Intraoperative Ultrasound of the Liver - An Overview

Introduction

Intraoperative ultrasonography (IOUS) has been extensively employed in hepatic surgery for diagnostic and therapeutic interventions. Intraoperative ultrasound (IOUS) is a medical imaging technique that enables direct-contact visualization of the target organ, offering a high spatial resolution level while minimizing potential disruptions from neighboring anatomical structures. Hence, intraoperative ultrasound (IOUS) can enhance the identification, classification, precise positioning, and assessment of hepatic neoplasms. It offers interactive information and important guidance throughout various medical operations.

What Is the Procedure for Performing IOUS?

IOUS allows intraoperative diagnosis and treatment of focal hepatic lesions because of its real-time imaging. If IOUS detects a suspicious hepatic lesion, IOUS-guided biopsy can validate the extrahepatic malignancy's resectability and estimate the degree of hepatic resection.

• IOUS is commonly performed after partial hepatic mobilization and ligament incision as needed during hepatic surgery.

• Hepatic mobilization is necessary to make the lesion accessible and scan the liver well, but it can distort the hepatic anatomy, making it difficult for inexperienced radiologists to determine it.

• IOUS of the liver is usually done by placing the ultrasound probe directly on the liver so subcutaneous fat, intestinal gas, and ribs do not degrade picture quality.

• Low-frequency convex probes can also be used in IOUS to provide a general image of the liver and detailed information on the relationship between hepatic focal lesions and other structures, including main arteries and neighboring organs.

• Thus, different probes or combinations must be used in IOUS depending on the principal indications. Because liver visibility is important, a lower-frequency convex probe may be used to check for new hepatic focal lesions not discovered in preoperative imaging investigations.

• Preoperatively identified hepatic focal lesions with IOUS may be hard to locate during surgery due to anatomical displacement. A lower-frequency probe can scan a large area to discover the target lesion, including anatomical markers like the hepatic veins and non-target lesions like cysts. After identifying the target lesion, a linear probe with greater frequency can give excellent spatial resolution for lesion characterization.

What Are the Various Applications of IOUS?

Interventional Operating Room Ultrasound (IOUS) has many applications to enhance surgical decision-making, provide guidance during surgical procedures, and ultimately enhance patient outcomes. Below are typical instances of its utilization:

• Determining the Lesion’s Stage: Hepatic lesions are already identified to establish the severity of the known disease and examine the proximity of the lesions to important structures such as the hepatic and portal veins. This approach for primary liver tumors can facilitate staging.

• Preoperative Imaging: The identification of hidden lesions that were not found during preoperative imaging. Preoperative computed tomography (CT) or magnetic resonance imaging (MRI) may fail to detect subcentimeter metastatic lesions. These factors' numerical values and geographical positions can influence the surgical strategy—the reported sensitivity of Intraoperative Ultrasound (IOUS) for detecting hepatic lesions.

• Operative Planning: Operative planning involves considering that resection planes may not align with anatomic segments. Consequently, it is crucial to accurately define the mass and its proximity to hepatic or biliary pedicles to provide sufficient drainage of hepatic veins and bile. Several investigations have demonstrated that Intraoperative Ultrasound (IOUS) can modify the surgical strategy in a range where the initial plan was established using preoperative imaging.

• The selection of specific lesions for biopsy. If an unforeseen lesion is detected during a surgical procedure, intraoperative ultrasound (IOUS)-)-guided biopsies can assist in ascertaining the subsequent course of action.

• The precise localization of lesions facilitates therapeutic ablation procedures, specifically utilizing microwave or cryotherapy techniques. The management of metastatic disease, such as colorectal liver metastases, often necessitates the utilization of a multimodality therapeutic strategy to attain the most effective disease control.

What Role Does Intraoperative Ultrasound Play in the Treatment of Liver Diseases?

Ultrasound is primarily used to diagnose and evaluate liver tumors, such as colonic metastasis. Intraoperative ultrasound can be utilized during both open and laparoscopic procedures; each technique has its probe. The ultrasound image of liver tissue is obscured when the probe is placed directly on the liver without interfering with the epidermis and abdominal wall.

Utilization of IOUS in various diseases:

1. Benign liver conditions.

2. Cancerous liver tumors.

Non-malignant Liver Disease: The liver is a vital intra-abdominal organ involved in various diseases that originate in the liver itself or another part of the body and involve the liver, such as hepatic metastasis of cancer. Imaging modalities such as ultrasound, computed tomography, and magnetic resonance imaging are utilized to diagnose benign liver diseases.

