Disclosure
A perianal abscess is one of the common complaints seen in the field of pediatric surgery. It occurs most often in infants younger than 1 year. However, its exact prevalence and incidence is not well established. Perianal abscesses are defined as collections of pus outside the anus, which start as an infection in the anal crypt glands. The abscess often appears as a raised, red lesion under the skin lateral to the anus, where it may grow and become painful. Some abscess may spontaneously drain pus and heal, whereas others may require surgical intervention. Despite its relatively simple nature, a perianal abscess can cause significant morbidity if improperly treated. Frequency: Although the precise incidence of perianal and perirectal abscesses is not known, approximately 0.5-4.3% of all abscess occur in children. No racial predilection is reported, and the condition may occur in any age group. In infants, the distribution is equal among boys and girls. However, in younger than 2 years, these abscesses occur more frequently in boys. Approximately 57-86% of patients with perianal abscess present before 1 year of age. Etiology: In most cases, particularly in infants, perianal and perirectal abscess thought to be secondary to abnormal anal crypt formation. Although the exact etiology for abnormal crypt formation is unclear, some have suggested that androgen excess or androgen-estrogen imbalance might predispose an individual to the formation of abnormal crypts of Morgagni and a tendency to develop cryptitis and/or abscess. Pathophysiology: The development of a perianal abscess can be divided into an acute phase (abscess) and a chronic phase (fistula-in-ano). The vast majority of the perianal abscesses and fistulas originate from infected anal crypt glands. The infection then penetrates the internal sphincter and spreads into the intersphincteric space. The etiology of abnormal crypt formation is still unidentified. Interestingly, the crypts of infants with fistulas tend to be deeper (3-10 mm) than those in healthy infants (1-2 mm). Such observations support the hypothesis of a congenital anomaly as the basis for perianal abscess formation in infants. Clinical: Patients often present within the first few months of life. Perianal abscesses can appear as red, swollen, tender areas lateral to the anus. The child may be irritable or hold his or her bowel movements. Elements in the history that are suggestive of perianal abscess include constipation, fever, painful defecation, refusal to walk, and rectal pain. Weight loss, failure to thrive, diarrhea, and abdominal pain are the symptoms associated with Crohn disease, for which perianal disease may be a presenting symptom. Infants with perianal abscesses generally do not have underlying medical conditions that predispose them to abscesses. Superficial lesions may occur secondary to an infected diaper rash. Most abscesses are self-limited and spontaneously drain and resolve without surgical intervention. However, as many 50% can progress to fistula-in-ano with chronic drainage. For lesions that persist, a fistulotomy is required. For older children, 52% of perianal abscess may be secondary to an underlying medical condition. Such conditions include inflammatory bowel disease (IBD) disease (especially Crohn disease), immunocompromised states (due to leukemia, AIDS, medications), diabetes, and foreign body or external trauma. Abscesses may also be seen as sequelae of surgical intervention for Hirschsprung disease or imperforate anus. Antibiotics play a limited role in the primary therapy of perianal abscesses.
The usual treatment of perianal abscess is incision and drainage. In infants, this procedure can be performed with local, topical anesthetic. General anesthesia may be required for older children. Without intervention, as many as 85% of children with perianal abscess present with a recurrent abscess or progression to fistula. Patients with perianal abscesses that recur after adequate incision and drainage require an examination under anesthesia to identify the fistula. Recurrent, nonhealing, complex, or multiple abscess and fistulas may indicate Crohn disease. Appropriate investigations should be initiated to rule out this possibility.
Relevant Anatomy: Most abscesses and fistulas are lateral to the anus. The infection generally begins in the anal crypts, where it penetrates the intersphincteric space. The infection may then extend to the perianal skin or superiorly within the intersphincteric space. Patients with complex abscesses involving the ischiorectal space or the contralateral side of the anus (horseshoe abscess) need to be thoroughly evaluated for Crohn disease. This is especially true for patients with abscesses extending above the levator ani (supralevator). Patients with nonhealing and recurrent abscesses and/or fistulas should undergo further evaluation as well. |
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Medical therapy: Controversy exists regarding the use of antibiotics for perianal abscesses. Antibiotics are generally not indicated in otherwise healthy children, even as an adjunct to incision and drainage. However, for immunocompromised patients or those with Crohn disease, antibiotic therapy may be indicated. Aspirates of pus from perirectal abscesses in children most frequently reveal coliform bacilli. Other organisms that may be identified include other mixed enteric flora, Staphylococcus aureus, Bacteroides fragilis, and group C streptococci. Surgical therapy: The optimal management of perianal abscess is incision and drainage. Preoperative details: The abscess is located by means of palpation and rectal digital examination. Needle aspiration may aid in locating the abscess and obtaining culture material. Intraoperative details: The optimal management of perianal abscess is incision and drainage. Incision and drainage may be associated with a recurrence rate as high as 50%. A careful exploration for a coexisting fistula is required in these cases. With appropriate anesthesia and analgesia, the abscess is incised over its most fluctuant portion. A cruciate or elliptical incision may be used; with the latter, the skin edges are excise. The abscess cavity is then copiously irrigated to remove debris, and any remaining loculations are removed. Packing is unnecessary in infants but may be introduced into the cavity in older patients. For patients with an abscess and a fistula, the preservation of anal continence is imperative. In general, unroofing of a simple, superficial fistula with curettage of the fistula tract works well. For fistula extending superiorly or for those involving most of the internal sphincter complex, simple unroofing can lead to fecal incontinence. In these situations, gradual fistula closure over several weeks can be achieved with the placement of a seton. Postoperative details: After surgery or spontaneous rupture of the abscess, pus samples should be sent for culture to identify the organism, and the wall of the abscess may be sent for histopathologic analysis. In young patients, Sitz baths (2-3 times per day) and the application of warm compresses generally suffice after the initial packing is removed. Regular changes of the packing material and dressings, with appropriate analgesia, may be required in larger cavities and in older patients. After simple incision and drainage, fistula-in-ano develops in 50% of patients. Fistulas rarely heal spontaneously without treatment. In this situation, fistulotomy is indicated. Follow-up care: Good perianal hygiene can minimize postoperative complications and repeat infection. Sitz baths should be continued until the abscess resolves. Cleaning of the child with plain water is recommended. The patient should be seen within 1 week of drainage to confirm resolution of the abscess.
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. Generally, the path of the fistula is superficial and radially directed. However, in Crohn disease, the fistulas may be recurrent, nonhealing, complex, or multiple. Complicated fistulas should be treated with the placement of a seton because simple fistulotomy or fistulectomy may lead to fecal incontinence.
The prognosis for perianal abscess is excellent if treated appropriately. Incision and drainage often works well for abscesses in infants, but this approach may be associated with recurrence in older children, for whom surveillance may be required. Complex disease may be associated with underlying medical problems, especially Crohn disease. In patients with Crohn disease, perianal disease is often difficult to treat and causes significant morbidity. Conservative measures should always be used in these patients to prevent the risk of fecal incontinence.
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