Long-term histopathologic changes after bladder augmentation (BA) in rats using living-related partial bladder transplantation (LPBTx) or conventional ileocystoplasty (ICP) were compared. In this study, BA (n = 37), LPBTx (n = 18), and ICP (n = 19) were performed in 16-wk-old Lewis rats. Five donors and seven nontransplanted normal Lewis rats (controls) were also studied. Rats that survived >10 mo after BA were killed after blood biochemistry and neobladder imaging. Harvested bladders were examined with hematoxylin and eosin and proliferating cell nuclear antigen (PCNA). When the rats were killed, there were 16 rats in the LPBTx group and 12 rats in the ICP group; ICP rats were significantly smaller than LPBTx rats (p < 0.05). Mean duration of follow-up for the LPBTX group was 17.3 mo, for the ICP group was 13.7 mo, for the donor group was 16.1 mo, and for the control group was 19.7 mo. Mean serum pH in the LPBTx group was 7.41 +/- 0.78 and in the ICP group was 7.25 +/- 0.38. Mean base excess in the ICP group was significantly lower than in the LPBTx group (p < 0.05). Incidence of bladder calculi in the LPBTx group (6.3%) was significantly lower than in the ICP group (33.3%; p < 0.05). There was no dysplasia/malignancy/increase in PCNA in the LPBTx group. PCNA increased in the ICP group, compared with controls (p < 0.05); two (16.7%) of 12 of ICP rats had dysplasia with mitosis. Bladder capacity increased in LPBTx and ICP compared with controls (both p < 0.05). We hope to show that BA using LPBTx may result in a neobladder with fewer complications than BA using ICP; LPBTx may also decrease the risk for malignancy.