Intradermal methylene blue injection for the treatment of intractable idiopathic pruritus ani: results of 30 cases.

Some cases of idiopathic pruritus anu may be refractory to treatment with dietary and hygienic instructions and short-term topical medications. In this study, we documented our technique and results with methylene blue injection in a large series of patients with intractable idiopathic pruritus ani. The results of 30 adult patients with well-documented intractable idiopathic pruritus ani who were treated with intradermal methylene blue injection are reported. No antibiotic prophylaxis, anesthesia or sedation was used. A total of 15 ml of a 1% methylene blue solution was injected intracutaneously and subcutaneously in the affected perianal area. A second injection (rescue treatment) was offered one month later to patients who declared partial response, and follow-up was restarted. One month after injection, 24 patients (80%) were symptom-free, 5 declared partial remissions, and one patient still had the same degree of pruritus ani. Five patients with partial remission underwent a second methylene blue injection, which provided complete relief in four. Therefore, the early response rate was 80% with single injection and 93.3% (28 of 30) with the rescue treatment. At six months, three recurrences were noted, indicating to a success rate of 83.3% (25 of 30). At 12 months after treatment, 23 patients (76.7%) were symptom free. This study has shown that intradermal methylene blue injection is a safe, simple, fast and efficient method of treating intractable idiopathic pruritus ani.