Anorectal Abscess in Children 

Updated: Jul 05, 2018
Author: Nelson G Rosen, MD, FACS, FAAP; Chief Editor: Robert K Minkes, MD, PhD 

Overview

Background

Anorectal (perianal or perirectal) abscess is a relatively common condition in children. It occurs most often in male infants younger than 1 year but can occur in either sex and at any age. The exact incidence and prevalence are not well established. The treatment approach varies somewhat by age and, in most instances, differs from that used in adults (see Anorectal Abscess).

A perianal abscess is an infection characterized by a collection of pus that has formed under the skin within the soft tissue just outside the anus. The abscess often appears as a raised red lesion under the skin lateral to the anus, where it may grow and become painful. Some abscesses spontaneously drain pus and heal; others require surgical intervention. Some perianal abscesses heal incompletely, with or without surgery, leaving a tiny opening at the site of drainage (anal fistula, or fistula-in-ano), which may or may not require additional surgery.

The vast majority of anorectal abscesses develop spontaneously in completely healthy children and are self-limited; however, in older children, the condition can be associated with inflammatory bowel disease (IBD) or other conditions in which the immune system is compromised.

Controversies abound in the treatment of perianal and perirectal abscesses (see Treatment). The use of antibiotics alone (rather than surgical drainage) as a means of definitive treatment with the intention of decreasing the likelihood of eventual fistula-in-ano formation is quite controversial but is supported in the literature.[1] Nonoperative management of fistula-in-ano via observation alone in otherwise completely healthy male babies remains controversial but is also supported in the literature.[2]

Anatomy

The anal canal and the skin around it are the site of perianal abscesses and fistulas. Just inside the anal canal, about 1-2 cm from the anal verge in most babies, are small pits in the wall of the anal canal called anal crypts (or the crypts of Morgagni). It is believed that anorectal abscesses and fistulas originate as an infection in these anal crypts. The infection then erodes through the wall of the anal canal and extends into the fat beneath the perianal skin. From here, it can continue in one of two directions, as follows:

  • The infection can head toward the skin; this is the more common course
  • The infection can track deeper into what is referred to as the ischiorectal fossa, bounded superiorly by the levator ani muscles; infections in the ischiorectal fossa are rare in the pediatric population

Pathophysiology and Etiology

The pathophysiology and etiology of anorectal abscess and fistula-in-ano have not yet been fully defined. The prevailing theory is that an infection in an anal crypt, or crypt of Morgagni—that is, cryptitis—progresses and erodes through the wall of the anal canal into the surrounding soft tissue, where a collection of pus accumulates, forming the abscess.

When an anorectal abscess drains spontaneously by eroding through the skin or is surgically drained, a communication is formed between the abscess cavity and the skin. If the infection truly originates from an anal crypt, the abscess cavity must communicate with the lumen of the anal canal. The hole in the skin would therefore also communicate all the way into the anal lumen. When this communication persists over several weeks, it is called a fistula. It is unclear why fistulas form in some individuals but not in others.[1]

If the etiology of fistula is abscess drainage, either spontaneously or through surgical incision, it logically follows that efforts to cure the abscess before it drains, thereby avoiding completing the communication from the anal canal to the skin, may decrease the risk of fistulization. Various studies have followed this line of thinking (see Treatment).

Some authors have suggested that some infants have abnormal crypts, which predispose them to cryptitis and abscess formation. One study showed that the anal crypts of infants with fistulas tend to be deeper (3-10 mm) than those of healthy infants (1-2 mm).[3] It has been proposed that androgen excess or androgen-estrogen imbalance may predispose to the formation of these abnormal crypts.[4]

Epidemiology

The overall incidence of anorectal abscesses in children is unknown. It is a relatively common condition seen in a general pediatric or pediatric surgical practice. In infants, the pediatric subgroup among whom this condition is most prevalent, the estimated incidence is between 0.5% and 4.3%, with an overwhelming male preponderance. In older children, anorectal abscesses show no sexual predilection. No racial predilection is reported in any age group.

