Intraoperative Ultrasonographic Imaging in Liver Surgery: A Review

The use of intraoperative US was first reported in the 1960’s but the technique was not widely adopted because equipment was difficult to use and the images difficult to interpret. In the early 1980’s, with refinements in equipment, intraoperative US finally became a useful diagnostic technique7-9. Using real time B-mode scanners it is possible to recognize the 3-dimensional nature of lesions and their relationship to the blood vessels of the liver as well as to identify small and previously undetectable lesions. The method is essentially simple and involves placing a sterile probe directly on to the liver surface. Sterile jelly or normal saline solution can be applied to enhance sound transmission but this is usually unnecessary unless the liver surface is irregular as it is in macronodular cirrhosis. There exists a blind zone of 0.5 to 1 cm depth below the liver surface which can best be visualized by placing a water cushion approximately 2 cm in height between the liver and the probe1. Placement of a bulky probe in the uppermost portion of the liver may be handicapped by limited space. To overcome this, small probes can be used or the incision may need to be extended and rarely even a thoracotomy may be required11. However, retractors which clamp to the table and allow the costal margin to be forcibly elevated will allow adequate exposure in most cases.