Concise Review for CliniciansAcute Renal Failure: A Practical Update
Section snippets
EPIDEMIOLOGY
Rigorous study of ARF is complicated by the lack of a uniform definition. More than 20 definitions have been published in both basic science and clinical trials. Despite these difficulties, ARF occurs in approximately 1% of hospitalized patients, in as many as 20% of patients treated in ICUs, and as many as 4% to 15% of patients after cardiovascular surgery.1 Approximately 30% of patients who experience ARF will require renal replacement therapy.1 Community-acquired ARF occurs in approximately
ASSESSMENT OF THE PATIENT WITH ARF
Because of the various causes of ARF, effective use of history and medical chart review, physical examination, and laboratory testing are essential to recognize and correct the factors quickly that cause ARF. Results of these evaluations will help to classify patients into 1 of 3 major diagnostic categories of ARF: traditional prerenal, postrenal, and intrinsic renal.
POSTRENAL CAUSES
Postrenal causes account for 5% to 15% of cases of community-acquired ARF.1 A history of prostatism, urolithiasis, retroperitoneal disease, or use of medications known to cause crystalluria should prompt a thorough evaluation to rule out obstruction. Elderly and young patients are most commonly affected. Renal ultrasonography is an essential part of the work-up of any patient with ARF. However, ultrasonography is neither highly sensitive nor specific (sensitivity may be only 80%-85%); when the
RENAL CAUSES
Although the most common cause of ARF in the hospitalized patient is intrinsic renal failure due to ATN, the terms acute tubular necrosis and intrinsic renal failure are not synonymous. Delineating intrinsic ARF into the 4 distinct anatomical compartments of the kidney facilitates the most accurate categorization.
ARF IN THE RENAL TRANSPLANT RECIPIENT
The assessment of patients with ARF who have a renal allograft does not differ from that for the general population. Serum, urine, and radiographic studies are indicated. Therapeutic levels of immunosuppressive agents should be determined at the trough period.
Obstructive uropathy due to trauma, ureteral stenosis, or compression by lymphocoel is often seen; therefore, ultrasonography is a necessary first step in the evaluation. Doppler flow studies of the transplant's vascular supply are easily
THERAPY
The goal of any focused evaluation of ARF is immediate correction of its reversible causes. Recognition and relief of urinary outlet obstruction should be given the highest priority, especially for patients with anuria. Support of renal perfusion with either volume infusion or therapeutics that improve renal oxygen delivery should be considered before any attempt to improve urinary flow. Urinary indices should be examined before diuretic intervention.
Therapy to correct the pathophysiologic
SUMMARY
Acute renal failure is a multisystemic disorder that affects patients cared for by nearly all health care professionals. Its occurrence seems to be increasing in hospitalized patients. A structured approach to the evaluation of ARF will result in a quick diagnosis of the cause and facilitate rapid effective therapy. The clinician should recognize the growing list of medications and potential nephrotoxins that cause ARF.
Although morbidity statistics remain unacceptably high in patients with
Questions About ARF
- 1.
Which one of the following would not be associated with an elevated serum creatinine level, which may not reflect a decline in renal function?
- a.
Hypovolemia
- b.
Elevated serum ketone levels
- c.
Administration of select types of cephalosporin antibiotics
- d.
Elevated serum creatine kinase levels
- e.
Administration of cimetidine
- a.
- 2.
Which one of the following is not an indication for urgent dialysis therapy?
- a.
Pericarditis associated with severe azotemia
- b.
Hyperkalemia
- c.
Oliguria
- d.
Volume overload (congestive heart
- a.
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A question-and-answer section appears at the end of this article.