Ureteral Peristalsis Simulator

Peristaltic Wave

Contraction frequency 4 /min

Contraction amplitude (lumen closure) 85%

Wave propagation speed 3.0 cm/s

Bladder back-pressure 10 mmHg

Live Readouts

Ureterovesical junction competent

Urine transport rate

— mL/min

Peak luminal pressure

— mmHg

Boluses delivered

Wave transit time

— s

How it works

Urine does not simply drain by gravity: each renal calyx contains pacemaker cells that fire a spontaneous action potential, triggering a ring of circular smooth-muscle contraction that closes the lumen completely (coaptation) and sweeps distally at a fixed speed, trapping and pushing a discrete bolus of urine ahead of it — the same peristaltic-pump principle as the esophagus or intestine.

Transport rate ≈ f · V_bolus · η(amplitude)
η(A) = clamp((A − 0.5) / 0.5, 0, 1)   // no seal below ~50% closure → no net transport
P_peak ≈ P_tone + A · ΔP_max          // wall tension rises with contraction depth

The ureterovesical junction (UVJ) is a one-way flap valve: the ureter runs obliquely through the bladder wall inside a submucosal tunnel, so as bladder pressure rises during filling or voiding, the detrusor muscle compresses this tunnel shut. Its closing pressure scales with how vigorously that terminal segment contracts. When bladder back-pressure exceeds the junction's closing pressure — a short or poorly angled tunnel, or a weak terminal contraction — urine is forced backward into the ureter: vesicoureteral reflux, a real clinical mechanism behind recurrent pyelonephritis in children and in some bladder-outlet-obstruction cases.

Frequency — how often a new pacemaker-triggered wave launches from the renal pelvis (physiologic range ≈ 1–8/min).
Amplitude — how completely the contraction ring closes the lumen; below ~50% the wave no longer seals and net forward transport collapses.
Propagation speed — how fast the contraction ring itself travels down the ureter (physiologic range ≈ 2–6 cm/s), setting the wave's transit time.
Bladder back-pressure — raise it past the UVJ's closing pressure to see reflux occur live.

Urine bolus Refluxed urine

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