Long-term follow-up of intradermal injection of methylene blue for intractable, idiopathic pruritus ani

BACKGROUND: While various medical treatments such as topical steroid ointment, antihistamine agent, and sedatives have been used for treating idiopathic intractable pruritus ani, they are not long-term solutions, due to the high recurrence rate. The aim of this study was to determine the effect of methylene-blue intradermal-injection therapy for treating patients with idiopathic intractable pruritus ani. Symptom improvement and recurrence rates were determined with a long-term follow-up. METHODS: A retrospective study was conducted from January 2011 to October 2013 on consecutive patients with intractable pruritus ani treated with methylene-blue intradermal injection. The therapy included 5 ml of 1% methylene blue and 15 ml of 1% lidocaine. Follow-up included a physical exam and satisfaction-score survey (1 = much worse, 2 = worse, 3 = no improvement, 4 = much better, 5 = gone completely) before treatment, 6 weeks after treatment, and 3 years after treatment to check patient status and recurrence rate. RESULTS: Of 103 treated patients, 96 were able to attend the 6-week follow-up visit. There were 58 (60.4%) males and 38 (39.6%) females with a mean age of 48.34 ± 10.21 years. Their mean satisfaction score at 6 weeks was 4.23 ± 0.86. Of the total of 96 patients, 9 (9.4%) patients scored 3 or less in their satisfactions score at 6 weeks. 62 (64.6%) patients were evaluated 3-year post-treatment. The satisfaction score at 3 years after treatment was 4.74 ± 0.57. Besides the 9 patients who initially failed treatment, 4 of the remaining 53 patients scored 3 or less in their satisfaction score surveys. Thus, the recurrence rate at 3 years was 7.5% (4/53). CONCLUSIONS: Methylene-blue intradermal injection can result in a high symptom improvement rate with low recurrence rate for patients with idiopathic pruritus ani.