SAAG Calculator

Q: What is the most common cause of high SAAG ascites?

Cirrhosis. About 80% of people with ascites in the U.S. have it because of liver scarring from cirrhosis. Other high-SAAG causes are less common: Alcoholic hepatitis Heart failure Budd-Chiari syndrome (blocked liver veins) Portal vein blood clot Massive liver metastases

Q: How do you tell heart failure ascites from cirrhosis ascites?

Both give a high SAAG, so albumin alone will not separate them. Doctors add the total protein in the belly fluid: Total protein 2.5 g/dL or higher with a high SAAG points to heart failure or constrictive pericarditis. Total protein under 2.5 g/dL with a high SAAG points to cirrhosis. A blood BNP or NT-proBNP test and an echocardiogram help confirm a heart cause.

Q: Do diuretics change the SAAG result?

No. Water pills pull fluid out, so the albumin in both the blood and the belly fluid rises together. The gap between them stays about the same. This is one reason SAAG replaced the old transudate-exudate protein test, which does shift when a person is on diuretics.

Q: Does an albumin infusion affect the SAAG?

It can raise the serum albumin quickly, which may widen the gap for a short time. To avoid confusion, blood should be drawn before the infusion or at the same time as the tap. If the two samples are hours or days apart, the number may not be reliable.

Q: Can a person with cirrhosis have a low SAAG?

Yes, but it is rare (about 3% of cases). Common reasons: Serum albumin is so low (under about 1.1 g/dL) that a wide gap is not possible Blood and fluid were taken days apart Lab or unit error A second cause is present, like infection or cancer Repeating the test usually clears it up.

Q: What is mixed ascites?

Mixed ascites means two causes at once, such as cirrhosis plus cancer or cirrhosis plus tuberculosis. It happens in about 5% of cases. The SAAG usually stays high because portal hypertension is still there. A high fluid protein, abnormal cytology, or a poor response to treatment can be clues that something else is going on too.

Q: What other tests are run on ascitic fluid?

A first tap usually includes: Cell count with differential. 250 or more neutrophils per mm³ means spontaneous bacterial peritonitis (SBP) Culture. Bottles filled at the bedside Total protein. Helps sort heart vs. liver causes Albumin. For the SAAG Extra tests, added when needed: glucose, LDH, amylase (pancreas), cytology (cancer), and adenosine deaminase or AFB culture (TB).

Q: Does spontaneous bacterial peritonitis change the SAAG?

No. In SBP the SAAG stays high because the underlying cause is still portal hypertension. The infection shows up in the cell count , not in the albumin gradient. A neutrophil count of 250 or more per mm³ means antibiotics should start right away, even before culture results return.

Q: Can a bloody tap change the SAAG?

Yes. Blood carries albumin, so a bloody sample can raise the albumin in the fluid and make the gradient look smaller than it really is. Tell the lab if the tap was traumatic. Repeating the tap at a different spot usually gives a clean sample.

Q: How is ascitic fluid albumin collected?

Through a paracentesis. A doctor numbs a small spot on the lower belly, usually the left side, and uses ultrasound to find a safe pocket of fluid. A thin needle draws the fluid out. Only a few milliliters are needed for the albumin test. A diagnostic tap takes a few minutes and does not require fasting or stopping most medicines.

Introduction

The SAAG calculator works out the Serum-Ascites Albumin Gradient. This is the difference between the albumin in your blood and the albumin in the fluid in your belly (ascites). Doctors use this number to find out why the fluid built up.

The math is simple: SAAG = serum albumin − ascites albumin. But the answer tells you a lot. A SAAG of 11 g/L (1.1 g/dL) or higher points to high pressure in the portal vein, which is common in cirrhosis, heart failure, and Budd-Chiari syndrome. A SAAG under 11 g/L points to other causes, like cancer, TB, pancreatitis, or kidney problems. This test is about 97% accurate at telling these two groups apart, which is why the AASLD guideline favors it over the old "transudate vs. exudate" protein test.

Enter both albumin values and pick your units. The tool accepts g/dL or g/L, and it converts them for you, so mixed units will not give you a wrong answer. The result appears right away, along with a step-by-step solution and a chart that shows both values next to the 11 g/L cut-off.

