What’s Your Abdominal Diagnosis?

Interpretation of radiographs can be challenging. Many factors are involved, but these steps all relate to one central idea ... be systematic. It begins with production of good quality radiographs, moves to detection of radiographic abnormalities, coalesces into creation of differential diagnoses and a radiographic diagnosis and concludes with a plan for achieving a definitive diagnosis. Making quality radiographs involves correct radiographic technique. Using a technique chart that is tailored to your x-ray machine and film/screen combination or digital detector best facilitates this task. Proper patient positioning is important for consistent projection of anatomy. Even slight obliquity of structures may create a very different appearance of normal anatomy. A significant part of image interpretation is pattern recognition. To facilitate pattern recognition, images should be displayed in the same manner every time. A complete radiographic study has a minimum of 2 radiographic projections allowing for more precise localization of lesions. Making only one radiographic projection often leads to more questions than it answers. Viewing images in a dark room without extraneous light is ideal. A systematic approach starts with pattern recognition from which a list of differential diagnoses is derived. Next the list of differential diagnoses is prioritized based on signalment, physical examination findings, clinical data and other radiographic signs. Sometimes, the diagnosis is evident after this step, but often a plan must be formulated to arrive at a more definitive diagnosis. This plan may involve more imaging (contrast medium procedures, ultrasound, CT, MRI), additional lab tests or tissue aspirates/cytology. Without prioritization of the differential list, the correct plan for definitive diagnosis cannot be formulated. The ability to describe lesions will lead the interpreter to the correct conclusion. The best method for describing lesions is using Roentgen signs. The Roentgen signs are number, size, opacity, position/location, margin/contour, and shape. These signs should be described for all anatomy on the radiograph. Thankfully, most of the structures on a radiograph are normal and are usually not described. Next, each type of radiographic series is reviewed in a systematic manner to ensure that all structures are evaluated. Many methods for evaluating each study are available and should be tailored to the individual. A method for evaluating the thorax, abdomen and musculoskeletal system are provided below. Ideally, radiographs are interpreted without knowledge of clinical history. This helps avoid bias when interpreting radiographs. However, this is impractical for most veterinarians. One must be cautious and not try to make radiographs fit other clinical signs or laboratory data. Each set of radiographs record a disease process at one specific, short instant in time. Comparing the current radiographic study to any and all radiographic studies of the same patient helps establish trends. One can evaluate if a disease is improving, worsening or staying the same.