The role of ultrasonography in the assessment of renal function in the elderly.
BACKGROUND
Ageing is associated with a progressive loss of renal mass and kidney length and a decline in glomerular filtration rate (GFR). This study evaluated a possible correlation between renal function and kidney size measured by ultrasonography (US), and whether the latter helps estimate GFR in the elderly.


METHODS
Twenty-five medically stable elderly patients (mean age 85 +/- 5 yrs) were examined in a geriatric ward at a university hospital. Blood samples were taken to determine serum creatinine (Cr) levels. On the same day, 51chromium ethylenediamine tetraacetic acid (51Cr-EDTA) clearance was performed as the gold standard of GFR. US measured kidney length, transverse and anteroposterior dimensions.


RESULTS
Serum Cr (r=-0.67; p=0.0002), Cockcroft-Gault formula (r=0.82; p<0.0001), absolute length (r=0.51; p=0.008) and volume kidney (r=0.46; p=0.02) correlated significantly with GFR. After receiver operating curve (ROC) analysis, length was less specific than sensitive in detecting renal impairment. Adding length to the Cockcroft-Gault formula did not improve GFR estimation (p=0.44). In contrast, adding length to serum Cr levels improved GFR estimation (p=0.015).


CONCLUSIONS
In the elderly, kidney length and volume significantly correlated with GFR. However, length has a low specificity in predicting renal impairment. Therefore, in clinical practice, serum Cr levels and calculated Cr clearance are more useful in predicting renal impairment. However, normal kidney length can help to exclude renal impairment in the elderly at risk of GFR underestimation by a calculated Cr clearance.
Van Den Noortgate
Nele
N
Department of Internal Medicine, Division of Geriatric Medicine, Ghent University Hospital, Ghent, Belgium. nele.vandennoortgate@rug.ac.be
Velghe
Anja
A
Petrovic
Mirko
M
Vandewiele
Christophe
C
Lameire
Norbert
N
Voet
Dirk
D
Afschrift
Marcel
M
D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D012372:ROC Curve; D051437:Renal Insufficiency / Q000175:diagnosis; D012680:Sensitivity and Specificity; D014463:Ultrasonography
D003404:Creatinine