The pain in the left half of the buttocks is mainly considered clinically as the possibility of the following two diseases: 1. Inflammatory disease or bacterial infection, mainly seen in the perirectal canal infection, usually appearing local redness, swelling, pain and discomfort, need to be promptly treated with antibiotics. If the ultrasound or CT examination suggests abscess formation, it usually requires timely surgical incision and drainage treatment, and even tube drainage if necessary, or even continuous negative pressure flushing. 2, common in the left hip pain and discomfort caused by a herniated lumbar intervertebral disc compressing the nerve root, usually requires further CT examination of the lumbar spine to clarify the diagnosis, and treatment is mainly bed rest, and usually surgical treatment when symptoms are severe.