Conjugate diameter

The conjugate 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 conjugate diameter is the distance between the promontory and the cranial end of the pelvic symphysis, depicted by the pecten pubis.

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

• Boston terrier with normal parturition (7.5 +/- 1.1 kg) and dystocia (7.5 +/- 0.8 kg) respectively: 4.5 +/- 0.05 cm - 4.4 +/- 0.11 cm

• Scottish terrier with normal parturition (9.5 +/- 0.9 kg) and dystocia (9.8 +/- 0.8 kg) respectively: 4.5 +/- 0.06 cm - 4.3 +/- 0.07 cm

• English bulldogs with normal parturition (21.25 +/- 0.91 kg) and caesarean delivery (25.16 +/- 1.44 kg) respectively: 6.5 +/- 0.3 cm - 6.48 +/- 0.3 cm

• English bulldogs (range 18.1 to 30.8 kg, mean 23.56 kg) from both genders: 5.9 +/- 0.5 cm

• Non-brachycephalic dogs of various breeds and crossbred dogs (range 18 to 31.1 kg, mean 26.62 kg) from both genders (18-30 kg): 6.9 +/- 0.6 cm