• Knowledge of anatomy and physiology of the abdomen is important to avoid unexpected outcomes.

• Intestines and bladder lie immediately beneath the abdominal surface.

• Large volumes of ascitic fluid tend to float the air-filled bowel toward the midline, where it may be easily perforated during the procedure.

• The cecum is relatively fixed and is much less mobile than the sigmoid colon; therefore, bowel perforations are more frequent in the right lower quadrant than in the left.

• Peritoneal fluid is normally straw-colored, serous fluid secreted by the cells of the peritoneum. Grossly bloody fluid in the abdomen is abnormal.

• The peritoneal fluid collected is used to evaluate and diagnose the cause of ascites, acute abdominal conditions such as peritonitis or pancreatitis, and blunt or penetrating trauma to the abdomen.

• Therapeutic paracentesis is used to reduce intraabdominal and diaphragmatic pressures to relieve dyspnea and respiratory compromise and prevent hernia formation and diaphragmatic rupture.^12,15,16,19 These complications are seen in those patients with tense, refractory ascites with failed medical interventions such as sodium restriction and diuresis.^5,15,19

• Ascitic fluid is produced as a result of a variety of conditions.¹⁰ These conditions may include interference in venous return because of heart failure, constrictive pericarditis, or tricuspid valve insufficiency; obstruction of flow in the vena cava or portal vein; disturbance in electrolyte balance, such as sodium retention; depletion of plasma proteins because of nephrotic syndrome or starvation; lymphoma, leukemia, or neoplasms that involve the liver or mediastinum; ovarian malignant disease; chronic pancreatitis; and cirrhosis of the liver.

• Analysis of the ascitic fluid can determine the cause of ascites. A serum-to-ascites albumin gradient should be calculated by subtracting the ascitic fluid albumin level from the serum albumin value. This calculation differentiates portal hypertensive from nonportal hypertensive ascites.^{5,7,9,10,14,19}

• Paracentesis is contraindicated in patients with an acute abdomen, who need immediate surgery. Coagulopathies and thrombocytopenia are considered relative contraindications. Coagulopathy should preclude paracentesis only in the case of clinically evident fibrinolysis or clinically evident disseminated intravascular coagulation.^12,16

• Caution should be used when paracentesis is performed in patients with severe bowel distention, previous abdominal surgery (especially pelvic surgery), pregnancy (use open technique after first trimester), distended bladder that cannot be emptied with a Foley catheter, or obvious infection at intended site of insertion (cellulitis or abscess).

• The insertion site should be midline one third the distance from the umbilicus to the symphysis, or 2 to 3 cm below the umbilicus (Fig. 107-1). An alternate position is a point one third the distance from the umbilicus to the anterior iliac crest (left side preferred).^5,19

• Ultrasound scan can be used before paracentesis to locate fluid and during the procedure to guide insertion of catheter. The ultrasound scan may be performed by the practitioner performing the procedure or by other personnel trained to conduct the study. Ultrasound scan–guided paracentesis has a higher success rate when compared with the procedure performed with physical examination as the lone assessment tool.⁸ Endoscopic transgastric ultrasound scan has also been used in the diagnosis of malignant ascites.¹²

• A semipermanent catheter or a shunt may be an option for patients with rapidly reaccumulating ascites.^13,15,16

• When large-volume paracentesis (>5 L) is performed in patients with cirrhosis and other disorders, the infusion of albumin, 6 to 8 g/L of fluid removed, may prevent the onset of circulatory compromise associated with massive fluid shifting.^1,3,6,7,18

• Commercially prepared kit or the following: