A little pain in the waist when urinating may be caused by pyelonephritis, urinary tract stones, ureteral reflux disease and other reasons. 1. Pyelonephritis: when suffering from pyelonephritis, it can not only lead to the symptom of back pain when urinating, but also lead to the symptoms of urinary tract irritation such as frequent urination, urgency, and painful urination. 2. Urinary tract stones: diseases such as ureteral stones and kidney stones can lead to back pain when urinating. At the same time, it can also lead to the appearance of hematuria of the naked eye, urinary tract irritation signs (such as urinary frequency, urgency, urinary pain, etc.). 3. Ureteral reflux disease: For example, lesions at the ureteral orifice and tuberculosis in the urinary system can lead to reflux in the ureter, which can lead to reflux of urine through the ureter into the renal pelvis. At this time, some of the urine can be excreted with urination, but some of the urine will reflux into the kidneys, resulting in the symptom of back pain when urinating. If you experience back pain when urinating, it is recommended to go to the hospital in time for urine routine, urine culture, ultrasound of the urinary system and other related examinations to clarify the cause of the disease and to carry out targeted treatment under the guidance of the doctor.