Use of transrectal transducers in abdominal ultrasonography of horses: A review

Abdominal ultrasonography is an important diagnostic tool in the evaluation of colic, yet primary care equine veterinary practitioners are often limited by availability and access to low-frequency (2–5 MHz curvilinear array or sector) abdominal transducers. Use of high-frequency (5–10 MHz linear array) transrectal transducers has not previously been compared with use of abdominal transducers for transcutaneous abdominal ultrasonography. One recent pilot study established that there was no significant difference in organ detection by the two transducers on the right side of the equine abdomen, but the stomach, liver and kidney on the left side were less likely to be detected using the transrectal transducer in healthy horses. A clinical study found that the transrectal transducer can be used successfully using the FLASH protocol in horses presenting with colic, with high-quality images that detected abnormalities of the peritoneal fluid, small intestine and large intestine. The transrectal transducer had decreased visualisation of the stomach and left kidney and was less likely to detect pathology surrounding these organs. This is the first series of studies to evaluate use of transrectal transducers in abdominal ultrasonography of the horse, a tool that is readily accessible to the field practitioner.