Liver-enhancing modalities, such as portal vein embolization, are increasingly employed prior to major liver resection to prevent postoperative liver dysfunction. Selection criteria for such techniques are not well described. This study uses CT-based volumetric analysis as a tool to identify patients at highest risk for postoperative hepatic dysfunction. Between July 1999 and December 2000, a total of 126 consecutive patients who were undergoing liver resection for colorectal metastasis and had CT scans at our institution were included in the analysis. Volume of resection was determined by semiautomated contouring of the liver on preoperative volumetrically (helical) acquired CT scans. Hepatic dysfunction was defined as prothrombin time greater than 18 seconds or serum bilirubin level greater than 3 mg/dl. Marginal regression was used to compare the predictive ability of volumetric analysis and the extent of resection. The percentage of liver remaining was closely correlated with increasing prothrombin time and bilirubin level (P < 0.001). After trisegmentectomy, 90% of patients with </=25% of liver remaining developed hepatic dysfunction, compared with none of the patients with more than 25% of liver remaining after trisegmentectomy (P < 0.0001). The percentage of liver remaining was more specific in predicting hepatic dysfunction than was the anatomic extent of resection (P = 0.003). Male sex nearly doubled the risk of hepatic dysfunction (odds ratio = 1.89, P = 0.027), and having </=25% of liver remaining more than tripled the risk (odds ratio = 3.09, P < 0.0001). Hepatic dysfunction and </=25% of liver remaining were associated with increased complications and length of hospital stay (P < 0.0001 and P = 0.0003, respectively). Preoperative assessment of future liver volume remaining distinguishes which patients undergoing liver resection will most likely benefit from preoperative liver enhancement techniques such as portal vein embolization.