Stephan R. Orth

In the not-so-distant past, type 2 diabetes mellitus was thought to be a relatively benign condition, at least in the elderly, with relatively little effect on life expectancy or renal function.1 It has now become obvious that type 2 diabetes must be taken every bit as seriously as type 1 diabetes, in part because of its renal complications.2 However, some recent and encouraging evidence indicates that diabetic nephropathy and deterioration of renal function are to a certain extent preventable.EpidemiologyAccording to the reports of the U.S. Renal Data System,3,4 in the past two decades there has been a . . .

The nephrotic syndrome is defined by a urinary protein level exceeding 3.5 g per 1.73 m2 of body-surface area per day. At the turn of the century, clinicians distinguished a nephritic syndrome of inflammatory origin and a nephrotic syndrome of presumed degenerative origin. Today these concepts are outmoded, but the term “nephrotic syndrome” is clinically useful and has persisted, because heavy proteinuria, irrespective of its origin, is associated with a spectrum of clinically important sequelae, particularly sodium retention, hyperlipoproteinemia, and thromboembolic and infectious complications. The definition given above is arbitrary, however, and special significance should not be given to the . . .

Despite the high prevalence of chronic kidney disease (CKD), relatively few individuals with CKD progress to ESRD. A better understanding of the risk factors for progression could improve the classification system of CKD and strategies for screening. We analyzed data from 65,589 adults who participated in the Nord-Trøndelag Health (HUNT 2) Study (1995 to 1997) and found 124 patients who progressed to ESRD after 10.3 yr of follow-up. In multivariable survival analysis, estimated GFR (eGFR) and albuminuria were independently and strongly associated with progression to ESRD: Hazard ratios for eGFR 45 to 59, 30 to 44, and 15 to 29 ml/min per 1.73 m(2) were 6.7, 18.8, and 65.7, respectively (P < 0.001 for all), and for micro- and macroalbuminuria were 13.0 and 47.2 (P < 0.001 for both). Hypertension, diabetes, male gender, smoking, depression, obesity, cardiovascular disease, dyslipidemia, physical activity and education did not add predictive information. Time-dependent receiver operating characteristic analyses showed that considering both the urinary albumin/creatinine ratio and eGFR substantially improved diagnostic accuracy. Referral based on current stages 3 to 4 CKD (eGFR 15 to 59 ml/min per 1.73 m(2)) would include 4.7% of the general population and identify 69.4% of all individuals progressing to ESRD. Referral based on our classification system would include 1.4% of the general population without losing predictive power (i.e., it would detect 65.6% of all individuals progressing to ESRD). In conclusion, all levels of reduced eGFR should be complemented by quantification of urinary albumin to predict optimally progression to ESRD.

Although it is beyond any doubt that smoking is the number one preventable cause of death in most countries, smoking as an independent progression factor in renal disease has been questioned against the background of evidence-based criteria. This is because information from large, randomized, prospective studies that investigate the effects of smoking on renal function in healthy individuals as well as in patients with primary or secondary renal disease are lacking. Since 2003, a substantial number of clinical and experimental data concerning the adverse renal effects of smoking have been published, including large, prospective, population-based, observational studies. These more recent data together with evidence from experimental studies clearly indicate that smoking is a relevant risk factor, conferring a substantial increase in risk for renal function deterioration. This review summarizes the present knowledge about the renal risks of smoking as well as the increased cardiovascular risk caused by smoking in patients with chronic kidney disease. The conclusion is that smoking is an important renal risk factor, and nephrologists have to invest more efforts to motivate patients to stop smoking.