['The aim of this study was to evaluate the protective effect of intravesical oxybutynin on the bladder wall of rabbits with detrusor overactivity and partial bladder outlet obstruction (PBOO).', "Forty-five North Folk male rabbits were randomly distributed into GI, used as control (n\u2009=\u200915), GII-PBOO (n\u2009=\u200914), and GIII-PBOO + intravesical oxybutynin (n\u2009=\u200915). Connective tissue and elastic fibers were quantified as volumetric density on picrosirius red and Weigert's Fuchsin-Resorcin-stained sections, respectively.", 'In T2, bladder weight was significantly higher in animals in GII and GIII. Smooth muscle bundle diameter was increased by 42% in GII compared with GI (p\u2009<\u20090.02).Elastic fibers were significantly higher in GII and GIII as compared with control group. Collagen concentration in GIII and GII was significantly lower than G1 (p\u2009<\u20090.025).'] Does intravesical oxybutynin protect the vesical wall against functional and smooth muscle changes in rabbits with detrusor overactivity?