Blue urine after anal abscess surgery is considered to be caused by local injection of methylene blue injection after anal surgery, and methylene blue injection is excreted through urine. Methylene blue injection is used for postoperative pain relief in anal and intestinal diseases, the principle is that methylene blue injection has a strong affinity for peripheral nerve tissue, through reversible blockade of the nerve endings of the medulla, to play a long-lasting analgesic effect, methylene blue injection’s effect of slow rise and slow descent, its analgesic effect is generally seen in four hours, and its analgesic effect can be maintained for about three weeks. Methylene blue injection is commonly used after anal surgery long-lasting analgesic drugs, local injection can appear after the urine is blue phenomenon, in addition to local transient burning pain, but generally with local anesthesia drugs rarely appear. Clinical perianal abscess after surgery blue urine is generally a normal phenomenon, it is recommended that patients observe the urine, with time the blue urine will gradually reduce, if a long time blue need to communicate with the attending physician in a timely manner.