OVERESTIMATING THE SIZE OF HEPATIC MALIGNANCY ON HELICAL CT DURING ARTERIAL PORTOGRAPHY - EQUILIBRIUM PHASE CT AND PATHOLOGY

Purpose: Overestimating the size of hepatic malignancy with helical CT during arterial portography (CTAP) can be a potential pitfall in dete rmining liver resection area. We evaluated the prevalence and extent o f overestimation of hepatic malignancy on CTAP in correlation with hel ical equilibrium phase CT (EPCT) and pathologic findings. Method: CTAP and EPCT in 47 histologically proven malignant hepatic tumors [33 hep atocellular carcinomas (HCCs) and 14 metastases] in 39 patients were r etrospectively studied. Nineteen tumors were resected and pathological ly evaluated. Results: The size overestimation ratios (CTAP/EPCT) rang ed from 1.02 to 1.56 (mean +/- SD 1.24 +/- 0.16) in HCC and from 1.00 to 2.48 (1.34 +/- 0.42) in metastasis. In 19 surgical specimens, the o verestimation ratios (CTAP/specimen) ranged from 1.05 to 1.45 (1.20 +/ - 0.13) in HCC and from 1.10 to 1.38 (1.22 +/- 0.10) in metastasis. Hi stopathologically, flattening of parenchymal structures (100%), atroph y of hepatic cords (95%), sinusoidal congestions (95%), fibrosis and d uctular proliferation (58%), and no tumor were seen in peritumoral par enchyma corresponding to perilesional perfusion defects with CTAP. Con clusion: CTAP frequently and significantly overestimates the size of m alignant hepatic tumors. This phenomenon is attributable to either ben ign histopathological changes in the perilesional liver parenchyma cau sed by parenchymal compression or portal venous obstruction by maligna nt liver tumors or to a siphoning effect by hypervascular neoplasms.