On the other hand if the rate of ingestion over a period of time outweighs the rate of sand passage the horse begins to accumulate sand within the colon. Once this accumulation begins there is a likelihood that the sand will impair motility within the colon and additional accumulation will ensue. If no sand is detected using this test method one must then wonder if the horse is accumulating sand, because none of it is being passed in the feces. If very large quantities of sand are detected within the feces one can assume that the horse does have a sand problem. So although this test is used, the results are often hard to interpret and should always be scrutinized.
The second method, which is most commonly performed by a veterinarian, is to listen for sand in the colon. Utilizing his stethoscope your veterinarian can listen to the contractions of the colon within the abdomen and under certain conditions can actually hear the sound of sand moving within the colon. When the veterinarian discovers this sound and diagnoses a sand condition the results are reliable. Where this method encounters a shortcoming is when the sound is not detected, yet there is actually sand within the bottom of the colon. This can occur if the sand load is not moving either because the sand has impaired motility of the colon itself or the normal motility within the colon does not have the force to move the sand and thus create the sound.
The two methods that are completely reliable for sand detection are not readily accessible and are quite expensive. The first method is to radiograph the abdomen and diagnose the sand load based upon the radiograph results. Equine abdominal radiographs must be performed in a hospital or clinic, with a radiograph generator that is powerful enough to penetrate the equine abdomen. Although this method is non-invasive it is inconvenient and incurs considerable expense. The last method is not only impractical for many reasons, but it is also invasive and expensive. Exploratory abdominal surgery although totally reliable in detecting sand, is only chosen when a horse ill enough to undergo colic surgery to relieve the condition.