Mobile Sonography
Ultrasonography is the second most commonly used imaging format in veterinary practice. Although ultrasound can be used to evaluate most soft tissues, including muscles, tendons, and ligaments, the heart and abdominal organs still constitute the majority of examinations performed in small animals. In scanning of the abdomen, the abdominal structures should be systematically evaluated. Each sonographer develops his or her own system of completely evaluating the abdomen. Systematic evaluation ensures that all structures are scanned. In the past organs such as the pancreas and adrenal glands were only seen if diseased and enlarged, but modern ultrasound machines operated by an experienced and skilled sonographer produce images of such quality that the normal pancreas, adrenal glands, and lymph nodes are routinely imaged even in large dogs.
Changes in size and shape of organs, tissues, and structures are evident in most cases, but evaluation of the echo pattern is based on comparison with that of other organs and tissues the examiner has scanned in other animals. The person evaluating the scan must have a firm idea, developed from experience and comparison with known normalcy, of the normal echo pattern of each organ scanned with each transducer. Comparison of the echogenicity of several tissues must be made, because any organ may have increases or decreases in the echogenicity of its parenchyma.
Diseased organs may be either uniformly altered or exhibit focal or multifocal changes. Focal changes are usually easier to detect than uniform changes. Sonographic lesions are sometimes quite characteristic of a given disease process, but more often the changes are nonspecific. Although ultrasonography can be quite sensitive to detection of disease, the changes are not specific for a given disease in most cases unless a characteristic change in anatomic presentation is detected along with changes in echogenicity.
Ultrasound technology has improved the ability of sonographic examinations to detect disease previously not well characterized by sonographic evaluation. Pancreatitis is a primary example. For many years, the pancreas was not considered an organ that could be evaluated with ultrasound, but evaluating it with ultrasound has become mainstay of assessing animals with suspected pancreatic disease. However, it does not always agree with clinical pathologic evaluation or physical examination. In some cases the physical examination and clinical pathologic data will suggest pancreatitis, but it is not detected on sonographic examination. This is probably due to the great difficulty of interrogating the entire pancreas using ultrasound. In other cases, chronic pancreatitis may be indicated by sonographic examination but poorly characterized by clinical pathologic data because of the chronic status of the disease.
Ultrasonography can also be used to direct biopsy instruments to acquire tissue for specific pathologic diagnosis. This often times obviates the need for an open surgical exploration. Lesions buried within large organs such as the liver and kidneys that might not be detectable at surgery may be detected and biopsied with ultrasonographic guidance. Presurgical diagnosis permits more thorough and specific planning of surgical procedures and presurgical treatment of lesions. These procedures can be safely performed under heavy sedation and analgesia.
