Infrared Light Structured Sensor Three-dimensional Approach to Estimate Kidney Volume: A Validation Study

Objective: To validate a new procedure for the three-dimensional estimation of total renal parenchyma volumeusing a structured-light infrared laser sensor. Methods: To evaluate the accuracy of the sensor for assessing renal volume, we performed 3 experiments. Twenty freshly excised porcine kidneys were obtained. Experiment A, the water displacement method was used to obtain a determination of the renal parenchyma volume after immersing every kidney into 0.9% saline. Thereafter a structured sensor (Occipital, San Francisco, CA) was used to scan the kidney. Kidney sample surface was presented initially as a mesh and then imported into MeshLab (Visual Computing Lab, Pisa, Italy) software to obtain the surface volume. Experiment B, a partial excision of the kidney with measurement of the excised volume and remnant was performed. Experiment C, a renorrhaphy of the remnant kidney was performed then measured. Bias and limits of agreement (LOA) were determined using the Bland-Altman method. Reliability was assessed using the intraclass correlation coefficient (ICC). Results: Experiment A, the sensor bias was -1.95mL (LOA: -19.5 to 15.59, R2 = 0.410) with slightly overestimating the volumes. Experiment B, remnant kidney after partial excision and excised kidneyvolume were measured showing a sensor bias of -0.5mL (LOA -5.34 to 4.20, R2= 0.490) and -0.6mL (LOA: -1.97.08 to 0.77, R2 = 0.561), respectively. Experiment C, the sensor bias was -0.89mL (LOA -12.9 to 11.1, R2= 0.888). ICC was 0.9998. Conclusion: The sensor is a reliable method for assessing total renal volume with high levels of accuracy.