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Related Subjects: | Chronic liver disease | Cirrhosis | Alkaline phosphatase (ALP) | Liver Function Tests | Ascites Assessment and Management | Budd-Chiari syndrome | Autoimmune Hepatitis | Primary Biliary Cirrhosis | Primary Sclerosing Cholangitis | Wilson disease | Hereditary Haemochromatosis | Alpha-1 Antitrypsin (AAT) deficiency | Non alcoholic steatohepatitis (NASH) | Spontaneous Bacterial Peritonitis | Alcoholism and Alcoholic Liver Disease

The serum-ascites albumin gradient or gap (SAAG) is a calculation used to determine the cause of ascites. The SAAG may be a better discriminant than the older method of classifying ascites fluid as a transudate versus exudate. A SAAG = 11 g/L suggests ascites is due to portal hypertension

About

• Ascites is due to the collection of free fluid in the peritoneal space.
• Commonly associated with liver cirrhosis and malignancy.

Aetiology

• Hypoalbuminaemia
• Activation of RAA system causing sodium and water retention
• Portal hypertension

Clinical

• Abdomen is distended and there is central resonance due to bowel loops floating to the top of the fluid and leaving fluid dullness in flanks
• If the patient rolls on onto their from the supine position the gas-filled bowel loops again float on top of the fluid and the area that was dull and at the highest point becomes resonant.
• Ascites may be seen with any intra-abdominal pathology and with low albumin e.g. kwashiorkor

Investigations

• Protein levels: a useful test is to measure the difference in the protein level in Ascitic fluid compared with plasma.
• Gram stain and culture for Bacteria and TB in selected cases
• Cell count : Causes of a neutrophil count > 250 /ml is diagnostic of spontaneous bacterial peritonitis
• Glucose: A low glucose is seen with TB/Malignancy and a high amylase with pancreatitis.
• Cytology : Malignant cells
• Amylase : suggests related to pancreatitis
• USS: Can detect ascites. Clinically needs 500 mls to be detected and 1.5 L for reliable clinical detection

Classification

• Serum Albumin - Ascitic albumin) of > 11 g/l
  • Transudate as the Ascitic albumin is low
  • Portal hypertension, Cirrhosis, Alcoholic hepatitis
  • Hepatocellular carcinoma, Budd-Chiari syndrome
  • RV failure, Constrictive pericarditis, Myxoedema
  • Meig's syndrome (ovarian tumour, ascites, hydrothorax)
• Serum Albumin - Ascitic albumin) of < 11 g/L
  • Exudate as Ascitic albumin higher
  • Malignancy, Tuberculosis, Pancreatitis
  • Hypothyroidism, Nephrotic syndrome

Management

• Bed rest, salt restriction, daily weights and measure U&E
• Therapeutic paracentesis is the first-line treatment for patients with large or refractory ascites.
• Paracentesis of < 5 litres of uncomplicated ascites should be followed by plasma expansion with a synthetic plasma expander and does not require volume expansion with albumin.
• Large volume paracentesis should be performed in a single session with volume expansion being given once paracentesis is complete, preferably using 8 g of 20% Albumin for each litre of ascites removed (ie. 100 ml of 20% albumin per 3 L ascites)
• Close observation is needed. Sodium restriction to 2 g/day.
• Hold diuretics if intravascular low volume. May eventually need Spironolactone 50-400 mg /day or Furosemide 20-160 mg /day
• TIPS: TIPS can be used for the treatment of refractory ascites requiring frequent therapeutic paracentesis or hepatic hydrothorax with appropriate assessment of risk benefit ratio
• Transplant should be considered where useful in patients with cirrhotic ascites
• Patients with ascites and previous SBP should be on prophylactic antibiotics e.g. norfloxacin or Ciprofloxacin

References

• BGS guidelines on managing ascites
• Human albumin in the management of complications of liver cirrhosis