Prerenal Acute Renal Failure (ARF)

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

Overview

Prerenal ARF is characterized by inadequate blood circulation (perfusion) to the kidneys, which leaves them unable to clean the blood properly. Many patients with prerenal ARF are critically ill and experience shock (very low blood pressure). There often is poor perfusion within many organs, which may lead to multiple organ failure.

Causes

Some of the most notable causes of prerenal ARF are dehydration, heart failure, sepsis (severe infection), and severe blood loss.

Prerenal ARF is associated with a number of preexisting medical conditions, such as atherosclerosis ("hardening" of the arteries with fatty deposits), which reduces blood flow. Dehydration caused by drastically reduced fluid intake or excessive use of diuretics (water pills) is a major cause of prerenal ARF. Many people with severe heart conditions are kept slightly dehydrated by the diuretics they take to prevent fluid buildup in their lungs, and they often have reduced blood flow (underperfusion) to the kidneys.

Risk Factors

• Atherosclerosis
• Blood loss
• Chronic liver disease
• Heart disease

Signs and Symptoms

Symptoms of prerenal ARF include the following:

• Dizziness
• Dry mouth
• Low blood pressure (hypotension)
• Rapid heart rate
• Slack skin
• Thirst
• Weight loss

Urine output is usually low in people with prerenal ARF. The patient also may have symptoms of heart or liver disease.

Complications
Many prerenal ARF patients are critically ill and require admission to an intensive care unit. They may suffer from severe infection, such as viral hepatitis. Decreased perfusion can cause acute organ failure, such as cardiac or liver failure. Symptoms of heart failure include:

• Dyspnea (shortness of breath)
• Edema (fluid retention and swelling)
• Venous engorgement

Symptoms of liver failure include:

• Confusion, disorientation, stupor
• Sweet, ammoniacal odor

Diagnosis

A complete physical examination and a medical history help the physician to diagnose prerenal ARF. In addition, laboratory studies often reveal a high BUN to Cr ratio (BUN:Cr > 20:1), along with abnormal urine chemistry. The physician often must rule out postrenal and intrinsic renal causes of acute renal failure.

Treatment

The goal of treatment is to improve of kidney perfusion (blood circulation). This usually involves treating the underlying condition (e.g., infection, heart failure, liver failure). Intravenous (IV) fluids are administered to most patients to treat dehydration.

Prognosis
In general, patients with prerenal ARF improve dramatically with intravenous fluids. Urine output increases and renal function improves.

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