Post-obstructive diuresis
Post-obstructive diuresis is a marked increase in urine output that follows relief of urinary tract obstruction, driven by retained urea and solute excretion plus a tubular concentrating defect from the preceding obstructive injury. Management centers on distinguishing appropriate solute diuresis from ongoing volume/electrolyte loss requiring replacement, with close monitoring of urine output and serum electrolytes.
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What this article covers
- Overview
A physiologic-to-pathologic spectrum of polyuria after relief of obstruction: post-obstructive diuresis (POD) is a marked rise in urine output following catheterization, stenting, or surgical…
- Epidemiology
Occurs whenever high-grade or long-standing obstruction is relieved: a recognized complication after catheterization for posterior urethral valves and after bladder catheterization for adult bladder…
- Risk factors
Long-standing or high-grade obstruction: the longer and more complete, the greater the retained urea/solute load available to drive an osmotic diuresis once relieved.
- Pathophysiology
Obligate solute (osmotic) diuresis from retained urea: during obstruction, urea and other osmotically active solutes accumulate; once the obstruction is relieved and filtration resumes, this retained…
- Clinical features
Markedly increased urine output after decompression: a jump in urine output in the hours after bladder catheterization, ureteral stenting, or surgical relief of obstruction, in a patient known to have had urinary retention or obstruction.
- Differential diagnosis
Osmotic diuresis from hyperglycemia: glucosuria drives diuresis independent of obstruction; elevated serum and urine glucose, not recent decompression, explains it.
- Diagnosis
The diagnosis is clinical: the temporal relationship between relief of urinary tract obstruction and a marked rise in urine output, with laboratory findings consistent with a solute (osmotic)…
- Management
First, decompress the obstruction fully (bladder catheterization for lower tract obstruction; nephrostomy or ureteral stent for upper tract obstruction); the diuresis cannot resolve without adequate drainage.
- Complications
Volume depletion and prerenal azotemia: under-replacement of a genuine pathologic diuresis can produce hypotension and a secondary decline in kidney function.
- Prognosis
Physiologic post-obstructive diuresis is self-limited, typically tapering over 24 to 48 hours as the retained urea/solute load clears, with recovery tracking the duration and severity of the preceding obstruction.
- Prevention
Relieve obstruction promptly once identified: timely bladder catheterization or ureteral decompression limits the retained solute/volume load and the tubular injury producing the concentrating defect.
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