Prognosis

The prognosis of anorectal abscess in children is excellent for all cases that are unrelated to Crohn disease. With or without surgery, the condition will eventually be brought to a successful resolution with no impact or implications for the future.

Children with abscesses who undergo drainage are likely to develop a fistula. Fistulas in children usually resolve without intervention, but some patients require surgery for resolution. Treatment of any concomitant fistula may enhance the results of surgical treatment of first-time perianal abscesses in children.[5] Recurrent fistula after fistulotomy in an otherwise healthy child is very unlikely and should prompt an evaluation for other disease processes (eg, chronic granulomatous disesase or Crohn disease).

The prognosis of Crohn-related perianal pathology is complex and beyond the scope of this article.

 

Presentation

History and Physical Examination

Anorectal abscesses often present within the first few months of life. A perianal abscess, which in many ways is the same as a small pimple, appears as a red swollen area located just outside the anus; this is usually first noticed during a diaper change and may be tender to the touch. Affected children may appear to be irritable but are commonly asymptomatic. Differentiating simple irritability from true tenderness due to perianal abscess can pose a challenge to the clinician but is important for reassuring parents.[6, 7]

Infants with perianal abscesses generally do not have underlying medical conditions that predispose them to abscesses. Perianal abscess and fistula-in-ano are unrelated to diaper rash.

Older children with anorectal abscesses fall into two roughly equally sized categories. The first category consists of otherwise completely healthy children who have no significant risk factors or history of symptoms suggestive of inflammatory bowel disease (IBD). Many children are constipated; constipation is a risk factor for anal fissure but not for anorectal abscess.

The second category consists of older children with IBD. Some children with a known history of Crohn disease present with a new abscess or fistula. In many cases, the first manifestation of IBD or Crohn disease in a child is perianal abscess or fistula. Elements in the history that suggest IBD include weight loss, failure to thrive, diarrhea, and chronic abdominal pain.

Complications

Because the likelihood of recurrent abscess and fistula formation is high even after adequate surgical drainage, surveillance is necessary. Complex or nonhealing perianal abscesses and fistulas may be signs of Crohn disease. Chronic drainage or recurrent abscess may indicate a fistula.

In otherwise healthy patients, complications of anorectal abscess are extremely rare and are most commonly associated with Crohn disease, neutropenia, or an immunocompromised state.

 

Workup

Laboratory Studies

In otherwise healthy babies with anorectal abscess or fistula, no laboratory studies are required. A complete blood count (CBC), culture of perianal abscess drainage, or both may be warranted in some clinical scenarios; however, these studies are not of great utility in focusing therapy and can usually be omitted without risk or detriment to the patient.

Blood counts and cultures should be obtained in all patients with immune compromise from any cause (eg, inflammatory bowel disease, an immune disorder, or malignancy).

CT, Radiography, and MRI

No imaging studies are necessary for the evaluation of otherwise healthy infants with perianal abscess or fistula-in-ano. In older children with a greater likelihood of Crohn disease or in any older child who appears systemically ill, computed tomography (CT) of the pelvis may be required to rule out a deep-space infection.

Referral to a gastroenterologist is recommended in all children with suspected Crohn disease once the abscess has been treated. Studies that may be employed to evaluate for other Crohn disease manifestations include a contrast enema and a small-bowel contrast study.

Magnetic resonance imaging (MRI) may be useful for delineating the anatomy of a fistula or deep abscess, especially in children with Crohn disease.

Other Studies

Colonoscopy with biopsy may be needed to confirm Crohn disease. Endoscopy is not required in otherwise routine cases.

No histologic analysis is required in the routine treatment of perianal abscess and fistula. Biopsy may be performed in older children with a chronic fistula to evaluate for granulomas as a sign of Crohn disease.

 

Treatment

Approach Considerations

In infants younger than 1 year who present with a small perianal abscess, it is reasonable to try to attain full resolution with antibiotic therapy alone, without operative intervention or general anesthesia. Such an approach may decrease the likelihood of fistula formation.[1]

In children younger than 1 year who present with a large, red, bulging perianal abscess and who appear to be in significant distress, more aggressive treatment is indicated. The abscess should be drained, most commonly in the office, and oral antibiotics initiated. Children who show signs of true systemic illness (eg, weakness, lethargy, or fever) secondary to the infection should be admitted for intravenous antibiotic therapy; however, such cases are exceedingly rare.

