CHAPTER 6 David Feller‐Kopman Johns Hopkins Medical School, Baltimore, MD, USA Urinothorax is defined by the presence of urine within the pleural space and is most often associated with an obstructive uropathy. The mechanism behind the accumulation of urinothorax has not been consistently demonstrated in animals models, but many believe direct cephalad extension through the diaphragm and/or lymphatic transport are responsible. The true incidence of urinothorax is difficult to obtain as a recent review noted only 58 cases reported in the human literature. Some authors believe the true incidence is under‐reported, though it appears that the highest risk patients are those undergoing renal and/or ureteral manipulation, those with obstructive calculi, blunt abdominal trauma or those with genitourinary malignancy or infection. Aspiration of a urinothorax should reveal a straw‐coloured fluid, possibly even smelling like urine. The fluid is transudative and may present with a low pH, as urinary pH is often in the 5.0–7.0 range. Pleural glucose and protein levels are traditionally low; however, lactate dehydrogenase (LDH) levels may be high and run the risk of misclassifying the effusion as an exudate. A biochemical diagnosis has been classically obtained from a pleural fluid creatinine to serum creatinine ratio of greater than one. If further diagnostic studies are needed, the use of radionuclide scintigraphy (99mTc ethylene dicysteine) has been reported to be helpful. Treatment involves addressing the underlying genitourinary disease, as resolution of the effusion follows correction of the obstructive uropathy. If the effusion does not resolve within a few weeks, an alternative diagnosis should be sought. Yellow nail syndrome is a rare entity initially described in the 1960s associated with yellow or abnormal nails, lymphoedema, and respiratory symptoms including cough, dyspnoea and recurrent pleural effusions (Figures 6.1–6.3). The underlying mechanism has still not been elucidated but most believe functional and anatomical lymphatic problems are to blame. Figure 6.1 Dystrophic nail changes in a patient with typical yellow nail syndrome. Figure 6.2 CT of the thorax demonstrating a bland‐looking effusion in a patient with nail changes. Figure 6.3 Thoracentesis of fluid, demonstrating milky pleural fluid. Approximately 150 cases of yellow nail syndrome have been reported in the literature. Most patients present in the 4th–6th decade with bilateral pleural effusions. Yellow nail syndrome is a clinical diagnosis and though there are no pathognomonic features in pleural fluid analysis, they are typically exudative in nature. Thirty percent of patients present with a chylothorax. Effusions in yellow nail syndrome tend to be recurrent and difficult to control, but in those with chylothorax, thoracic duct ligation may be an option as are ventriculo‐peritoneal shunts (Figure 6.4). Figure 6.4 CT scan demonstrating a ventriculo‐peritoneal shunt.
Unusual Causes of Pleural Disease
Urinothorax
Yellow nail syndrome
Ovarian hyperstimulation syndrome
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