Abstract
Background
Hyponatraemia and urinary retention are common medical problems. Whilst associations between the two are documented, research has not clearly highlighted the prevalence of urinary retention in hyponatraemic patients.
Objectives
Determining the prevalence of urinary retention in hyponatraemic patients and assessing whether urinary catheter insertion itself affects the correction rate.
Methods
A prospective, single centre, observational study including patients hospitalised in internal medicine and geriatric wards. A total of 199 patients were investigated: 100 with hyponatraemia ≤129 mEq/L, of these, 70 had severe hyponatraemia ≤125 mEq/L and 99 normonatraemic controls. The incidence of urinary retention was checked in all groups. Hyponatraemic patients underwent complete assessment for the cause of hyponatraemia and sodium levels were followed up for 48 hours.
Results:
There was a marked increase in the incidence of urinary retention in hyponatremic patients as compared to those with normal sodium levels (41% vs 21% p=0.004). When comparing to those with severe hyponatraemia, a slightly greater difference was found (44% vs 21% p=0.001). When comparing the hyponatraemic patients with and without urinary retention, there was no difference in sodium correction rate between the two groups. Patients with polyuria secondary to post obstructive diuresis had a more rapid sodium correction (9.2±6.8mEq/L vs 5.8±4.8mEq/L (p=0.05))
Conclusions:
There is a significantly higher prevalence of urinary retention in patients with hyponatremia which is associated with the severity of hyponatraemia. Post obstructive diuresis following catheter insertion is a predictor of rapid sodium correction. We recommend a routine bladder scan for all patients with hyponatraemia.