess diagnosis is less substantiated.
  • In one population-based study where 1,419 adult patients with perianal abscess were compared to 7,095 randomly selected comparison patients without perianal abscess, patients with an abscess were 1.8 times more likely to receive a diabetes diagnosis during the 5-year follow-up period (p < 0.001).
  • Care providers should routinely screen patients with a history of perianal abscess for the development of diabetes and encourage immediate lifestyle changes to reduce the impact of modifiable risk factors.

Documentation guidelines

  • Physical findings of perirectal area: Drainage, edema, redness, tenderness
  • Response to comfort measures: Sitz baths, inflatable doughnuts, analgesia
  • Reaction to ambulation postoperatively
  • Presence of surgical complications: Poor wound healing, bleeding, foul wound drainage, fever, unrelieved pain
  • Output (stool): Appearance, consistency, odor, amount, color, frequency

Discharge and home healthcare guidelines

patient teaching.
Teach female patients to wipe from front to back to avoid the contamination of the vagina or urethra with drainage from the perirectal area. Teach the patient to avoid using bar soap directly on the anus because it can cause irritation to the anal tissue. Teach patients to dilute the soap with water on a washcloth to cleanse the area.

Explain the need to remain on a diet that will not cause physical trauma or irritation to the perirectal area. A diet high in fiber and fluids will help soften the stools, and bulk laxatives can help prevent straining. Emphasize to the patient the need to avoid spicy foods and hot peppers to decrease irritation to the perirectal area upon defecation.

Teach the patient the purpose, dosage, schedule, precautions and potential side effects, interactions, and adverse reactions of all prescribed medications. Encourage the patient to complete the entire prescription of antibiotics that are prescribed.

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