Naturally occurring large colon sand accumulations and their medical treatment in horses

Problems related to equine large colon sand accumulations have been known for at least a century, but evidence-based medicine on the subject remains scarce. The current medical treatments are largely based on case reports and small studies on research horses with artificial sand accumulation or without confirmed accumulation. Therefore, clinical studies on naturally acquired sand accumulation are needed. The main objectives of the present studies were to define clinical signs related to the presence and size of large colon sand accumulations and to determine the optimal way to medically treat horses with these accumulations. A questionnaire study was performed to determine whether certain clinical signs are linked to the amount of sand in the colon and to clarify associations between equine large colon sand accumulations and individual traits and management-related factors. Owners or caretakers of 447 horses that had been radiographed for suspected large colon sand accumulation, responded to an internet based survey on clinical signs and management of their horses. The most common clinical signs of large colon sand accumulation noted by the owner were colic, poor performance and changes in faecal consistency (diarrhoea, increased faecal water). Colic (odds ratio (OR) 2.03, confidence interval (CI) 1.42-2.91) and poor performance (OR 1.89, CI 1.33-2.68) alone were associated with the size of sand accumulation. Horses with combinations of clinical signs, such as diarrhoea and poor performance or colic and diarrhoea also had a higher probability of a large sand accumulation; OR 2.12, CI 1.42-3.44 for diarrhoea and poor performance, and OR 2.64, CI 1.69-4.13 for colic and diarrhoea. Dominant position in the herd was protective for large colon sand accumulation (Spearman rho 0.170, P=0.002), while greediness predisposed the horse to the condition (Spearman rho 0.184, P<0.001). No significant association was detected between the studied management-related factors and large colon sand accumulation. A retrospective clinical study compared the effectiveness of medical treatment of large colon sand accumulation with nasogastric intubation of psyllium and/or magnesium sulphate (MgSO4) (both 1 g/kg bodyweight (BW) once a day for 4 to 7 days, N=170 horses) with feeding psyllium (1 g/kg BW for 2 to 5 weeks, N=57 horses). The daily administration of psyllium and MgSO4 in hospital via a nasogastric tube removed the sand accumulation more efficiently than multiple weeks of feeding with psyllium alone (P<0.05). This finding raised the need to examine the effect of psyllium and MgSO4 further, using a comparative approach in a randomised prospective study. Based on the results of the aforementioned retrospective study, it was hypothesized that the combination treatment with psyllium and MgSO4 would remove more sand than either treatment alone, or no treatment. The effect of psyllium (1 g/kg BW, N=12) or MgSO4 (1 g/kg BW, N=10) alone or combined (1 g/kg BW each, N=12) was evaluated prospectively in hospitalized horses with naturally acquired sand accumulation treated utilising nasogastric intubation once a day for four days. There were significant differences between treatments. The combination of psyllium and MgSO4 removed accumulations over a four-day period more effectively than either medication alone (number of resolved horses: P=0.012 for psyllium, and P=0.03 for MgSO4, respectively). Of 12 horses treated with a combination of psyllium and MgSO4, nine fulfilled the pre-determined criteria for clearance of sand from the ventral colon within four days. In contrast, only 3/12 horses treated with psyllium and 2/10 horses treated with MgSO4 cleared the sand accumulation. Furthermore, the effects of combination of 1 g/kg BW psyllium and 1 g/kg BW MgSO4 in 20 horses were compared with 20 untreated, hospitalized control horses that were solely removed from the sand source. After four days, the treated horses had cleared their accumulation (median area of sand decreased from 250 cm2 to 0 cm2) significantly more (P<0.001) than the control horses (median area of sand decreased from 285 cm2 to 176 cm2). In conclusion, large colon sand accumulations should be considered a differential diagnosis not only when colic, poor performance or changes in faecal consistency are seen, but also when the horse presents with combinations of various clinical signs. The most effective treatment to remove sand accumulations that had developed naturally in the population studied was repeated nasogastric intubation of psyllium and MgSO4.