Improved liver and portal venous system enhancement with saline flush after contrast injection in portal venous phase computed tomography

Background The utility of saline flush in portal venous phase (PVP) contrast-enhanced computed tomography (CECT) for the liver remains controversial. Purpose To investigate the effect of saline flush after contrast injection on liver and portal venous system enhancement in PVP CECT. Material and Methods The saline flush group prospectively included 97 consecutive patients (52 women; median age = 68 years) who underwent PVP CECT with saline flush. The control group retrospectively comprised 105 patients (63 women; median age = 65 years) who underwent PVP CECT without saline flush. Scanning protocols, including contrast injection protocol and scan timing (65 s), were standardized. In the saline flush group, 20 mL of saline, determined through a phantom study, was injected after contrast injection. Two radiologists measured increased CT attenuations (ΔHUs) of the liver, portal vein (PV), superior mesenteric vein (SMV), and splenic vein (SV), and compared them between the two groups. The proportions of cases with liver ΔHU above and below 50 HU were also compared. Results ΔHUs were higher for the liver (69.4 HU vs. 64.4 HU; P = 0.004), PV (184.6 HU vs. 171.9 HU; P = 0.001), SMV (179.0 HU vs. 171.0 HU; P = 0.002), and SV (185.1 HU vs. 163.6 HU; P < 0.001) in the saline flush group than in the control group. The proportion of cases with liver ΔHU below 50 HU was not different between the two groups (5.2% in the saline flush group vs. 7.6% in the control group; P = 0.57). Conclusion Saline flush may increase liver and portal venous system enhancement on PVP CECT.