Iodine-131 ablation therapy for a patient receiving peritoneal dialysis

The authors describe a patient with follicular thyroid carcinoma who was re ceiving continuous ambulatory peritoneal dialysis to manage end-stage renal disease. To deliver radioiodine therapy to ablate thyroid remnants safely and under optimal conditions, the behavior of 37 MBq (1 mCi) I-131 was foll owed daily for 3 days. Blood activity and total body count decreased with a half-life of 100 hours (4.17 days). The daily iodide removal rate, estimat ed as a percentage of the total administrated activity, was low: 5.3% to 8. 6% in peritoneal dialysate and 1.3% to 2.2% in urine. The thyroid uptake, m easured using a probe, was 2.4% to 2.1% from day 1 to day 3 and 1.9% rater at day 8. The volume of thyroid remnants was determined by ultrasonography to be 0.6 g, The patient received a reduced ablative I-131 dose of 814 MBq (22 mCi), Radiation emitted from the patient after I-131 therapy, monitored using a radiation monitor probe located at a distance of I meter, decrease d with an effective half-life of 70 hours (2.9 days). The integration of th e curve from t = 0 showed a level always Less than 25 mu Sv/hour as early a s 24 hours after treatment. Because the iodine removal rate is continuous b ut low in a case of peritoneal dialysis, smaller therapeutic doses must be administered to deliver maximal radiation to residual thyroid tissue while minimizing excessive radiation exposure to patients, their families, and me dical staff.