UREA

What is Urea?

Urea is the major end product of protein metabolism.

• Formed in the liver via the urea cycle
• Excreted mainly by the kidneys
• Measured as Serum Urea or Blood Urea Nitrogen (BUN)

Normal Reference Range

• Serum urea: 15–40 mg/dL
• BUN: 7–20 mg/dL

(Values vary slightly by laboratory.)

1️⃣ Indicator of Renal Function

Urea is widely used to assess kidney function, though less specific than creatinine.

↑ Urea (Azotemia)

Occurs when:

• Decreased renal excretion
• Increased protein breakdown
• Dehydration

2️⃣ Types of Azotemia

A. Prerenal Azotemia

Cause: Reduced renal blood flow

Seen in:

• Dehydration
• Shock
• Congestive heart failure
• Severe burns

Features:

• ↑ Urea more than creatinine
• BUN/Creatinine ratio > 20:1

B. Renal Azotemia

Cause: Intrinsic kidney disease

Seen in:

• Acute kidney injury
• Chronic kidney disease
• Glomerulonephritis

Features:

• Both urea and creatinine ↑
• Ratio ~10–15:1

C. Postrenal Azotemia

Cause: Urinary obstruction

Seen in:

• Prostatic enlargement
• Renal stones
• Tumors

3️⃣ Increased Urea (Non-Renal Causes)

• High-protein diet
• Gastrointestinal bleeding
• Fever
• Severe infection
• Corticosteroid therapy
• Hyperthyroidism

4️⃣ Decreased Urea

Less common. Seen in:

• Severe liver disease (impaired urea cycle)
• Malnutrition
• Pregnancy
• Overhydration

5️⃣ Uremia

Marked elevation of urea with symptoms:

• Nausea and vomiting
• Fatigue
• Confusion
• Pericarditis
• Uremic frost (advanced cases)