Perianal cellulitis is a localized bacterial infection targeting the skin immediately surrounding the anus. It affects the deeper layers of the skin, including the dermis and subcutaneous tissues. Although it causes significant discomfort, it is manageable and responds well to specific medical treatment.
Defining Perianal Cellulitis and Its Cause
Perianal cellulitis is predominantly caused by Group A Streptococcus (Streptococcus pyogenes), the same bacterium responsible for common strep throat infections. This infection is localized to the skin and underlying soft tissues in the perianal region, distinguishing it from more widespread forms of cellulitis.
The bacteria usually enter the skin through a break in the protective barrier, such as an abrasion, a fissure, or an area of irritation. Contamination often occurs through autoinoculation, where the bacteria are transferred from the nose or throat, frequently via unwashed hands. Poor hygiene practices or inadequate wiping can contribute to the bacteria establishing an infection in this moist, warm environment.
The condition is most frequently diagnosed in prepubescent children, particularly those between six months and ten years old. This age group is susceptible due to factors like developing hygiene habits and close contact with family members who may be asymptomatic carriers of Group A Strep. Although less common, perianal cellulitis can also affect adults, especially those with predisposing skin conditions or a compromised immune system.
Identifying the Distinctive Symptoms
The affected skin presents as a sharply demarcated, bright redness (erythema). This intense red patch is confined to the skin immediately around the anal opening, often resembling a severe, well-outlined rash. This redness does not fade easily, distinguishing it from other perianal issues such as simple diaper rash or irritation.
Localized pain and tenderness accompany the redness, ranging from a persistent ache to intense discomfort. Patients often experience intense itching (pruritus) in the affected area, which can lead to scratching and further skin breakdown. The swelling and pain frequently cause difficulty during bowel movements, sometimes leading to painful defecation and subsequent constipation due to avoidance.
Severe inflammation can cause small tears or fissures in the perianal skin. These fissures may result in blood-streaked stools or a small amount of bright red blood on toilet paper. While the infection is generally localized, some people, particularly children, may experience mild systemic symptoms like low-grade fever or a general feeling of being unwell (malaise).
Diagnosis, Treatment, and Preventing Recurrence
Diagnosis begins with a physical examination where the healthcare provider observes the characteristic bright red, well-defined patch. To confirm the diagnosis, a bacterial swab is taken from the affected skin. This sample is sent for culture to definitively identify the presence of Streptococcus pyogenes or other causative bacteria.
Treatment involves a course of oral antibiotics specifically effective against Group A Strep, typically penicillin or amoxicillin. The entire course of medication, usually lasting ten to fourteen days, must be completed even if symptoms clear up sooner. Stopping antibiotics prematurely can lead to a return of the infection or contribute to antibiotic resistance.
Supportive measures are utilized to manage discomfort and promote healing. Warm sitz baths, where the patient soaks the affected area in shallow water, can help soothe pain and tenderness. Topical antibiotic ointments, such as mupirocin, may be prescribed in addition to oral medication. However, they are not effective as a standalone treatment because the infection affects deeper tissues.
Recurrence occurs in approximately 20% of cases, often due to re-exposure or incomplete eradication of the bacteria. Prevention focuses on meticulous hygiene practices to reduce reinfection. This includes rigorous hand washing, especially after using the toilet, and keeping the perianal area clean and dry.
Since the bacteria can be carried in the nose and throat, managing household contacts with concurrent strep throat is important for preventing spread and recurrence. If a family member has strep throat, they should be treated to eliminate the source of the bacteria. For cases of repeated recurrence, a longer course of oral antibiotics may be necessary to fully clear the colonization.