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

BackgroundWhile 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.MethodsA 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 5ml of 1% methylene blue and 15ml 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, 6weeks after treatment, and 3years after treatment to check patient status and recurrence rate.ResultsOf 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 48.3410.21years. 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 3years 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 3years 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.