Ascites refers to fluid that accumulates within the peritoneal cavity. Although ascites is most commonly observed in patients with cirrhosis and resulting portal hypertension (approximately 85% of cases), 7% to 10% of patients with ascites develop secondary to a malignancy.1

The most common malignancies associated with the development of ascites include cancers of the colon/rectum, ovary, breast, lung, pancreas, liver, and lymphoma.2

Approximately 50% of patients with malignant ascites have peritoneal carcinomatosis with an additional 13% of patients having extensive liver metastases resulting in portal hypertension.2

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Malignant ascites can develop through several mechanisms: blocked lymphatic channels as a result of malignancy, direct production of fluid into the peritoneal cavity by highly active cancers, and when “functional” cirrhosis develops in patients with extensive hepatic metastases resulting in portal hypertension.

The development of malignant ascites carries a poor prognosis, with the median survival reported anywhere between 1 and 4 months.3,4

Patients with malignant ascites clinically present similarly to those with ascites secondary to cirrhosis. These patients might have similar physical exam findings to those with cirrhotics including spider angiomas, distended umbilical veins (caput medusa), sclera icterus, jaundice, anasarca, and a distended abdomen.

Upon closer examination of the abdomen, patients with malignant ascites may have increased dullness to percussion or shifting dullness.

Patients can complain of increasing abdominal girth, generalized abdominal pain and shortness of breath. Weight loss is a relatively non-specific symptom, but may be more common in those with an underlying malignancy.

An abdominal ultrasound can be performed to confirm the presence of ascites within the abdomen. Upon verification of ascites, patients can undergo paracentesis in order to remove ascitic fluid for analysis.

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Common studies conducted on ascitic fluid include cell count and differential, albumin, protein, cytology, and cultures. 

These studies can be used to evaluate the patient for both infectious and non-cancerous etiologies of the ascitic fluid. An absolute neutrophil count (ANC) of 250 cells/mm3 or more indicates spontaneous bacterial peritonitis (SBP) and is usually treated with antibiotics such as ceftriaxone. However, close to 10% of patients with peritoneal carcinomatosis will meet the criteria for diagnosis of SBP based on an ascitic ANC of 250 cells/mmor more.2