Size of the unaffected kidney in children with unilateral hydronephrosis

Compensatory renal growth due to neonatal ureteral obstruction: implications for clinical studies

In response to unilateral ureteral obstruction (UUO), the contralateral kidney undergoes compensatory renal growth, which is enhanced in early development. We investigated the renal growth response to UUO in the neonatal rat. Within 2 days of birth, animals were subjected to sham-operation, complete UUO, or variable partial UUO, and kidneys were harvested 3-60 days later. Contralateral kidney weight increased after only 7 days of complete UUO. Increase in contralateral kidney weight was not significant for partial UUO until 45 days, but kidney/body weight ratio increased after only 14 days of 0.3 mm partial UUO. The rate of contralateral renal growth increased with age and with increasing severity of UUO. In rats subjected to 45 days UUO, glomerular area was proportional to kidney/body weight ratio (r =0.61, p <0.01). We conclude that the rate of compensatory renal growth is dependent on the severity and duration of obstruction, and takes place at the single nephron level. The results suggest that biologic variability limits the early detection of compensatory renal growth, which is compounded by limitations in measuring renal size by clinical imaging. Factoring kidney length (or volume) by intervertebral length (or body surface area) should improve the precision of tracking renal growth.

Compensatory hypertrophy effectively assesses the degree of impaired renal function in unilateral renal disease

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.

Kidney growth after pyeloplasty in childhood

The postoperative increase of the renal parenchyma, measured with planimetry on repeated urography films, was studied in 24 infants and children. All patients had been operated on because of unilateral stenosis of the pelvioureteral junction. When the results were analyzed in a pair-control manner the paired members were almost identical for age at operation, affected side, sex, presenting clinical sign and length of followup. The 12 patients who underwent a dismembered pyeloplasty displayed a significantly stronger mean catch-up growth of the relative parenchymal area than the 12 patients who underwent a nondismembered technique. Speculatively, this difference may reflect in part the protection of the growing renal parenchyma by the preoperatively compliant and wide renal pelvis, which had led to resection and dismembered correction.

Renal size parameter. A sonographic method for measuring lumbar vertebral height in children

A method for measuring the L1-L3 and L1-L4 distance by sonography is presented, and the results are compared with measurements from radiography. For 35 children aged 2 months to 13 years (mean 5.2 years) sonographic measurements displayed a mean percentage variation of 2.4 to 3.2 per cent from radiographic values. The coefficient of correlation was about 0.98. As sonography is suitable for kidney length estimation, the additional information obtained by the method presented makes it possible to perform the same kidney size evaluation by means of the same length/vertebral body-related diagrams already used in radiographic kidney size evaluation.

Kidney size in children assessed by ultrasonography and urography

The accuracy of ultrasonographic evaluation of kidney size using the parameter of kidney length was compared with radiographic kidney length assessment by urography. The examination was performed in 102 children 0 to 14 years old in which 427 length comparisons for the right and left kidney were made. Approximately 85 per cent of all differences noted were within a variation interval of 0 to 1.0 cm which was considered to be a good accuracy and consistent with results previously reported. Ultrasonography was therefore regarded as a reliable and suitable alternative to urography in periodic controls of kidney size and growth in children.