Elsevier

Mayo Clinic Proceedings

Volume 84, Issue 2, February 2009, Pages 129-133
Mayo Clinic Proceedings

ORIGINAL ARTICLE
Pleural Fluid Characteristics of Chylothorax

https://doi.org/10.4065/84.2.129Get rights and content

OBJECTIVE

To determine the biochemical parameters of chylous pleural fluids and better inform current clinical practice in the diagnosis of chylothorax.

PATIENTS AND METHODS

We retrospectively reviewed 74 patients with chylothorax (defined by the presence of chylomicrons) who underwent evaluation during a 10-year period from January 1, 1997, through December 31, 2006. The biochemical parameters and appearance of the fluid assessed during diagnostic evaluation were analyzed.

RESULTS

The study consisted of 37 men (50%) and 37 women (50%), with a median age of 61.5 years (range, 20-93 years). Chylothorax was caused by surgical procedures in 51%. The chylous pleural fluid appeared milky in only 44%. Pleural effusion was exudative in 64 patients (86%) and transudative in 10 patients (14%). However, pleural fluid protein and lactate dehydrogenase levels varied widely. Transudative chylothorax was present in all 4 patients with cirrhosis but was also seen with other causes. The mean ± SD triglyceride level was 728±797 mg/dL, and the mean ± SD cholesterol value was 66±30 mg/dL. The pleural fluid triglyceride value was less than 110 mg/dL in 10 patients (14%) with chylothorax, 2 of whom had a triglyceride value lower than 50 mg/dL.

CONCLUSION

Chylothoraces may present with variable pleural fluid appearance and biochemical characteristics. Nonmilky appearance is common. Chylous effusions can be transudative, most commonly in patients with cirrhosis. Traditional triglyceride cutoff values used in excluding the presence of chylothorax may miss the diagnosis in fasting patients, particularly in the postoperative state.

Section snippets

PATIENTS AND METHODS

We conducted a computer-assisted search of the electronic medical records at Mayo Clinic's site in Rochester, MN, and identified 103 consecutive adults (≥18 years) with chylothorax diagnosed during the 10-year period from January 1, 1997, through December 31, 2006. We included only patients with chylomicrons present in the pleural fluid as demonstrated by lipoprotein analysis. Of these patients, 74 (72%) had biochemical data available for the purpose of classifying the pleural fluid as

Demographic and Clinical Features

The 37 men (50%) and 37 women (50%) had a median age of 61.5 years (range, 20-93 years). Pleural effusion was unilateral in 58 patients (78%). Of these 58 patients, the effusion involved the right hemithorax in 39 (67%) and the left hemithorax in 19 (33%). Pleural effusion was bilateral in the remaining 16 patients (22%).

Surgical procedures were the cause of chylothorax in 38 patients (51%). These procedures included thoracotomy with lung resection and mediastinal lymphadenectomy (16 patients),

DISCUSSION

In the current study, gross appearance of the fluid was not a sensitive diagnostic criterion in identifying chylothorax. Less than half of chylous pleural effusions (44%) had the classic milky appearance attributed to chylothorax. This finding likely relates to the variable lipid content of the effusion, a direct consequence of the nutritional status of the patient. In some cases, another factor may have contributed to the formation of pleural effusion (eg, surgical trauma). Gross appearance of

CONCLUSION

Chylothoraces may present with variable pleural fluid appearance and biochemical characteristics. Nonmilky appearance is a common presentation and may cause the diagnosis of chylothorax to be overlooked. Chylous effusions may be associated with a wide range of total protein and LDH values, sometimes resulting in a transudative character by currently used criteria. Because triglyceride levels also vary in patients with chylothorax, traditional triglyceride cutoff values used in excluding the

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