The liver has a unique capacity for self-repair, allowing surgeons to remove a significant portion of it without causing permanent failure. This procedure, known as a partial hepatectomy or liver resection, is a common surgical approach for treating various liver diseases. Partial liver removal is only possible if the remaining tissue is healthy enough to sustain the body’s functions while it regrows. This regenerative ability makes liver surgery distinct from operations on most other solid organs.
The Unique Biology Allowing Partial Removal
The ability to safely remove a section of the liver stems from its regenerative capability, which is unlike any other solid organ. Following a partial hepatectomy, the remaining liver tissue begins to enlarge rapidly. This process is driven by hypertrophy, where existing cells grow in size, and hyperplasia, where cells actively divide. The liver can restore nearly its original size within a few weeks to months, with the most intense regrowth occurring in the first week after surgery.
This regeneration is initiated by a complex cascade of signals responding to the sudden loss of liver mass and changes in blood flow. An increase in pressure and shear stress in the remaining portal vein system acts as an initial trigger, prompting cells to enter the growth cycle. Cytokines, such as Interleukin-6 (IL-6), and growth factors, like Hepatocyte Growth Factor (HGF), are released to coordinate cell proliferation.
The amount of liver that can be safely removed depends heavily on the health of the remaining tissue, known as the future liver remnant. In a healthy liver, it is safe to remove up to 70% to 75% of the total volume. If the liver has underlying damage from conditions like cirrhosis, chronic hepatitis, or chemotherapy, the minimum safe remnant must be larger, often requiring 30% to 40% or more of the original volume.
Medical Reasons Requiring Liver Resection
Partial liver removal is performed primarily for abnormal growths or for living donation. The most frequent indication is the treatment of cancerous tumors found within the organ. This includes primary liver cancers, such as hepatocellular carcinoma (HCC) and cholangiocarcinoma, which originate in the liver itself.
Liver resection is also used for cancers that have spread to the liver from other parts of the body, a condition called liver metastasis. Colorectal cancer is a common example, as it frequently metastasizes to the liver. Removing these secondary tumors can significantly improve a patient’s long-term outcome. The procedure involves taking out the tumor along with a margin of healthy tissue to ensure complete removal.
Other Indications for Resection
Liver resection may be necessary to address large or symptomatic benign tumors, such as hemangiomas or large cysts. Localized infections or abscesses unresponsive to antibiotic treatment may also require surgical removal of the affected segment. In these cases, the goal is removing the diseased portion while preserving enough healthy tissue for the organ to function and regenerate.
Living donor liver transplantation is another reason for partial liver removal. A healthy person volunteers to donate a segment of their liver, typically the larger right lobe for an adult recipient. This procedure is possible because both the remaining part in the donor and the transplanted segment in the recipient will regenerate to a functional size.
Surgical Procedures and Post-Operative Regeneration
Liver resection requires planning, often involving preoperative imaging to map the liver’s vascular anatomy and calculate the future liver remnant volume. Surgeons categorize removal based on the liver’s eight functional segments. Terms used include lobectomy for removal of a large lobe or segmentectomy for a smaller portion.
The surgical approach varies, including traditional open surgery, which involves a large abdominal incision, or minimally invasive techniques. Minimally invasive methods include laparoscopic or robotic-assisted surgery, using small incisions and specialized instruments. These methods often result in less post-operative pain, a shorter hospital stay, and a faster recovery. Open surgery may be necessary for very large tumors or complex resections located deep within the liver.
Following the procedure, recovery is monitored to confirm the remaining liver is successfully regenerating and functioning adequately. Liver function tests, measuring enzymes like AST and ALT, and bilirubin levels, are taken frequently after surgery. These levels often peak around day three before beginning to decline as the liver recovers. Imaging studies, such as CT or MRI scans, are used to physically measure the increase in volume of the remaining liver tissue.
The rapid recovery of function and mass is a testament to the liver’s unique biology, allowing it to resume its hundreds of metabolic tasks even while actively regrowing. For a healthy donor, the liver often returns to a near-normal volume within a few months. The success of the regeneration process converts this major surgical intervention into a viable and life-saving treatment option.