Large Colon Sand Impaction Colic
Sand is one the causes of colic in horses but it is important to determine the amount of sand, avoiding over-diagnosis (Ruohoniemi et al., 2001; Korolainen and Ruohoniemi, 2002; Korolainen et al., 2003; Keppie et al., 2008, Kilcoyne et al., 2017). Korolainen and Ruohoniemi (2002) found utrasonography to be practical and reliable and have a specificity and a sensitivity of 87.5% in detecting sand accumulations, although small and dorsally located accumulations and the height of the sand sacculations were difficult to detect and evaluate, risking to underestimate the amount of sand. For this reason ultrasonography cannot entirely replace radiology (Korolainen and Ruohoniemi, 2002), but it is a valuable method for monitoring sand accumulation resolution, evaluating length of the impaction, shape and smoothness of the ventral abdomen and gut motility. Cranio-ventral radiographs have been used by Ruohoniemi et al. (2001) for sand resolution monitoring, although smoothness and gut motility cannot be assessed, so ultrasound is helpful to also minimize radiation exposure (Korolainen et al., 2003).
A minimum of three latero-lateral views are advised by Kendall et al (2008), as sand accumulations usually lay ventrally and they recommend to include ribs so to prevent underexposure. Keppie et al. (2008) suggest to perform a full abdominal radiographic evaluation so to detect sand locately more dorsally or caudally. To decrease radiation exposure a long handled plate helps increasing the distance of personnel from the primary beam. It is impossible to determine the volume of accumulations as radiography is a 2D diagnostic imaging technique (Kendall et al., 2008).
Regarding the radiographic scoring system of sand accumulations several methods have been described in literature: Korolainen and Ruohoniemi (2002) designed a scoring system, where grade 0 is the absence of sand and grade 4 is a mass > 5 × 15 cm or >15 × 5 cm or a thin accumulation (<5 cm but longer than 15 cm). A limitation of their study is the lack of association with the patient’s size.
Kendall et al. (2008) found grade 1 and 2 to be a frequent finding in horses without any clinical relevance. Keppie et al. (2008) standardised the height and length of sand accumulation to the width of the midbody of a caudal rib, the closest to the film, so to decrease the effect of the magnification in the radiograph. They also evaluated the location, opacity and homogeneity of the accumulations. This method was more objective and with an higher inter-observers agreement. Kilcoyne et al. (2017) disagree about the use of height and width measurements, because sand impactions are usually undulated, describing instead the use of total surface area and cross sectional area of sand as a more objective measurement.
Hart et al. (2013) evaluated the most cranio-ventral abdominal radiographic view comparing the maximal width of the colonic sand accumulation with the colonic lumen in the affected segment, giving a radiographic score 0-3 grades (0 = no visible colonic sand accumulation; 3 = 60%).
If all margins can be defined and the size of the accumulation can be measured then accumulations are separated (Korolainen and Ruohoniemi, 2002).
Surgical treatment by laparotomy is directly correlated with the presence of gas on both radiographs and transrectal examination and not with the amount of sand (Kilcoyne et al., 2017), although in 50% of surgical cases of sand colic there were multiple sand impactions (Specht and Colahan,1988; Ragle et al., 1989; Granot et al., 2008).
Future medical management may include a combination of Psyllium and Magnesium Sulphate (MgSO4), which was found by Niinistö et al (2018) to be superior than psyllium.
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· Niinistö, K.E., Ruohoniemi, M. O., Freccero, F. and Raekallio M.R. (2018) Investigation of the treatment of sand accumulations in the equine large colon with psyllium and magnesium sulphate, Equine Veterinary Journal, Vol 238, pp: 22-26
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· Specht TE, Colahan PT. (1988) Surgical treatment of sand colic in equids: 48 cases (1978–1985). J Am Vet Med Assoc; 193:pp. 1560–1564.
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