Diagnosis of Chylous Ascites
The diagnosis of chylous ascites is established by demonstrating a triglyceride level >200 mg/dL (often >1,000 mg/dL) in ascitic fluid obtained by paracentesis, which typically appears white and milky on gross examination. 1
Diagnostic Approach
Initial Fluid Appearance
- White, milky fluid on gross examination is the hallmark visual finding that should immediately raise suspicion for chylous ascites 1
- The characteristic appearance results from lipid-rich lymph accumulation in the peritoneal cavity due to lymphatic disruption 2
Confirmatory Testing
- Ascitic fluid triglyceride level >200 mg/dL confirms the diagnosis 1, 3
- Triglyceride levels often exceed 1,000 mg/dL in true chylous ascites 1
- This biochemical threshold distinguishes chylous ascites from other causes of turbid or cloudy ascitic fluid 3
Standard Ascitic Fluid Analysis
When chylous ascites is suspected, perform routine screening tests on the initial paracentesis specimen 1:
- Cell count with differential to assess for infection or malignancy 1
- Albumin concentration to calculate the serum-ascites albumin gradient (SAAG) 1
- Total protein concentration 1
- Culture if infection is suspected 1
Determining Underlying Etiology
- Calculate SAAG to distinguish portal hypertension-related causes (SAAG ≥1.1 g/dL indicates portal hypertension with 97% accuracy) 1
- Malignancy and cirrhosis account for approximately two-thirds of chylous ascites cases in Western countries 2, 3
- In adults, malignancies (particularly lymphomas) are responsible for the majority of cases, while congenital lymphatic anomalies predominate in children 4
Additional Diagnostic Investigations
When Further Workup is Needed
For cases requiring identification of the specific site of lymphatic disruption 5:
- Lymphoscintigraphy to assess lymphatic flow patterns 5
- Lymphography combined with CT using lipid-soluble contrast to define lymphatic dysplasia 5
- MRI when lymphography cannot adequately define the dysplasia or when lymphatic dilatation is present 5
- Diagnostic laparoscopy to directly visualize the peritoneal cavity, identify leakage sites, and assess extent of lymphatic abnormalities 5
Critical Pitfalls
- Do not rely solely on appearance: Turbid fluid can also result from infection or tumor cells, so triglyceride measurement is essential for definitive diagnosis 1
- Consider the clinical context: In adults with new chylous ascites, aggressive diagnostic evaluation including lymph node biopsy or laparotomy should be pursued early given the high likelihood of malignancy and poor prognosis (many patients die within 3 months) 4
- Pediatric cases differ: Conservative management should be attempted first in children before aggressive interventions, as congenital lymphatic anomalies are more common and many cases resolve spontaneously 4