Transabdominal ultrasonographic determination of fetal gender in the horse during mid-gestation – a comparative study using randomized video images to investigate variation in diagnostic performance among raters, and the effect of month of gestation

Abstract

Summary: Late pregnancy check ups in mares during advanced gestation by transabdominal ultrasound bring reliable results on fetomaternal and fetal well-being. Fetal gonads can be scanned as well. Aim of this study was to evaluate accuracy of fetal gender determination by using B-Mode and Doppler ultrasonography video images analyzed by different raters. The accuracy of these diagnoses was compared among the raters. Pregnancy checks were performed on different stud farms in the mid-west of Germany. The day of gestation was derived from breeding records, and the mares were examined between 70 -240 days pregnant. Fetal sex was determined as well by B-Mode and Doppler sonography. Examinations were videotaped. Gonads with homogenous structure and a hyperechogenic line along the longitudinal axis, or an intense Doppler signal along this axis were assigned to be male. Gonads with bizoned echogenicity and a strong circular Doppler signal were assigned female. To review the practicability and repeatability of gender determination 100 videotapes were selected and shown to 20 voluntary raters who correlated videotapes and fetal gender. Confirmation of gestation and fetal well-being during advanced gestation (90 -240 days) by transabdominal ultrasound examination is practicable. Gender determination can be accomplished by a combination of B-Mode and Doppler sonography. The best results can be accomplished during 4th (75 %) and 5th (62 %) month of gestation, especially by using Doppler ultrasonography. Practitioners who are unexperienced in gender determination can complete the task based on videotapes showing fetal gonads. Characteristic optical features can be identified better referring to vascularisation detected by colour Doppler ultrasonography. In conclusion gender determination by transabdominal sonography can be conducted by using a combination of B-Mode and Doppler sonography. Optimal working conditions and videotaping the examination can increase the accuracy. Using colour Doppler helps to find distinctive features and determine the gender with greater accuracy. The accuracy of the diagnoses is optimal between 4-5 month of gestation.Keywords: mare / gender determination / transrectal ultrasonography / transabdominal sonography / reproduction Citation: Tönissen A., Martinsson G., Pricking S., Otzen H., Ertmer F., Rau J., Sielhorst J., Rohn K., Sieme H. (2016) Transabdominal ultrasonographic determination of fetal gender in the horse during mid-gestation -a comparative study using randomized video images to investigate variation in diagnostic performance among raters, and the effect of month of gestation. Pferdeheilkunde 32,[29][30][31][32][33][34][35]

Equine foetal gender determination in mid‐ to late gestational mares: A practical inquiry

“…The best timing for early FGD is between 60 and 70 days of pregnancy (Curran & Ginther, 1989;Holder, 2000Holder, ,2014aHolder, ,2014b. The short time frame, the necessary experience and the evaluation of only one distinctive feature are the main disadvantages of this approach (Toenissen et al, 2016).…”

“…Female gonads are more heterogeneous on ultrasound and show a central circular echogenic structure, lining the cortical border of the ovary. Doppler ultrasonography accentuates the ring of vascularization between the cortical and medullar layer (Resende et al, ; Toenissen et al, ) (Figure ).…”

“…This line represents the mediastinum of the testicle. Visualization of the vascularization in the plexus pampiniformis on the caudolateral side of the testicle is possible by the use of Doppler ultrasonography (Resende, Carmo, Ramires, & Alvarenga, 2014;Toenissen et al, 2016). The testicular mediastinum and the outer lining of the testicle are in most cases also clearly visible with Doppler ( Figure 1).…”

Geschlechtsbestimmung bei Pferdefeten mittels zwei- und dreidimensionaler Sonografie in der Frühgravidität

“…Die transrektale Geschlechtsdiagnose mithilfe des konventionellen 2D-Ultraschalls erfordert viel Erfahrung, was sich auch in den Ergebnissen widergespiegelt hat: So war die Untersucherin BK, die schon viele Jahre die Geschlechtsbestimmung bei Pferdefeten durchführt, deutlich schneller und stellte mehr korrekte Diagnosen als die relativ unerfahrenen Untersucher. Dies steht im Gegensatz zu den Ergebnissen von Toenissen et al [14], die beeinflussende Faktoren (tierärztliche Erfahrung, Trächtigkeitsmonat und Sonografiemodus) der Geschlechtsbestimmung untersuchten. Sie stellten keine Korrelation zwischen der tierärztlichen Erfahrung und der Höhe der erzielten Übereinstimmungen fest [14].…”

“…Dies steht im Gegensatz zu den Ergebnissen von Toenissen et al [14], die beeinflussende Faktoren (tierärztliche Erfahrung, Trächtigkeitsmonat und Sonografiemodus) der Geschlechtsbestimmung untersuchten. Sie stellten keine Korrelation zwischen der tierärztlichen Erfahrung und der Höhe der erzielten Übereinstimmungen fest [14]. Im Unterschied zur vorliegenden Studie führten die Probanden der zitierten Studie die Ultraschalluntersuchungen nicht selbst durch, sondern evaluierten nur Videoaufnahmen.…”