Kidney function after radical nephrectomy: Assessment by quantitative SPECT of Tc-99m-DMSA uptake by the kidneys

To determine the function of the remaining contralateral kidney after the r emoval of a functioning kidney, 30 consecutive patients (18 men, 12 women; average age, 67 y; age range, 34-87 y) who were undergoing unilateral radic al nephrectomy were evaluated by sequential quantitative Tc-99m-dimercaptos uccinic acid (DMSA) SPECT (QDMSA) studies. Methods: The 30 patients were un dergoing radical nephrectomy for renal tumors. The first study was done bef ore surgery. Follow-up studies were performed 2-23 mo after surgery. Clinic al evaluations and determinations of serum creatinine level were performed at the same time as the QDMSA studies. Results: The relative contribution o f the resected kidneys to the global renal function before surgery was 43.2 % +/- 7.3%. After surgery the uptake of the remaining kidney increased from 13.4% +/- 4.0% to 18.3% +/- 5.8% (t = 5.7; P = 0.0000). The relative funct ion of the remaining kidney increased from 56.8% +/- 7.1% to 79.1% +/- 23.6 % (t = 4.9; P < 0.0001) of the global renal function before nephrectomy. In creases in the renal volume (from 211 +/- 62 cm(3) to 229 +/- 68 cm(3); t = 4.5; P = 0.0001) and in the percentage injected dose per cubic centimeter (%ID/cm(3)) of the remaining kidney (from 0.066 +/- 0.02 %ID/cm(3) to 0.085 +/- 0.03 %ID/cm(3): t = 4.6; P = 0.0001) were associated with this change. Nine patients had 2 follow-up studies performed 3-4 mo after surgery and 1 2-14 mo after surgery. The volume of the remaining kidney (209.22 +/- 46.20 cm(3) versus 217.88 +/- 58.85 cm(3); t = 0.962; P = 0.364), the %ID/cm(3) (0.09 +/- 0.016 %ID/cm(3) versus 0.093 +/- 0.025 %ID/cm(3); t = 0.362; P = 0.726), and the percentage uptake (19.26% +/- 4.45% versus 20.11% +/- 7.01% ) did not change significantly between these 2 QDMSA studies. Conclusion: T he results of this study suggest that adaptive changes causing hyperfunctio n of the remaining kidney may occur after nephrectomy of a functioning kidn ey in adults. These changes occur soon after surgery, persist for at least 1 y, and are evident on QDMSA studies.