Structured hydration accelerates I-131 clearance, reduces bladder dose, and enables earlier discharge

Background and objective The optimal hydration strategy to enhance radioactive iodine (I-131) clearance without compromising therapeutic efficacy remains undefined. This study aimed to evaluate whether a structured high-hydration regimen accelerates I-131 clearance, reduces radiation exposure to nontarget organs, and shortens isolation time. Methods In this prospective cohort study, 456 women with papillary thyroid carcinoma receiving I-131 therapy were assigned to a high-hydration group ( ∼ 2500 ml/day) or a low-hydration group ( ∼ 1900 ml/day). Key measures included I-131 effective half-life (T_eff), time to hospital discharge, bladder cumulative dose, residual tumor uptake, and short-term reproductive outcomes. Results The high-hydration group demonstrated a significantly shorter T_eff (22.4 ± 6.2 vs. 28.0 ± 7.3 h; P < 0.001), earlier discharge (median 2.0 vs. 3.0 days; P < 0.001), and a lower bladder cumulative dose (18.5 ± 5.7 vs. 22.1 ± 6.9 mGy; P < 0.001). Tumor uptake remained comparable between groups ( P = 0.552). No significant differences were observed in 12-month reproductive outcomes. The benefits were more pronounced in obese patients ( P -interaction = 0.02–0.04). Conclusion A structured high-hydration regimen significantly accelerates I-131 clearance, reduces bladder radiation exposure, and facilitates earlier discharge without impairing therapeutic efficacy or short-term reproductive safety. These findings support the implementation of tailored hydration protocols, particularly for obese patients, to minimize radiation exposure and optimize posttherapy management.