Aim To investigate the effects of rhubarb enema treatment using a 5/6 nephrectomized rat model and study its mechanisms. Methods Twenty-eight Sprague Dawley rats were divided into three groups: sham operation group (n = 8), 5/6 nephrectomized (5/6Nx) (n = 10), and 5/6Nx with rhubarb enema treatment (n = 10). The rhubarb enema was continuous for 1.0month. Serum creatinine, serum indoxyl sulfate (IS) level, renal pathology, tubulointerstitial fibrosis, and renal oxidative stress were assessed. Results 5/6Nx rats showed increasing levels of serum creatinine and severe pathological lesions. Their serum creatinine levels obviously decreased after rhubarb enema treatment (P < 0.05 vs 5/6Nx group). The administration of rhubarb enema attenuated the histopathological changes in 5/6Nx rats. In addition, 5/6Nx rats showed an enhanced extent of tubulointerstitial fibrosis compared with sham rats, and administration of rhubarb enema to 5/6Nx rats ameliorated tubulointerstitial fibrosis. 5/6Nx rats showed increased serum levels of IS, renal oxidative stress, and NF-kappa B compared with sham rats, whereas administration of rhubarb enema to 5/6Nx rats decreased serum levels of IS, renal oxidative stress, and NF-kappa B levels. Conclusion Rhubarb enema treatment ameliorates tubulointerstitial fibrosis in the kidneys of 5/6Nx rats, most likely by alleviating IS overload and reducing kidney oxidative stress and inflammatory injury.