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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 1. Etiologically it is due to a disruption of the lymphatic system, most commonly obstructive due to a mass or traumatic (which maybe iatrogenic).
- abdominal distension
- abdominal discomfort
- dyspnea: splinting of the diaphragm by ascites
- sequelae of hypoproteinemia: edema
- acute abdomen: acute chylous peritonitis 2
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.
The pathogenesis of chylous ascites relies upon a disruption to the normal lymphatic pathways 1,2:
- 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
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.
On CT, chylous ascites is indistinguishable from water on density measurements. Fat-fluid levels are common.
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 2.
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