Nature and perfusion dynamics of peritumoral ring enhancement of small (5-9 mm) and very small (less than 5 mm) hypovascular liver metastases: dynamic CT during hepatic arteriography data analysis

Aim. To study the nature and perfusion dynamics of peritumoral ring enhancement (PRE) of small (5–9 mm) and very small (<5mm) hypovascular liver metastases during prolonged contrast materials injection into the hepatic artery with dynamic CT during hepatic arteriography.

Material and methods. Dynamic CT during hepatic arteriography was performed in 10 patients with histologically proven colorectal (n=4), pancreatic (n=1), lung (n=1), prostate (n=1) and breast (n=2) cancer liver metastases and GIST (n=1) liver metastases during 40 sec on one breath-hold. Duration of contrast materials injection into the hepatic artery was 40 sec (n=2), 35 sec (n=2), 30 sec (n=4) and 25 sec (n=2) with rate 2 ml/sec.

Results. All small and very small metastases regardless of their morphological affiliation had a PRE. During prolonged contrast materials injection density of PRE gradually increased and eventually has always been much higher than density of the liver parenchyma, and, especially, than density of tumor tissue. Dynamic of contrasting of PRE zone has always been a clear correlation with the dynamics of contrasting of the tumor tissue, i.e. it was a derivative from her function. Vascularization of metastases, intratumoral perfusion parameters and, consequently, the intensity of the PRE, were directly dependent on the tumor diameter. Therefore, PRE of small and particularly, very small metastases «appeared» considerably later and it was significantly less pronounced, compared with PRE of metastases medium (10–19 mm) and large (20–29 mm) diameter, situated in the same liver.

Conclusion. PRE of small and very small hypovascular liver metastases occurs due to the accumulation of contrast materials in the peritumoral area of venous stasis, caused by uncontrolled retrograde discharge of blood, flowing from the metastases to the surrounding sinusoids and portal venules of healthy liver parenchyma, on the one hand, and compression of draining hepatic venules by the tumor, on the other hand