Identifying abdominal emergencies on radiographs and sonograms (part 2) (Proceedings)
Abdominal, non-GI issues are frequent in the ER and assessment of these cases typically involves imaging, radiographs and/or ultrasound. While obtaining abdominal radiographs is a common and somewhat uncomplicated occurrence, interpretation of abdominal radiographs is anything but. Of all the imaging modalities, radiographs are the most ubiquitous and most difficult to interpret. Radiographs have poor contrast and spatial resolution when compared to ultrasound and CT but there are certain subtle radiographic principals, or roentgen findings, that should not be missed in an ER situation. Ascites is a common, and sometimes challenging finding, on radiographs. Retroperitoneal fluid can also be missed due to its infrequent occurrence.
While emergency GI cases may benefit from either radiographs or ultrasound, non-GI ER cases typically benefit more from an abdominal ultrasound. Ultrasound is typically more rewarding than radiographs when ascites, retroperitoneal fluid or a mass is present. In cases of scant or mild ascites or when masses are present ultrasound can be used for both imaging and sample collection.
Mass vs. Mass effectWhile the difference between a mass and mass effect is an easy concept, the two are commonly incorrectly used interchangeably. A mass is defined by a space occupying lesion where borders can be visualized. A mass effect is defined by a space occupying lesion where borders cannot be visualized.
Ascites/ retroperitoneal fluid
On radiographs a scant amount of fluid in the peritoneal or retroperitoneal space can be identified by visualizing a wispy or web like pattern either between the liver and spleen, on the lateral view, or caudal to the kidneys. On ultrasound and with the patient in dorsal recumbency fluid pockets in the craniolateral "gutters" or lateral to the splenic body. The region lateral to the spleen is the most likely location to obtain a sample.
All abdominal organs can be affected by similar pathology however the presentation of this pathology can differ by organ. For instance a splenic laceration or rupture will have a much different appearance than a urinary bladder rupture due to fluid type. Urinary bladder rupture typically results in chemical peritonitis which can cause the small bowel to have a corrugated appearance. Besides laceration or rupture abdominal organs can be affected by infection or neoplasia. Parenchymal abscessation can be a life threatening condition with subtle radiographic changes. Identifying parenchymal gas is an important skill. Lastly, the spleen and liver lobes can become torsed leading to congestive organomegaly. While liver and splenic torsions have a non-specific appearance on radiographs, their appearance on ultrasound is more characteristic. The congestion or increase in fluid within the affected region results in a hypoechoic and characteristic "starry night" appearance.