The liver is a unique organ with a remarkable capacity to regrow, making the surgical removal of a portion, known as a hepatectomy, a viable treatment option. This ability allows surgeons to remove significant diseased tissue while ensuring the remaining healthy tissue can recover and sustain the body’s metabolic functions. The success of a resection relies on leaving a sufficient volume of healthy liver to handle immediate demands and initiate the regrowth process. Precise calculations based on the liver’s regenerative limits must be made before proceeding with any removal.
The Liver’s Unique Ability to Regenerate
The liver’s exceptional power to regrow stems from the ability of its primary cells, the hepatocytes, to re-enter the cell cycle and divide rapidly. Unlike most other organs, which heal primarily through scar tissue formation, the remaining liver tissue begins a rapid process of compensatory growth shortly after a portion is removed. Regeneration involves the enlargement of remaining segments to restore the necessary mass and function, rather than creating new tissue in the exact shape of the removed section. This rapid increase in functional volume is achieved through both cell enlargement (hypertrophy) and cell division (hyperplasia). The speed and scale of this biological response determine how much tissue can be safely removed, as the body must maintain function during the period of regrowth.
Determining the Safe Amount for Removal
The decision regarding how much liver can be safely removed is based on precise volumetric planning that focuses on the Future Liver Remnant (FLR). The FLR is the portion of the liver that will remain after the surgery, and its volume is typically measured as a percentage of the Total Liver Volume (TLV) using pre-operative imaging like CT or MRI scans. Surgeons use three-dimensional modeling to calculate this percentage, allowing for a highly individualized surgical plan.
For a patient with an entirely healthy liver, the minimum safe threshold for the Future Liver Remnant (FLR) is generally 20% to 25% of the Total Liver Volume (TLV). This percentage represents the smallest amount of healthy tissue capable of managing immediate metabolic needs and reliably regenerating. If pre-operative calculations show the FLR is below this minimum, the risk of developing post-hepatectomy liver failure is considered high.
If the calculated FLR is too small, portal vein embolization (PVE) may be used weeks before surgery. PVE blocks blood flow to the portion planned for removal, stimulating the FLR to grow larger before the actual resection. This pre-conditioning ensures the remaining liver exceeds the minimum required volume, allowing for a safer removal of a larger total volume.
Factors That Decrease Safe Removal Capacity
The standard 20% to 25% minimum FLR applies only when the liver tissue is completely healthy and undamaged. Many patient-specific conditions can compromise the liver’s ability to regenerate or function, requiring the surgeon to leave a much larger remnant. These conditions reduce the quality of the remaining tissue, making a higher volume necessary to compensate for reduced functional capacity.
Hepatic steatosis, or fatty liver disease, is a limiting factor often associated with obesity or metabolic syndrome. Steatosis impairs the liver’s ability to withstand surgical stress and regenerate, often necessitating a minimum FLR of 30% to 40% of the TLV. Prior chemotherapy treatments can also cause microscopic damage, such as steatohepatitis, further impeding the regenerative process.
Liver tissue that is already scarred, known as cirrhosis, presents the greatest challenge to safe removal limits. Cirrhosis severely impairs both the function and the regenerative capacity of liver cells, meaning the required minimum FLR may be as high as 40% to 50% of the TLV. The severity of the underlying disease determines the precise threshold, requiring surgeons to use specialized functional tests in addition to volume calculations.
Post-Surgery Recovery and Long-Term Function
Following a successful hepatectomy, the remaining liver begins to regenerate almost immediately to restore functional mass. Volumetric regeneration, the physical increase in size, is often rapid, with the liver mass returning to nearly its original volume within four to six weeks. However, the full functional recovery may take a few months longer. The recovery process is closely monitored through routine blood tests, including liver function tests (LFTs), which track enzymes and proteins. Monitoring these functional markers is a better indicator of recovery than simply tracking the volume, as it confirms the new tissue is working effectively.