A Comparative Study of X‐Ray Pelvimetry and CT Pelvimetry

EDITORIAL COMMENT: This paper compares conventional X‐ray pelvimetry with CT pelvimetry and the authors conclude that the latter is preferable due to the lower radiation dose, patient comfort and shorter time of examination; surprisingly they commented that the 2 procedures had no significant difference in cost. Ultrasonography has virtually replaced radiography in obstetric practice The exception is X‐ray pelvimetry which is still performed in many centres in the management of breech delivery at term, and in patients in whom a trial of vaginal delivery is planned after previous Caesarean section although the latter indication is not accepted in many centres (e.g. Dublin). In our mixed Australian community, moderate to severe pelvic contraction, even predominantly of the pelvic outlet (and hence especially relevant to breech delivery) is a reasonably common finding. Not all radiologists will agree with the conclusions in this paper. Our reviewers pointed out that the actual radiation doses were not measured but were quoted from references, those for conventional pelvimetry being 1962 and 1963 references. It should be noted that with modern X‐ray technique the radiation dose has been considerably reduced and ‘the radiation dose from CT pelvimetry including the 2 scout films and one axial slice using a reduced MAS is comparable to conventional pelvimetry including 2 films, the erect lateral film and the tube shift film for the transverse diameters but excluding the outlet view!’ Our reviewers believe that both methods of pelvimetry are comparable and require meticulous technique; they agreed that there was no significant interobserver variability reporting the pelvimetries in this study. The take away message seems to be that there is still a place for pelvimetry in obstetric practice and CT pelvimetry is likely to become more popular. We agree with the practice of postpartum pelvimetry to avoid fetal irradiation and provide information for management of subsequent pregnancies in nulliparas who were delivered by Caesarean section or difficult forceps delivery. Summary: In this study 24 patients who had conventional erect lateral X‐ray pelvimetry had a CT pelvimetry done after delivery to complete the pelvimetry views. The erect lateral pelvimetry was read independently by a Consultant Radiologist, Consultant Obstetrician and a Medical Officer training in Obstetrics and Gynaecology. Using CT pelvimetry as the ‘gold standard’ (as the error of measurement was known with the machine used) the 3 readings were compared. There was no statistical difference in the values suggesting that X‐ray pelvimetry is comparable to CT pelvimetry. However CT pelvimetry is preferred, if available, because of the lower dose of radiation involved, more comfort for the patient and shorter time in performing the procedure. Measurements done are easily read directly from the CT console.