Background and Epidemiology
Anal warts (condyloma acuminata) occur as a result of infection with the human papillomavirus (HPV). According to the Centers for Disease Control and Prevention, HPV infection affects approximately 20 million people and more than 50% of all sexually active individuals. High-risk populations such as homosexual men can have a prevalence of HPV approaching 95%. Overall, approximately 5 million new cases of anal or genital warts occur every year.
HPV is a human-specific, double-stranded DNA virus that is incorporated into the genome of epithelial keratinocytes. It has an incubation period of 1 to 6 months. More than 90% of genital warts are caused by the HPV subtypes 6 and 11, although other subtypes such as 16, 18, 31, 33, and 35 also may be involved. These latter subtypes are more often associated with squamous cell cancer. Infection with HPV occurs through direct contact with the virus, most commonly via sexual contact, although transmission also can occur through nonsexual contact. Perianal infection with the virus can occur in the absence of anoreceptive intercourse. The virus is present in secretions at the base of the scrotum and the vagina and can track along the perineum to the perianal skin, and thus condoms do not necessarily provide protection from HPV infection. Groups at high risk for HPV infection and subsequent condyloma include those who test positive for human immunodeficiency virus (HIV; up to 30% prevalence) and those who are immunosuppressed. Up to a 4% incidence of anal condyloma occurs after kidney transplantation.
Recently, vaccines have been developed to prevent HPV infection. Two commonly used vaccines that are clinically available are effective against the strains that cause squamous cell cancers (subtypes 16 and 18). One vaccine (Gardasil, Merck and Co, Whitehouse Station, N.J.) is also effective against the subtypes that cause almost all cases of condylomatous disease (subtypes 6 and 11). The vaccines are typically given to children of both sexes starting at age 11 years and can be given up until the age of 26 years. It is recommended that they be administered to high-risk groups (i.e., young homosexual men, HIV-positive persons). Persons who have already been infected with HPV can still receive the vaccine, which should provide protection against strains other than those with which they are infected.
Presentation of Disease and Diagnosis
Patients with perianal or anal condyloma present with pruritus, burning, discharge, bleeding, difficulty with perianal hygiene, and palpable lesions. Persons with intra-anal or larger lesions may note changes in bowel habits or tenesmus. In most patients, the diagnosis is made upon physical examination. Examination should include anoscopy or proctoscopy because the disease can be seen internally in more than 75% of patients. Patients also should be evaluated for genital warts, including a penile examination in men and examination of the vulva, vagina, and cervix in women. High-resolution anoscopy (HRA) can be performed as an adjunct to physical examination and endoscopy, as well as for treatment of microscopic HPV disease. To perform HRA, the perianal region and anal canal are covered with a 3% acetic acid solution and viewed through an operating colposcope or microscope. Areas infected with HPV will become acetowhite. Lugol’s solution can then be applied to differentiate between low-grade lesions, normal tissue (which will appear black), or high-grade lesions (which will appear yellow or mahogany). This procedure facilitates targeted biopsies or ablation of these areas.
Upon examination, condyloma have a “cauliflower-like” appearance and vary in size from small, single lesions to large coalesced masses ( Fig. 11-1 ). They vary in color from pink to gray-white, can be flat, sessile, pedunculated, or exophytic, and can range in size from a millimeter to large fungating lesions measuring several centimeters.
Microscopically, condyloma appear to have fingerlike projections in the epidermis with acanthosis, parakeratosis, and hyperkeratosis ( Fig. 11-2 ). Koilocytes—that is, large polygonal shaped squamous cells with shrunken nuclei within a large cytoplasmic vacuole—are also commonly seen. Condylomas themselves typically do not undergo malignant degeneration because they are usually caused by low-risk HPV subtypes. Condylomas can be associated with low-grade dysplasia. The high-risk HPV subtypes (16 and 18) are associated with high-grade dysplasia and cancer.
For patients at high risk for anal HPV disease (such as HIV-positive and homosexual men), screening using an anal Papanicolaou (Pap) smear has become common. This procedure is performed by inserting a swab or cytology brush into the anal canal and rotating it to collect cells, which are then placed on a slide and evaluated in a similar manner to a cervical Pap smear. Results are then classified as a normal, low-grade squamous intraepithelial lesion, a high-grade squamous intraepithelial lesion, squamous cell cancer, or atypical cells of undetermined significance. High-resolution anoscopy can then be used for further evaluation and treatment of the anal Pap smear findings.
Treatment of Anal Condyloma
Many methods of treatment are available for anal condyloma. The choice of treatment depends on several factors, including location (intra-anal vs. perianal) and the volume of disease that is present. Treatment is aimed at removing the visible manifestations of the disease and not eradication of the underlying HPV. Close follow-up is necessary to treat recurrent visible disease early. HIV status should not affect choice of treatment, although it is important to note that in immunocompromised patients the treatment may be less effective and recurrence rates may be higher than in patients whose immune system is not compromised. Treatment can be divided into medical (cytotoxic or immunologic) or physically ablative therapies and can be categorized as patient-applied therapies versus physician-directed therapies ( Table 11-1 )
|Trichloracetic acid (cytotoxic)
|Bichloracetic acid (cytotoxic)
|Interferon alpha (immunomodulator)