Chronic renal failure

The kidneys perform a number of roles, which include regulation of water and inorganic ion balance, removal of metabolic waste products from the blood, and secretion of certain hormones. Chronic renal failure is a state in which there has been irreversible loss of these functions, sufficient to cause an impact on an individual’s health. Given that there is a significant amount of ‘‘renal reserve,’’ this only occurs when more than 50% of renal excretory capacity has been lost; for example, removal of a single kidney from a healthy person (e.g., living kidney donors) does not cause any long-term sequelae. Traditionally, serum creatinine has been used as a marker of renal function. This has always posed two problems. First, creatinine is affected by a number of variables apart from glomerular filtration rate (GFR), such as age, gender, race and body mass. Second, serum creatinine tends not to rise outside the normal range until around 50% of GFR has been lost. As a consequence certain groups of patients with renal disease—the frail and the elderly—tend to be detected late. Estimated GFR (eGFR) is now being used to provide a more accurate assessment of kidney function. This utilizes the four-variable modification of diet in renal disease (MDRD) equation, which takes into account age, gender, and race as well as serum creatinine, to give a measure of renal function. The U.S. Kidney Disease Outcomes Quality Initiative (K/DOQI) has introduced the term chronic kidney disease (CKD) to replace chronic renal failure. This classifies renal impairment into five stages on the basis of eGFR (Table 1) (1). All stages are associated with hypertension as well as an increased risk of cardiovascular disease. From stage 3 onward complications of renal failure such as renal anemia and renal bone disease start to develop. Stage 4 tends to be the point at which uremic symptoms occur. Stage 5 should prompt consideration of initiating renal replacement therapy (RRT), unless a conservative management plan has been agreed. The chief advantage to this classification is that it allows early identification of those patients who are at risk of progressive renal impairment (i.e., stages 1 and 2). In addition, it provides a standardized nomenclature worldwide for severity of chronic renal disease.