The volume drained in the first 10 to 15 minutes after catheterisation helps distinguish acute from chronic retention and guides follow-up. Large residuals, typically over about 1 litre, raise the possibility of chronic retention with risk to the upper tracts, especially with a raised creatinine.
Retention also has precipitants beyond the prostate: constipation, anticholinergic or opioid drugs, decongestants, urinary infection, recent surgery or immobility. Correcting these improves the chance of a successful trial without catheter.
- Record the residual volume drained in the first 10 to 15 minutes.
- Check creatinine, and consider renal ultrasound when the residual is large or creatinine is raised.
- Review medications for anticholinergics, opioids and decongestants.
- Treat constipation and urinary infection before the trial without catheter.
- Watch for post-obstructive diuresis after draining a large chronic residual.
Why it matters
Missing chronic high-pressure retention risks kidney damage, and missing a reversible cause risks an avoidable failed trial without catheter.
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