The ureters are two paired muscular tubes that arise from the kidneys and transport urine to the urinary bladder. They are continuous superiorly with the renal pelvis in the renal sinus. The length of each ureter is around 10 to 12 inches (25 - 30 cm).

The renal pelvis narrows as it travels through the renal hilum and becomes continuous with the ureter at the ureteropelvic junction. Inferior to this junction, each ureter passes downward along the posterior wall of the abdominal cavity. Ureters are located retroperitoneally, and they lie anterior on the medial side of the psoas major muscle.

Each ureter crosses either the common iliac artery or the beginning of the external iliac artery at the pelvic brim (at the level of the sacroiliac joint). Then it enters the pelvic cavity and descends further to reach the bladder.

Ureters enter the bladder at the opening called the ureteral orifice.

Each ureter has three parts:

Abdominal part - goes from the hilum of the kidney down to the pelvic inlet;
Pelvic part - from the pelvic inlet until the wall of the bladder;
Intramural (intravesical) part - goes through the wall of the bladder.

The ureters are constricted at three points along their course, and these points are:

First constriction - at the ureteropelvic junction, where the renal pelvis continues as the ureter;
Second constriction - where the ureters cross the common or external iliac vessels in the pelvic inlet;
Third constriction - where the ureters enter the wall of the bladder (ureterovesical junction).

The constricted areas are the most common sites of the ureters for renal stones to get stuck. Overall the diameter of the ureter is about 0.3 inches (7 - 8 mm), but in the constriction sites, it is only around 0.1 - 0.2 inches (3 - 4 mm) wide.

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Ureters