Accuracy of noninvasive ultrasonic volume measurements on human kidney transplants. Presentation of a new formula.

PURPOSE

To evaluate the precision in volume measurement on human kidney transplants with the aid of noninvasive ultrasonic technique.

MATERIAL AND METHODS

A Philips P700 ultrasound machine was used for noninvasive volume determination of 28 porcine kidneys compared to plethysmography. Also, the volume of 46 human transplanted kidneys in situ were measured by ultrasound. Since the configuration of the two types of kidneys differed, a new formula for volume measurement, suitable for kidney transplants, was developed with the aid of clay model experiments.

RESULTS

With the standard ellipsoid formula the accuracy of ultrasonic volume determination of the porcine kidneys was good compared with plethysmography, with intra- and interobserver variability of 10.9 and 9.2%, respectively. However, since the width and depth in relation to length of the transplanted kidneys were greater than in the porcine ones (55 vs. 47.5% and 54 vs. 28%, p < 0.01), a new ellipsoid formula was created (r = 1.0, p < 0.0001).

CONCLUSION

Noninvasive ultrasonic kidney volume measurements show an acceptable reproducibility (CV 10%). Since the previously used formula for calculating kidney volume was inaccurate on human kidney transplants, a new and accurate ellipsoid formula fitting for human transplanted kidneys is suggested.