Incidentally polycystic kidney disease identified by SPECT/CT with post-therapy radioiodine scintigraphy in a patient with differentiated thyroid carcinoma

RATIONALE Post-therapy or diagnostic whole-body radioiodine scintigraphy is widely employed to evaluate the residual, recurrence, or metastases of differentiated thyroid carcinoma because of the high sensitivity and accuracy. However, it has pitfalls. PATIENT CONCERNS We described a 63-year-old male with a history of papillary thyroid carcinoma who was referred for iodine-131 ablation therapy. The post-therapy iodine-131 whole-body images demonstrated abnormal increased uptake of the tracer in the regions of bilateral upper abdomen. DIAGNOSES The single photon emission computed tomography/computed tomography (SPECT/CT) showed the abnormal Iactivity was corresponded to multiple irregular cystic low densities in the both kidneys on the low-dose computed tomography images, so the diagnosis of polycystic kidney disease was confirmed. INTERVENTIONS AND OUTCOMES The patient responded well to the lifestyle-based treatments. LESSONS Polycystic kidney disease was one of the etiologies of the false-positive findings in the radioiodine scintigraphy.