To analyze bowel and urinary function in patients with posterior deep infiltrating endometriosis (DIE) >30 mm in largest diameter at transvaginal ultrasound before and after surgical nerve-sparing excision. Prospective observational study (Canadian Task Force classification III). Tertiary care university hospital in Bologna, Italy. Twenty-five patients with posterior DIE were included in the study between June 2011 and December 2012. Patients did not receive hormone therapy for at least 3 months before and 6 months after surgery. Patients underwent urodynamic studies and anorectal manometry before and after nerve-sparing laparoscopic excision of the posterior DIE nodule. Intestinal and urinary function was evaluated in patients with bulky posterior DIE using urodynamic and anorectal manometry. Results of urodynamic studies and anorectal manometry were similar before and after nerve-sparing surgical excision of the posterior DIE nodule. Urodynamic studies demonstrated a high prevalence of voiding dysfunction, whereas anorectal manometry showed no reduction in rectoanal inhibitory reflex and hypertone of the internal anal sphincter. Patients with posterior DIE >30 mm in greatest diameter demonstrate preoperative dysfunction at urodynamic study and anorectal manometry, probably due to DIE per se. The nerve-sparing surgical approach seems not to influence the motility or sensory capacity of the bladder and the rectosigmoid colon.