Sex differences in kidney size and clinical features of patients with uremia.

Background: Ultrasonographic evaluation of the kidney size is a useful method for assessment of the progression and, in some cases, the type of nephropathy. Ultrasonography (USG) also plays an important role in the evaluation of both acute and chronic renal failure.

Objective: To investigate the ultrasonographic appearance of the kidneys in patients with uremia, underlying renal diseases and clinical characteristics, including biological sex, were studied.

Methods: This was a retrospective study of data from consecutive adult patients with uremia starting a dialysis program between January 2005 and December 2006 at the nephrology department of a university hospital in Taiwan. Kidney size was determined by USG; demographic and clinical data were obtained prior to initiation of dialysis.

Results: Of the patients (167 men, 151 women) included in the analysis, diabetes mellitus (DM) was the leading cause of uremia (127/318; 39.9%). The distribution of DM was similar between male and female patients. In addition to levels of blood urea nitrogen and hemoglobin, body mass index was similar between male and female patients (mean [SD], 22.9 [3.1] vs 22.1 [3.4] kg/m(2), respectively). Female patients had significantly lower serum creatinine levels (P < 0.05) and higher estimated glomerular filtration rates (P < 0.01) than did male patients when they initiated chronic dialysis therapy. Among those with DM, male patients were younger and had larger kidney size on initiation of dialysis therapy than did female patients (age, 59.9 [9.4] vs 64.6 [11.9] years; right renal length, 10.3 [1.4] vs 9.5 [1.5] cm; left renal length, 10.4 [1.5] vs 9.5 [1.4] cm; all, P < 0.05). These sex differences in age and kidney size at the start of dialysis were not observed in patients who did not have DM. Patients with DM had significantly larger kidney size than those without DM (P < 0.05).

Conclusions: The kidney size of these uremic patients varied considerably, depending on sex and the underlying disease. Male patients with DM at the terminal stage of renal failure had larger kidney size and were younger at the start of dialysis therapy than female patients with DM. In uremic patients without DM, no such discrepancy was observed, and both male and female patients started dialysis therapy at a comparable age and kidney size.