COMPARISON OF HOUNSFIELD UNITS OF THE RENAL PAPILLAE IN KIDNEY STONE FORMERS AND NON STONE FORMERS

Objective: To investigate whether renal papillae of patients with nephrolithiasis are more radiodense than that of control patients and to evaluate the predictibility of urolithiasis events using papillary density differences between stone and non stone formers. Material and Method: Hounsfield unit (HU) values of the papillae of 212 patients with unilateral nephrolithiasis and 108 patients in the control group at the level of the upper pole, middle region and lower pole of both kidneys were evaluated. Results: Mean HU density of all papillae of kidneys with stones was higher than that of stone free kidneys in nephrolithiasis patients (27.21 +/- 2.83 vs 25.66 +/- 2, p=0.000). Mean HU density of renal papillae of stone patients in calyces with stones was significantly higher than that of all papillae in control patients (25,82 +/- 1.97 vs 30,25 +/- 4,03, p<0,001). Mean HU density of all papillae in stone-free kidneys of nephrolithiasis patients was not significantly different from that of control patients (25.82 +/- 1.97 vs 25.66 +/- 2.57, p=0.642). When the values for control and patient groups according to stone laterality was evaluated, the difference was significant only between right upper and right lower calyces for the right nephrolithiasis and the left middle region for the left nephrolithiasis. (26.32 +/- 3.30 vs. 27.90 +/- 3.92 and 25.10 +/- 3.34 vs. 26.95 +/- 4.73, p=0.003 and p=0.009 and 25.70 +/- 3.67 vs 27.15 +/- 3.77 p=0.001, respectively). Conclusion: Only the kidneys with stones and especially the patients with papillae facing the stones in nephrolithiasis have higher renal papillary HU. This fact implies the impossibility of HU per se in predicting future urolithiasis events and/or patients; opposing to the findings of a few previous studies.