PURPOSE: The purpose of this study was to evaluate the feasibility of using proton and
sodium magnetic resonance imaging (
MRI) to detect fluid accumulation produced by
fludrocortisone and
nifedipine - two
drugs known to cause
salt/
water retention by different mechanisms. MATERIALS AND METHODS: Twelve young healthy male subjects were
randomly assigned to one of two groups and treated with either
fludrocortisone or
nifedipine for 14 or 25 days, respectively. The change in
sodium MRI, as well as in proton T(2) value and T(1)-
weighted signal
intensity in the calf following postural change [referred to here as 'postural delta signal'(PDS)], was evaluated before, during and after
drug administration. The changes in
MRI PDS were compared to conventional physiological parameters, including
body weight, calf volume and
pitting edema. RESULTS: When compared to the baseline pretreatment values, the subjects treated with
fludrocortisone showed a 5.5% increase in
sodium MRI PDS (P=.01), a 2-ms increase in proton T(2) PDS of the
gastrocnemius muscle (P=.06) and a
body weight gain of 2.3% (P=.001) within 1 week. In the nifedipine-treated subjects, the
sodium MRI PDS increased by 6% versus baseline (P=.03), while the proton T(2) PDS of the
gastrocnemius muscle increased by 3.7 ms (P=.01), associated with a 0.5% weight
gain (P=.55), within 3 weeks. No significant changes were noted in the T(1)-weighed images following postural change. Measurements of calf circumference, volume and
pitting edema did not show consistent changes associated with the
drug administration. CONCLUSION: The postural change in
sodium MRI and proton T(2) signals provides a sensitive method for detecting the fluid accumulation produced by
fludrocortisone and
nifedipine. The
MRI results are consistent with treatment-induced increases in
extracellular fluid volume and
correlate well with the observed weight
gain. These findings support the potential
utility of
MRI for the evaluation of medication-induced fluid retention.
