The ureters are two thick tubes which act to transport urine from the kidney to the bladder. They are 25cm long, and are situated bilaterally, with one ureter draining each kidney.
The ureteric walls are comprised of smooth muscle, which contracts to produce peristaltic waves. This propels the urine towards the bladder.
In this article, we shall look at the anatomical course of the ureters, their neurovascular supply, and any clinical relevance.
The ureters arise in the abdomen as a continuation of the renal pelvis. They terminate in the pelvic cavity, where they drain into the bladder. It is therefore useful to divide the anatomical course of the ureters into the abdominal and pelvic components.
The ureters arise from the renal pelvis – a funnel like structure located within the hilum of the kidney. The renal pelvis receives urine from the major calyces. The point at which the renal pelvis narrows to form the ureter is known as the ureteropelvic junction.
After the ureteropelvic junction, the ureters descend down the abdomen, along the anterior surface of the psoas major. Here, the ureters are a retroperitoneal structure (located behind the peritoneum).
At the area of the sacroiliac joints, the ureters cross the pelvic brim, thus entering the pelvic cavity. At this point, they also cross the bifurcation of the common iliac arteries.
Once within the pelvic cavity, the ureters run down the lateral pelvic walls. At the level of the ischial spines, they turn anteromedially, moving in a transverse plane towards the bladder.
Upon reaching the bladder wall, the ureters pierce its lateral aspect in an oblique manner. This creates a one way valve, where high intramural pressure collapses the ureters, preventing the back-flow of urine.
Clinical Importance: Relationship to Other Structures in the Pelvis
The anatomical course of the ureters is of surgical importance, as they travel close to other structures in the pelvis. They must be identified during pelvic surgery to ensure that they are not accidentally damaged.
As they cross the pelvic brim, the ureters are in close proximity to the ovaries. Care must be taken not the damage the ureters during an ovariectomy, especially during the ligation of the ovarian arteries.
Approximately 2cm superior to the ischial spine, the ureters run underneath the uterine artery. During a hysterectomy, where the uterus and uterine artery are removed, the ureter is in danger of being accidentally damaged. The relationship between the two can be remembered using the phrase ‘water under the bridge’.
In men, instead of the uterine arteries, the vas deferens cross the ureters anteriorly.
The arterial supply to the ureters can be divided into abdominal and pelvic supply:
- Abdominal: Renal artery and testicular/ovarian artery.
- Pelvic: Superior and inferior vesical arteries.
Venous drainage is carried out by vessels that correspond to the aforementioned arteries.
Nervous supply to the ureters is delivered via the renal, testicular/ovarian and hypogastric plexuses. Sensory fibres from the ureters enter the spinal cord at T11-L2, with ureteric pain referred to those dermatomal areas.
Clinical Relevance: Ureteric Calculus
A ureteric calculus (or kidney stone), is the presence of a solid stone in the urinary tract, formed from minerals within the urine. These can obstruct urinary flow, causing pain and haematuria (blood in the urine).
There are three locations where the ureters are at their narrowest – this is where a stone is more likely to become stuck:
- Uretopelvic junction
- Pelvic brim
- Where the ureter enters the bladder
The gold standard investigation for suspected ureteric calculus is CT scan of the kidneys, ureters and bladder (CT-KUB).