chylous ascites

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Chylous ascites (also known as chyloperitoneum) is defined as the abnormal intraperitoneal accumulation of milky lymphatic fluid with a triglyceride level >110 mg/dL . Etiologically it is due to a disruption of the lymphatic system, most commonly obstructive due to a mass or traumatic (which maybe iatrogenic).

Clinical presentation

abdominal distension
abdominal discomfort
dyspnea: splinting of the diaphragm by ascites
sequelae of hypoproteinemia: edema
acute abdomen: acute chylous peritonitis

For fluid aspirated from the abdomen to be chyle, triglycerides need to be elevated above 110 mg/dL (two to eightfold more than normal plasma concentration) with a specific gravity >1.012.

Pathology

Etiology

The pathogenesis of chylous ascites relies upon a disruption to the normal lymphatic pathways :

obstruction of the lymphatics: usually a mass e.g. malignancy
fistula between the lymphatics and the peritoneum/mesentery: usually trauma or surgery
leakage of retroperitoneal megalymphatics: usually congenital

Radiographic features

Large volume fluid in the peritoneal cavity is the normal finding. However, if the patient is allowed to remain supine for a short interval then the fat commonly rises to the top of the fluid (fat is less dense than water), producing a fat-fluid level (cf. chyluria), which is highly specific for chyloperitoneum.

CT

On CT, chylous ascites is indistinguishable from water on density measurements. Fat-fluid levels are common.

MRI

On MRI, due to its high fat content, chylous ascites often demonstrates distinctive signal drop out on fat saturated sequences.

History and etymology

Morton described a case of a boy dying from chylous ascites caused by tuberculosis in 1694, the first known appearance of this condition in the literature .