defecography: how to do that for having fixed parameters?

background: in most of defecography films, the symphysis pubis is obscured, especially in obese patients, and the parameters will change in values if x-ray is interpreted by different reviewers or if the patient changes his/her position between the phases. this study was carried out to determine how to do the defecography to obtain fixed parameters. â  methods: eighty patients that had been candidates for defecography were randomly divided into two equal groups. in group a defecography was performed according to the conventional protocol. in group b, a piece of a radio opaque metal was stacked on the most anterior site of the symphysis pubis of the patients and the same protocol was followed. the x-rays were reviewed by two radiologists and one colorectal surgeon. they were asked to identify the most anterior site of the pubic bone. then the parameters were measured accordingly. â  results: in group b, the most anterior site of the pubic bone could be distinguished in all x-rays with certainty. in group a, only in12.5% of the x-rays, the 3 reviewers marked the most anterior site of the pubic bone in the same place. at least in 17.5% of the x-rays, one of the radiologists was not able to find the anterior site of the pubic bone. in 20%, at least one of the reviewers was in doubt to mark the most anterior site of the pubic bone, precisely. if there is no metal marker on pubic bone, the difference of measurement of parameters may be seen in up to 95% of the cases. â  conclusion: by placing a metallic element on the most anterior site of the symphysis pubis, the parameters in defecography will be accurately evaluated and measured. â