Presentations

Abstract

Introduction: The "jumping deer sign" is a finding on liver ultrasonography representing normal anatomic relationships of often confusing tubular structures within the liver parenchyma. The structures that make up and are identified as parts of the jumping deer sign include the portal vein and its primary branches, the gallbladder, and the IVC. Signs and other memory or pattern recognition heuristics are essential to identifying and characterizing pathology. Just as important, but much rarer, are those reassuring signs, whose presence is reassuring rather than frightening. The "jumping deer sign" is one such sign when evaluating for liver conditions that may distort adjacent structures.

Main Body: The portal vein and its primary branches comprise the head and body of the jumping deer. The anatomy of the portal venous system can vary widely, which often leads to misinterpretation and being erroneous mistake with intrahepatic ducts or systemic veins and vice versa. Accurately distinguishing portal veins from bile ducts is crucial for evaluating conditions such as portal hypertension, primary biliary cholangitis, and primary sclerosing cholangitis. Portal hypertension can be detected intrahepatically on ultrasound by identifying a dilated portal vein or hepatofungal (reversed) blood flow in the portal vein. Conversely, liver pathologies involving the intrahepatic biliary ducts may present with distinct sonographic features, including intrahepatic ductal dilatation and thickened ductal walls. Identifying these pathologies requires thorough understanding of and ability to identify normal anatomy. Finding the jumping deer sign on ultrasound can help confirm the veracity of presumed anatomical structures and reduce the risk of confusing portal veins with dilated ducts. As the "deer" leaps forward over the "log", it is trailed by its bushy, somewhat bulbous tail, a structure that is in reality the gallbladder. Ultrasound is a highly effective imaging modality for detecting gallbladder pathologies. It is often the first choice due to its accessibility, non-invasiveness, and ability to provide detailed images of the gallbladder and surrounding structures. Emphysematous cholecystitis is an often life-threatening condition, with a mortality rate of up to 25%, caused by gas-forming bacteria infecting the gallbladder wall. This condition may present as echogenic foci with posterior dirty shadowing or reverberation artifacts within the gallbladder wall. Unfortunately, this is very similar in appearance to bowel gas, with posterior shadowing obscuring detail behind said gas and potentially leading to confusing one for the other. Identifying the normal anatomy, made easier by seeing the jumping deer's tail, may help differentiate emphysematous cholecystitis from bowel gas. Furthermore, a "clipped tail" in the ultrasound image may suggest a cholecystectomy, particularly if surgical clips are visible in the area where the tail would normally be. Finally, the obstacle over which the "deer" can be seen jumping over is, in reality, the inferior vena cava (IVC). Measurement of the IVC using ultrasound is a valuable tool for assessing hydration status, especially in critically ill patients. The size and collapsibility of the IVC can provide insights into intravascular volume and right atrial pressure. A distended, non-collapsible IVC may indicate fluid overload or elevated central venous pressure (CVP), which is often seen in conditions such as heart failure. Conversely, a small, collapsible IVC usually suggests low intravascular volume and hypovolemia. Therefore, assessing IVC collapsibility is crucial for management decisions. A recent study found that sonographic IVC diameter measurements are accurate and correlate well with direct CVP measurements made by catheterization, which had previously been the gold standard. These results suggest that sonographic IVC measurement could potentially replace more invasive techniques. Easy and rapid identification of the IVC in a window not obscured by bowel gas, such as that offered intrahepatically via the jumping deer sign is therefore very advantageous in the management of acutely ill patients.

Conclusion: In conclusion, the "jumping deer sign" offers a unique and valuable framework for interpreting liver ultrasonography, enhancing diagnostic accuracy and reducing potential misinterpretations of liver anatomy. By recognizing the portal vein, gallbladder, and inferior vena cava, clinicians can better distinguish between normal anatomical variations and pathologic conditions. Overall, the "jumping deer sign" demonstrates the utility of pattern recognition in ultrasound, offering both clarity and reassurance in the complex field of liver imaging.