[1] Univ Sao Paulo, Ribeirao Preto Med Sch, Dept Surg & Anat, Div Coloproctol, BR-05508 Sao Paulo, Brazil
[2] Univ Sao Paulo, Ribeirao Preto Med Sch, Dept Surg & Anat, BR-05508 Sao Paulo, Brazil
[3] Univ Sao Paulo, Ribeirao Preto Med Sch, Div Clin Oncol, BR-05508 Sao Paulo, Brazil