MANAGING CHRONIC RENAL INSUFFICIENCY: DETECTION OF CHRONIC RENAL INSUFFICIENCY
The paucity of specific symptoms and signs in early renal insufficiency necessitates vigilance to detect renal failure. Depending on muscle mass, the serum creatinine concentration becomes elevated only after 60 to 70% of glomerular filtration rate is lost.
In actuality, therefore, what is generally described as “early” or “mild” chronic renal failure, usually referring to a rise in serum creatinine concentration to 2 to 3 mg/dL, represents a patient with less than 25% of normal glomerular filtration. Accordingly, in patients with a systemic disease known to cause renal failure such as polycystic kidney disease, annual measurements of the serum creatinine level should be obtained. Despite its imperfections as a surrogate for glomerular filtration rate, the serum creatinine concentration is an inexpensive and uniformly available satisfactory screening test for renal function. Once an elevated serum creatinine is detected, creatinine clearance should be measured. The patient will need follow-ups more frequently than once per year.
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Creatinine clearance can be estimated by the method of Cockroft and Gault (creatinine clearance = (140 age)(weight kg)/72 x (serum creatinine inmg/dL);less 15% for women), or it could be calculated by measuring 24-hour urine creatinine excretion (urine creatinine in grams per 24 hours x 70, divided by serum creatinine in mg/dL).
Also, many causes of renal failure first present with proteinuria, hematuria or exacerbation of hypertension preceding azotemia, and should trigger nephrologic evaluation. Among those with diabetes and a negative qualitative test for proteinuria, a first morning urine test for microalbuminuria—if positive—should be followed by a timed urine collection for measurement of protein and creatinine clearance annually.
APPROPRIATE REFERRAL TO THE NEPHROLOGIST
A National Institutes of Health consensus development panel on dialysis morbidity and mortality recommended that women with a serum creatinine concentration of 31.5mg/dL (132.6 micromoles/ liter) and men with a serum creatinine concentration 3of 2 mg/dL (176.8 micromoles/liter) should be referred to a nephrologist. Because serum creatinine concentration correlates with body mass and age, a small-sized (child) or geriatric patient whose serum creatinine doubles from 0.7 mg/dL (61.9 micromoles/liter) to 1.4 mg/dL (123.8 micromoles/liter) should be evaluated for renal failure.
Appropriate referral of a newly azotemic patient permits the nephrologist to: (a) identify reversible or treatable causes of renal insufficiency; (b) institute interventions to slow progression of renal failure, (c) manage and/or prevent complications of renal failure, and (d) educate patients and their families about renal failure to select the best applicable renal replacement therapy (Table 1).
Table 1. RELATIVE ROLES OF NON-NEPHROLOGIST AND NEPHROLOGIST
a)Early recognition and detection
c) Avoid further renal injury
d)Preserve arm blood vessels
e)Aggressive blood pressure control
f) Prompt referral to the nephrologist
a) Comprehensive initial evaluation, including urine microscopy, kidney sonography and kidney biopsy
b) Treatment of underlying etiology— cyclophosphamide, and steroids in some cases of glomerulonephritis
c) Interventions to slow progression of renal failure
d) Prevent or manage complications of chronic renal failure
e) Adequate preparation for renal replacement therapy
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No randomized prospective studies show that appropriate referral to a nephrologist favorably effects either survival or cost of care in patients with progressive renal insufficiency. Several nonrandomized studies, however, conclude that early referral improves patient outcomes, whereas delayed referral increases morbidity (acidosis and anemia), and prolongs hospital stay at initiation of dialysis (Table 2).
Table 2. CONSEQUENCES OF DELAYED REFERRAL OF PATIENTS WITH CHRONIC RENAL FAILURE
a) Missed Opportunity to Identify Reversible or Treatable Causes of Chronic Renal Failure.
b) Excess morbidity associated with complications of renal failure: anemia, etc.
c) Lack of adequate preparation for renal replacement therapy and exploration of options in uremia therapy.
d)Unmeasured effects, i.e., starting uremia therapy under emergency conditions without adequate preparation is a turn-off. May foster a negative attitude about dialysis therapy and may result in noncompliance.
e)Possible increased cost of care?
f) Delayed initiation of renal replacement
therapy. May be associated with excess
mortality among those with end-stage renal
Currently, 33% to 60% of patients with chronic renal insufficiency are not evaluated by a nephrologist until four months before the need for renal replacement therapy, precluding diagnostic evaluation. Delayed referral for nephrologic care is most common in the uninsured, blacks, Hispanics and older patients. As detailed below, initiation of a renoprotective strategy may delay progression to ESRD. generic cialis 20mg