Overview
Definition:
Segment 4A and 4B resection refers to the surgical removal of segments 4A and 4B of the liver, which are located in the anterior and superior portions of the liver, respectively
Segment 4A is part of the medial segment, adjacent to the falciform ligament, while Segment 4B is the superior portion of the medial segment
These resections are performed for various benign and malignant liver pathologies.
Epidemiology:
Hepatic resections, including those involving segment 4A/4B, are performed for a range of conditions, with hepatocellular carcinoma (HCC) being a significant indication, particularly in endemic regions of India
Other indications include colorectal liver metastases, cholangiocarcinoma, and benign liver tumors
The incidence of liver resections varies by geographic location and the prevalence of underlying liver diseases.
Clinical Significance:
Effective management of liver tumors and other pathologies often necessitates precise hepatic resection
Understanding the anatomy of segment 4A and 4B, their vascular supply, and biliary drainage is crucial for achieving adequate oncologic margins and minimizing morbidity
Successful resections improve patient survival and quality of life, making this a critical skill for surgical residents preparing for DNB and NEET SS examinations.
Indications
Malignant Tumors:
Hepatocellular carcinoma (HCC), cholangiocarcinoma, liver metastases (e.g., from colorectal, neuroendocrine tumors)
Consideration of tumor size, location, resectability, and patient liver function (Child-Pugh score, MELD score).
Benign Tumors:
Large or symptomatic hepatic adenomas, hemangiomas, or focal nodular hyperplasia when conservative management is not feasible or indicated.
Other Indications:
Liver abscesses not amenable to percutaneous drainage, focal hepatic trauma requiring resection, or for donor hepatectomy in liver transplantation (though less common for isolated 4A/4B segments).
Preoperative Preparation
Diagnostic Imaging:
Contrast-enhanced CT scan and MRI with hepatobiliary phase are essential to delineate tumor extent, vascular involvement, and relation to major vessels and bile ducts
Portal venography or CT angiography may be required.
Liver Function Assessment:
Comprehensive assessment of liver reserve using Child-Pugh classification and MELD score
Indocyanine green (ICG) retention test to evaluate hepatic functional reserve.
Nutritional Support:
Optimize nutritional status, especially in patients with chronic liver disease, to improve wound healing and reduce complications.
Informed Consent:
Detailed discussion with the patient and family regarding the risks, benefits, alternatives, and potential complications of the surgery.
Procedure Steps
Approach:
Laparoscopic or open approach
Laparoscopic surgery offers benefits of smaller incisions, reduced pain, and faster recovery but requires advanced expertise.
Vascular Control:
Identification and control of hepatic artery and portal vein branches supplying segment 4A/4B
Intraoperative ultrasound is invaluable for precise anatomy.
Biliary Dissection:
Careful dissection and identification of bile duct branches serving the segments to be resected
Ligation or reconstruction as needed.
Parenchymal Transection:
Use of harmonic scalpel, ultrasonic dissector, or advanced energy devices for parenchymal transection, with careful ligation of hepatic veins and arteries
Ligamentum teres and falciform ligament are key landmarks.
Hemostasis And Drainage:
Meticulous hemostasis
Placement of drains for monitoring and fluid collection
Intraoperative cholangiography may be performed to confirm biliary integrity.
Postoperative Care
Monitoring:
Close monitoring of vital signs, urine output, and fluid balance
Serial laboratory tests including liver function tests (LFTs), electrolytes, and coagulation profile.
Pain Management:
Adequate pain control using patient-controlled analgesia (PCA) or epidural anesthesia.
Enteral Nutrition:
Early initiation of enteral feeding as tolerated to promote gut integrity and recovery
Parenteral nutrition reserved for cases of prolonged ileus.
Complication Surveillance:
Vigilant monitoring for signs of hepatic insufficiency, bile leak (bilio-peritonitis), post-hepatectomy liver failure (PHLF), hemorrhage, infection, and DVT/PE.
Complications
Early Complications:
Postoperative bleeding, intra-abdominal hematoma or abscess, bile leak (biloma, cholangitis), hepatic insufficiency/failure, pleural effusion, atelectasis, pancreatitis.
Late Complications:
Biliary strictures, recurrent disease, incisional hernia, chronic pain, adhesions
Post-hepatectomy liver failure (PHLF) is a major concern and is graded based on ISGLS criteria.
Prevention Strategies:
Accurate preoperative assessment of liver function, meticulous surgical technique with precise vascular and biliary control, appropriate intraoperative fluid management, early mobilization, and judicious use of antibiotics.
Prognosis
Factors Affecting Prognosis:
Type and stage of the primary tumor, completeness of resection (R0 vs
R1/R2), patient's underlying liver health, surgical expertise, and management of postoperative complications.
Outcomes:
For benign conditions, outcomes are generally excellent
For malignant tumors, prognosis depends heavily on oncologic principles
Early stage HCC with adequate resection has good survival rates
Outcomes for metastatic disease depend on the primary tumor's behavior.
Follow Up:
Regular follow-up with imaging (CT/MRI) and tumor markers to detect recurrence
Frequency depends on the underlying pathology and stage of the disease
Liver function should be monitored long-term.
Key Points
Exam Focus:
Understand the segmental anatomy of the liver, particularly the boundaries and vascular supply of segments 4A and 4B
Know the indications for resection in common liver pathologies like HCC and metastases.
Clinical Pearls:
Preoperative assessment of liver function is paramount
Intraoperative ultrasound is essential for precise anatomical localization
Adequate hepatectomy margins are critical for oncologic outcomes
Consider laparoscopic approach for appropriate cases.
Common Mistakes:
Inadequate assessment of liver reserve leading to postoperative liver failure
Incomplete tumor resection due to poor understanding of segmental anatomy
Insufficient control of hepatic pedicle or veins leading to significant bleeding
Failure to identify and manage bile leaks.