What Are the Different Types of Non-malignant Liver Lesions?

The use of IOUS altered the therapy of various benign liver lesions.

• Liver Hydatid Disease: Liver hydatid disease, also known as hepatic hydatidosis (hydatid cysts, which are larval stages of cestodes from the genus Echinococcus, are responsible for the occurrence), is a parasitic infection caused by the larval stage of the tapeworm Echin.

1. Surgery for hydatid liver disease employs intraoperative ultrasound.

2. Once the abdomen is opened, manually examine the liver to determine the location of the cysts.

3. To determine the number of cysts, a T-shaped ultrasound instrument was sterilized, and the liver was examined by a team of surgeons who performed IOUS and ultrasound examinations.

Intraoperative ultrasound is superior and more informative than CT and MRI for hepatic hydatid disease, and it is useful for the following:

1. Cyst localization is relative to the main blood vessels and the bile duct.

2. Assist in planning hepatotomy to reach lesions located deep within the liver.

3. Pair technique for aspiration and injection of deep-seated lesions.

4. IOUS is used to conduct the operation on the patient and to remove the offspring cysts from the bile duct after the common bile duct is opened. As the endocyst is removed, the residual cavity collapses, as observed by IOUS.

• Hepatic Cysts: Hepatic cysts are fluid-filled sacs that develop within the liver. Intraoperative ultrasound identifies and investigates the relationship between benign liver cysts, which can be acquired in the bile duct and blood vessels.

• Liver Pustule/Abscesses: Liver abscesses are a pathological condition characterized by the formation of pus-filled cavities inside the liver; intraoperative ultrasonography can assist in localizing and aspirating (the act of producing a strong burst of air) the infection.

• Liver Cancers

1. Liver cancers, often known as hepatic cancers, refer to malignant tumors that originate in the liver.

2. IOUS is a great tool for staging primary liver tumors and hepatocellular carcinomas, helping to find any little lesions.

3. In the cirrhotic liver, it is highly beneficial to determine the extent of the lesion and the relationship between the lesion and the blood vessel.

4. Using contrast-enhanced ultrasonography makes it more beneficial.

5. With the use of IOUS, limited liver tumor resection can be performed in a non-segmental manner. It will improve patient survival, particularly in a patient with hepatocellular carcinoma and a history of chronic liver disease characterized by progressive destruction.

6. It helps in the removal of a portion of liver malignant tumors and will improve patient survival by taking safe liver resection.

7. In a fatty liver, IOUS can have trouble picking up on minor liver lesions; contrast-enhanced ultrasonography will be more beneficial in this situation.

What Are the Applications of Intraoperative Ultrasound (IOUS) In the Context of Hepatic Malignant Tumors?

When combined with interventional ultrasound for liver reconstruction, the IOUS scan for malignant liver lesions enhances outcomes. It helps determine the tumor's size and proximity to large blood vessels and the bile duct.

• Liver Lesion Biopsies: IOUS is used during colonic tumor primary surgery; this procedure is discovered to provide more details about the tumor's stage. It is more effective than ultrasound and CT scanning medical procedures.

• Transplanting a Liver:

1. A liver transplantation procedure involves the surgical removal of a liver that is afflicted by disease or damage, followed by the replacement of the impaired organ with an organ that is normally functioning.

2. It is employed to harvest the liver and monitor the integrity of blood vascular anastomosis.

Conclusion

Ultrasound is often used to diagnose liver ailments traditionally treated with ultrasound. Using IOUS for liver disease would alter treatment; it is used to treat hydatid liver disease, liver cysts, bile duct stones, and tumors. During surgery, it can replace cholangiography (a medical imaging technique used to visualize the bile ducts within). IOUS offers better liver involvement information than ultrasound, CT scan, or MRI; it shows small lesions that other modalities may miss; it helps outline the resection line when liver resection is planned; it shows blood vessel-lesion relationships; it shows bile duct anatomy; and it can replace intraoperative cholangiogram. IOUS liver surgery is expensive and may not be possible in resource-constrained hospitals. There has been a growing interest in contrast-enhanced intraoperative ultrasound (IOUS), IOUS elastography, and IOUS-guided hepatic surgery to diagnose liver disease.