Urinary Obstruction & Stasis
Obstruction matters for one reason above all: it destroys kidneys.
The big picture
Obstruction matters for one reason above all: it destroys kidneys. Urine that cannot drain backs up under pressure, the system dilates (hydroureteronephrosis), and the kidney slowly atrophies toward failure. Worse, stagnant urine invites infection, which accelerates the damage and can turn septic. So the urologist's instinct with any obstruction is the same: find the level, relieve the pressure, and protect the kidney before it is lost.
The framework: classify the obstruction (by cause, duration, degree, level), understand how the tract responds upstream (bladder hypertrophy → decompensation; ureteric dilation; renal back-pressure damage), then relieve it — and anticipate post-obstructive diuresis afterward.
Mechanism pathway
Tap any step to see why it happens.
Diagnostic algorithm
Each step answers one question. Tap to expand.
Board traps
Obstruction silently destroys the kidney — relieve pressure early.
In children, get a VCUG — otherwise posterior urethral valves or reflux are missed.
Bladder goes compensation → decompensation under chronic outlet obstruction.
Anticipate post-obstructive diuresis after relieving chronic (especially bilateral) obstruction.
DTPA = glomerular, MAG3 = tubular radionuclide agents for drainage/function.
Stagnant urine invites infection — obstruction + infection is a dangerous, potentially septic combination.