Ultrasound-guided renal and hepatic biopsy techniques.

Diagnostic ultrasound is an easy, accurate method of locating both kidneys and liver in the horse. Good contact between the transducer and body wall is essential for clear, precise images. The greatest limitation to ultrasonic organ localization and biopsy guidance is the inability of ultrasound to transmit through gas-filled structures and bone. These structures act as barriers to sound-beam penetration and prevent visualization of soft-tissue structures deep to them. Organ parenchyma can be evaluated with ultrasonography. Focal and/or diffuse lesions can alter the normal parenchymal pattern and result in an increased or decreased echogenicity of the diseased area. Under ultrasound guidance, the biopsy instrument can be directed into these areas to insure that the sample is representative of the disease process within that organ. Biopsy-associated complications can be identified early and monitored until resolution. Equine renal and hepatic biopsies are not innocuous procedures, but ultrasonographic guidance has helped to reduce the risks involved with the biopsy techniques.