Case report: the need for caution when using the spleen to assess renal blood flow in renography

Visual assessment of renal blood flow from renography is usually achieved by comparing the count rate from the kidney with that of the spleen during the first pass of the radiopharmaceutical agent. This is not justifiable if splenic blood flow is abnormal. In nine subjects without evidence of renal or other significant disease, the mean ratio of the slopes of the first pass curves over the left kidney and the spleen was 1.7 (SD 0.32). However, an additional patient, a 67-year-old female with type-II cryoglobulinaemia, illustrated the need for caution when using this approach. Her splenic blood flow was significantly elevated, resulting in a kidney/spleen slope ratio of only 0.66, even though her renal function was thought to be normal.