Introduction Several attempts to invent implantable devices have done, and it is also necessary to develop biocompatible packaging materials for implantable devices. Thus, we evaluated the biocompatibility of polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA) by analyzing of the changes of macrophage, macrophage migratory inhibitory factor (MIF) and inflammatory cytokines of the bladder. Materials and methods A 2 mm-sized, ball-shaped lead was made and coated with PDMS or PMMA. After 1-, 2-, and, 4-week intravesical implantation with each lead balls in the bladder of the rats, the inflammatory changes by foreign body reaction were evaluated. Results At 1 week, the increased activity of macrophages and increased expression of MIF in the urothelium was observed except control group, however the significantly decreased activity of macrophages and MIF expression in rats implanted with PDMS- or PMMA-coated lead were noted at 2 and 4 weeks. In addition, significant decreased levels of inflammatory cytokines such as IL-1β, IL-6, and TNF-α were observed with time. In this study, we noticed the expression of MIF in the urothelium and presented the changes of MIF as well as macrophages and other inflammatory cytokines. Conclusions We suggest that the role of MIF in the foreign body response. After the intravesical implantation with PDMS or PMMA, the lower inflammatory response was observed in the bladder. Therefore, PDMS or PMMA are suggested for the biocompatible polymers in the bladder.