“…In 13 studies (4.2%) 53 , 58 , 65 , 108 , 111 , 142 , 143 , 145 , 159 , 316 , 337 , 343 , 351 non‐validated questionnaires were used. Anal manometry was used in 126 studies (41.2%) 50 , 53 , 55 , 57 , 61 , 65 , 72 , 73 , 77 , 78 , 80 , 82 , 83 , 85 , 86 , 91 , 92 , 95 , 96 , 98 , 103–107 , 109 , 111 , 115 , 122 , 123 , 125 , 127 , 134 , 141 , 142 , 146 , 151–153 , 155 , 162–165 , 167 , 168 , 170 , 174–176 , 178 , 179 , 183 , 191 , 193 , 199–201 , 204 , 206 , 213 , 217 ,…”