Early results on canine fetal kidney development: Ultrasonographic evaluation and value in prediction of delivery time.

To date there have been no studies that describe the ultrasonographic evaluation of kidney development in canine fetuses. The aim of this prospective and longitudinal study was to monitor fetal kidney development with ultrasound and use fetal kidney measurements as a complementary biometric index for estimation of gestational age. Ultrasonographic examinations were performed on 15 clinically healthy pregnant bitches every four days from 30th day of pregnancy, until visualization of the fetal renal pelvis was no longer possible. Four distinct periods of ultrasonographic canine fetal kidney development were defined. Kidney length and renal pelvis distention were measured on longitudinal plane images. The fetal kidney ranged from 0.40 cm to 2.30 cm in length, and diameter of the pelvis ranged from 0.06 cm to 0.17 cm, however by the end of gestation the renal pelvis was no longer dilated and so its diameter could not be measured. Statistical analysis confirmed a relationship between gestational age and fetal kidney growth. Ultrasonographic evaluation of fetal kidney development is simple to perform. There is a strong correlation between gestational age and kidney length, which allowed generation of an equation to estimate delivery date with high sensitivity between 48 and 52 days of pregnancy. Fetal organ development can be considered complete when the renal pelvis is no longer dilated, this finding can assist the ultrasonographer in staging the gestation by prompting examination for fetal intestinal motility which begins at the same gestational age. Measurement of fetal kidney length can be used in conjunction with other methods to estimate gestational age and predict delivery time.