An identical approach can be followed in older children without a history of inflammatory bowel disease (IBD), with perhaps a shorter threshold to perform drainage in any patients initially deemed suitable for treatment with antibiotics alone. Older children who have complex fistulas or are in extreme pain during the examination require general anesthesia for examination and treatment.

Babies who present with a fistula after surgical or spontaneous drainage of an abscess should undergo a period of nonoperative observation and should be observed until age 18 months, provided that they remain otherwise happy and healthy.[2] After this time, it is reasonable to consider surgical fistulotomy for resolution. Older children with fistulas secondary to Crohn disease should be referred to a pediatric surgeon with significant IBD experience or to an adult colorectal surgeon.

Nonoperative Therapy

Treatment of both anorectal abscess and fistula-in-ano remains controversial. Antibiotics were originally believed to play a limited role in primary therapy for perianal abscesses but were frequently initiated by pediatricians before surgical referral. The concept that abscesses must be drained in order to heal is perhaps the closest thing to a universally accepted incontrovertible surgical law that one can find. It can be argued, however, that such thinking perpetuates dogma and stifles advances in care.

A 2007 study brought into question the benefit of draining perianal abscesses and suggested a potential advantage to treating with antibiotics alone.[1] The data presented in this study support the idea that in otherwise healthy babies, not draining abscesses decreases the risk of fistula formation, and adding antibiotics further decreases the risk.

Once a fistula has formed, the optimal approach to treatment is also controversial. Historically, babies with fistula-in-ano were treated in exactly the same way as adults (see Anorectal Abscess) and underwent surgical fistulotomy; in some cases, such patients underwent seton placement. Current evidence indicates that this procedure is largely unnecessary and may be reserved for the rare cases that do not resolve after a sufficient period of nonoperative management.[2]

Older children with no evidence of IBD can be treated with the approaches described above, with more aggressive intervention added if symptoms persist or worsen. Children in whom IBD is suspected should undergo evaluation for that condition.

It is important to note that the evolution of treatment strategies in the direction of less aggressive intervention should not be confused with the adoption of a more conservative therapeutic approach. The term conservative, with respect to therapy, should be reserved for treatments that are tried and true and that are considered almost certain to yield a positive outcome. From this viewpoint, conservative treatment of an anorectal abscess in a pediatric patient would be drainage.

When first proposed, nonoperative treatment of a small perianal abscess in an otherwise healthy baby was considered radical. Time, experience with a large number of patients, and a supporting body of evidence are required to transform a radical therapy into a conservative therapy. Thus, when properly understood, the terms radical and conservative have nothing whatsoever to do with how much physician intervention and treatment is required, be it surgical or nonsurgical.

This understanding is critical for the treatment of children with anorectal abscess and fistula. If a child of any age is ever appearing sick or toxic, treatment should revert to the most conservative approach possible. This would include the addition of antibiotics if they had been withheld thus far, the drainage of any abscesses, and the search for deep infection in the ischiorectal fossa via computed tomography (CT). Such deep infections occur in the adult population but are virtually unheard of in the pediatric population.

Antibiotics

The use of antibiotics to treat anorectal abscesses remains controversial. Traditional teaching holds that drainage alone is sufficient for abscess treatment in otherwise healthy patients. A 2007 study by Christison-Lagay et al demonstrated that antibiotic use for perianal abscess decreased the likelihood of fistula formation.[1]

All immunocompromised patients with infections should receive antibiotics as a component of their therapeutic plan. Patients with Crohn disease require antibiotic therapy in addition to the medical therapy used to treat their Crohn disease.

