SpaceOAR Persistence on MRI at 59 Weeks Postplacement in a Patient With Stage IV CKD

External beam radiation therapy is commonly used to treat prostate cancer, and gel spacers such as SpaceOAR Hydrogel (Boston Scientific, Marlborough, MA) are approved to limit local rectal radiation toxicity. SpaceOAR is usually reabsorbed in 12 to 24 weeks and excreted renally. It has a known low rate of rectourethral fistula that is usually associated with ectopic placement into the rectal wall. We present a case of a SpaceOAR Hydrogel insert persisting in a patient with chronic kidney disease on serial MRI scans for 59 weeks after placement with colovesical fistula development 81 weeks after placement of unclear association.