Introduction and Objectives: to date there have been several hypotheses on the causes of kidney stone formation. Compromised intrarenal blood flow might play one of major roles in stone formation. Advances in software and 3D technologies have unveiled the nature of contrast medium flow in the intrarenal structures. Mathematical analysis and 3D rendering of computed tomography (CT) scans was utilized for inrarenal contrast medium flow assessment in patients with stone kidney disease. This study aimed at assessing split glomerular filtration rate (sGFR) in patients at the initial stage of stone kidney disease (SKD). sGFR was measured by means of mathematical analysis of 3D rendering abdominal contrast enhanced CT scans. As well as that, possible correlations between irregular inrarenal contrast medium flow and causes of stone formation were considered.
Materials and Methods: 23 patients of both sexes with stone kidney disease (SKD) were recruited. They underwent US/Dopler investigation of the kidneys and the bladder, plain X-ray, histopathological evaluation of the tissues (those patients who were operated on), spectroscopic analysis of the stone(s). Mathematical analysis of 3D rendering of CT scans was utilized for sGFR assessment (sGFR reference value: 0,55% of contrast medium per second). Inclusion criteria are as follows: 1) newly diagnosed SKD; 2) stone size less than 1,5-2,0 cm 3) stones that do not block urine flow 4) non-operated young patients; 5) patients free of comorbidities. Inclusion criteria were set to mitigate the effects of other factors that might influence on intrarenal blood flow and conduct the study
per se.
Results: Mathematical analysis of 3D rendering of CT scans allowed to elucidate changes in sGFR in 22 (95,6%) patients out of 23. HypErfiltration (hyperF) was detected in 10 (43,5%) patients, hypOfiltration (hypoF) was detected in 11(47,8%) patients. sGFR values were statistically significantly different in these groups both on the left (p=0,000142) and on the right (p=0,00068). No significant gender differences were observed (hypoF group aged 25–67 years with the mean age of 43,5 years; hyperF group aged 17-57 years with the mean age of 39 years (p=0,563). Ultrasound Doppler renal resistive index in renal arteries was within the normal range in both groups with no statistically significant difference between the groups. However, 1 patient demonstrated no sGFR changes. Another patient had hyporfiltration on the left (0,48%) and hyperfiltration on the right (0,62%) Conclusions: sGFR alterations (hypo- or hyperfiltration) were detected in the majority of the patients with SKD (95,6%). This in turn might be suggestive of compromised intrarenal blood flow. Further studies are needed to elucidate the optimal management of these patients.

Keywords: stone kidney disease, split renal function assessment, filtration, 3D-models, MSCT, GFR