**Abstract**

Intraoperative ultrasound (IOUS) in colorectal surgery can be used both in benign and in malignant lesions. In benign cases, such as Crohn's disease and diverticulitis, it can orient toward the extension of the surgical intervention. In malignant cases, such as colorectal cancer with liver metastases, IOUS/CE-IOUS (contrast-enhanced) improved the intraoperative management of liver metastases by dictating the resection margins in relation to the tumor extension. The IOUS method allows for exact tumor location, intestinal wall visualization, and malignant tumor penetration. The IOUS revealed the tumor and its margin in rectal lesions, making the sphincter-sparing operation easier to perform. In patients with small polyps and early colon and rectum cancers, IOUS works well as a one-of-akind intraoperative localization technique. In comparison with IOUS, CE-IOUS offered better detection and resection guidance. Intraoperative ultrasound enables surgeons to easily localize small, non-palpable lesions of the large bowel. Furthermore, it can determine even the aggressive potential of these lesions with high precision.

**Keywords:** colorectal, intraoperative ultrasound, laparoscopic ultrasound, colorectal surgery, robotic ultrasound

## **1. Introduction**

Intraoperative ultrasound is a complex and highly interactive imaging study field that is one of the ultrasonography's fastest growing fields. Intraoperative ultrasound has a wide spectrum of uses, which are expanding all the time.

Intraoperative ultrasound is used effectively in neurosurgery to operate on the brain and spinal cord, and it is mostly used in intra-abdominal surgery to operate on the liver, biliary tract, and pancreas.

Intraoperative vascular surgical disease assessment and intraoperative ultrasound imaging can also guide endarterectomy interventions. In patients with colorectal liver metastases, liver resections with negative margins increase survival (CRLM).

Intraoperative ultrasound (IOUS) is a useful tool that provides information about liver lesions, allowing surgeons to adjust their surgical technique to ensure total removal and, as a result, increase disease-free survival (DFS). Another important use of intraoperative ultrasound in colorectal surgery is to localize lesions at the level of the colon and of the rectum in order to properly adjust the extension of the resection (**Figure 1**).

**Figure 1.** *Intraoperative monitor of ultrasound and various types of ultrasound probes.*
