Objective      To investigate the CT characteristics of renal secondary lymphoma

and to improve the understanding and diagnosis of this disease.      Methods      Retrospective analysis was performed in 7 patients with non-Hodgkin lymphoma accompanied by renal secondary lymphoma. The patients were examined by abdominal plain and contrast-enhanced CT.      Results      In the 7 patients with renal secondary lymphoma

5 patients were diagnosed as nodular (mass) type including 2 multiple types and 3 solitary types; one patient was diagnosed as a type of direct extension from the adjacent lesion

and 1 was a perinephric lymphoma type. The diameters of the renal lesions ranged from a few millimeters to 7.2 cm. The plain CT showed that the density of all lesions were homogeneous

including 4 isodense and 3 slightly hyperdense

and the values were 30.6 to 38.3 HU (with a mean value of 34.6 HU). The CT values in the enhanced arterial phase

venous phase and equilibrium phase were 42.7 to 65.7 HU (with a mean value of 49.7 HU)

50.5 to 86.5 HU (with a mean value of 64.1 HU) and 55.3 to 115.2 HU (with a mean value of 71.3 HU)

respectively. The contrast-enhanced CT showed 3 moderate and 4 overt homogeneously delayed enhancements.      Conclusion      The CT characteristics of the renal secondary lymphoma are diverse

the density is homogeneous

and a progressively delayed enhancement is observed by the contrast-enhanced CT. CT scan in the equilibrium phase can elevate the detection rate of small lesions，which combined with the clinical information can help us make a definite diagnosis.