Differential Diagnosis for SAAG Ratio Less Than 1.1

The Serum-Ascites Albumin Gradient (SAAG) is a useful tool in determining the cause of ascites. A SAAG ratio less than 1.1 typically indicates a non-portal hypertensive cause of ascites. Here's a differential diagnosis categorized for clarity:

• Single Most Likely Diagnosis

  • Peritoneal Carcinomatosis: This condition, where cancer spreads to the peritoneum, is a common cause of ascites with a low SAAG ratio. The mechanism involves the direct involvement of the peritoneal surface by tumor, leading to fluid accumulation.

• Other Likely Diagnoses

  • Tuberculous Peritonitis: A form of tuberculosis that affects the peritoneum, leading to ascites. It's more common in areas with high TB prevalence and can present with a low SAAG.
  • Pancreatic Ascites: Leakage from a pancreatic duct or a pseudocyst can cause ascites with a low SAAG ratio.
  • Bacterial Peritonitis: Spontaneous bacterial peritonitis (SBP) can occur without portal hypertension, especially in the context of a perforated viscus or other sources of infection.
  • Nephrotic Syndrome: Although less common, severe nephrotic syndrome can lead to ascites due to hypoalbuminemia, which would result in a low SAAG ratio.

• Do Not Miss Diagnoses

  • Spontaneous Bacterial Peritonitis (SBP) in Cirrhotic Patients with Portal Hypertension but Low SAAG: Although the SAAG ratio suggests a non-portal hypertensive cause, cirrhotic patients can occasionally have a low SAAG due to other factors like severe hypoalbuminemia. Missing SBP can be fatal.
  • Intra-abdominal Sepsis: Any cause of intra-abdominal infection (e.g., perforation, abscess) can lead to ascites with a low SAAG and requires prompt diagnosis and treatment to avoid high mortality.

• Rare Diagnoses

  • Chylous Ascites: Due to obstruction or disruption of the lymphatic system, leading to the accumulation of chyle in the peritoneal cavity.
  • Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, which can lead to ascites.
  • Sclerosing Encapsulating Peritonitis: A rare condition where the small bowel is encapsulated by a thick, fibrotic membrane, potentially leading to ascites among other symptoms.

Each of these diagnoses has a distinct pathophysiology and clinical presentation, but they can all present with a SAAG ratio less than 1.1, highlighting the importance of a thorough diagnostic workup in patients with ascites.