How can I differentiate between transudative and exudative ascites based on laboratory findings?

To differentiate between transudative and exudative ascites based on laboratory findings, the Serum-Ascites Albumin Gradient (SAAG) is the most accurate and widely used parameter [3, Huang et al. 2014]. The SAAG is calculated by subtracting the ascitic fluid albumin concentration from the serum albumin concentration [3, Huang et al. 2014].

Transudative ascites is indicated by a SAAG of 1.1 g/dL or greater (≥ 1.1 g/dL) [3, Huang et al. 2014]. This type of ascites is typically caused by portal hypertension, commonly seen in conditions such as cirrhosis or heart failure [3, Huang et al. 2014].

Exudative ascites is indicated by a SAAG of less than 1.1 g/dL (< 1.1 g/dL) [3, Huang et al. 2014]. Exudative ascites is generally associated with inflammation, infection, or malignancy [3, Huang et al. 2014].

While SAAG is the primary differentiator, other ascitic fluid parameters can provide further diagnostic clues, particularly for exudative causes [3, Huang et al. 2014]. These include total protein, lactate dehydrogenase (LDH), glucose, and cell count with differential [3, Huang et al. 2014]. For instance, a high ascitic fluid total protein concentration (typically > 2.5 g/dL) was historically used to classify exudates, but SAAG is now considered superior [3, Huang et al. 2014].