Many findings can be adequately interpreted based on their ultrasound features, whereas others will require additional studies. The leading criterion in the differential diagnosis of focal hepatic lesions is echogenicity.Ĭircumscribed changes in the liver parenchyma are often challenging for the sonographer. The posterior portions of the liver located farther from the transducer were already visualized through the subcostal approach. The areas located close to the chest wall and transducer are the areas that are poorly visualized in subcostal longitudinal, oblique, and transverse scans. When you have done this exercise, picture the portions of the liver that you have scanned. Stick to this routine in the beginning, even if it seems somewhat tedious. Next, move the transducer to the medially adjacent ICS and carefully repeat the process. Then slide the transducer cranially and caudally within the same ICS and repeat the sectoring maneuver. Define the liver, and angle the transducer to sector the scan through the accessible liver segment ( Fig. Take care to direct the scan plane parallel to the ribs. Place the transducer in a laterally and somewhat posteriorly situated intercostal space (ICS). 4b.įollow a three-step routine for intercostal scanning:ġ Scan through the liver in a fan-shaped pattern.Ģ Slide the transducer along the ICS and repeat step 1.Ħ Move the transducer to the next ICS, repeat steps 1 and 2. This scan corresponds to the section in Fig. 5 shows the appearance of a liver that is difficult to scan. You should keep this in mind if you do not achieve the desired result right away. 4 were selected to illustrate good scanning conditions. It can be helpful to have the patient breathe in deeply and inflate the abdomen. Visualization often becomes poor at this point, especially in obese patients and when there is interposed gas in the right colic flexure. As the transducer moves farther to the right, the angle of the inferior hepatic border becomes increasingly blunted ( Fig. With luck, the right kidney may also be seen. As you scan past the vena cava, the gallbladder can be identified as a “black” structure in the fasted patient. As you track across the abdomen, you will recognize the aorta and then the vena cava. Now return to the starting point and scan past it toward the right side. The image is now dominated by a chaotic pattern of highly contrasting light and dark areas with no discernible shape, caused by the gas and liquid contents of the stomach. Its roughly triangular outline becomes progressively smaller and finally disappears. You can do this by varying the pressure on the transducer as needed.Īs the transducer moves farther to the left, the cross section of the liver diminishes in size. Also, make sure that the inferior border of the liver stays at the right edge of the image. Now slide the transducer to the left, keeping it in a longitudinal plane while following the line of the costal arch as closely as possible. This should bring the sharp inferior hepatic border into view ( Fig. Press the caudal end of the transducer a bit more deeply into the abdominal wall than the cranial end, so that the scan is directed slightly upward. Place the transducer longitudinally on the upper abdomen, slightly to the right of the midline. This inferior border is easy to demonstrate with ultrasound. The liver tapers inferiorly to a more or less sharp-angled border. If there is intervening gas in the right colic flexure, have the patient take a deep breath to expand the abdomen. To define the inferior border of the liver in longitudinal sections, press the caudal end of the transducer a little more firmly into the abdominal wall than the cranial end.īy varying the pressure on the transducer, you can keep the inferior border of the liver at the right edge of the image. 3 illustrates the view of the liver that is acceptable for organ identification. Now ask the patient to take a deep breath, expanding the abdomen, and the liver will appear on the screen as a region of homogeneous echo texture. Mentally picture the liver lying beneath the ribs, and angle the scan upward. Start with the transducer placed transversely against the right costal arch, at the level where you would palpate the inferior border of the liver. One disadvantage of holding the breath is that it is followed by a period of hyperventilation, especially in older patients. Place the patient in the supine position and have him or her take a deep breath and hold it to expand the abdomen. To make the liver more accessible, have the patient raise the right arm above the head to draw the rib cage upward. Even so, he is unable to see the man sitting in one corner of the room. Moving from window to window, he views the center of the room several times and sees corners a total of five times. In this analogy, an observer is looking into a room through three windows.
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