• Peritoneal fluid analysis is often indicated to diagnose the causes of ascites.
• Peritoneal fluid is obtained via paracentesis, a procedure performed (often at bedside with sterile techniques) by inserting a needle/ catheter into the pleural cavity to drain out as much fluid as possible to both relieve discomfort (therapeutic benefit) and obtain the peritoneal fluid for analysis.
• The first step in the analysis is to determine whether the ascites is caused by hepatic congestion or other causes using SAAG (serum-ascites albumin gradient).
• Additional information can be obtained via peritoneal gross appearance, polymorphonuclear neutrophil (PMN) count, amylase, adenosine deaminase activity (ADA), triglyceride, urea, creatinine, cytology, microbiology, and other tests.
• SAAG (serum-ascites albumin gradient) is used to determine whether the ascites is caused by portal hypertension or something else
If SAAG > 1.1, the underlying cause is most likely portal hypertension
If SAAG < 1.1, the possible causes could be malignancy, infection, trauma, among others (as listed below)
• Additional information can be obtained via peritoneal gross appearance, polymorphonuclear neutrophil (PMN) count, amylase, adenosine deaminase activity (ADA), triglyceride, urea, creatinine, cytology, microbiology, and other tests.
• Among those, the most important test would be PMN count because it aids in the diagnosis of SBP (spontaneous bacterial peritonitis), a potentially life-threatening condition.
