Ultrasonographic evaluation of the linea alba before and after laparotomy in warmblood horses

Abstract

Ultrasonographic evaluation of laparotomy wounds has been used for the diagnosis of incisional complications during hospitalisation. Ultrasonographic examinations for the follow-up of the post-incisional healing process of the linea alba over a prolonged period have not been presented until now. Aim of this study was the description of ultrasonographic findings of the linea alba before and after surgery. A further aim was to evaluate, whether a differentiation of horses with and without laparotomy on the basis of the sonography is possible. Ten warmblood horses were included in this study, which underwent a standardized median laparotomy for harvest of tissues specimens. Ultrasonographic examinations of the ventral abdominal wall were undertaken prior to surgery as well 8 weeks, 12 weeks and 12 months post operationem. Surgical sites were divided into three regions: caudal (region 1), middle (region 2) and cranial (region 3). In this study, sonographic findings were described and, furthermore, width of the linea alba and abdominal wall thickness were measured. A comparison of clinical and ultrasonographic findings was performed 12 month after surgery. From caudal to cranial, both, the width of the linea alba and the abdominal wall thickness, decreased. Prior to surgery, the following median values (interquartile range) were measured for width of region 1, 2 and 3:5.85 (3.15) mm; 5.00 (3.43) mm und 4.15 (2.88) mm. Following surgery, the appearance of the muscular parts of M. rectus abdominis altered. Moreover, width of linea alba in all regions increased in comparison to baseline values, which were significant 12 weeks and 12 month post operationem. A cut-off value of all three regions to distinguish horses following surgery from those prior surgery of 12.2 mm was determined with a specifity of 99%. Regarding the thickness of the abdominal wall in all three regions, a significant increase in comparison to the findings prior to surgery was only detectable at the intersection 8 weeks after surgery. In only two horses, no clinical abnormal findings could be detected at 12 months after surgery. However, in both cases, ultrasonographic findings were consistent with a previous laparotomy. Following laparotomy significant morphological alterations occur in the linea alba and the abdominal wall, which could be definitely identified by ultrasonography at least up to 12 months post surgery. For this purpose, width of the linea alba, as well as the appearance of the M. rectus abdominis, seem appropriate, as both parameters will differ significantly from the initial preoperative condition. Evaluation of thickness of the abdominal wall is less suitable to distinguish between horses with and without laparotomy.