SAFETY AND FEASIBILITY OF RENAL BLOOD-FLOW DETERMINATION DURING KIDNEY-TRANSPLANT SURGERY WITH PERFUSION ULTRASONOGRAPHY

Contrast-enhanced perfusion patterns of newly transplanted kidneys were determined in 10 patients. Albumin-stabilized sonicated microspheres were injected into the iliac-renal artery of the transplanted kidney while continuous two-dimensional ultrasound images were recorded. Doppler derived resistance index (RI) of the transplanted kidney's blood flow before injection of contrast (0.68 +/- 0.8) did not differ significantly from RI measured immediately after injection (0.72 +/- 0.13) or RI 24 h after surgery (0.69 +/- 0.11), Heart rate, mean arterial pressure, central venous pressure, and electrocardiogram (ECG) signs for ischemia did not change during contrast injections. Renal scintigraphy and renal biopsy revealed acute tubular necrosis and/or rejection in two patients at 24-48 h. Videodensitometry was used to assess the ratio of inner to outer peak pixel intensity from the recorded tomographic images in six patients. In both patients with acute rejection, the inner to outer cortex peak pixel intensity was greater than 1, whereas it was less than 1 in the remaining four patients with normal postoperative renal function. Visual scores (0-3) of contrast enhancement for three doses of Albunex(R) were evaluated (0.5 mL, 1.0 mL, 2.0 mL). Two milliliters always enabled perfusion assessment. In seven patients the identical dose of Albunex(R) was injected immediately before and 30 s after 2 mg of verapamil was injected directly into the renal artery at the time of surgery. The contrast enhancement score before verapamil (1.4 +/- 0.6) was significantly less than the enhancement score af ter (2.1 +/- 0.6), implying greater renal blood flow after verapamil. Evaluation of renal blood flow during kidney transplant surgery using contrast ultrasonography with sonicated albumin microspheres is feasible. Further applications for assessing regional renal blood flow changes during surgery (nontransplant) may be possible.