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)].