A longitudinal study of kidney structure and function in adults.
BACKGROUND
Although kidney size is commonly measured in patients with chronic kidney disease (CKD), its relationship with kidney function is poorly understood. We conducted this longitudinal study to better understand the relationship between kidney size and function.


METHODS
We retrospectively studied 178 kidneys measured by ultrasound in 93 patients with CKD who did not have autosomal polycystic kidney disease. Renal function was measured using estimated glomerular filtration rate (GFR). A mixed model that accounted for repeated measurements or nested observations was used for statistical analysis.


RESULTS
In cross-sectional analyses, the following independent variables emerged as predictors of kidney size: estimated GFR along with its squared term, height, age and interactions of each of these two independent variables with aetiology of CKD. In longitudinal analyses over a median follow-up of 3.7 years, after accounting for predictors of baseline kidney size such as aetiology, height and estimated GFR, we found that kidney atrophy occurred at a rate of 0.072 cm/year (SD 0.016, P = 0.007). This atrophy was 'blunted' with declining GFR. Each 1 mL/min/1.73 m(2)/year greater decline in eGFR abrogated kidney atrophy by 0.015 cm/year (P = 0.024).


CONCLUSIONS
Although in cross-sectional surveys kidney size is directly related to function, the longitudinal relationship between form and function is inverted. Since the rate of change in GFR determines kidney atrophy, we conclude that kidney size is a determinant of renal prognosis.
Kariyanna
Shathabish S
SS
Division of Nephrology, Indiana University, Indianapolis, IN, USA.
Light
Robert P
RP
Agarwal
Rajiv
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001284:Atrophy; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000473:pathology*; D007676:Kidney Failure, Chronic / Q000503:physiopathology*; D007677:Kidney Function Tests; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012189:Retrospective Studies; D014463:Ultrasonography; D055815:Young Adult