Although the use of intraoperative radiology, such as intraoperative cholangiography, began in the 1930s, the first use of intraoperative ultrasound was not until the early 1960s. Early use of ultrasound in the operating room utilized A-mode imaging (see Chap.​ 2), which consisted of one-dimensional amplitude spikes on a display screen. Schlegel and colleagues [1] introduced A-mode ultrasound to locate renal calculi during nephrolithotomy in 1961. Following this, other investigators used ultrasound in the operating room to locate biliary stones. The initial clinical report was by Hayashi and colleagues [2], followed by Knight and Newell [3]. Despite these reports, the use of ultrasound in the operating room did not gain widespread acceptance due to challenges in understanding and interpreting A-mode imaging.

By the 1970s, A-mode imaging had given way to the development of real-time brightness, or B-mode, imaging (see Chap.​ 2), which is the more familiar ultrasound used today. This refined imaging overcame the difficulties of previous technologies, given its real-time and two-dimensional image advantages. The initial reports of this ultrasound technology were in the mid- to late 1970s, when Cook and Lytton [4] reported the intraoperative detection of renal calculi and Makuuchi et al. [5] reported the intraoperative localization of liver tumors. The less-complicated image interpretation of this B-mode imaging led to A renewed interest in intraoperative ultrasound. Despite this, acceptance of intraoperative ultrasound was still slow in the 1980s.

In 1989, Machi and Sigel reported a 10-year experience in operative ultrasound during 2,299 abdominal (including liver, pancreas, biliary, gastrointestinal, kidney), thoracic, cardiovascular, neurologic, and endocrine operations [6]. Intraoperative ultrasound was deemed useful in 91.5 % of cases. In a subsequent report, Machi and colleagues wrote specifically on their experience in 357 hepatic, 735 biliary, and 242 pancreatic cases [7]. In this follow-up report, they found the sensitivity, specificity, and accuracy in diagnosing colorectal liver metastases to be 93, 95, and 94 %, respectively, and in diagnosing common bile duct stones to be 92, 99, and 99 %, respectively. Furthermore, intraoperative ultrasound of the pancreas was found to be beneficial in 73 %. With increasing numbers of reports focusing on the advantages and benefits of intraoperative ultrasound, such as those by Machi and Sigel [6, 7], the use of ultrasound became more widespread and accepted. By the mid-1990s, surgeons had recognized the value of ultrasound during certain procedures and real-time B-mode imaging was applied routinely for various operations including liver, biliary, pancreatic, endocrine, and vascular surgeries. Even with the improvement of preoperative imaging in the new millennium, such as multidetector computed tomography and magnetic resonance imaging, intraoperative ultrasound remains a necessary and indispensable tool of the abdominal surgeon [8–15].

Realizing the value of surgical ultrasound is fundamental to motivating the surgeon to train for proficiency in performing, interpreting, and utilizing ultrasound in practice. While the challenge of training on a different imaging modality may seem formidable, it should be recognized that this situation is in no way unique. Surgeons routinely use techniques that require special training and time to master. Although the learning curve in ultrasound may appear steep, a surgeon’s knowledge of three-dimensional anatomy enables his/her understanding of ultrasound images and thus the slope of the curve is lessened.

The main obstacle to overcome in incorporating ultrasound into a surgical practice is the difficulty in obtaining sufficient training in ultrasound. For those in training, ultrasound may be integrated within surgical residency and fellowship programs. However, for surgeons in practice, a formalized curriculum and consistent practice are paramount. Formalized training in surgical ultrasound can be obtained through the American College of Surgeons and, most recently, through the Americas Hepato-Pancreato-Biliary Association. Practical application following observational experience is extremely important to gaining skill in ultrasound. According to Machi and Sigel with their colleagues, the learning curve for intraoperative ultrasound depends on the purpose of intraoperative ultrasound, the target organ of interest, and the complexity of the imaging procedure [7]. They suggest that about 25 ultrasound examinations are required to overcome the learning curve for screening for colorectal liver metastases. Similarly, about 25 examinations are required for screening for bile duct stones. As ultrasound guidance procedures require two-handed skill, a greater number of examinations are needed. For ultrasound guidance operations, for example, about 25–40 pancreas and 50 liver examinations/procedures are needed. In Chap.​ 20, training issues are reviewed in detail.