Sonographically determined kidney length correlates with kidney function

Sonographic measurements of kidney length can provide valuable information about kidney function in transplant patients and donors, according to a study by Italian researchers. Kidney length correlated with glomerular filtration rate, the gold standard for measuring kidney function.

Renal function is usually calculated using a formula including serum creatinine concentration, age, sex, height, weight, and sometimes race to find the glomerular filtration rate.

Dr. G. Paleologo and colleagues at the division of nephrology and transplantation at Pisa Hospital in Italy studied the relationship between sonographic renal dimensions and glomerular filtration rate. They published their research in the July-August 2007 issue of Transplantation Proceedings.

Serum creatinine, serum cystatin, and glomerular filtration rate were measured in 33 kidney donors and 30 recipients. Two formulas for predicting glomerular filtration rate were also included in the comparison: the Cockcroft-Gault formula and the simplified Modification of Diet in Renal Disease formula.

The researchers used sonography to measure the renal sinus and the kidney's length, width, and depth. Analysis showed kidney length had the best correlation with the glomerular filtration rate of all the sonographic measurements.

Kidney length had a slightly closer correlation in donors than recipients, but in both cases, the correlation of kidney length to glomerular filtration rate was as strong as the correlation between the two prediction formulas and the measured rate. Kidney length was statistically as accurate an indicator of glomerular filtration rate impairment as labratory tests, although in kidney donors the Cockcroft-Gault formula showed better accuracy.