A pneumoperitoneum is ascites, and causes of pneumoperitoneum are commonly seen in diseases of the liver. It can also be seen in kidney disease, poor heart function, malnutrition, severe infection, trauma, and tuberculous peritonitis and malignancy. Patients with cirrhosis have increased intracapillary pressure and increased plasma colloid osmotic pressure due to hypoproteinemia and portal hypertension, which cause a large amount of water to leak into the abdominal cavity to form peritoneal fluid. The presence of nephrogenic ascites, in patients with nephrotic syndrome and uremia, can also lead to peritoneal effusion because of hypoproteinemia. If the patient has afternoon hypothermia, cough, night sweats, abdominal tenderness, and rebound pain, consider peritoneal effusion due to tuberculous peritonitis. Digestive tract malignancies that have retroperitoneal metastases can also cause peritoneal effusion. Kidney cancer and bladder cancer can also cause peritoneal effusion. Patients with right heart failure can also cause peritoneal effusion because of obstructed venous return, liver stasis, and water and sodium retention.