Prospective evaluation of intra-observer variability of the hydronephrosis index in sonographic examination of 44 patients with acute renal colic

PURPOSE: The aim of our prospective designed study was to confirm the intra-observer agreement of assessments of the hydronephrosis index (HI) with a sonographic technique that potentially provides additional information in patients with acute renal colic (ARC).

METHODS: Sonographic measurement of HI and valuation of common clinical criteria were performed in 44 consecutive patients presenting with unilateral stone-related ARC. HI of colic side was recorded twice in predefined time intervals. Intra-observer agreement was evaluated with the Spearman's rank correlation/rho (ρ) for attributive-metric characteristics. Data of HI-measurement on the colic side were compared with data of the unaffected side using t test.

RESULTS: Intra-observer agreement was significant for HI in the colic side (ρ = 0.918, p < 0.001) and in the unaffected side (ρ = 0.826, p < 0.001). The mean HI between colic and unaffected side differed significantly on the first evaluation (85.2 vs. 93.7, respectively; p < 0.001) and on the second evaluation (85.1 vs. 93.6, respectively; p < 0.001) as well.

CONCLUSIONS: The HI method is a slightly feasible examination method in patients presenting with stone-related renal colic. Moreover, it offers a solid discrimination between obstruction and non-obstruction. Our prospective trial illustrates HI as a reproducible method with a high-grade intra-observer agreement. However, potential change of values under medical expulsive therapy and coherency with the functionality of the obstructed kidney may lead to bias and therefore remain to be analyzed. Further studies to specify exact thresholds for this method and to state our findings are required.