Non-invasive monitoring of renal oxygenation using BOLD-MRI: a reproducibility study.

Blood oxygenation level-dependent (BOLD) MRI was shown to allow non-invasive observation of renal oxygenation in humans. However, clinical applications of this type of functional MRI of the kidney are still limited, most likely because of difficulties in obtaining reproducible and reliable information. The aim of this study was to evaluate the reproducibility and robustness of a BOLD method applied to the kidneys and to identify systematic physiological changes potentially influencing the renal oxygenation of healthy volunteers. To measure the BOLD effect, a modified multi-echo data image combination (MEDIC) sequence was used to acquire 12 T2*-weighted images within a single breath-hold. Three identical measurements were performed on three axial and three coronal slices of right and left kidneys in 18 volunteers. The mean R2* (1/T2*) values determined in medulla and cortex showed no significant differences over three repetitions and low intra-subject coefficients of variation (CV) (3 and 4% in medulla and cortex, respectively). The average R2* values were higher in the medulla (16.15 +/- 0.11) than in the cortex (11.69 +/- 0.18) (P < 0.001). Only a minor influence of slice orientation was observed. Mean R2* values were slightly higher (3%) in the left than in the right kidney (P < 0.001). Differences between volunteers were identified (P < 0.001). Part of these differences was attributable to age-dependent R2* values, since these values increased with age when medulla (P < 0.001, r = 0.67) or cortex (P < 0.020, r = 0.42) were considered. Thus, BOLD measurements in the kidney are highly reproducible and robust. The results allow one to identify the known cortico-medullary gradient of oxygenation evidenced by the gradient of R2* values and suggest that medulla is more hypoxic in older than younger individuals. BOLD-MRI is therefore a useful tool to study sequentially and non-invasively regional oxygenation of human kidneys.

Implementation of recommendations in the diagnosis of vesicoureteric reflux after urinary tract infections in Swiss children.

BACKGROUND: Efforts are now routinely made for early detection of vesicoureteric reflux after urinary tract infections in order to limit secondary renal damage. METHODS: The age at diagnosis of reflux after urinary tract infections was analysed in 162 Swiss patients (46 boys and 116 girls) referred by primary care physicians to the Division of Paediatric Nephrology, University of Bern, Switzerland between 1978 and 1999. The figures noted in Switzerland were also compared with those noted in 102 Australian patients (35 boys and 67 girls) reported by Lenaghan in 1976. RESULTS: In Switzerland the median age at diagnosis was 23 months in 74 subjects diagnosed between 1978 and 1988 and 10 months in 88 subjects diagnosed between 1989 and 1999. The difference was statistically significant in girls but not in boys. In Australia the median age at diagnosis was 15 months for boys and 78 months for girls; in Switzerland, the corresponding figures were 12 and 29 months (between 1978 and 1988), respectively 5 and 14 months (between 1989 and 1999). The difference between Australia and Switzerland was statistically significant in girls but not in boys. CONCLUSIONS: In Switzerland vesicoureteric reflux is now detected earlier than in the past. This trend is more marked in girls than in boys but the detection of reflux is still earlier in boys than in girls.