The prevalence of chronic kidney disease (CKD), generally defined as a long-standing, irreversible impairment of kidney function, is substantially greater than the number of pts with end-stage renal disease (ESRD), now ≥500,000 in the United States. There is a spectrum of disease related to decrements in renal function; clinical and therapeutic issues differ greatly depending on whether the glomerular filtration rate (GFR) reduction is moderate (stage 3 CKD, 30–59 mL/min per 1.73 m2) (see Table 46-1), severe (stage 4 CKD, 15–29 mL/min per 1.73 m2), or “end-stage renal disease” (stage 5 CKD, <15 mL/min per 1.73 m2). Dialysis is usually required once GFR <10 mL/min per 1.73 m2. Common causes of CKD are outlined in Table 139-1.
TABLE 139-1COMMON CAUSES OF CHRONIC RENAL FAILURE |Favorite Table|Download (.pdf) TABLE 139-1COMMON CAUSES OF CHRONIC RENAL FAILURE
|Diabetic nephropathy |
|Hypertensive nephropathya |
|Renovascular disease (ischemic nephropathy) |
|Polycystic kidney disease |
|Reflux nephropathy and other congenital renal diseases |
|Interstitial nephritis, including analgesic nephropathy |
|HIV-associated nephropathy |
|Transplant allograft failure (“chronic rejection”) |
The first step in the differential diagnosis of CKD is establishing its chronicity, i.e., disproving a major acute component. The two most common means of determining disease chronicity are the history and prior laboratory data (if available) and the renal ultrasound, which is used to measure kidney size. In general, kidneys that have shrunk (<10–11.5 cm, depending on body size) are more likely affected by chronic disease. While reasonably specific (few false positives), reduced kidney size is only a moderately sensitive marker for CKD, i.e., there are several relatively common conditions in which kidney disease may be chronic without any reduction in renal size. Diabetic nephropathy, HIV-associated nephropathy, and infiltrative diseases such as multiple myeloma or amyloidosis may in fact be associated with relatively large kidneys despite chronicity. Renal biopsy, although rarely performed in pts with CKD, is a more reliable means of proving chronicity; a predominance of glomerulosclerosis or interstitial fibrosis argues strongly for chronic disease. Hyperphosphatemia, anemia, and other laboratory abnormalities are not reliable indicators in distinguishing acute from chronic disease.
Once chronicity has been established, clues from the physical examination, laboratory panel, and urine sediment evaluation can be used to determine etiology. A detailed history will identify important comorbid conditions, such as diabetes, HIV seropositivity, or peripheral vascular disease. The family history is paramount in the workup of autosomal dominant polycystic kidney disease or hereditary nephritis (Alport’s syndrome). An occupational history may reveal exposure to environmental toxins or culprit drugs (including over-the-counter agents, such as analgesics or Chinese herbs).
Physical examination may demonstrate abdominal masses (i.e., polycystic kidneys), diminished pulses or femoral/carotid bruits (i.e., atherosclerotic peripheral vascular ...