Modern combination chemotherapies, mainly including oxaliplatin or irinotecan, have demonstrated a significant increase in response rates. This led to the concept of down-sizing irresectable liver metastases from colorectal cancer, thereby achieving secondary resectability and possibly cure. However, these benefits of preoperative chemotherapy must be weighed against potential side effects to the surrounding normal liver tissue. In particular, in patients with pre-existing liver disease combination therapy can cause liver damage which may exceed mere steatosis of hepatocytes and lead to inflammation, cholestasis and bleeding. In correspondence to the "non-alcoholic steatohepatitis" (NASH) the term "chemotherapy associated steatohepatitis" (CASH) has been proposed in the literature. Platinum derivatives, in particular, can lead to damage of the hepatic microcirculation and the so-called sinusoidal obstruction syndrome (SOS). Few reports mention an increase in perioperative morbidity after combination chemotherapy. However, there are no comprehensive data on the individual risk of a patient for postoperative complications. If elevated liver enzymes are detected before chemotherapy and cannot readily be explained through liver involvement by the tumor, then close monitoring of enzymes should be performed and a biopsy may be considered in unclear cases. We recommend that the histological changes observed in the liver be quantified and classified by a unifying scoring system and propose, in correspondence to the hepatitis activity scores, a modified scoring system.