Segments and physiological narrowings
Anatomically, the ureter is an elongated tube topographically divided into two main segments:
- Abdominal part (pars abdominalis) — located retroperitoneally.
- Pelvic part (pars pelvina) — lies in the subperitoneal tissue of the lesser pelvis.
The lumen of the ureter is not uniform throughout its length: dilated areas (where the diameter reaches 0.5–1.0 cm) systematically alternate with narrower zones. In clinical anatomy, three physiological narrowings are distinguished:
- Upper constriction — located at the very beginning of the tube, in the area where the renal pelvis directly transitions into the ureter.
- Middle constriction — projected at the level of the pelvic brim, where the ureter crosses the iliac blood vessels.
- Lower constriction — located near the opening of the tube into the wall of the urinary bladder. This is the narrowest point of the urinary tract, where its diameter decreases to a critical 2–3 mm.
Clinical significance: Knowledge of the localization of these narrowings is extremely important for surgeons and urologists, as migrating stones in urolithiasis most commonly get trapped in these anatomical "bottlenecks".
General topography and relations to nerves
On their downward path, the ureters lie tightly against the psoas major muscle (m. psoas) and its covering fascia. Descending into the lower lumbar region, they cross the gonadal vessels: testicular in males (vasa testicularia) or ovarian in females (vasa ovarica). Upon reaching the level of the pelvic brim, the ureters cross the iliac vessels, lying strictly anterior to them.
The relationship between the ureters and the nerve trunks of the retroperitoneal space is of particular clinical significance. Above the crossing with the iliac vessels, the posterior surface of the ureter is in direct contact with the genitofemoral nerve (n. genitofemoralis).
Clinical significance: This topographical fact explains the characteristic radiation of pain during a renal colic attack. During stone passage and ureteral wall spasm, the adjacent nerve is irritated, causing acute pain to radiate to the inguinal region, scrotum, and penis in male patients, or the labia majora in females.
Syntopy of the right and left ureters
Topographical relationships with adjacent abdominal organs differ significantly depending on the side.
Syntopy of the right ureter:
- Medially: borders the inferior vena cava.
- Laterally: adjacent to the medial margin of the cecum and ascending colon.
- Anteriorly and superiorly: covered by the descending part of the duodenum.
- Anteriorly and inferiorly: crossed by the root of the mesentery of the small intestine.
Throughout the rest of its course, the right ureter is covered anteriorly by the parietal peritoneum of the right colic sinus. In the tissue layer between the peritoneum and the tube itself run the ileocolic (vasa ileocolica) and right colic (vasa colica dextra) vessels accompanied by lymphatic channels and nodes.
Syntopy of the left ureter:
- Medially: runs parallel to the abdominal aorta.
- Laterally: lies adjacent to the medial margin of the descending colon.
- Anteriorly and superiorly: covered by the parietal peritoneum of the left colic sinus.
- Anteriorly and inferiorly: crossed by the root of the sigmoid mesocolon.
Branches of the inferior mesenteric vessels along with regional lymph nodes run between the peritoneum and the left ureter.
Blood supply, lymph drainage, and innervation
- Blood supply: Arterial blood to the lumbar segment is supplied by branches of the renal arteries (a. renalis), as well as gonadal arteries — testicular (a. testicularis) or ovarian (a. ovarica).
- Lymphatic drainage: Lymph from the walls of the ureter drains to lymph nodes located around the major vessels of the retroperitoneal space — the abdominal aorta and inferior vena cava.
- Innervation: Autonomic innervation is segmental in nature. The abdominal segment receives nerve fibers from the renal plexus (plexus renalis), while the pelvic segment is innervated by branches arising from the hypogastric plexuses (plexus hypogastricus).
Briefly: answers to topical questions
What are the anatomical parts of the ureter?
Anatomically, the ureter is divided into two main parts, and also has a segment within the urinary bladder wall.
- Abdominal part (pars abdominalis) — located retroperitoneally.
- Pelvic part (pars pelvina) — lies in the subperitoneal tissue of the lesser pelvis.
Additionally, an intramural part is distinguished, along which the ureters pierce the bladder wall from top to bottom and from outside inwards.
Which arteries supply blood to the pelvic segment of the ureter?
The blood supply to the pelvic segment of the ureter is provided by the following arteries:
- Middle rectal arteries (aa. rectales mediae).
- Inferior vesical arteries (aa. vesicales inferiores).
Where does lymphatic drainage from the ureters go?
Lymphatic drainage from the ureters goes to the lymph nodes of the retroperitoneal space and pelvis.
The direction of drainage depends on the specific segment of the organ:
- From the abdominal part, lymph drains to nodes located around the abdominal aorta and inferior vena cava.
- From the pelvic segment of the ureters, lymphatic drainage occurs into the iliac lymph nodes.
Remembering the three physiological narrowings of the ureter is easy using the "P-I-B" rule (from top to bottom): Pelvis (pelviureteric junction), Iliac vessels (crossing at the pelvic brim), Bladder (opening into the wall).
Class and exam questions
Where do stones most commonly get trapped during renal colic?
Calculi typically get trapped in one of the three physiological narrowings: at the pelviureteric junction, at the crossing of the iliac vessels, or at the narrowest point — before opening into the urinary bladder (where the diameter decreases to 2–3 mm).
Why does pain radiate to the groin and genitalia as a stone passes down the ureter?
This is because the posterior surface of the ureter (above the crossing with the iliac vessels) is in close contact with the genitofemoral nerve (n. genitofemoralis). Irritation of this nerve causes characteristic radiation of pain to the scrotum, penis, or labia majora.
Which major magistral vessels border the ureters medially?
The right ureter is adjacent to the inferior vena cava on its medial side, while the left ureter lies medially against the abdominal aorta.
What else to study on this topic
- Topography and syntopy of the pelvic segment of the ureter in males and females
- Blood supply to the pelvic segment of the ureter (sources of arterial blood supply in the lesser pelvis)
- Histological structure of the ureteral wall (layers, muscular coats)
- Surgical approaches to the ureters in the retroperitoneal space
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