Draw both samples on the same day for the best result. This calculator is a learning and support tool. It does not replace your doctor's judgment or a full workup.

How to use our SAAG Calculator

Enter two lab values: the albumin in your blood and the albumin in your ascites fluid. The SAAG calculator subtracts one from the other and shows the serum-ascites albumin gradient in g/L and g/dL, plus what that result means.

Serum Albumin: Type the albumin level from the blood test taken the same day as the tap. Pick g/dL or g/L from the drop-down next to the box. Normal is about 3.5 to 5.5 g/dL (35 to 55 g/L).

Ascites Albumin: Type the albumin level measured in the ascitic fluid sample. Pick g/dL or g/L for this value too. There is no normal range for this one.

Chart & table units: Choose g/L or g/dL to set how the bar chart and the value table show the numbers. This does not change your answer, only how it is displayed.

The result updates as you type. Press Calculate to refresh it, or Clear to start over. A SAAG of 11 g/L (1.1 g/dL) or higher points to portal hypertension. A lower SAAG points to other causes, like cancer or infection.

What Is the Serum-Ascites Albumin Gradient (SAAG)?

Ascites is fluid that builds up in the belly. The SAAG test helps doctors find out why that fluid is there. It compares the amount of albumin (a protein made by the liver) in the blood with the amount of albumin in the belly fluid. The bigger the gap, the more likely the cause is high pressure in the portal vein, the large vein that carries blood to the liver.

How SAAG Works

The formula is simple:

SAAG = Serum albumin − Ascites albumin

Both samples should be taken on the same day. Blood is drawn for the serum albumin. Belly fluid is taken during a paracentesis, a procedure where a thin needle removes fluid from the abdomen. Labs report albumin in g/dL or g/L. 1 g/dL equals 10 g/L.

What the Numbers Mean

The cutoff is 11 g/L (1.1 g/dL).

SAAG 11 g/L or higher (high gradient): Portal hypertension is likely. Common causes are cirrhosis, alcoholic hepatitis, heart failure, and Budd-Chiari syndrome. This fluid is usually transudative.
SAAG under 11 g/L (low gradient): Portal hypertension is unlikely. Common causes are cancer spread to the lining of the belly, tuberculosis, pancreatitis, and nephrotic syndrome. This fluid is usually exudative.

Why Doctors Use It

SAAG is about 97% accurate at sorting ascites into these two groups. That beats the older transudate-exudate test based on total protein. Knowing the group narrows down the cause fast and guides treatment, such as salt limits and diuretics for advanced liver disease, or cancer care for malignant ascites.

Things to Keep in Mind

SAAG tells you if portal hypertension is present. It does not name the exact disease.
A result close to 11 g/L can flip sides with normal lab variation. Repeat testing may help.
A person can have more than one cause at once, such as cirrhosis plus cancer.
A negative result (ascites albumin higher than serum albumin) usually means a mix-up in samples or units. Check the report.
Ascitic fluid should also be checked for cell count, culture, and total protein to look for infection like spontaneous bacterial peritonitis.

Reference: Runyon BA; AASLD Practice Guidelines Committee. Management of adult patients with ascites due to cirrhosis: update 2012. Hepatology. 2009;49(6):2087-2107.

Formulas used

Unit conversion to g/L

C_{\text{g/L}} = C_{\text{g/dL}} \times 10

Serum-Ascites Albumin Gradient (g/L)

\text{SAAG}_{\text{g/L}} = \text{Serum Albumin}_{\text{g/L}} - \text{Ascites Albumin}_{\text{g/L}}

SAAG expressed in g/dL

\text{SAAG}_{\text{g/dL}} = \frac{\text{SAAG}_{\text{g/L}}}{10}

Interpretation threshold

\text{SAAG} \ge 11\ \text{g/L}\ (1.1\ \text{g/dL}) \Rightarrow \text{portal hypertension likely};\quad \text{SAAG} < 11\ \text{g/L} \Rightarrow \text{portal hypertension unlikely}

Frequently asked questions

What is the most common cause of high SAAG ascites?

Cirrhosis. About 80% of people with ascites in the U.S. have it because of liver scarring from cirrhosis.

