Vertical diameter

The vertical diameter is a pelvic measurement used to assess the anatomy of the pelvic area, particularly in the context of parturition, obstructive dystocia and constipation. It is determined from a laterolateral radiograph or multiplanar reconstructed CT images of the pelvis.

The vertical diameter has been defined as the vertical distance between cranial end of the pelvic symphysis (depicted by the pecten pubis) and the sacrum (or a caudal vertebra), perpendicular to the pelvic symphysis. The anatomic landmarks for the vertical diameter are very similar to those for the sacral diameter in the dog. These two values are therefore very close.

The following values have been published in the literature for the vertical diameter in dogs:

• Boston terrier with normal parturition (7.5 +/- 1.1 kg) and dystocia (7.5 +/- 0.8 kg) respectively : 4.4 +/- 0.06 cm - 4.1 +/- 0.16 cm

• Scottish terrier with normal parturition (9.5 +/- 0.9 kg) and dystocia (9.8 +/- 0.8 kg) respectively : 4.6 +/- 0.08 cm - 4.3 +/- 0.07 cm

• English bulldogs with normal parturition (21.25 +/- 0.91 kg) and caesarian delivery respectively (25.16 +/- 1.44 kg) : 6.32 +/- 0.3 cm - 6.15+/- 0.3 cm