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Urinothorax: a rapidly accumulating transudative pleural effusion in a 64-year-old man.

Abstract: We report the case of a 64-year-old man who developed a rapid, right-sided pleural effusion. On initial presentation to the emergency room, the patient had fever and flank pain consistent with a ureteral obstruction (due to a bladder tumor) and associated hydronephrosis that had required previous placement of a pericuta-neous nephrostomy tube. After a 10-day stay in the hospital, the patient's urine output ceased. Symptomatic dyspnea with radiographic evidence of a new pleural effusion soon followed. Urinothorax was the etiology of the effusion.

Key Words: urinothorax, nephropleural fistula, pleural effusions, percutaneous nephrostomy


Urinothorax, the presence of urine within the pleural cavity, is a very rare cause of transudative pleural effusions. The most obvious and frequently reported causes involve urinary tract obstruction/trauma leading to hydronephrosis and urioma formation within the retroperitoneum. This, we feel, is the most likely explanation for the accumulation of urine within our patient's lung.

Case Report

Our patient, a 64-year-old man, presented to the emergency room with complaints of nausea and vomiting, flank pain, and a fever of 102[degrees]. He had a prior diagnosis of bladder cancer, small cell variant, and no surgical treatment was initiated. Records noted that 2 weeks prior, a right nephrostomy tube was placed due to ureter obstruction and associated hydronephrosis.

Upon physical examination, the patient appeared to be in no acute distress. The right lower lung was noted to have decreased breath sounds, and crackles were noted in the right middle lobe. The abdomen was mildly distended, and there was bilateral flank tenderness on palpation. A nephrostomy tube was noted to be emerging from the posterior right thoracic cage at the level of T10.

Laboratory results yielded a normal, complete blood count. Basic metabolic panel showed a glucose of 143 mg/dL, BUN of 29 mg/dL, and a creatinine of 2.5 mg/dL. Urinalysis was positive for large numbers of bacteria (4+), 80 to 100 white blood cells (WBC), 40 to 50 red blood cells (RBC), and 100 + protein. In addition, a 24-hour urine total protein was 1092 mg (<150). Urine culture revealed no growth at 48 hours. Sputum culture grew P aeruginosa. Admission chest x-ray showed right basilar atelectasis with possible pneumonia (Fig. 1).

The patient was administered antibiotics and remained stable over the next 10 days. On day 11, his serum creatinine increased to 5.3 mg/dL and urinary output ceased. This trend continued into day 12 when a pulmonary consult was requested due to severe dyspnea. Repeat LDH was 149 mg/dL and creatinine was 6.6 mg/dL. The chest x-ray (Fig. 2) and computed tomography (Fig. 3) scan revealed a large fluid collection in the right lower lobe with compression of the right lung.

Our patient's differential was somewhat challenging. The pleural fluid was a transudate, with a normal pH, and a pleural to serum ratio of LDH (0.168). The key criteria for the diagnosis of urinothorax, a pleural to serum creatinine ratio of >0.6, was present however, with a documented level at 1.96. (1,2)

Thoracentesis was performed and yielded 1.5 L of straw-colored fluid. Fluid analysis revealed a total protein of less than 1.0, pH of 7.5, LDH 25 mg/dL, glucose 115 mg/dL, creatinine 13 mg/dL, WBCs of 164, and RBCs of 208. Significant effusion persisted and a chest tube was inserted with 3.0 L of residual fluid removed. The patient died one week later due to his declining renal function and other causes.


Few cases of urinothorax have been reported. In 2004, Garcia-Pachon and Navas (3) found only 53 cases documented in the literature. However, lack of reported cases may in large part be due to lack of suspicion. Few pulmonologists list urine accumulation in their differentials when encountering a rapidly accumulating pleural effusion.

While most cases of urinothorax are due to obstruction, secondary to tumor/metastasis, or trauma of the ureter, there have been other reported causes. Retroperitoneal fibrosis, shock wave lithotripsy, and removal/blockage of nephrostomy tubes may result in the formation of an urioma. (3-5) A nephropleural fistula may form, allowing urine to enter the pleural cavity. (6) Another reported cause, and the likely origin of our case, is the placement of nephrostomy tubes too cephalically in the thorax. It is estimated that 0.5 to 1% of patients requiring pericutaneous nephrostomy placement may develop nephropleural fistulas. (7,8)

Diagnosis of urinothorax is similar to any pleural effusion. A chest x-ray and ultrasound are often obtained first, but in many cases a CT scan is required. If there is radiographic evidence of fluid, a diagnostic and therapeutic thorocentesis is indicated. (4-11) The evaluation to differentiate between transudates and exudates usually follows Light criteria (12) (Fig. 4) and include the following laboratory modalities: cytology, protein, LDH, pH, Gram stain, and culture and sensitivity. (3,13)



