Ureter anatomy

General features

• About 25–30 cm long, half abdominal and half pelvic; retroperitoneal throughout.
• Three narrowings where stones lodge: pelviureteric junction, pelvic brim (crossing the iliac vessels), vesicoureteric junction (the narrowest and commonest site of impaction in both sexes).
• Peristalsis is myogenic: pacemaker cells in the calyces and renal pelvis, spread by gap junctions in single-unit smooth muscle; a denervated transplant ureter still works. Each bolus enters the bladder as a jet, seen on colour Doppler.

Histology

• Lined by urothelium (transitional epithelium), with umbrella cells and uroplakin plaques that make it impermeable and let it stretch. The lumen is star-shaped when empty.
• Lamina propria without glands or muscularis mucosae, then the muscle coat, then adventitia carrying the vessels.

• This is the reverse of the gut (inner circular, outer longitudinal).
• Urothelial (transitional cell) carcinoma is the commonest tumour of the renal pelvis, ureter and bladder and appears as a filling defect on urography.

Abdominal course

• Descends on psoas major, with the genitofemoral nerve behind it.
• Crossed in front by the gonadal (ovarian) vessels; the right ureter lies behind the duodenum (second part) and the root of the mesentery.
• Enters the pelvis crossing the bifurcation of the common iliac artery in front of the sacroiliac joint. The left ureter lies behind the apex of the sigmoid mesocolon.
• At the brim the ovarian vessels in the infundibulopelvic ligament lie just in front of it, so blind clamping of this ligament at oophorectomy can catch the ureter.

Pelvic course in the female

• Runs down the lateral pelvic wall in front of the internal iliac artery, adherent to the peritoneum, forming the posterior boundary of the ovarian fossa. When the peritoneum is opened it is reflected medially with it.
• At about the level of the ischial spine it turns forward and medially into the base of the broad ligament (cardinal ligament, parametrium).
• Here it passes under the uterine artery ("water under the bridge") about 1.5–2 cm lateral to the cervix at the level of the internal os.
• It then runs just above the lateral vaginal fornix (a stone here can be felt vaginally) and in front of the vagina, and enters the bladder obliquely.
• The intramural course (about 1.5–2 cm) acts as a flap valve; a short tunnel causes vesicoureteric reflux in children.
• In the male the vas deferens crosses above and in front of the ureter near the bladder, the counterpart of the uterine artery.

Blood supply

• Segmental branches from the renal artery, aorta, gonadal, common and internal iliac, uterine and vesical arteries, joined by a longitudinal plexus in the adventitia.

• At ureterolysis for pelvic endometriosis the surgeon frees the medial side and leaves the lateral attachments, which carry the arterial twigs. Never strip the adventitia, or ischaemic necrosis and stricture follow.

Pain and nerves

• Pain afferents run with sympathetic fibres to T11–L2.

• Lower ureteric pain reaches the scrotum or labium through the genital branch of the genitofemoral nerve and the ilioinguinal nerve (L1). A stone at the VUJ also irritates the trigone, causing frequency and urgency.
• Colic causes vomiting because kidney and gut share visceral afferent pathways.

Stones and their passage

• Stones under about 5 mm usually pass; larger ones at the distal ureter often impact.
• Tamsulosin (alpha-1A blocker) relaxes distal ureteric smooth muscle, which is rich in alpha-1 receptors, helping a distal stone pass (medical expulsive therapy). It does not relieve pain directly; NSAIDs provide analgesia and also reduce ureteric oedema.
• Obstruction leads to hydroureter and hydronephrosis; infection above a blockage is an emergency needing drainage.

Sites of injury at gynaecological surgery

• Clamps are kept close to the uterus or cervix, and the bladder is pushed down first. The ureter is recognised by peristalsis when pinched; stents help in difficult cases. Cystoscopy checks efflux from both orifices.
• Deep endometriosis can encase the ureter, causing silent hydronephrosis. Cervical cancer at the side wall causes sciatic pain, leg oedema and hydronephrosis.

How injury presents

• Free fluid after surgery: measure its creatinine. Fluid creatinine many times the serum level (for example 900 µmol/L, 10.2 mg/dL, against 80 µmol/L, 0.9 mg/dL) proves it is urine; serous or reactive fluid has a creatinine close to serum.
• Three-swab test with methylene blue in the bladder: blue top swab, vesicovaginal fistula; blue lowest swab, urethrovaginal; swab wet but not blue, ureterovaginal fistula.

Congenital variants and pregnancy

• The ureter, pelvis, calyces and collecting ducts come from the ureteric bud of the mesonephric duct. A bud that does not form or reach the metanephric blastema gives renal agenesis with an absent ureter.
• Bifid ureter: the bud splits early. Duplex ureter: two separate ureteric buds. In a duplex system the upper-pole ureter opens lower and more medially (Weigert–Meyer rule) and may be ectopic or end in a ureterocele; the lower-pole ureter refluxes.
• Pregnancy: dilatation starts in the first trimester (progesterone relaxes smooth muscle); later the uterus compresses the ureter at the brim. It is right more than left because the uterus rotates to the right and the sigmoid colon cushions the left. Stasis favours pyelonephritis.

Remember Water under the bridge: the ureter (water) passes under the uterine artery (bridge) 1.5–2 cm lateral to the cervix at the internal os.

Exam trap The pelvic ureter gets its arteries from the lateral side, the abdominal ureter from the medial side; mobilise on the opposite side.

Exam trap Continuous leakage with normal voiding after hysterectomy means a ureterovaginal fistula, not a vesicovaginal one.

How FCPS asks about this

• Relation of the uterine artery to the ureter: artery crosses above and in front of the ureter about 1.5–2 cm lateral to the cervix.
• Ureter injured while ligating the ovarian artery: at the pelvic brim, behind the infundibulopelvic ligament.
• Commonest site of stone impaction: vesicoureteric junction, the narrowest point.
• Pelvic ureter lies anterior to: the internal iliac artery; it forms the back of the ovarian fossa.
• Referred pain from a lower ureteric stone to the scrotum or labium: genitofemoral nerve (genital branch), L1.
• Epithelium and muscle of the ureter: transitional epithelium; lower third has inner longitudinal, middle circular, outer longitudinal muscle.
• Duplex ureter: two ureteric buds; bifid ureter is an early split of one bud.