The word ascites is derived from the Greek askos meaning “bag” or “sac.” Ascites, an abnormal accumulation of fluid in the abdominal cavity, has important implications diagnostically, therapeutically, and prognostically. Cirrhosis of the liver, which is usually related to alcoholism, accounts for 75% of cases of ascites; malignancy accounts for an additional 10% to 12%, and cardiac failure for another 5%. The remaining cases have a variety of etiologies.1 Unfortunately, the physical examination is not very reliable when it comes to detecting ascites, making paracentesis and ultrasound (US) important clinical tools.2 US-guided paracentesis has two key benefits. It not only facilitates performance of the procedure, but it also identifies patients in whom the procedure is not warranted or could potentially be harmful.3
Peritoneal aspiration of ascitic fluid or paracentesis was first described by Saloman in the early twentieth century.4 With the introduction of diuretics as well as a fear of procedure-related complications, paracentesis fell out of favor in the 1950s, being replaced by medical management. At that time, large-bore needles were being used and complication rates were significant. Clinical studies published in the late 1980s demonstrated that performing a paracentesis was, in fact, a safe procedure.5,6 Nowadays, the procedure is commonplace in Emergency Departments.
Paracentesis is an important diagnostic tool for patients with new-onset ascites to determine its etiology and in those patients with long-standing ascites to detect the presence of infection. Spontaneous bacterial peritonitis 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.7 It is well known that some patients with spontaneous bacterial peritonitis are asymptomatic, making peritoneal fluid aspiration, analysis, and cultures imperative.8 In addition to the diagnostic usefulness of paracentesis, large volumes of ascitic fluid can be removed therapeutically by this procedure in order 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 as well as in some cases of malignancy. Malignant ascites may occur with carcinoma of the ovary, pancreas, stomach, colon, breast, testes, and a variety of sarcomas and lymphomas.
The gross anatomy of the abdomen is well known to the Emergency Physician and is important to review in preparing for a paracentesis. The abdominal cavity is lined by the peritoneum and is protected from the environment by the abdominal wall musculature, fat, and skin. The right and left rectus muscles, which are nourished by 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 anterior abdominal wall structures vary above and below the level of the anterior superior iliac spine (Figure 65-1).