Anorectal abscesses often grow mixed flora and can be well covered by various antibiotic choices. Common oral agents administered for routine infection include cephalexin and amoxicillin-clavulanate. Methicillin-resistant Staphylococcus aureus (MRSA) is rarely implicated in perianal abscesses but should be considered as a pathogen in patients who are not responding to traditional antibiotic choices. Trimethoprim-sulfamethoxazole is available in liquid form and can cover MRSA.

Surgical Intervention

When it has been determined that medical management is not sufficient, surgical treatment is indicated.

Preparation

No preoperative preparation is required for simple abscess drainage in otherwise healthy children. Children undergoing general anesthesia should avoid eating solid food for at least 8 hours before the surgical procedure. Surgeons may require some form of bowel preparation to clean the anus and rectum in preparation for a fistulotomy.

Management of abscess

Surgical treatment of a perianal abscess consists of incision and drainage. Most babies can easily undergo this procedure in the office.

A dependable assistant is required to hold the child still. The procedure itself takes little time but is not possible without an experienced pediatric assistant who can firmly hold the baby motionless for the few seconds during which sharp items are being used.

The area over the abscess is swabbed with povidone-iodine or an equivalent skin preparation solution. The skin immediately overlying the abscess is anesthetized by using a tuberculin syringe and local anesthetic to raise a small wheal. Whether this step is warranted is debatable; some believe that the pain caused by the local anesthetic is comparable to the pain caused by the incision. However, the author prefers to use local anesthesia.

A No. 11 scalpel is used to make an incision directly into the abscess. Pus is then expressed. A simple incision is sufficient, and no packing is required. Once the pus is drained, the remaining local anesthetic in the syringe can serve as a skin wash, and dry gauze is applied. There is usually only minor bleeding, which can be controlled with just a few minutes of pressure. Once the procedure is concluded, the best analgesia is to return the infant to the arms of a parent.

Management of fistula

Surgical treatment of a superficial fistula-in-ano consists of fistulotomy (unroofing of the fistulous tract). This requires anesthesia and takes place in an operating room. Fistulectomy, in contrast, is a procedure whereby the entire fistulous tract is stripped out, either by surgical means or by the use of fistulotomy and curettage. This procedure is not required in the pediatric population.

The patient is positioned in the lithotomy position. Once the child has been fully anesthetized, the fistulous opening is identified within the anal canal, either via gentle probing of the skin opening with a lacrimal probe or through the use of anoscopy. Once the opening has been identified, a probe is passed through the entire length of the fistula from the skin side all the way into the anal lumen.

Next, the fistulous tract is then opened up completely by cutting the tissue between the anal lumen down to the probe, so that the probe is free and within the anal lumen. The cut may be made with a fine needle-tip electrocautery to aid in hemostasis. Once the probe is free and the fistulous tract therefore completely opened, the procedure is complete.

Patients with Crohn disease rarely undergo fistulotomy; instead, they usually undergo a procedure in which the fistulous tract is identified in a similar manner, and a noncutting seton (often a long soft rubber or silicone band called a vessel loop, used in vascular surgery to isolate blood vessels) is placed through the tract to facilitate drainage and help control the localized sepsis.

At one time, cutting setons were also used to treat fistulas in pediatric patients. In this technique, a thick suture (the seton) is placed through the fistulous tract and tied to itself. It is then tightened progressively over several weeks so that it slowly cuts through the tissue while allowing scar tissue to form on the other side of the cut; thus, at no point is the sphincter cut completely open.

The use of cutting setons is a painful technique that has proven essentially unnecessary in children and thus has been largely abandoned in the pediatric population. The main issue with this technique is the possibility that cutting open the fistulous tract will cut the sphincter and risk incontinence. This is a major concern for large high fistulas that track above the sphincter (referred to as suprasphincteric fistulas).

If a suprasphincteric fistula is encountered on examination under anesthesia, it can be treated initially by placing a bioprosthetic fistula plug (an absorbable device made specifically for this purpose).[8] The plug is inserted by passing a suture through the tract, tying the suture to the plug, and pulling the plug completely into the tract. The plug is then tacked into position by suturing it at the entrance into the anal canal, as well as at the skin. A literature review of this technique in the adult population quotes a 54% closure rate.

