Procedural ultrasound 303 ultrasound for procedure

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Procedural ultrasound 303 Ultrasound for procedure guidance
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eight patients with fluid in the flank region, air-filled loops of bowel were interposed between the abdominal wall and the fluid collection. It was suggested that a blind approach could have injured the bowel. Overall, the investigators concluded that ultrasound is helpful for selecting the puncture site so as to avoid intraperitoneal structures during the paracentesis. A more recent study randomized patients to ultrasound-guided versus standard paracentesis. In patients where fluid was visualized, there was a 95% success rate in paracentesis, compared to 65% success without the use of ultrasound. Of the failed paracenteses in the landmark-based group, ultra- sound guidance found no fluid in two cases and was able to guide successful aspiration in all others [ 8 ]. Joint effusions and arthrocentesis Ultrasound is more accurate and reproducible than clinical evaluation for effusions [ 9 , 10 ]. There are multiple clinical situations where it is not obvious that there is an effusion. Ultrasound can not only assist in making this diagnosis but can also guide aspiration to ensure success. Focused questions 1. Is there a joint effusion? 2. Where is the optimal location for arthrocentesis? Anatomy In visualizing joints on ultrasound, recall that fluid appears anechoic, and bone will be a bright reflector with distal shadowing. Thus, in normal joint sonography, the intersection of two bones will appear as a V-shaped gap, sometimes referred to as the “seagull sign” ( Figure 16.8 ). Figure 16.8 Joint anatomy. Note the bright, crisp white lines delineating bone, and the V-shaped space (superimposed white lines) between adjacent bones creating the joint space. 304 Procedural ultrasound Ultrasound for procedure guidance
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Technique Probe selection Ultrasound of the joints should be performed with a high-frequency (5–10 MHz) linear probe. Special equipment A marking pen may be used. Setup Place the patient in a comfortable position (based on which joint is involved) for the procedure. Scan over the area in question to search for signs of effusion in the joint space. Using the bony landmarks discussed previously (the “seagull sign”) can be helpful if the superficial anatomy is obscured by edema or effusion. When an area demonstrating adequate fluid is located, mark the spot with a pen, and prep and drape the area in the usual sterile fashion. Procedure The rest of the procedure should be carried out using standard technique, being careful to maintain the same position used when mapping the fluid collection. In some cases it is useful to directly visualize the path of the needle from skin to joint. This is performed using an in-plane (long-axis) dynamic guidance approach as detailed in Chapter 15 .
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