Ureter anatomy: the tubes that carry urine from kidney to bladder

What it is

The ureter is a muscular tube carrying urine from the renal pelvis to the urinary bladder.

Location

It runs retroperitoneally about 25 to 30 cm down on the psoas major, crosses the pelvic brim at the common iliac bifurcation and enters the posterolateral bladder wall obliquely.

Function

It propels urine to the bladder by peristalsis.

Body system

Urinary · paired (left and right)

FMA ID

FMA15572 (Foundational Model of Anatomy)

Key facts

• Lined with transitional epithelium (urothelium).
• Three normal narrowings: pelviureteric junction, pelvic brim and bladder entry.
• In the pelvis it passes under the uterine artery (female) or vas deferens (male).

Clinical relevance

Kidney stones commonly lodge at the three constrictions; ureters can be injured during pelvic surgery.

There are two ureters, a right and a left. Each starts at the renal pelvis, the funnel inside the kidney where the calyces meet, and ends in the urinary bladder. OpenStax gives a length of about 30 cm and notes that the kidneys and ureters are completely retroperitoneal, held between the parietal peritoneum and the back wall of the abdomen. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

Radiopaedia gives a length of 25 to 30 cm and a diameter of about 3 mm, and divides the ureter into three parts: an abdominal part from the renal pelvis to the pelvic brim, a pelvic part from the brim to the bladder, and an intravesical (intramural) part inside the bladder wall. (Radiopaedia: Ureter.)

Kenhub describes the ureters as collapsible, S-shaped channels about 25 cm long, widest at the renal pelvis and narrowing progressively towards the bladder. Published lengths therefore range from about 25 to 30 cm. (Kenhub: Ureters.)

The renal pelvis itself tapers down to continue as the ureter. Its shape varies from a single wide sac to several funnel-shaped branches. (Radiopaedia: Renal pelvis.)

The job of the ureter is to move urine from the kidney to the bladder. Urine does not simply drain down by gravity: it is pushed along by waves of muscle contraction called peristalsis. This is why urine still reaches the bladder when you are lying down. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

At the lower end, each ureter turns medially and passes through the bladder wall at a slant. This slanted course acts as a one-way valve that stops urine flowing back up towards the kidney (vesicoureteral reflux). Children in whom this oblique course is not well formed are more likely to have reflux. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

Both divisions of the autonomic nervous system can increase ureteric peristalsis. The sympathetic supply comes from about T10 to L1 through the renal plexus, and the parasympathetic supply from the hypogastric plexuses and pelvic splanchnic nerves. (Kenhub: Ureters.)

The ureters leave the kidneys behind the renal vessels and run down over the front of the psoas major muscle. The right ureter passes behind the duodenum, and the left ureter runs lateral to the inferior mesenteric vessels. (Kenhub: Ureters.)

In the abdomen the ureter lies along the medial edge of psoas, in front of and slightly medial to the tips of the transverse processes of L2 to L5. It enters the pelvis in front of the sacroiliac joint, crossing the point where the common iliac artery divides. It then runs down the side wall of the pelvis in front of the internal iliac artery, turns forwards and medially at the level of the ischial spine, and finishes with a 1 to 2 cm oblique course through the bladder wall. (Radiopaedia: Ureter.)

TeachMeAnatomy describes the same path: over the pelvic brim near the sacroiliac joints, across the bifurcation of the common iliac arteries, then anteromedially at the ischial spines to enter the bladder obliquely. (TeachMeAnatomy: The Ureters.)

Behind the abdominal ureter on both sides lie the psoas muscle, the genitofemoral nerve, the common iliac vessels and the tips of the L2 to L5 transverse processes. (Radiopaedia: Ureter.)

In front of the right ureter are the second part of the duodenum, the right gonadal vessels, the right colic and ileocolic vessels and the root of the small bowel mesentery; the inferior vena cava lies medial to it. In front of the left ureter are the left gonadal artery, the left colic artery, loops of jejunum and the sigmoid mesocolon and colon; the aorta and the inferior mesenteric vein lie medial to it. (Radiopaedia: Ureter.)

In the pelvis only one structure crosses in front of each ureter, and it differs by sex: the ductus deferens (vas deferens) in males and the uterine artery, inside the broad ligament, in females. Near the bladder the ureter lies above the seminal vesicle in males and above the lateral fornix of the vagina in females, where the cervix lies medial to it. (Radiopaedia: Ureter.)

