From the Guidelines
The workup for small ascites found on ultrasound should begin with a thorough clinical assessment, including history, physical examination, abdominal doppler ultrasound, laboratory assessment of liver and renal function, serum and urine electrolytes, and a diagnostic paracentesis for analysis of the ascitic fluid, as recommended by the American Association for the Study of Liver Diseases in 2021 1.
Initial Evaluation
The initial evaluation of ascites should consider various potential causes, including cirrhosis, malignancy, heart failure, tuberculosis, and pancreatic disease. A detailed medical history should focus on risk factors for these conditions, and a comprehensive physical examination should look for signs of chronic liver disease, heart failure, or malignancy.
Laboratory Tests and Paracentesis
Laboratory tests should include:
- Complete blood count
- Comprehensive metabolic panel (including liver function tests, albumin, total protein)
- Coagulation studies
- Serum-ascites albumin gradient (SAAG) if paracentesis is performed Diagnostic paracentesis is crucial and should include:
- Cell count with differential
- Total protein
- Albumin
- Glucose
- Lactate dehydrogenase
- Gram stain
- Culture
- Cytology
Additional Tests and Imaging
Additional tests may include:
- Serum alpha-fetoprotein, carcinoembryonic antigen, and CA-125 if malignancy is suspected Further imaging such as contrast-enhanced CT or MRI of the abdomen and pelvis may be necessary to evaluate for liver cirrhosis, portal hypertension, malignancy, or other causes. Echocardiography should be considered if cardiac causes are suspected, as recommended by the American Association for the Study of Liver Diseases in 2021 1.
Classification of Ascites
The classification of ascites can be done according to the amount of fluid accumulation, with Grade 1 being mild ascites only detected by ultrasound, Grade 2 being moderate ascites with symmetric distension of the abdomen, and Grade 3 being large or gross ascites with marked distension of the abdomen, as outlined in the 2021 practice guidance by the American Association for the Study of Liver Diseases 1.
Key Points
- A thorough clinical assessment is essential to determine the underlying cause of ascites
- Diagnostic paracentesis is crucial for analyzing the ascitic fluid
- Laboratory tests and imaging studies should be guided by the clinical assessment and suspected underlying cause
- The classification of ascites can help guide management and treatment decisions, as recommended by the American Association for the Study of Liver Diseases in 2021 1.
From the Research
Diagnostic Approach
The workup for small ascites found on ultrasound involves a combination of physical examination, laboratory tests, and imaging studies.
- A careful history and physical examination should be performed to rule out conditions that mimic ascites 2.
- Ultrasonography should be performed in questionable cases of ascites since physical examination and radiographic signs of ascites are unreliable 2, 3.
- Abdominal paracentesis with appropriate ascitic fluid analysis is a cost-effective method of determining the cause of ascites 4.
Ascitic Fluid Analysis
Ascitic fluid analysis should include:
- Serum-ascites albumin gradient (SAAG) to determine the cause of ascites 5, 4
- Total protein concentration
- Cell count and differential
- Optional tests: cholesterol, fluid culture, cytology, tumor markers, lactate dehydrogenase, adenosine deaminase (ADA), triglyceride, amylase, glucose, brain natriuretic peptide (BNP) 4
Imaging Studies
- Ultrasound is a reliable tool for ascites detection and can be used to guide paracentesis 3, 6
- Pocket ultrasound devices can be used as a complement to physical examination for ascites evaluation and guided paracentesis 3, 6
Diagnostic Algorithm
A diagnostic algorithm for patients with new-onset ascites should include: