Yin distension generally refers to the pubic distension and pain in the middle of the night, the pubic distension and pain in the middle of the night, a small stool will be fine, may be caused by too much urine, or to consider is caused by prostatitis, cystitis and other diseases. 1. too much urine: if you drink too much water during the day, resulting in too much urine in the body, if you do not urinate in a timely manner, can lead to a full bladder, local pressure symptoms, timely urination can be relieved, the performance of the pubic distension pain in the urine is fine. 2. Prostatitis: Prostatitis may be caused by pathogen infection, irregular sexual life, sedentary, alcoholism and other factors. Patients may experience perineal heaviness, frequent urination, urinary urgency, incomplete urination and other symptoms, some patients will appear in the middle of the night in the pubic region distension, in the case of relief after urination. 3. Cystitis: Cystitis may be caused by bacterial infection, medication, low immunity and other factors. Symptoms are frequent urination, urinary urgency, lower abdominal pain, lower abdominal pressure, etc., the patient will appear in the middle of the night pubic distension and pain in the small stool is fine. There are many other reasons for the swelling and pain in the pubic area in the middle of the night, and it is recommended that patients go to the regular hospital in time to seek treatment and strive for a speedy recovery.