In females the ureter passes under the uterine artery about 2 cm above the ischial spine. Students remember this as 'water under the bridge'. It also lies near the ovarian vessels at the pelvic brim. These relations put the ureter at risk when the ovarian vessels are tied during removal of an ovary (oophorectomy) or when the uterine artery is tied during hysterectomy. (TeachMeAnatomy: The Ureters.)

The 3D model is based on an adult male (BodyParts3D), so it shows the male relations; the uterine artery and other female pelvic organs are not in the model.

The ureter has three natural narrow points: the pelviureteric (ureteropelvic) junction, where the renal pelvis becomes the ureter; the pelvic brim, where it crosses the common iliac artery bifurcation; and the vesicoureteric (ureterovesical) junction, where it passes through the bladder wall. These are the commonest places for a kidney stone to block the ureter. (Radiopaedia: Ureter.)

A stone that is small enough to leave the kidney can still be too wide for these narrow segments, so it stops there and blocks the flow of urine. TeachMeAnatomy notes that newer evidence points to the upper ureter and the ureterovesical junction as the main sites of impaction. A blocked ureter causes renal colic, a sudden, severe pain in the loin, often with blood in the urine (haematuria). CT of the kidneys, ureters and bladder (CT-KUB) is the gold-standard test. (TeachMeAnatomy: The Ureters.)

If urine cannot pass, it builds up in the renal pelvis, a condition called hydronephrosis. Left untreated, obstruction can lead to kidney dysfunction, acute renal failure and eventually shrinking (atrophy) of the kidney. Causes include kidney stones, an ectopic kidney and obstruction at the ureteropelvic junction. (Kenhub: Ureters.)

Because the ureter is long, it takes arteries from whatever large vessels lie nearby. The upper end is supplied by the ureteric branch of the renal artery, the middle part by the testicular or ovarian artery and direct branches of the abdominal aorta, and the lower part by ureteric branches of the superior and inferior vesical arteries. Veins follow the arteries. (Kenhub: Ureters.)

Radiopaedia lists the renal arteries, the aorta and the superior and inferior vesical arteries as the main supply, and notes that some texts add the gonadal, middle rectal and uterine arteries. Lymph from the abdominal ureter drains to the aortocaval and common iliac nodes, and from the pelvic ureter to the internal and external iliac nodes. (Radiopaedia: Ureter.)

Pain fibres from the ureter enter the spinal cord at T11 to L2, so ureteric pain is felt (referred) in the skin areas (dermatomes) supplied by those spinal segments. The nerve supply comes from the renal, testicular or ovarian, and hypogastric plexuses. (TeachMeAnatomy: The Ureters.)

The ureter wall has three layers. The inner mucosa is lined with transitional epithelium (urothelium), which can stretch, plus scattered goblet cells that make protective mucus. The middle muscular layer has longitudinal and circular smooth muscle that produces peristalsis. The outer adventitia of collagen and fat anchors the ureter in place. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

Radiopaedia lists the main ureteric variants as a duplex collecting system, a bifid ureter, an ectopic ureter (one that opens somewhere other than its normal place in the bladder) and a ureterocele. (Radiopaedia: Ureter.)

The names are easy to mix up. There are two ureters, and they carry urine from the kidneys to the bladder. There is one urethra, and it carries urine from the bladder to the outside of the body. The ureters open into the bladder at the two upper corners of the trigone, a triangular area at the base of the bladder; the urethra leaves from its lowest corner. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

The female urethra is short, about 4 cm, while the male urethra averages about 20 cm. OpenStax notes that the short female urethra is less of a barrier to faecal bacteria than the longer male urethra. (OpenStax Anatomy and Physiology 2e, 25.2: Gross Anatomy of Urine Transport.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Descending colon · digestive
• Psoas major · muscular
• Ileal vein · cardiovascular
• Ileal artery · cardiovascular
• Anterior cecal artery · cardiovascular
• Common iliac artery · cardiovascular
• Sigmoid vein · cardiovascular
• Sigmoid artery · cardiovascular
• Appendicular artery · cardiovascular
• Ileocolic vein · cardiovascular