Abdominal Ultrasound: Case Discussions
Takayoshi Miyabayashi Japan
In this presentation, real-time ultrasound clips are used to illustrate abnormal appearances of abdominal organs. In addition, interventional methods such as fine needle aspirate and ultrasound guided biopsy techniques are demonstrated. Guidelines for ultrasound guided or directed interventional procedures are summarized as follows:
Tissue Sampling Procedures
Tissue sampling methods include fine needle aspirate and biopsy. Both can be done through an ultrasound guide. However, with experience, most operators prefer to perform the procedure as a free-hand technique.
Fine needle aspirate
Fine needle aspirates can be done using a variety of needles. Commonly, a 22-gauge or 25-gauge hypodermic needle (one inch length) is connected to a 5 or 6 mL syringe. Sampling of deeper tissue is more difficult and often requires use of a long spinal needle.
In most cases, sedation is not necessary but certainly facilitates good sampling. The area of the aspirate should be cleaned with alcohol. The skin surface should be kept as flat as possible. The needle is inserted in a tissue or organ under real-time ultrasound guidance. The operator should make sure that the ultrasound probe and needle insertion plane remain parallel. As the needle is advanced, the tip should be always visible. If the needle tip is not visible, the plane should be re-examined. It is helpful to look down the transducer and needle to see if the planes match.
There are different aspiration techniques. In a solid tissue, a negative pressure exerted by a syringe is necessary to gain samples. However, some prefer to insert a needle into the area of interest to sample the tissue. This method is often rewarding in case of congested organs or blood-rich lesions. To prevent blood clotting, cytology slides should be made immediately. Fine needle aspirate does not carry a severe risk; however, it is advisable to check blood-clotting factors prior to the procedure.
Tissue core biopsy
This procedure carries somewhat of a risk. Patient selection should be carefully assessed. In some cases, surgical or laparoscopic biopsy may yield more information than ultrasound-guided core biopsy. This is a sterile procedure, and the area of the biopsy should be prepared accordingly. Hemorrhage is certainly a common complication. Blood clotting tests should be utilized to screen potential problems.
A skin incision is needed to make sure that the biopsy needle moves freely. The peritoneum can then be penetrated easily by the biopsy needle. There are many needles in the market. It is imperative to use automatic types rather than manual types. The manual types increase the chance of complications and do not usually yield a core sample.
For an inexperienced operator, it is a good idea to use a guide. The guide may not show the actual needle path during the procedure; however, a free hand technique has so many factors that can go wrong. It is much safer to use the guide than the free-hand procedure.
One should limit the number of attempts. If you cannot get a sample after two or three attempts, the procedure should be aborted. The obtained core sample should be immediately placed in an appropriate fixation fluid. In addition, care should be taken not to loose a small sample. We use a plastic cassette with sponge inserts. Both sponges are wet with the fixation fluid prior to closing, making it easy for the histology technologists to remove the sample.
The area of the biopsy should be re-examined immediately after the procedure for potential bleeding. If bleeding is suspected in next few hours, the area should be re-examined.
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