On the prognosis of IDDM patients with large kidneys.

Background: Approximately 10-30% of IDDM patients develop diabetic nephropathy depending on the metabolic control. Previous examinations on the significance of the kidney size prior to the manifestation of nephropathy produced varying results.

Methods: The present study, therefore, was designed to assess the correlation between sonographically determined kidney size and kidney function over 8 years in a follow-up examination, and to evaluate a potential risk pattern. Data could be collected from 73 (66%) of 110 IDDM patients with initially normal serum creatinine whose sonographically determined kidney volume (cm3 = L cm x W cm x D cm x pi/6) and kidney function (creatinine, albuminuria, beta2-microglobulin in serum) had been examined in 1986, and who had a diabetes duration of 1 month to 25 years at that time.

Results: 30% (11 of 37) patients with large kidneys (>170 cm3) reached at least one serious renal end-point (increase of serum creatinine by more than 50%, requirement of dialysis or kidney transplantation, or death in end-stage renal disease) versus one of 36 patients with normal kidney size (P<0.002). As many as 42% of patients with large kidneys developed abnormal creatinine values (>106 micromol/l) in contrast to only 20% of the patients with normal kidney volume (P<0.05). Six of seven patients with a more than 50% increase of serum creatinine from baseline showed large kidneys in 1986, but had a normal serum creatinine, and four also a normal urine albumin excretion. Furthermore all five patients with more severe end-points (two deaths in end-stage renal disease and three patients presently requiring dialysis) exhibited either an increased serum creatinine or large kidneys at baseline; four of these, however, were still in the normoalbuminuric state in 1986.

Conclusions: These results indicate that large kidneys might be a morphological marker for subsequent diabetic nephropathy, and as a consequence, renal insufficiency.