Individual patient variation and inter-rater reliability of lower calyceal infundibular width on routine intravenous pyelography.

ABSTRACT

OBJECTIVE: To standardise infundibular width (IFW) measurement, to determine patient variability, and to determine inter-rater variability on intravenous pyelography (IVP). PATIENTS AND METHODS: Fifty outpatient IVP films were randomly drawn from two hospitals between 1 July 1998 and 31 August 1999, and examined to measure the lower calyceal IFW on the 5, 10 and 20 min films with compression, and after voiding. Kidneys with previous renal surgery, hydronephrosis or renal anatomical anomalies were excluded; in all, 81 kidneys from 50 patients were examined. The IFW was measured at the narrowest point along the infundibulum. All 50 films were then reviewed by two urologists unaware of their origin, to determine the inter-rater reliability of the infundibular measurements. RESULTS: Analysis of variance (anova) with posthoc analysis showed a significant difference in IFW at each phase of the IVP (repeated measures anova, P < 0.001). The mean (95% confidence interval) IFW was greatest on the compression film, at 4.4 (2.6) mm, and least on the postvoid film, at 1.6 (2.1) mm. Overall inter-rater reliability was 0.9780 (intraclass correlation coefficient), and the Pearson correlation between each rater for the IFW at each phase of the IVP was >/= 0.886. CONCLUSIONS: There is wide variability in lower calyceal IFW among the various IVP films in a given study. Thus any predictive value of the IFW must be standardized for the timing and IVP film type (compression, postvoid, etc.). The inter-rater reliability of IFW is high, suggesting that if used correctly it may be more useful in predicting the outcome after shock wave lithotripsy.