Chylous ascites is a less common form of ascites resulting from a collection of lymph in the abdominal cavity due to an interruption in the lymphatic system. It is also called milky ascites because of the milky appearance of the fluid.
By definition, the presence of more than 200 mg per dl triglycerides in ascitic fluids is defined as chylous ascites though some use 110 cut off.
The incidence of this ascites has increased, probably due to the longer survival of cancer patients and greater frequency of abdominal and cardiothoracic procedures.
Chylous ascites accounts for less than 1% of cases. No difference in sex distribution is noted.
Pathophysiology and Causes
Long-chain fatty acids are converted into triglycerides in intestinal cells [enterocytes] and then coated with lipoprotein, cholesterol, and phospholipid to form chylomicrons.
These chylomicrons enter the lymphatic system which ultimately enters cisterna chili in front of the second lumbar vertebra.
Descending thoracic, right and left lumbar, and liver lymphatic trunks, join to form the thoracic duct which ultimately ends in the venous system.
A blockage in these channels may lead to chylous effusions.
Chylous ascites might occur due to
- Lymph flow obstruction due to pressure by (mass) leading to leakage
- Fistula into the peritoneal cavity
- Congenital lymphangiectasia
- Traumatic thoracic duct obstruction
Causes of Chylous Ascites
Following are known causes of chylous ascites
- Abdominal malignancy (most common)
- Small bowel lymphoma
- Small bowel angiosarcoma
- Retroperitoneal lymphoma
- Abdominal tuberculosis
- Spontaneous bacterial peritonitis
- Trauma following abdominal surgeries
- Aneurysm repair
- Lymph node dissection
- Inferior vena cava removal
- Peritoneal dialysis catheter implantation
- Splenorenal shunts
- Liver transplantation
- Fibrosis following radiotherapy
- Acute or chronic pancreatitis
- Constrictive pericarditis (Increased lymph production due to increased liver congestion)
- Idiopathic retroperitoneal fibrosis
- Whipple’s disease
- Nephrotic syndrome
- Carcinoid tumors
- Blunt abdominal trauma
- Pediatric patients
- Primary lymphatic hypoplasia or hyperplasia
- Yellow-nail syndrome – yellow discolored nails, lymphedema, pleural effusions, and/or chylous ascites
- Lymphangiectasia, mesenteric cyst, and idiopathic “leaky lymphatics.
- Battered child syndrome
Abdominal distention is the most common symptom. The presentation is often as painless progressive abdominal distention over the course of weeks to months.
However, in the case of abdominal or thoracic surgery, the presentation is acute.
Other signs are weight gain and shortness of breath in patients with chylous ascites.
One or more following non-specific symptoms may be associated
- Abdominal pain
- Weight loss in long-standing cases
- Steatorrhea (Fat-laden stools)
- Early satiety
Fever and night sweats are seen often in lymphoma patients.
It is worth emphasizing that often, clinical features of primary illness dominate.
Sepsis is the most common complication.
The biochemical and hematological profile would vary from disease to disease.
Following are the usual findings
- Decreased levels of albumin in the blood ( hypoalbuminemia)
- Decreased levels of lymphocytes (lymphocytopenia)
- Decreased hemoglobin (anemia)
- Increased levels of alkaline phosphatase and liver enzymes (more so in disseminated cancers)
- Decreased levels of sodium in the blood (hyponatremia)
- Normal serum cholesterol and triglyceride levels
Ascitic Fluid Studies
The ascitic fluid is removed by peritoneocentesis.
In chylous ascites, the fluid is milky in color. That is why this ascites is also called milky ascites.
Typical findings of chylous ascitic fluid are
- Triglyceride level above 200 mg/dL*
- Total leucocyte count above 500 (lymphocytic predominance)
- Total protein 5 and 7.0 g/dL
- SAAG below 1.1 g/dL
- Cholesterol ascites/serum ratio < 1
- Lactate dehydrogenase between 110 and 200 IU/L
- Glucose below 100 mg/dL
*Some authors use 110 mg/dl as cut off to diagnose chylous ascites
Cytology is useful in finding malignancy.
Culture may be positive in tuberculosis. Other tests done for tuberculosis diagnosis are smear examination and adenosine deaminase levels measurement.
Raised levels of amylase are found in pancreatitis.
Depending on the causation, the following additional tests may be conducted
- Lymph node biopsy
- Diagnostic laparoscopy or laparotomy
- Bone marrow examination
CT scan is the imaging of choice. MRI is not that helpful.
CT scan is useful in
- Finding extent and localization of fluid
- Finding Intra-abdominal lymph nodes and masses
- Determining the extent and localization of fluid
Lymphangiography and lymphoscintigraphy
- Assist in detecting abnormal retroperitoneal nodes
- Find leakage from dilated lymphatics
- Lymphangiography is the gold standard in defining cases of obstruction
- Lymphangiography [can temporarily worsen the chylous ascites due to use of oily contrast medium].
- Other complications are
- Tissue necrosis
- Fat embolism
The treatment of chylous ascites involves supportive measures, dietary changes and addressing the underlying cause.
- Paracentesis to drain built-up fluid – provides immediate relief but reaccumulation occurs. Repeated procedures increase the risk of bacterial peritonitis.
- Salt and water restriction
- Diuretic therapy,
It is known that lymphatic flow increases after a meal is taken. A low-fat diet with medium-chain triglyceride supplementation can reduce the flow of chyle into the lymphatics.
Bowel rest and parenteral nutrition may be considered for cases where dietary modification does not help.
Postsurgical chylous ascites usually resolves with supportive therapy. Surgical closure of the leak can be considered in patients who are a good candidate for surgery.
A small study has found that lymphangiography with lipiodol has been found to lead the resolution of lymphatic leakage in postoperative chylous ascites by stimulating a local inflammatory reaction.
Lymphangiography has been combined with lymphatic embolization in cases of refractory chylous ascites.
Peritoneovenous shunting has been used successfully in small numbers of patients with chylous ascites but shunt failure is common.
Treatment of the Primary cause
Malignant chylous ascites requires specific therapy directed at the primary cause as well as supportive therapy.
The underlying cause should be addressed whenever feasible.
Most of the cases will result in resolution of the symptoms and the ascites when underlying causes have been treated. This is especially true in patients who have an infectious, inflammatory, or hemodynamic cause.
Surgery may benefit patients with a postoperative, neoplastic, and congenital cause.
In adult patients, chylous ascites has a poor prognosis in case of malignancy and severe liver disease.
Adult patients with postsurgical and posttraumatic chylous ascites have a favorable prognosis. Pediatric patients also have a favorable prognosis.
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