Urinothorax: Unexpected Cause of a Pleural Effusion

Abstract

To the Editor: Urinothorax is a rare type of pleural effusion, defined as urine in the pleural space. We report a case of urinothorax after a surgical ileal conduit and placement of bilateral percutaneous nephrostomy tubes. A 53-year-old man with a history of metastatic bladder cancer was admitted to our hospital. Three months previously, he had undergone radical cystoprostatectomy with formation of an ileal conduit and urinary diversion to an ostomy; subsequently, cellulitis occurred in the abdominal area. Because of the severity of the cellulitis, bilateral percutaneous nephrostomy tubes were placed in attempt to divert urine away from the stoma site and promote healing. However, the patient experienced ileal conduit leakage and required surgical revision to reposition the ileal conduit. During this surgery the nephrostomy tubes were removed. The next day, the patient developed rapidly worsening dyspnea and had a marked decrease in urinary output from the ileostomy. A chest x-ray film showed a new large right-sided pleural effusion (Figure 1). Therapeutic and diagnostic thoracentesis resulted in withdrawal of 3 L of straw-colored pleural fluid. Pleural fluid analysis revealed a transudative effusion with a pH of 7.24, protein level of 0.2 g/dL, and lactate dehydrogenase (LDH) level of 47 U/L. Simultaneous measurement of the serum protein and LDH revealed levels of 6.7 g/dL and 1179 U/L, respectively. The pleural fluid creatinine level was 12.2 mg/dL, and the serum creatinine level was 4.0 mg/dL. Cytologic studies, Gram stain, and cultures of the pleural fluid were negative. We suspected that this patient had urinothorax due to the sudden onset of respiratory distress, decrease in urinary output, and development of a large pleural effusion after removal of the nephrostomy tubes. To confirm urinothorax, it was necessary to perform thoracentesis so that the retrieved fluid could be evaluated for 3 critical diagnostic criteria1Hendriks J Michielson D Van Schil R Wyndaele J Urinothorax: a rare pleural effusion.Acta Chir Belg. 2002; 102: 274-275Crossref PubMed Scopus (13) Google Scholar: (1) the pleural fluid must be a transudate, (2) the pleural fluid-serum creatinine ratio must be greater than 1.0, and (3) the pH must be less than 7.3. On the basis of criteria of Light et al,2Light RW Macgregor MI Luchsinger PC Ball Jr, WC Pleural effusions: the diagnostic separation of transudates and exudates.Ann Intern Med. 1972; 77: 507-513Crossref PubMed Scopus (1202) Google Scholar pleural fluid is considered a transudate if 1 or more of the following are present: pleural fluid protein divided by serum protein is less than 0.5, pleural fluid LDH divided by serum LDH is less than 0.6, or pleural fluid LDH is less than two thirds of the upper limit of normal for the serum LDH. Usually, pleural fluid with a low pH is an exudate. However, with urinothorax, acidic urine migrates into the pleural space, causing a transudate with low pH.3Miller KS Wooten S Sahn SA Urinothorax: a cause of low pH transudative pleural effusions.Am J Med. 1988; 85: 448-449Abstract Full Text PDF PubMed Scopus (32) Google Scholar In our patient, urinothorax was confirmed by finding a transudative effusion with a pleural fluid pH of 7.24 and a pleural fluid-serum creatinine ratio of 3.05. Urinothorax was first described in 1968 by Corriere et al4Corriere Jr, JN Miller WT Murphy JJ Hydronephrosis as a cause of pleural effusion.Radiology. 1968; 90: 79-84Crossref PubMed Scopus (54) Google Scholar when they studied ureteral obstruction in dogs. Since then, only a few cases of urinothorax in humans have been reported in the literature. Reported causes are urinary obstruction, failed tube nephrostomy, inflammatory or malignant process of the urinary tract, blunt renal trauma, shock wave lithotripsy, and posterior urethral valves.5Oguzulgen IK Oguzulgen AI Sinik Z Kokturk O Ekim N Karaoglan U An unusual cause of urinothorax.Respiration. 2002; 69: 273-274Crossref PubMed Scopus (30) Google Scholar Once urinothorax is diagnosed, surgical revision of the obstruction usually results in resolution of the pleural effusion.6Kamble RT Bhat SP Joshi JM Urinothorax: a case report.Indian J Chest Dis Allied Sci. 2000; 42: 189-190PubMed Google Scholar Our patient had metastatic bladder cancer, an indication that his overall prognosis was poor, and his chance of surviving and recovering from another surgery was low. In accordance with the patient's previous wishes, his family decided it would be best not to pursue another surgery to correct the urinary leak; he died several hours later.