For patients who experience a recurrence after a fistula plug insertion, a rectal advancement flap can be used to cover the fistulous opening.

Postoperative Care

After abscess drainage, acetaminophen may be useful for postoperative pain, but most patients feel better once the pus is no longer under pressure. Parents should be counseled that a drop of blood in the diaper or dressing is not unusual but that persistent bleeding is a problem calling for pressure and perhaps a return to the office.

After abscess drainage, babies should undergo a brief warm bath after every bowel movement to ensure that the area is being adequately cleaned. Older children who undergo abscess drainage or fistulotomy should take a sitz bath (to sit and dunk the bottom in a warm tub, traditionally but not necessarily with Epsom salts) after every bowel movement, a minimum of 2-3 times each day.

The opening often closes within several days and resolves completely, but many patients who undergo drainage eventually form a fistula. Dressings are required only as long as the opening is draining. Panty liners make excellent dressings and have an adhesive strip that holds them in place in the underwear.

Long-Term Monitoring

All patients receiving antibiotics alone require close follow-up and should be seen a few days after therapy is initiated and then weekly until the infection is completely resolved.

Patients who underwent surgical drainage of an abscess should be seen weekly until the abscess is completely resolved and the skin opening healed. Thereafter, the author prefers to see these patients every 3 months until at least 6 months have passed without any evidence of the hole reopening (proof that a fistula has not formed).

Patients who underwent surgery for a fistula need acute and long-term follow-up similar to that indicated for those who underwent acute abscess drainage.

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity, prevent complications, and eradicate the infection. Anorectal abscesses often grow mixed florae and can be well covered by various antibiotic choices.

Antibiotics

Class Summary

Antibacterial therapy must cover all likely pathogens in the context of the clinical setting.

Cephalexin (Keflex)

Cephalexin is a first-generation cephalosporin that arrests bacterial growth by inhibiting bacterial cell-wall synthesis. It has bactericidal activity against rapidly growing organisms. Its primary activity is against skin flora; it is used for skin infections or prophylaxis in minor procedures.

Trimethoprim/sulfamethoxazole (Bactrim, Bactrim DS, Septra DS)

Trimethoprim/sulfamethoxazole (TMP-SMZ) discourages bacterial growth by inhibiting the synthesis of dihydrofolic acid.

Amoxicillin and clavulanic acid (Augmentin)

This drug combination treats bacteria resistant to beta-lactam antibiotics. For children older than 3 months, base the dosing protocol on amoxicillin content. Because of different amoxicillin/clavulanic acid ratios in the 250-mg tablet (250/125) versus the 250-mg chewable tablet (250/62.5), do not use the 250-mg tablet until the child weighs more than 40 kg.

 

Questions & Answers

Overview

What is anorectal abscess in children?

What is the anatomy of the anal canal relevant to anorectal abscess in children?

What is the pathophysiology of anorectal abscess in children?

What is the prevalence of anorectal abscess in children?

What is the prognosis of anorectal abscess?

Presentation

Which clinical history findings are characteristic of anorectal abscess in children?

What are the possible complications of anorectal abscess in children?

Workup

What is the role of lab testing in the diagnosis of anorectal abscess in children?

What is the role of imaging studies in the diagnosis of anorectal abscess in children?

What is the role of colonoscopy and biopsy in the diagnosis of anorectal abscess in children?

Treatment

How are anorectal abscesses in children treated?

What is the role of nonoperative therapy in the treatment of anorectal abscesses in children?

What is the role of antibiotics in the treatment of anorectal abscesses in children?

When is surgery indicated for anorectal abscesses in children?

What is included in preoperative care for anorectal abscesses in children?

What is the surgical treatment for anorectal abscesses in children?

How is fistulotomy performed for the treatment of anorectal abscesses in children?

What is included in postoperative care following surgery for anorectal abscesses in children?

What is included in the long-term monitoring of anorectal abscesses in children?

Medications

What is the goal of drug treatment for anorectal abscess?

Which medications in the drug class Antibiotics are used in the treatment of Anorectal Abscess in Children?