Ultrasonographic evaluation of the width, thickness, and length of the normal linea alba in standing and dorsal recumbent horses.

OBJECTIVE: To determine the variability in length, width, and thickness of the equine linea alba (LA) and the effect of a standing vs dorsal recumbent position on these measurements. STUDY DESIGN: Descriptive anatomical comparative study. ANIMALS: Standing horses (N = 75; in 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing). METHODS: Linea alba length was measured in standing position from xiphoid to umbilicus, and transverse ultrasonographic images were obtained at five reference points to measure LA width and thickness. In 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing. RESULTS: There was wide variation in LA width and thickness between standing horses, with gradual increase from xiphoid (range, 0.14-0.64 cm) to umbilicus (range, 0.2-2.97 cm). Linea alba length in standing position was 51.09 ± 6.219 cm. Width was independent of the size of the horse; thickness and length were correlated at some reference points to height (r = 0.346-585, P < .05) and weight (r = 0.324-0.642, P < .05). Different LA shapes could be identified. In dorsal recumbency, the LA was smaller in width at all reference points (15%-23%, P < .05) and shorter (20%, P < .001) compared with standing. CONCLUSION: In addition to the wide variability in LA measurements and shapes between horses, there was a significant decrease in LA width and length when horses changed from standing to dorsal recumbency. CLINICAL SIGNIFICANCE: The difference in LA length and width between dorsal recumbency and when standing could increase tension on sutures after laparotomy and should be taken into account when surgeons are closing the abdomen.