In new onset ascites, the serum-ascites albumin gradient (SAAG) helps determine the presence of portal hypertension. The difference between the serum albumin level and ascites albumin level is the gradient. A gradient > 1.1 g/dL suggests a transudative ascites from portal hypertension, whereas a gradient <1.1 g suggests an exudative etiology.

Causes of portal hypertension are cirrhosis, alcoholic hepatitis, congestive heart failure, and liver metastases. Less common considerations are fulminant hepatic failure, Budd-Chiari syndrome, portal vein thrombosis, venous occlusive disease, fatty liver of pregnancy, myxedema, and mixed ascites.

Causes of a low gradient include nephrotic syndrome, peritoneal carcinomatosis, tuberculous peritonitis, pancreatic ascites, and connective tissue disease serositis. History of breast, colon, gastric or pancreatic cancers or signs and symptoms of malignancy raise suspicion for peritoneal carcinomatosis. The tap may be sanguinous. Cytology may differentiate among malignancies.

Patients with uncomplicated ascites from cirrhosis have an ascitic white blood cell (WBC) count < 500 cells/mL. In spontaneous bacterial peritonitis, the patient will have symptoms of fever and abdominal pain and a WBC count > 250 cells/mL with greater than 50% polymorphonuclear leukocytes (PMN). The ascitic fluid may be turbid. A Gram stain is usually not helpful, but cultures are useful.

Pitfalls

• Allowing the patient to move after marking the entry site, resulting in a dry tap or bowel perforation.
• Not mapping or identifying abdominal structures, such as bowel and bladder, leading to perforation.

Conclusion

Ultrasound may be used statically for paracentesis to mark the largest pocket of ascitic fluid or used dynamically for small fluid collections, increasing procedural success. It may also be used to identify anatomic structures to avoid.

Contributor Disclosures

Contributors

Dr. Scheer is an Ultrasound Fellow at SUNY Downstate, Kings County Hospital Center, Department of Emergency Medicine. Dr. Mehta is the Emergency Ultrasound Fellowship Director at SUNY Downstate/Kings County Hospital Center, Department of Emergency Medicine. Dr. Secko is Director of the Emergency Ultrasound Division at SUNY Downstate, Kings County Hospital Center, Department of Emergency Medicine. Dr. Robert Solomon is Medical Editor of ACEP News and editor of the Focus On series, core faculty in the emergency medicine residency at Allegheny General Hospital, Pittsburgh, and Assistant Professor in the Department of Emergency Medicine at Temple University School of Medicine, Philadelphia.

Disclosures

Dr. Scheer, Dr. Mehta, Dr. Secko, and Dr. Solomon have disclosed that they have no significant relationships with or financial interests in any commercial companies that pertain to this article.