How Much Sand Is Too Much? A Weight-Based Radiographic Cut-Off for Equine Sand Enteropathy

Radiographic area of large intestinal sand accumulation in horses may determine clinical significance

I. G. Entwisle; D. P. Byrne; G. D. Lester; E. J. McConnell

Background

Sand enteropathy is a common cause of gastrointestinal disease in horses, particularly in sand-rich environments. Although radiographic detection of intestinal sand is frequently used in clinical practice, the presence of sand does not invariably result in clinical disease. Prior radiographic scoring systems are largely subjective and do not account for horse size, limiting their clinical utility. The aim of this study was to establish a weight-indexed radiographic cut-off for large intestinal sand accumulation that differentiates clinically normal horses from those with clinically significant sand enteropathy.

Methods

This cross-sectional study compared abdominal radiographs from 70 clinically normal horses and 57 horses diagnosed with clinical sand enteropathy. Left lateral radiographs of the cranioventral abdomen were reviewed, and sand accumulation was quantified by manually tracing the sand area (cm²) using region-of-interest software. Sand area was indexed to body weight (cm²/kg). Receiver operating characteristic (ROC) curve analysis was used to determine the optimal weight-adjusted cut-off value to distinguish clinically relevant sand enteropathy from incidental sand accumulation.

Results

Sand was present radiographically in 61% of clinically normal horses, but the median sand area was small (1 cm² per 100 kg). Horses with sand enteropathy had substantially larger sand burdens, with a median of 118 cm² per 100 kg. ROC analysis identified a cut-off value of >21 cm² per 100 kg as optimal for diagnosing clinical sand enteropathy, yielding a sensitivity of 98.25% and a specificity of 92.54%. The area under the ROC curve was 0.9935, indicating excellent discriminatory performance.

Limitations

Limitations included the retrospective identification of clinical cases, lack of prospective follow-up of control horses, and differences in breed distribution between groups, with greater representation of pony and miniature breeds in the sand enteropathy cohort. Radiographic density and potential magnification effects were not evaluated, which may have influenced area measurements.

Conclusions

A weight-based radiographic cut-off of >21 cm² per 100 kg effectively differentiates clinically significant sand enteropathy from incidental sand accumulation in horses, with excellent sensitivity and good specificity. This objective, size-adjusted threshold may improve clinical decision-making by helping veterinarians determine when radiographically detected sand is likely to be of clinical consequence and warrants treatment.

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