Diuretic-induced renal length changes in the estimation of renal function with MR urography

The impact of hydration on renal measurements and on cortical echogenicity in children

BACKGROUND

Kidney ultrasonography is frequently performed in children; to date there are no specific guidelines regarding hydration before the examination.

OBJECTIVE

Because certain renal measurements can be indicative of pathology, we used sequential US images to investigate the effect of standardised hydration in children relative to renal size, echogenicity and pelvic expansion.

MATERIALS AND METHODS

Thirty-one children (7 years to 14 years old) underwent US examinations before hydration (T0) and at 30 min (T30) and 60 min (T60) after ingesting water. We measured bladder volume, inter-polar kidney size, renal volume and anterior-posterior diameter of the pelvis. Cortical echogenicity was compared to that of the liver and spleen.

RESULTS

On the right side the increase in average inter-polar renal size was 2.5% at T30 and 2.6% at T60 (P < 0.05) compared to T0. On the left the increase was 3.8% at T30 and 4.3% at T60 (P < 0.05). Volume expansion for the right kidney was 16.8% at T30 and 14.0% at T60 (P < 0.05). On the left it was 12.9% at T30 and 10.2% at T60 (P < 0.05). Cortical echogenicity progressed from hypoechogenicity to isoechogenicity (P < 0.05). The percentage of expanded pelves increased with hydration (T0: 3.2%, T30: 9.7%, T60: 22.6%).

CONCLUSION

Oral hydration influences renal length, volume and echogenicity in children. Hydration results in expansion of the pelvis. We recommend standardisation of hydration before US examination.

Sonographic measurement of diuretic-induced renal length changes: are they correlated with renal function?

OBJECTIVES

The purposes of this study were to prospectively identify diuretic-induced renal length changes and to determine whether the percentages of the renal length changes allow estimation of the differential renal function.

METHODS

Twenty-three children (14 boys and 9 girls; mean age, 7.83 years) who were undergoing technetium Tc 99m diethylenetriamine pentaacetic acid or technetium Tc 99m mercaptoacetyltriglycine diuretic renography were included in this study. Renal lengths were measured by sonography just before and 15 to 20 minutes after diuretic injection. The Spearman test was used to assess the correlation between renal length increases due to diuretic injection and the differential renal function.

RESULTS

The mean renal lengths ± SD measured before and after diuretic administration were 91.52 ± 20.87 and 95.38 ± 21.46 mm, respectively. The increase in renal length after diuretic administration was statistically significant (P < .001). There was a positive correlation between the renal length change and functional status (P = .006).

CONCLUSIONS

Renal length may change after diuretic injection according to the functional status, and the sonographic measurements of these changes may be used as an alternative to other imaging methods in estimation of renal function.