Urinothorax should be suspected if the sample is straw colored or has a urine-like odor. (4,6) Measurement of pleural creatinine to serum creatinine has been found to be the most reliable laboratory value and should be the definitive evaluation of urinothorax. (9,13) The average pleural fluid to serum creatinine ratio reported in 12 cases by Garcia-Parcho was 9.15 (range 1.09-19.8). (1-3) Secondly, due to the pH of urine, fluid in a urinothorax may be both transudative and acidic (<7.30). (3,9-11) Finally, a subtle deviation from Light criteria (12) may be found when pleural fluid contains urine; LDH levels may be high in comparison to serum levels. (3,13)

This case suggests that Light criteria (12) for the diagnosis of exudative pleural fluid will correctly differentiate between exudates and transudates, thus aiding the physician in the diagnosis. In addition, in the presence of urine, the pleural fluid will contain a higher creatinine level than in the serum. Urinothorax should be included in the differential in patients with hydronephrosis, (14) renal pathology or recent placement of a percutaneous nephrostomy tube.


Our sincerest gratitude is extended to Abingdon Internal Medicine and Associates, Johnston Memorial Hospital, and Edward Via Virginia College of Osteopathic Medicine.


1. Hendriks J, Michielsen D, Van Schil P, et al. Urinothorax: a rare pleural effusion. Acta Chir Belg 2002;102:274-275.

2. Miller KS, Wooten S, Sahn SA. Urinothorax: a cause of low pH transudative pleural effusions. Am J Med 1988;85:448-449.

3. Garcia-Pachon E, Padilla-Navas I. Urinothorax: Case report and review of the literature with emphasis on biochemical diagnosis. Respiration 2004;71:553-556.

4. Ray K, Rattan S, Yohannes T. Urinothorax: Unexpected cause of a pleural effusion. Mayo Clin Proc 2003;78:1433-1434.

5. Salcedo JR. Urinothorax: report of 4 cases and review of the literature. J Urol 1986;135:805-808.

6. Light RW. Clinical practice. Pleural effusion. N Engl J Med 2002;346:1971-1977.

7. Lallas CD, Delvecchio FC, Evans BR, et al. Management of nephropleural fistula after supracostal percutaneous nephrolithotomy. Urology 2004;64:241-245.

8. Munver R, Delvecchio FC, Newman GE, Preminger GM. Critical analysis of supracostal access for percutaneous renal surgery. J Urol 2001; 166:1242-1246.

9. Light RW. Update: Management of the difficult to diagnose pleural effusion. Clinical Pulmonary Medicine 2003;10:39-46.

10. Maskell NA, Butland RJA. BTS guidelines for the investigation of unilateral pleural effusion in adults. Thorax 2003;58:8-17.

11. Peek GJ, Morcos S, Cooper G. The pleural cavity. BMJ 2000;320:1318-1321.

12. Light RW, Macgregor MI, Luchsinger PC, et al. Pleural effusions: the diagnostic separation of transudates and exudates. Ann Intern Med 1972; 77:507-513.

13. Stark DD, Shanes JG, Baron RL, Koch DD. Biochemical features of urinothorax. Arch Intern Med 1982;142:1509-1511.

14. Belie JA, Milan DF. Pleural effusion secondary to ureteral obstruction. Urology 1979;14:27-29.
Do just once what others say you can't do, and you will never pay
attention to their limitations again.
--Captain James Cook

Samuel Deel, MS-4, BS, and Emory Robinette Jr, MD, FCCP

From Edward Via Virginia College of Osteopathic Medicine, Abingdon Internal Medicine Associates, and Johnston Memorial Hospital, Blacksburg, VA.

Reprint requests to Edward Via Virginia College of Osteopathic Medicine, c/o Sam Deel, 2265 Kraft Drive, Blacksburg, VA 24060. Email:

Accepted July 12, 2006.


* Urinothorax should be considered in patients with described renal pathology.

* Light criteria for pleural fluid diagnosis should be followed.

* It is important to evaluate both the pleural and serum creatinine levels in patients with rapidly accumulating effusions.
Light Criteria (5)

1) Pleural fluid protein/serum protein ratio greater than 0.5.
2) Pleural fluid LDH/serum LDH ratio greater than 0.6.
3) Pleural fluid LDH greater than two thirds the upper limits of normal
 of the serum LDH.

Fig. 4 Light criteria for pleural fluid diagnosis.
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Title Annotation:Case Report
Author:Robinette, Emory, Jr.
Publication:Southern Medical Journal
Date:May 1, 2007
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