Pseudoenhancement of renal cyst study of multiple phases of contrast enhancement with multi-slice CT / 中华放射学杂志

ABSTRACT

Objective To evaluate the rules and features of the pseudoenhancement phenomenon of renal cysts during the multi-phases of contrast enhanced MSCT scan.Methods Ninety one patients with 112 simple renal cysts with B-ultrasound,CT examination,improved clinically enrolled in this retrospective study.The attenuation of the renal cysts were measured blindly in the images of CT plain scan and scans of arterial,venal and secrete phases,and the attenuation change of the cysts between pre-and post-enhanced scans were calculated; the accuracies of pseudoenhancement judging were calculated with 10 HU,15 HU and 18 HU as a threshold;the size were recorded; degree of intra renal parenchyma of the cyst were also confirmed,and so renal cysts were divided into three groupstype Ⅰ,Ⅱ and Ⅲ; The differences of attenuation among 3 enhancement phases,different size,different type were analyzed statistically with the Kruskal-wallis rank sum test,the correlation between the diameter and the pseudoenhancement in each enhancement phases were analyzed statistically with Spearman test.Results The attenuation median of the 112 cysts in plain scan,arterial,venal and secrete phase was 6.0 HU,11.0 HU,12.0 HU and 12.0 HU respectively,there was significant difference(x2=53.32,P＜0.01).The attenuation of the cysts in enhanced phases was higher than unenhanced.The range of attenuation change of the cysts between pre-and postenhanced scans was-10 to 31 HU,the number of cysts in groups of pseudoenhancement of 1 to 5 HU and 6 to 10 HU in each enhanced phase was dominant.The pseudoenhancement median of arterial,venal and secrete phase was 4.0 HU,5.0 HU and 6.0 HU respectively,There was significant difference among three groups(x2=10.062,P＜0.01).Taking 10 HU,15 HU and 18 HU as threshold for judging pseudoenhancement,the accuracy was 83.0％(239/288),95.1％(274/288) and 96.9％(279/288) respectively; Pseudoenhancement of small cysts(≤10 mm) was higher than other groups in each enhancement phase,and there was significant difference(P＜0.05).Type Ⅰ,Ⅱ and Ⅲ renal cysts were 62,23 and 27 respectively,the pseudoenhancement median of type Ⅰ renal cyst was 5.0 HU,6.0 HU and 8.0 HU respectively in arterial,venous,and excretion phase,which were higher than Type Ⅱ and Ⅲ (P＜0.05).It showed low negative correlation between pseudoenhancemen and diameter in arterial,venous and secrete phase(r =-0.326,-0.332 and-0.447,P＜ 0.01).Conclusion The pseudoenhancement correlated with the renal cyst size,the type and the enhance phases,which should be considered when making diagnosis.