What is a pain in the waist when you hold your urine?

After holding urine, it shows low back pain. It is considered that urine reflux to the kidneys, causing increased renal pressure, thus causing pain. Under normal circumstances, urine flows from the kidneys to the bladder through the ureter, and then through the urethra. Urine flows from top to bottom without reflux. Because there is sphincter at the junction of the ureter and bladder, it plays an anti-reflux mechanism. However, if the pressure in the bladder is too high, part of the urine will flow back to the kidneys, causing increased renal pressure, resulting in symptoms of low back pain. Long-term reflux, but also cause hydronephrosis, renal insufficiency, and even uremia.