Hidden pain on the left side when holding urine, usually manifested as pain in the left lower abdomen, is mainly considered to be caused by urinary tract infection, ureteral stone, vesicoureteral reflux, and female adnexitis. 1. Urinary tract infection: bacterial-induced inflammation of the urinary system may usually show urinary urgency, frequent urination, accompanied by pain in the left lower abdomen. For example, urethritis, cystitis, ureteral inflammation, etc. 2. Ureteral stones: generally triggered by urinary tract infections, metabolic abnormalities in the body, resulting in ureteral blockage caused by pain, generally can be treated conservatively with oral medications such as stone pellets, urolithiasis, etc., such as the symptoms are serious, surgery can be considered to remove the stone. 3. Vesicoureteral reflux: When holding urine is serious, the urine in the bladder may reflux along the left ureteral orifice to the left renal pelvis, causing pain in the left lower abdomen. 4. Female adnexitis: Female adnexitis may also cause pain in the left lower abdomen, usually accompanied by increased vaginal discharge, and can be treated with antibiotics such as metronidazole or ornidazole. The above drug selection and dosage should be carried out under the guidance of a doctor, the cause of abdominal pain when holding urine is more complex, it is recommended to go to the hospital to clarify the cause of the disease and then do the corresponding treatment.