Serum-Ascites Albumin Gradient Interpretation
A 57-year-old man with hepatitis C cirrhosis has progressive abdominal distension and ankle swelling. Examination shows spider angiomas, shifting dullness and pitting pedal edema, with no jugular venous distension. The serum-ascites albumin gradient is 16 g/L, ascitic total protein is 14 g/L, the polymorphonuclear count is 90 cells/mm³, cytology is negative and adenosine deaminase is not elevated. What does this ascitic fluid profile most strongly indicate?
- A.Right-sided heart failure with congestion
- B.Portal hypertension from cirrhosisCorrect
- C.Peritoneal carcinomatosis
- D.Tuberculous peritonitis
Explanation
A serum-ascites albumin gradient of 11 g/L or more, equivalent to 1.1 g/dL, indicates that ascites is driven by portal hypertension, and this gradient has about 97 % accuracy for that determination. The gradient works on Starling principles: high portal hydrostatic pressure forces relatively protein-poor ultrafiltrate into the peritoneal cavity, so ascitic albumin stays low while serum albumin remains comparatively higher, and the difference between them is wide. In cirrhosis the process is compounded by splanchnic arterial vasodilation, effective arterial underfilling and secondary activation of the renin-angiotensin-aldosterone system with avid sodium and water retention. The second-step discriminator is the ascitic total protein: a value below 25 g/L points to cirrhosis, where the hepatic sinusoids are already leaky and the sinusoidal barrier is damaged, whereas a value of 25 g/L or above with a high gradient points to cardiac ascites or Budd-Chiari syndrome, in which sinusoids remain intact and leak protein-rich fluid. Here the ascitic protein of 14 g/L, absent jugular venous distension and a normal echocardiogram exclude cardiac ascites. Peritoneal carcinomatosis and tuberculous peritonitis both produce a low gradient below 11 g/L with high ascitic protein, and are further excluded by the negative cytology and normal adenosine deaminase. A polymorphonuclear count of 90 cells/mm³ is below the 250 cells/mm³ threshold, so spontaneous bacterial peritonitis is not present. Treatment is sodium restriction to about 2 g daily plus spironolactone and furosemide in a 100 mg to 40 mg ratio, with large-volume paracentesis and albumin for tense ascites.
Why each option
- A.
- Cardiac ascites also gives a high gradient but with ascitic protein of 25 g/L or more, raised jugular venous pressure and abnormal cardiac function.
- B.
- Correct. A serum-ascites albumin gradient of 16 g/L with ascitic protein below 25 g/L in a cirrhotic patient indicates portal hypertensive ascites.
- C.
- Peritoneal carcinomatosis produces a low gradient with high ascitic protein and positive cytology.
- D.
- Tuberculous peritonitis produces a low gradient with lymphocyte predominance and elevated adenosine deaminase.
Reference: AASLD Practice Guidance: Diagnosis, Evaluation and Management of Ascites and Hepatorenal Syndrome, 2021
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