Novel 3D capsule device to restrict kidney volume expansion on polycystic kidney progression: feasibility study in a rat model.

BACKGROUND: Cystogenesis in polycystic kidney disease (PKD) is likely accelerated by various renal insults, including crystal deposition, that activate renal tubule obstruction and dilation. We developed a capsule-based device that can be applied to cystic kidneys to restrict tubular lumen dilatation and cyst expansion. METHODS: Kidney capsule devices were designed from computed tomography images of wild-type and Cy/+ rats. Capsule devices were surgically implanted on kidneys in six surgical sessions over a period of 14 months in 7 wild-type rats of 6.5-8 weeks (3 sham operations, 2 right, 2 left) and 6 Cy/+ rats of 6.5 weeks (2 sham, 3 left, 1 bilateral). After surgery, the rats were followed for 5.4-12.4 weeks' growth and sacrificed to retrieve the kidneys. During the follow-up, serum creatinine was measured and retrieved kidneys were weighed. Histological analysis including cystic area measurement and immunohistochemistry was performed. RESULTS: Morphometric capsule devices were configured and developed by an image processing technique and produced using a 3D printer. Encapsulated Cy/+ kidneys (n = 5; mean weight 3.64 g) were consistently smaller in size (by 21-36%; p < 0.001) than unencapsulated Cy/+ kidneys (n = 7; mean weight 5.52 g). Encapsulated Cy/+ kidneys (mean %cyst area: 29.4%) showed smaller histological cystic area (by 28-58%; p < 0.001) than unencapsulated Cy/+ kidneys (mean %cyst area 48.6%). Cell proliferation and macrophages were also markedly reduced in encapsulated Cy/+ kidneys, compared to unencapsulated Cy/+ kidneys. CONCLUSIONS: We report a pilot feasibility study for the application of a novel morphometric 3D capsule device to the Cy/+ rat model showing restricted kidney volume expansion on polycystic kidney disease progression.

Novel approach to estimate kidney and cyst volumes using mid-slice magnetic resonance images in polycystic kidney disease.

OBJECTIVE: To evaluate whether kidney and cyst volumes can be accurately estimated based on limited area measurements from magnetic resonance (MR) images of patients with autosomal dominant polycystic kidney disease (ADPKD). MATERIALS AND METHODS: MR coronal images of 178 ADPKD participants from the Consortium for Radiologic Imaging Studies of ADPKD (CRISP) were analyzed. For each MR image slice, we measured kidney and renal cyst areas using stereology and region-based thresholding methods, respectively. The kidney and cyst 'observed' volumes were calculated by summing up the area measurements of all the slices covering the kidney. To estimate the volume, we selected a coronal mid-slice in each kidney and multiplied its area by the total number of slices ('PANK2' for kidney and 'PANC2' for cyst). We then compared the kidney and cyst volumes predicted from PANK2 and PANC2, respectively, to the corresponding observed volumes, using a linear regression analysis. RESULTS: The kidney volume predicted from PANK2 correlated extremely well with the observed kidney volume (R(2) = 0.994 for the right kidney and 0.991 for the left kidney). The linear regression coefficient multiplier to PANK2 that best fit the kidney volume was 0.637 (95% CI: 0.629-0.644) for the right kidney and 0.624 (95% CI: 0.616-0.633) for the left kidney. The correlation between the cyst volume predicted from PANC2 and the observed cyst volume was also very high (R(2) = 0.984 for the right kidney and 0.967 for the left kidney). The least squares linear regression coefficient for PANC2 was 0.637 (95% CI: 0.624-0.649) for the right kidney and 0.608 (95% CI: 0.591-0.625) for the left kidney. CONCLUSION: Kidney and cyst volumes can be closely approximated by multiplying the product of the mid-slice area measurement and the total number of slices in the coronal MR images of ADPKD kidneys by 0.61-0.64. This information will help save processing time needed to estimate total kidney and cyst volumes of ADPKD kidneys.