INTRODUCTION

All patients with renal disease (whether acute or chronic) should undergo an assessment of renal function by estimating the glomerular filtration rate (GFR). This measurement is used clinically to evaluate the degree of renal impairment, to follow the course of the disease, and to assess the response to therapy. An attempt must also be made to obtain a specific diagnosis. The first step in this process is a careful urinalysis.

DEFINITIONS AND CLASSIFICATION

The definition and classification of chronic kidney disease may help identify affected patients, possibly resulting in the early institution of effective therapy. To achieve this goal, guidelines were proposed from the National Kidney Foundation of the United States through its Kidney Disease Outcomes Quality Initiative (K/DOQI) program . These guidelines have been reviewed and accepted internaBased upon these definitions, the following is the recommended classification of chronic kidney disease by stage and the estimated prevalence within the United States of each stage, as determined by a National Health and Nutrition Examination Survey (NHANES) performed in 1999 to 2004]:

  • Stage 1 disease is defined by a normal GFR (greater than 90 mL/min per 1.73 m2) and persistent albuminuria (1.8 percent of the total United States population)
  • Stage 2 disease is a GFR between 60 to 89 mL/min per 1.73 m2 and persistent albuminuria (3.2 percent)
  • Stage 3 disease is a GFR between 30 and 59 mL/min per 1.73 m2 (7.7 percent)
  • Stage 4 disease is a GFR between 15 and 29 mL/min per 1.73 m2 (0.21 percent)
  • Stage 5 disease is a GFR of less than 15 mL/min per 1.73 m2 or end-stage renal disease (2.4 percent for stages 5) tionally.

GENERAL MANAGEMENT OF CHRONIC KIDNEY DISEASE — The general management of the patient with chronic kidney disease involves the following issues [26]:

  • Treatment of reversible causes of renal dysfunction
  • Preventing or slowing the progression of renal disease
  • Treatment of the complications of renal dysfunction
  • Identification and adequate preparation of the patient in whom renal replacement therapy will be required

Reversible causes of renal dysfunction — In addition to exacerbation of their original renal disease, patients with chronic renal disease with a recent decrease in renal function may be suffering from an underlying reversible process, which if identified and corrected may result in the recovery of function

Decreased renal perfusion — Hypovolemia (such as vomiting, diarrhea, diuretic use, bleeding), hypotension (due to myocardial dysfunction or pericardial disease), infection (such as sepsis), and the administration of drugs which lower the GFR (such as nonsteroidal antiinflammatory drugs [NSAIDs] and ACE inhibitors) are common causes of potentially reversible declines in renal function.

Urinary tract obstruction — Urinary tract obstruction should always be considered in the patient with unexplained worsening renal function although, in the absence of prostatic disease, it is much less common than decreased renal perfusion. Patients with slowly developing obstruction typically have no changes in the urinalysis, no symptoms referable to the kidney, and initially maintain their urine output. Given this lack of clinical clues, renal ultrasonography is often performed to exclude urinary tract obstruction in patients with an unexplained elevation in the serum creatinine.

Slowing the rate of progression — Studies in experimental animals and humans suggest that progression in chronic kidney disease may be due at least in part to secondary factors that are unrelated to the activity of the initial disease. The major factors are thought to be intraglomerular hypertension and glomerular hypertrophy (which are primarily responsible for the adaptive hyperfiltration described above), leading to glomerular scarring (glomerulosclerosis). Additional causes may include hyperlipidemia, metabolic acidosis, and tubulointerstitial disease.

Treatment of the complications of renal dysfunction — A wide range of disorders may develop as a consequence of the loss of renal function. These include disorders of fluid and electrolyte balance, such as volume overload, hyperkalemia, metabolic acidosis, and hyperphosphatemia, as well as abnormalities related to hormonal or systemic dysfunction, such as anorexia, nausea, vomiting, fatigue, hypertension, anemia, malnutrition, hyperlipidemia, and bone disease. Attention needs to be paid to all of these issues.