Ureter Constrictions
The ureter has three physiological constrictions where renal calculi most commonly lodge. Knowing their locations and associated clinical features guides imaging and intervention.
✦ The Mnemonic
"Precisely Bracing Valves"
Pelviureteric Junction · Pelvic Brim · Vesicoureteric Junction — the three ureteric constrictions
Clinical Breakdown
The ureter is 25–30 cm long, running from the PUJ to the VUJ. It is entirely retroperitoneal, crossing anterior to the psoas major and bifurcation of the common iliac artery. The ureter is remembered to cross anterior to the iliac vessels and posterior to the gonadal vessels ('water under the bridge' — ureter under the vas deferens/round ligament).
At the VUJ, the ureter runs obliquely through the bladder wall for 1.5–2 cm — this oblique course acts as a valve, preventing reflux. In vesicoureteric reflux (VUR), this mechanism fails. The VUJ is also the narrowest part of the ureter — most calculi (>90%) that pass the kidney lodge here.
Renal colic: ureteric stone causes severe colicky loin-to-groin pain (the pain follows the dermatomal distribution of the ureter — T10 to L1). Haematuria (micro or macro) is present in 90%. An obstructing stone proximal to the VUJ can cause ipsilateral hydroureteronephrosis. CT KUB (without contrast) is the investigation of choice — 95% sensitivity.
⭐ Clinical Pearl
'Water under the bridge': the vas deferens (or round ligament of the uterus) arches over the ureter at the level of the bladder — 'the water (ureter) passes under the bridge (vas deferens)'. This is surgically critical — the ureter can be mistaken for the vas during pelvic dissection. Ureteric injury during hysterectomy or pelvic surgery has a quoted rate of 0.5–2%.