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.