Acute Renal Failure (ARF)

Home » Acute Renal Failure (ARF) » Overview, Types, Symptoms, Causes, Diagnosis, Treatment, Prognosis

Overview

Acute renal failure (ARF) is the rapid breakdown of renal (kidney) function that occurs when high levels of uremic toxins (waste products of the body's metabolism) accumulate in the blood. ARF occurs when the kidneys are unable to excrete (discharge) the daily load of toxins in the urine.

Based on the amount of urine that is excreted over a 24-hour period, patients with ARF are separated into two groups:

• Oliguric: patients who excrete less than 500 milliliters per day (< 16 oz/day)
• Nonoliguric: patients who excrete more than 500 milliliters per day (> 16 oz/day)

In nonoliguric patients, the urine is of poor quality (i.e., contains little waste) because the blood is not well filtered, despite the fact that an adequate volume of urine is excreted.

Both kidneys are failing when ARF occurs. One normally functioning kidney can maintain adequate blood filtering.

Types

The three types of ARF are named for their location within the renal (kidney) system:

Prerenal ARF Postrenal ARF Intrinsic renal ARF

Click here to view enlarged image.

Incidence
ARF affects approximately 1% of patients on admission to the hospital, 2% to 5% during the hospital stay, and 4% to 15% after cardiopulmonary bypass surgery.

Signs and Symptoms

Acute renal failure does not produce a classic set of symptoms. The most common symptom is decreased urine output, which occurs in 70% of patients.

Diagnosis

ARF is most easily diagnosed by an increase in blood levels of creatinine and blood urea nitrogen (BUN). The blood level of creatinine typically increases by 0.5 milligrams per tenth of a liter (mg/dL) every day.

Treatment

There are several modalities of renal replacement therapy (RRT) for patients with acute renal failure:

• Intermittent hemodialysis
• Continuous hemodialysis (used in critically ill patients)
• Peritoneal dialysis (rarely used)

Prognosis
Before the development of renal replacement therapy (RRT), many people with ARF died from severe electrolyte imbalance (hyperkalemia, acidosis) or from the uremic toxins themselves. Patients with ARF are at risk for numerous complications that may lead to death, such as seizures, bleeding, and coma. Since dialysis effectively treats the life-threatening complications of ARF, advanced age and underlying diseases are more likely to determine the risk for a patient's dying from ARF.

Oliguric ARF patients continue to have a high mortality rate, despite the availability of RRT. Almost uniformly, these patients have other acute and/or chronic medical problems. Patients with nonoliguric ARF tend to have a more favorable prognosis and are often easier to treat. Nonoliguric ARF patients often have fewer systemwide complications because their condition typically is caused by drug-related toxicity and interstitial nephritis.

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