Ascitic Fluid LDH Levels

Function

Lactate Dehydrogenase (LDH) is an enzyme found in almost all body tissues. When cells are damaged or destroyed, LDH is released into the surrounding fluid. In the context of ascitic fluid (fluid accumulation in the abdomen), measuring LDH levels is a critical step in differentiating the cause of the effusion.

Why it is Ordered

Physicians order an ascitic fluid LDH test to help distinguish between transudative and exudative ascites. It is part of 'Light’s Criteria' (modified for peritoneal fluid) to evaluate the severity of inflammation or to detect the presence of malignancy and infection.

Associated Conditions

• Spontaneous Bacterial Peritonitis (SBP): Elevated LDH levels, combined with high neutrophil counts, often indicate an active infection within the peritoneal cavity.
• Malignancy: High levels of LDH in the fluid are frequently associated with peritoneal carcinomatosis (cancer that has spread to the abdominal lining).
• Secondary Peritonitis: Very high LDH levels (often greater than the upper limit of normal for serum) may suggest a hollow viscus perforation or an abscess.
• Cirrhosis: Typically presents with lower LDH levels in the fluid unless a secondary complication is present.

Summary

Understanding the LDH concentration in ascitic fluid allows clinicians to determine if the fluid buildup is due to systemic pressure changes (like heart failure or cirrhosis) or local abdominal pathology (like infection or cancer).