The narrowest part of the ureter is where the bladder joins the ureter. The ureter is a long tube that connects the kidneys to the bladder at the front and back. The ureter has three narrowing points along its entire length: where the ureter joins the renal pelvis, where the ureter crosses the iliac vessels, and where the bladder joins the ureter. The bladder-ureter junction is the narrowest of the three. Patients who have urinary stones may cause obstruction at one of the three ureteral strictures. It is recommended that patients who suffer from kidney stones and suddenly experience discomfort such as back pain, lumbar pain, hematuria, etc., must go to a regular hospital as soon as possible for treatment and strive for early recovery.