🗺️ The Course of the Ureter

The ureter is a muscular tube approximately 25–30 cm long, running from the renal pelvis to the posterolateral angle of the bladder. It is entirely retroperitoneal throughout its course. Its wall has an inner transitional epithelium, a middle muscularis (inner longitudinal + outer circular smooth muscle), and an outer adventitia.

It can be divided into an abdominal part (renal pelvis to pelvic brim) and a pelvic part (pelvic brim to bladder). Urine is propelled by peristalsis — rhythmic coordinated contraction of the smooth muscle, not gravity. This is why obstruction causes colicky pain and why urine can still drain against gravity.

In its abdominal course, the ureter lies on the medial part of psoas major, behind the peritoneum. It is crossed obliquely by the gonadal vessels (testicular or ovarian). The right and left ureters differ in their immediate anterior relations:

Once it crosses the pelvic brim, the ureter runs downward along the lateral pelvic wall, anterior to the hypogastric (internal iliac) artery and medial to the obturator nerve. It then turns anteromedially toward the bladder.

In the male, the vas deferens loops over the external iliac vessels and then crosses medial to the ureter near the bladder — the ureter and vas deferens cross just before entering the bladder. The seminal vesicle lies just anterior to the ureter’s entry point.

In the female, the ureter forms the posterior boundary of the ovarian fossa on the lateral pelvic wall. It then runs medially on the lateral aspect of the cervix and upper vagina. The uterine artery accompanies it for ~2.5 cm before crossing anteriorly — the classic “water under the bridge” relation (~2 cm lateral to the cervix).

Blood Supply — The “Multiple Sources” Principle

The ureter has a segmental blood supply from multiple sources. It is critical to understand that the vessels approach from the medial side in the abdomen and the lateral side in the pelvis — so surgical dissection should always be on the opposite side to avoid devascularisation.

Nerve Supply — Why It Causes Colic

The ureter is innervated by T10–L1 (autonomic fibres via the renal, aortic, and hypogastric plexuses). Sensory pain fibres travel with sympathetic fibres back to T10–L2 spinal levels. This explains why ureteric colic classically radiates from loin to groin — and why pain may radiate to the inner thigh (genitofemoral nerve, L1–L2) or scrotum / labium majus (ilioinguinal nerve).

The ureteric wall has three coats. Understanding the muscular arrangement is useful for explaining peristalsis and why the ureter can be identified intraoperatively by pinching it.