BACKGROUND: It is thought that Randall’s plaques, calcium deposits in the papillae of patients with nephrolithiasis, may serve as a nidus for stone formation. We examined the computed tomography (CT) Hounsfield density of renal papillae in stone formers to determine whether nephrolithiasis is associated with radiographic changes in renal papillae.
METHODS: Hounsfield density measurements of a 0.2cm² area of the renal papilla of 19 patients with a single renal calyceal calculus and 19 age-matched control patients were performed. Measurements were done for upper, middle, and lower pole calyces. Statistical comparisons were made using the student’s t-test.
RESULTS: Stone formers and control patients did were similar with respect to mean age (42.6 versus 40.8, p = 0.67) and baseline serum creatinine (0.86 versus 0.93, p=0.21). Mean Hounsfield density of renal papillae in calyces with stones was significantly greater than that of location-matched papillae from control patients (50.9 versus 33.8, p<0.0001). Mean Hounsfield density of all papillae in stone-formers was significantly greater than that of control patients (50.6 versus 33.7, p<0.001). When comparing affected and non-affected sides within the group of stone formers, there was no difference in mean papillary Hounsfield density (50.3 versus 50.9, p=0.65).
CONCLUSIONS: Hounsfield density of the renal papilla is significantly increased in patients with nephrolithiasis when compared with age-matched controls. This is true of calyces where stones are located as well as calyces in which there are no calculi. There is no difference in renal papilla Hounsfield density between affected and non-affected kidneys of stone-forming patients. In the future, this information may be useful in predicting which patients may develop nephrolithiasis.