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Compensatory hypertrophy effectively assesses the degree of impaired renal function in unilateral renal disease
D C O'Sullivan1, P A Dewan, E J Guiney
1Our Lady's Hospital for Sick Children, Dublin, Ireland.
Insights
Clinically detected compensatory hypertrophy in children with unilateral kidney disease may indicate severe contralateral impairment. Renal size index (RSI) can help identify kidneys with significantly reduced function.
Area of Science:
- Pediatric Nephrology
- Diagnostic Imaging
- Renal Physiology
Background:
- Unilateral renal disease in children often presents with normal overall renal function.
- Compensatory hypertrophy of the healthy kidney is a common adaptation.
- The clinical significance of compensatory hypertrophy in predicting contralateral renal impairment requires clarification.
Purpose of the Study:
- To determine if clinically detectable compensatory hypertrophy indicates severe contralateral renal impairment in children.
- To evaluate the utility of the renal size index (RSI) in assessing contralateral renal function.
- To establish correlations between RSI and percentage of total renal function.
Main Methods:
- Retrospective review of 66 children with unilateral renal disease and normal total renal function.
- Isotope renography (99mTc-DTPA or 99mTc-DMSA) to determine individual kidney function contribution.
- Kidney length measurement from radiographs or IVU to calculate RSI.
Main Results:
- 36 out of 37 kidneys with RSI > 2 standard deviations from the mean had <15% of total function in the contralateral diseased kidney.
- RSI selection levels demonstrated high sensitivity and specificity for identifying kidneys with <10% or <15% total renal function.
Conclusions:
- Clinically detectable compensatory hypertrophy, quantified by RSI, is a strong indicator of severe contralateral renal impairment in pediatric unilateral renal disease.
- RSI is a valuable tool for identifying kidneys with significantly diminished function, aiding in clinical assessment and management.
Abstract:
A series of 66 children with unilateral renal disease and normal total renal function were reviewed with the aim of determining whether clinically detectable compensatory hypertrophy indicated severe contralateral renal impairment. The proportion of total renal function that was contributed by each kidney was determined using isotope renography (99mTc-DTPA for 46 children, 99mTc-DMSA for 20). Kidney length was measured from plain abdominal radiographs or intravenous urograms and hypertrophy was expressed as the renal size index (RSI). Of 37 kidneys with a RSI greater than 2 standard deviations from the mean, 36 had less than 15% of total function in the contralateral diseased kidney. Kidneys with less than 10 or 15% of total renal function could be selected with 97 or 80% sensitivity and 84 or 97% specificity, respectively, using the same RSI selection level.