What exams, procedures, and tests diagnose the cause of ascites?
The diagnosis of ascites is based on physical examination in conjunction with a detailed medical history to ascertain the possible underlying causes since ascites is often considered a nonspecific symptom of other diseases. If ascites fluid is greater than 500ml, it can be demonstrated on physical examination by bulging flanks and fluid waves performed by the doctor examining the abdomen. Smaller amounts of fluid may be detected by an ultrasound of the abdomen. Occasionally, ascites are found incidentally by an ultrasound or a CT scan done for evaluating other conditions.
Diagnosis of underlying conditions causing ascites is the most important part of understanding the reason for a person to develop ascites. The medical history may provide clues to the underlying cause and typically includes questions about the previous diagnosis of liver disease, viral hepatitis infection and its risk factors, alcohol abuse, family history of liver disease, heart failure, cancer history, and medication history.
Blood work can play an essential role in evaluating the cause of ascites. A complete metabolic panel can detect patterns of liver injury, functional status of the liver and kidney, and electrolyte levels. A complete blood count is also useful by providing clues to underlying conditions. Coagulation (clotting) panel abnormalities (prothrombin time) may be abnormal because of liver dysfunction and inadequate production of clotting proteins.
Sometimes the possible underlying causes of ascites may not be determined based on the history, examination, and review of laboratory data and imaging studies. Analysis of the fluid may be necessary to obtain further diagnostic data. This procedure is called paracentesis, and it is performed by trained physicians. It involves sterilizing an area on the abdomen and, with the guidance of ultrasound, inserting a needle into the abdominal cavity and withdrawing fluid for further analysis.
For diagnostic purposes, a small amount (20cc, less than a tablespoon, for example) may be enough for adequate testing. Larger amounts of up to a few liters (large volume paracentesis) can be withdrawn if needed to relieve symptoms associated with abdominal ascites.
The analysis is done by sending the collected fluid to the laboratory promptly after drainage. Typically, the number and components of white blood cells and red blood cells (cell count), albumin level, gram stain and culture for any possible organisms, amylase level, glucose, total protein, and cytology (study of any cells in the fluid looking for malignant or cancerous cells) are analyzed in the laboratory. The results are then analyzed by the treating doctor for further evaluation and determination of the possible cause of ascites.