Preoperative assessment of liver function.
At the present time, the decision to resect and the choice of the extent ofa hepatic resection are largely based on surgical judgment. The CP score is the best assessment tool we can now employ. There is uniform agreement that even segmental resections are not possible in the vast majority of Child Class B patients, CP score 7 to 9. The CP score can be augmented by radiographic testing, ICG retention testing, and by assessing tumor extent and the severity of the patient's cirrhosis at surgery. Surgeons need a simple means to assist with liver function evaluation--a test to augment the CP score. Although determining ICG retention is simple, it is questionable whether it adds to one's ability to define the poor-risk patient with better accuracy than the CP score. Abundant data exist to dispute the accuracy and reproducibility of ICG retention. That surgeons use it says more about the fervent desire to find a test that supports clinical judgment in these difficult patients than the scientific validity of the test. Whether a series of tests would better define the Child-Pugh Class A patient who is also a relatively poor risk is not clear at present. Many investigations demonstrate the correlation of various assessment tools with each other, yet nothing distinguishes them in predicting risk beyond what is learned from the CP score. In a group of CP Class A patients, the extent of the disease, the nature of underlying cirrhosis, and the extent of resection provide the clinical backdrop against which a decision for resection must be made. It may well be that one test may not do it, or that one single assessment of the ICG or the 15-minute receptor volume of GSA may be inadequate to project the nuances of liver function. Thus, 99m-Tc GSA scintigraphy will provide volumetric receptor data, as well as kinetic distribution curves, and may prove a useful test in the future. Whether GSA is ultimately to be proven useful requires a correlation of the test with actual clinical outcomes, rather than correlation with other tests or with the CP score. Discovering which patients are the poor risk Child Class A patients is the desired goal. To have value, the GSA scan must augment, not mimic, the CP score. In view of the fact that experienced surgeons appear to be astute in their ability to select patients for hepatic resection, finding a more refined test will require large numbers of patients at several centers to correlate the test results and the outcomes against the spectrum of postoperative liver failure, including death. It appears that one lesson learned from portal vein embolization is that functional liver volume can be preserved. The compensatory hyperplasia that occurs in the contralateral hepatic lobe demonstrates two important features: (1) function of the opposite lobe has been transferred when evaluated by 99m-Tc-GSA, and (2) one considerable metabolic drain on the postoperative recovery from hepatic resection (ie, liver regeneration) can be attended to before the surgery. Cirrhotic livers do regenerate, but more slowly. Thus, pregrowing the remnant section of liver eliminates one stress on liver reserves following liver resection. For hepatocellular carcinoma or metastasis in cirrhotic patients, portal vein occlusion may be the best way to improve hepatic functional reserve. ICG retention may not corroborate return-to-baseline hepatic function within 2 weeks of portal vein occlusion,but may demonstrate a return to baseline when studied 6 to 8 weeks following the procedure. 99m-Tc-GSA is presently the best means to document compensatory hyperplasia and, possibly, a shift of functional reserve to the planned remnant of a more than four-segment hepatic resection. Whether this will predict the safe outcome of resection remains to be seen.