What is postobstructive diuresis?
After obstruction is relieved, a physiologic diuresis occurs with the excretion of excess total body water, along with an osmotic diuresis stimulated by the excretion of urea.
This process can lead to a pathologic diuresis, with negative fluid balance and electrolyte deficiencies.
Pathologic postobstructive diuresis is caused by decreased expression of aquaporin channels in the collecting duct, excessive presence of atrial natriuretic peptide, and concentrating defects in the corticomedullary gradient.
Patients should have electrolytes checked and replaced regularly with free access to oral fluids.
If intravenous fluids are required, their type and amount should be determined by serum and urinary electrolyte levels.
Postobstructive diuresis is most likely to occur after relief of obstruction in patients with severe urinary retention, high serum creatinine, and elevated serum bicarbonate.