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Ascites is an abnormal accumulation of fluid in the abdominal cavity (Figure 83-1). It has important implications diagnostically, prognostically, and therapeutically. Cirrhosis of the liver is usually related to alcoholism and accounts for 75% of cases of ascites.1,2 Malignancy accounts for an additional 10% to 12% and cardiac failure for another 5%. The remaining cases have a variety of etiologies. The physical examination is not very reliable when it comes to detecting ascites, making paracentesis and ultrasound (US) important clinical tools.3 US-guided paracentesis has two key benefits. It facilitates performance of the procedure and identifies patients in whom the procedure is not warranted or could potentially be harmful.4
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Peritoneal aspiration of ascitic fluid or paracentesis was first described in the early twentieth century.5 Paracentesis fell out of favor in the 1950s with the introduction of diuretics and the fear of procedure-related complications and was replaced by medical management. Large-bore needles were being used at that time, and complication rates were significant. Clinical studies published in the late 1980s demonstrated that performing a paracentesis was a safe procedure.6,7 A paracentesis is now common in Emergency Departments.
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Paracentesis is an important diagnostic tool for patients with new-onset ascites to determine its etiology and in patients with long-standing ascites to detect the presence of an infection. Spontaneous bacterial peritonitis (SBP) can be a very subtle disease. Infection occurs in as many as 27% of cirrhosis patients admitted for evaluation of symptoms associated with their ascites.8 It is well known that some patients with SBP are asymptomatic.9 This makes peritoneal fluid aspiration, analysis, and cultures imperative.10 Large volumes of ascitic fluid can be removed therapeutically to improve a patient’s respiratory status and comfort level from the pressure of tense ascites. This often occurs in patients with end-stage liver disease and some cases of malignancy. Malignant ascites may occur with carcinomas (e.g., breast, colon, ovary, pancreas, stomach, and testes), lymphomas, and sarcomas.
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ANATOMY AND PATHOPHYSIOLOGY
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The abdominal cavity is partially lined by a serous membrane known as the peritoneum. The abdominal cavity is protected from the environment by the abdominal wall musculature, fat, and skin. The peritoneum serves as protection for its encased organs, secretes nutrients, and secretes proteins. Intraperitoneal organs include the stomach, first portion of the duodenum, jejunum, ileum, appendix, transverse colon, sigmoid colon, part of the rectum, liver, spleen, and the tail of the pancreas. The right and left rectus muscles are nourished by the epigastric vessels. The epigastric vessels meet in the midline at the avascular linea alba. The umbilicus is located along the lower portion of the linea alba. The layers of the ...