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.