Secondary Abdominal Approaches
Alternative surgical approaches to access the most oral limits of the descending colon include left paramedian (De Oliveira et al 2009) or left flank laparotomy (Turek et al 2019). In both instances, an initial ventral midline celiotomy was used for exploration, diagnosis and localization of the obstruction, and determination that it was not accessible through a ventral midline approach. In the De Oliveiraet al (2009) report, sufficient exposure of the affected descending colon for enterotomy through the secondary paramedian approach was facilitated by elevating the obstructed segment of the oral descending colon by a surgeon with their arm through the ventral midline incision. The details of the location and surgical technique left flank laparotomy approach in Turek et al (2019) were not sufficiently described to determine if it was a paramedian approach while the horse was in dorsal recumbency or if the horse was repositioned into right lateral recumbency (after closing the original celiotomy incision). Other reports describing flank laparotomy for descending colon lesions were based on financial or patient constraints and flank laparotomy was not performed to improve access to the oral or aboral limits of the descending colon (Herbert et al 2021). A right flank laparotomy was used to access an obstruction within the descending duodenum when a ventral midline approach was not successful (Durham 1998).
For very aboral descending colon obstructions, either a paramedian approach or a parainguinal approach (Barrett and Munstermann 2013; Tureket al 2019) can be used to improve access for exteriorization. Similar to the secondary paramedian approach described by De Oliveiraet al (2009), elevation of the descending colon to a parainguinal or parainguinal incision can be facilitated by a surgeon with their arm through the ventral midline incision. Barrett and Munstermann (2013) utilized a right parainguinal approach for their surgery; however, they comment that a left parainguinal approach may be more advantageous based on the descending colon anatomy (Barrett and Munstermann 2013; Klohnen 2013). The sidedness for the parainguinal incision could be determined in surgery via a ventral midline celiotomy or through manipulation of a palpable obstruction via rectal palpation based on which side allows easier elevation, as well as the preferences of the surgeon (which depends on their handedness and where they stand relative to the horse (caudal or craniolateral)).