How to Perform a Transrectal Ultrasound Examination of the Lumbosacral and Sacroiliac Joints

There is increasing interest in pathology of the lumbosacral and sacroiliac joints giving rise to stiffness and/or lameness and decreased performance in equine sports medicine. Pain arising from these regions can be problematic alone or in conjunction with lameness arising from other sites (thoracolumbar spine, hind limbs, or forelimbs). Localization of pain to this region is critically important through clinical assessment, diagnostic anesthesia, and imaging. In general, diagnostic imaging of the axial skeleton and pelvis is difficult to perform and to interpret. Radiography is infrequently performed. To obtain good-quality diagnostic radiographs, general anesthesia, a high-output radiographic generator, and special techniques must be performed. Variation in the size and shape of the sacroiliac joints and sacral wings and caudal sacral osteophytes are common; special techniques for taking radiographs have allowed for identification of these structures and the inter-transverse joints. These authors urge caution in the interpretation of lesions identified on radiography in the absence of other diagnostic imaging and clinical examination. Nuclear scintigraphy is an important component of work-up for sacroiliac region pain, but limitations exist. Several reports exist detailing the anatomy and technique findings in normal horses and findings in lame horses. Patient motion, camera positioning, and muscle asymmetry can cause errors in interpretation. In normal horses, the appearance of the sacroiliac region varies with age but is generally symmetric. In horses with sacroiliac problems, it is more difficult to distinguish the tubera sacrale from the sacroiliac joint than in normal horses, and, in horses with lameness, there is more asymmetry detected. Techniques for percutaneous and transrectal ultrasound examination have been described, and