Can a ct , without contrast tell the difference between liver cysts or liver tumours?

Yes...: A ct of the liver without contrast can easily differentiate between a cyst and solid tumor. A cyst has the density of water which is different from solid tumors. The contrast helps mostly with differentiating the solid tumors. An us is perhaps the best test for detecting liver cysts and is free of radiation. Hope this helps.

Depends on size: If a liver lesion is less than 1 cm in size, it is technically too small to adequately characterize on a ct scan with or without contrast. Regardless, IV contrast is strongly preferred when evaluating the liver on a ct scan. The normal liver tissue enhances and makes small lesions more apparent. Also, the contrast helps differentiate between types of solid lesions.