Anatomical Course of the Ureter
The ureter is a retroperitoneal muscular tube that extends from the renal pelvis to the bladder, typically measuring 25-30 cm in length and following a predictable anatomical course that can be divided into distinct segments for surgical and diagnostic purposes.
Anatomical Divisions and Course
The ureter is conventionally divided into three segments: upper (abdominal), middle, and lower (pelvic) thirds, with the iliac vessels serving as the anatomical landmark separating the middle from the lower third 1.
Upper Third (Abdominal Ureter)
- Originates at the ureteropelvic junction at the level of the renal pelvis
- Descends along the anterior surface of the psoas muscle in the retroperitoneum
- Lies medial to the tips of the lumbar transverse processes
- Crosses anterior to the genitofemoral nerve 2
Middle Third
- Continues its descent along the psoas muscle
- Crosses anterior to the bifurcation of the common iliac artery (or over the iliac vessels)
- This crossing point represents a critical surgical landmark where the ureter is at risk during pelvic surgery 1
Lower Third (Pelvic Ureter)
- Enters the pelvis by crossing the iliac vessels (typically at the bifurcation of the common iliac artery)
- In females, the ureter courses along the lateral pelvic wall and passes beneath the uterine artery ("water under the bridge") before entering the bladder base
- In males, the ureter passes lateral to the vas deferens
- The ureter enters the bladder obliquely through the posterolateral bladder wall, creating a natural anti-reflux mechanism 1
Key Anatomical Relationships in the Female Pelvis
Specific measurements from cadaveric studies demonstrate the ureter's relationship to surgical landmarks 3:
- Distance from ureter to pelvic floor at the ischial spine: 3.2 cm
- Distance from ureter to pelvic floor at the obturator canal: 3.2 cm
- Distance from ureter to pelvic floor at the arcus tendineus insertion on pubic bone: 1.6 cm 3
Points of Anatomical Narrowing
The ureter has three natural points of narrowing where stones commonly lodge:
- Ureteropelvic junction
- Crossing point over the iliac vessels
- Ureterovesical junction 1
Blood Supply Considerations
The ureteral blood supply is segmental and longitudinal, requiring careful surgical technique to avoid devascularization 1:
- Upper ureter: supplied by branches from the renal artery
- Middle ureter: supplied by branches from the gonadal vessels, aorta, and common iliac arteries
- Lower ureter: supplied by branches from the internal iliac, vesical, and uterine/vaginal arteries 2
During surgical repair, ureteral devascularization must be minimized, and anastomoses should be covered with peritoneum or other tissue when possible 1.
Clinical Implications for Surgical Approach
For upper and middle third injuries, ureteroureterostomy is the first-line repair, while distal injuries (caudal to the iliac vessels) typically require ureteral reimplantation into the bladder (ureteroneocystostomy) 1. This is because the traumatic insult in the lower third may jeopardize the segmental blood supply 1.
Structural Characteristics
The ureter is a non-layered muscular tube composed of muscle bundles with heterogeneously oriented smooth muscle cells that function through nexus junctions to create coordinated peristalsis 4. The urothelium is water-impermeable and multilayered, surrounded by a smooth muscle layer that enables unidirectional urine flow 5, 4.