Application of Lithotripsy
Lithotripsy has been used to fragment uroliths in the horse (Katzmanet al 2016; De Bernadris et al 2019; Nolazco Sassotet al 2020), as well as other mineralized concretions in horses. This article describes application of the pneumatic lithotripsy to enteroliths. The efficacy and efficiency of lithotripsy in fragmenting mineralized concretions appears to be dependent on the size of the concretion and on its composition. Uroliths as large as 10-12 cm have been fragmented within the bladder of female horses (Nolazco Sassotet al 2020), whereas <10 cm urolith size have been described for male horses (De Bernadris et al 2019; Katzmanet al 2016). This size difference is attributed to the ease of removing urolith fragments from the bladder in the relatively large and expansile mare urethra compared to the narrower and more limited access via a perineal urethrotomy in male horses.
The composition and surface characteristics of the mineralized concretion is also important when considering the efficiency of lithotripsy. The article by Machado Amaral Rosa et al (2023) noted that smooth surfaced enteroliths were more difficult to fragment than irregularly surfaced enteroliths, as were enteroliths with rigid cores and less porosity. Similarly, type 1 calcium carbonate uroliths in horses have been described as easier to fragment than the harder and smoother type 2 calcium carbonate uroliths (De Bernadris et al2019). Although ingesta and foreign bodies, such as hay nets, twine, plastic, or rope, can serve as a nidus for mineralized concretions, most enteroliths have small, solid niduses, such as metal fragments, rocks, or grains of sand (Hassel 2002; Pierce 2009). Clinical experience, supported by available geochemical analysis of typical equine enteroliths, would suggest that the majority of enteroliths are not hollow-centered formations (Hassel et al 2001; Rouff et al2018; Dechant, personal observation).
Machado Amaral Rosa et al (2023) stated that advantages of their pneumatic lithotripsy technique for management of enteroliths include ability to use smaller enterotomies through sites that are remote to the site of obstruction and reduced surgical time. Comparisons for surgery time were made to an isolated case report describing a particularly difficult presentation of obstructive enterolithiasis (Barrett and Munstermann 2013). In another report of surgical management of enterolithiasis, mean surgery time was 128 +/- 31 minutes (range 70-200 minutes) with 13% requiring 1 enterotomy, 83% of surgeries requiring 2 enterotomies, and 4% requiring 3 enterotomies (Torrent Crosa et al 2020). In this case series, mean surgery time was 135 minutes (range 120-145 minutes) with 4 cases requiring 1 enterotomy and 1 case requiring 2 enterotomies (Machado Amaral Rosa et al 2023). This suggests that while the time advantage of pneumatic lithotripsy for enterolithiasis proposed by Machado Amaral Rosa et al (2023) may not be as profound as described.
In a studies evaluating survival following surgical management of ascending colon or descending colon enterolithiasis, short-term survival was 95-96% with no difference in incidence of complications between enterotomies of the pelvic flexure or descending colon (Pierce et al 2010; Hassel et al 1999). Pneumatic lithotripsy as described in this case series does require an enterotomy to introduce the instrument. Although the enterotomy may be smaller than those needed to directly remove an enterolith, the proximity of the enterotomy and the non-sterile lithotripter to the abdominal incision and the time needed to fragment the enterolith which prolongs the time the intestinal lumen is open should be balanced against the benefits of a smaller enterotomy.
Pierce et al (2010) documented that 87% of horses with descending colon enterolithiasis had some degree of mural damage. Although Machado Amaral Rosa et al (2023) did not experience full thickness intestinal perforation with their technique, one case did develop partial thickness penetration of the intestinal wall despite the lithotripsy procedure being directed at an enterolith that was well exteriorized from the abdomen and readily accessible in a location 30 cm from the pelvic flexure. In lithotripsy disruption of ureteroliths in people, ureteral perforation or extra-ureteral migration of ureteral calculi occurred in approximately 0.85% of cases, with surgeon inexperience and longer operative times being associated with increased complication rates (Georgescu et al 2014). An ex vivo study comparing lithotripsy damage on urinary tract tissue found that tissue damage and risk of perforation was affected by the type of lithotripter, tissue type, probe force and duration of contact between probe and tissue (Sarkissian et al 2015). While it is not known how this information extrapolates to equine intestine, equine surgeon experience is likely to be limited with this technique and it is important to be as careful when using pneumatic lithotripsy as the authors of this case series emphasize (Machado Amaral Rosa et al 2023).
Pneumatic lithotripsy as described in this case series (Machado Amaral Rosa et al 2023) is a useful tool for the surgeon to have in their toolbox when presented with obstructive enterolithiasis. Pneumatic lithotripsy is limited to mineralized concretions, and other types of intraluminal obstructions can occur, such a foreign body or faecalith obstructions. It is important for the surgeon to be knowledgeable about other techniques for mobilizing intraluminal obstructions because other techniques may be more appropriate or preferred by the surgeon.