What is the significance and management of a high Serum-Ascites Albumin Gradient (SAAG) score indicating portal hypertension?

SAAG Score: Diagnostic Significance and Management

What is SAAG?

The Serum-Ascites Albumin Gradient (SAAG) is calculated by subtracting the ascitic fluid albumin concentration from the serum albumin concentration (measured on the same day), and serves as a highly accurate diagnostic tool that differentiates portal hypertension-related ascites from non-portal hypertension causes with approximately 97% accuracy. 1

Interpretation of SAAG Values

High SAAG (≥1.1 g/dL)

• Indicates portal hypertension as the cause of ascites with 97% accuracy 1
• Common causes include: 1
  • Cirrhosis (most common)
  • Cardiac ascites (right heart failure)
  • Budd-Chiari syndrome
  • Sinusoidal obstruction syndrome

Low SAAG (<1.1 g/dL)

• Suggests non-portal hypertension causes of ascites 1
• Common causes include: 1
  • Peritoneal carcinomatosis
  • Tuberculous peritonitis
  • Nephrotic syndrome
  • Pancreatic ascites

Initial Diagnostic Workup

The initial laboratory investigation of ascitic fluid should include an ascitic fluid cell count and differential, ascitic fluid total protein, and SAAG. 2

• If infection is suspected, culture ascitic fluid at the bedside in blood culture bottles prior to initiating antibiotics 2, 1
• Order additional testing based on clinical suspicion (cytology for malignancy, amylase for pancreatic ascites) 2, 1
• Do NOT test serum CA125 in patients with ascites—this test is nonspecific and can lead to unnecessary gynecologic surgery 2

Distinguishing Cardiac from Cirrhotic Ascites

When SAAG is ≥1.1 g/dL, check the ascitic fluid protein concentration to differentiate cardiac from cirrhotic causes: 1, 3

• High SAAG (≥1.1 g/dL) + High protein (>2.5 g/dL) = Cardiac ascites 1, 3
• High SAAG (≥1.1 g/dL) + Low protein (<2.5 g/dL) = Cirrhotic ascites 3

Management Based on SAAG

High SAAG Ascites (≥1.1 g/dL): Portal Hypertension

Patients with high SAAG ascites typically respond to sodium restriction and diuretics. 2, 1

Treatment Algorithm:

1. Dietary sodium restriction to 2000 mg/day (88 mmol/day) 2, 3

   • More stringent restriction is not recommended as it worsens malnutrition 2

2. Initiate oral diuretics: 3

   • Start with spironolactone 100 mg daily plus furosemide 40 mg daily
   • Maximum doses: spironolactone 400 mg/day and furosemide 160 mg/day

3. Treat the underlying liver disease: 2

   • Alcohol cessation is critical for alcoholic cirrhosis—patients with Child-Pugh class C who stop drinking have approximately 75% 3-year survival, but all who continue drinking die within 3 years 2
   • Antiviral treatment for decompensated hepatitis B can produce dramatic improvement 2
   • Consider liver transplantation evaluation for less reversible causes once ascites develops 2

4. Monitor response: 3

   • Measure 24-hour urinary sodium excretion if weight loss is inadequate
   • Target urinary sodium >78 mmol/day indicates adequate response

For Cardiac Ascites Specifically:

• Evaluate for right heart failure with echocardiography 3
• Optimize heart failure therapy 3
• Use the same sodium restriction and diuretic regimen as above 3
• Prognosis depends heavily on successful treatment of underlying heart failure 3

Low SAAG Ascites (<1.1 g/dL): Non-Portal Hypertension

Patients with low SAAG ascites generally do not respond to sodium restriction and diuretics (except nephrotic syndrome) and require treatment of the underlying disorder. 2, 1, 4

• Focus on treating the specific cause (chemotherapy for malignancy, anti-tuberculous therapy for TB peritonitis, etc.) 4
• Therapeutic paracentesis may be needed for symptomatic relief 4

Special Considerations and Pitfalls

Mixed Ascites

• Approximately 5% of patients have two or more causes of ascites 1, 4
• Patients with portal hypertension plus a second cause still have SAAG ≥1.1 g/dL 1
• This can complicate interpretation and treatment response 4

Correlation with Portal Hypertension Severity

• A SAAG value ≥1.435 g/dL predicts the presence of esophageal varices with 87.5% positive predictive value 5
• Higher SAAG values correlate with increased likelihood of varices (100% prevalence when SAAG ≥2.0 g/dL) 5
• However, SAAG level does not correlate with varix size 5

Rare Presentations

• Heart failure can rarely present with low SAAG ascites, requiring additional imaging (triphasic CT) to confirm portal hypertension 6
• When evaluating cardiac ascites, don't rely solely on SAAG without checking protein concentration 1

Large-Volume Paracentesis

• For tense ascites, perform large-volume paracentesis for rapid symptomatic relief 3
• Administer intravenous albumin at 8g per liter of fluid removed to prevent circulatory dysfunction 3
• Resume diuretics after paracentesis to prevent rapid reaccumulation 3

Prognostic Implications

Development of ascites indicates poor prognosis, with approximately 20% mortality in the first year. 3