Other high-SAAG causes are less common:

Alcoholic hepatitis
Heart failure
Budd-Chiari syndrome (blocked liver veins)
Portal vein blood clot
Massive liver metastases

How do you tell heart failure ascites from cirrhosis ascites?

Both give a high SAAG, so albumin alone will not separate them. Doctors add the total protein in the belly fluid:

Total protein 2.5 g/dL or higher with a high SAAG points to heart failure or constrictive pericarditis.
Total protein under 2.5 g/dL with a high SAAG points to cirrhosis.

A blood BNP or NT-proBNP test and an echocardiogram help confirm a heart cause.

Do diuretics change the SAAG result?

No. Water pills pull fluid out, so the albumin in both the blood and the belly fluid rises together. The gap between them stays about the same.

This is one reason SAAG replaced the old transudate-exudate protein test, which does shift when a person is on diuretics.

Does an albumin infusion affect the SAAG?

It can raise the serum albumin quickly, which may widen the gap for a short time. To avoid confusion, blood should be drawn before the infusion or at the same time as the tap.

If the two samples are hours or days apart, the number may not be reliable.

Can a person with cirrhosis have a low SAAG?

Yes, but it is rare (about 3% of cases). Common reasons:

Serum albumin is so low (under about 1.1 g/dL) that a wide gap is not possible
Blood and fluid were taken days apart
Lab or unit error
A second cause is present, like infection or cancer

Repeating the test usually clears it up.

What is mixed ascites?

Mixed ascites means two causes at once, such as cirrhosis plus cancer or cirrhosis plus tuberculosis. It happens in about 5% of cases.

The SAAG usually stays high because portal hypertension is still there. A high fluid protein, abnormal cytology, or a poor response to treatment can be clues that something else is going on too.

What other tests are run on ascitic fluid?

A first tap usually includes:

Cell count with differential. 250 or more neutrophils per mm³ means spontaneous bacterial peritonitis (SBP)
Culture. Bottles filled at the bedside
Total protein. Helps sort heart vs. liver causes
Albumin. For the SAAG

Extra tests, added when needed: glucose, LDH, amylase (pancreas), cytology (cancer), and adenosine deaminase or AFB culture (TB).

Does spontaneous bacterial peritonitis change the SAAG?

No. In SBP the SAAG stays high because the underlying cause is still portal hypertension. The infection shows up in the cell count, not in the albumin gradient.

A neutrophil count of 250 or more per mm³ means antibiotics should start right away, even before culture results return.

Can a bloody tap change the SAAG?

Yes. Blood carries albumin, so a bloody sample can raise the albumin in the fluid and make the gradient look smaller than it really is.

Tell the lab if the tap was traumatic. Repeating the tap at a different spot usually gives a clean sample.

How is ascitic fluid albumin collected?

Through a paracentesis. A doctor numbs a small spot on the lower belly, usually the left side, and uses ultrasound to find a safe pocket of fluid. A thin needle draws the fluid out.

Only a few milliliters are needed for the albumin test. A diagnostic tap takes a few minutes and does not require fasting or stopping most medicines.

What SAAG do you see in cancer-related ascites?

Usually low, under 11 g/L (1.1 g/dL), with a high fluid total protein. This happens when cancer coats the lining of the belly (peritoneal carcinomatosis).

The exception: if cancer has spread widely through the liver or blocks the portal vein, the SAAG can be high. Cytology on the fluid is the test that finds cancer cells.

Does the SAAG need to be repeated?

Usually not. Once the gradient is known, it rarely changes. Repeat it only if the picture shifts, such as new fever, fast weight gain, or fluid that stops responding to treatment.

Repeat taps are still done to check for infection or to drain large amounts of fluid, but the albumin gradient does not need rechecking each time.

What is the SAAG in tuberculous peritonitis?

Low, under 11 g/L (1.1 g/dL), with a high total protein and many lymphocytes in the fluid.

Because TB cultures are slow, doctors often add an adenosine deaminase (ADA) test. TB in someone who also has cirrhosis can still show a high SAAG.

What are the signs of ascites?

Common signs:

Swollen, tight belly
Fast weight gain over days or weeks
Shortness of breath when lying flat
Feeling full after small meals
Swollen ankles

New belly pain, fever, or confusion in someone with ascites needs urgent care, since these can mean infection.

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