Urinothorax: An uncommon cause of pleural effusion
Article Outline
Abstract
Urinothorax is a rare cause of pleural effusion, and is typically the result of either obstructive uropathy or injury to the kidney or urinary tract. We report a case of a man who developed a right-sided urinothorax following percutaneous nephrolithotomy, and briefly discuss the pathophysiology, diagnosis, and management of this uncommon problem.
Keywords: Urinothorax, Urinary fistula, Pleural effusion, Percutaneous nephrolithotomy
1. Introduction
A 50-year-old man presented with dyspnea one month after a right percutaneous nephrolithotomy performed for calcium oxalate stones. A computed tomography (CT) scan showed a large right pleural effusion, which was drained with a CT-guided pleural catheter and yielded 1500
ml of clear yellow fluid. Fluid analysis showed a creatinine of 10.5mg/dl (serum level=4.2mg/dl), LDH of 822 units/ml (serum level=116 units/ml), pH of 7.28, total protein of 300mg/dl, and glucose of 115mg/dl. Retrograde pyelogram, ureteroscopy, and renal endoscopy failed to demonstrate any leakage of fluid from the ureters or kidney. Once output via the pleural catheter decreased to <100ml/day, the catheter was clamped for 48h. There was no reaccumulation of the pleural effusion, and the catheter was removed.
Over the next four days, however, the patient again became increasingly dyspneic. CT scan showed a large right loculated pleural effusion that required tube thoracostomy. A renal scan with technetium-99m labeled mercaptoacetyltriglycine (MAG-3) was performed, which showed extravasation of radiotracer from the kidney to the right chest cavity (Fig. 1). Repeat pyelogram and ureteroscopy again failed to demonstrate an urinothoracic fistula. Ultrasound revealed dilated right upper pole calices; however, a nephrostogram showed no communication of these calices with the rest of the collecting system. A percutaneous nephrostomy tube was placed in the dilated calices. Chest tube output decreased over the next nine days. Repeat MAG-3 scan demonstrated resolution of the extravasation from the right kidney to the pleural space (Fig. 2), and the chest tube was removed with no recurrence of the pleural effusion.
Fig. 1
MAG-3 scan demonstrating extravasation of urine from right kidney to right thorax.
Fig. 2
Repeat MAG-3 scan demonstrating resolution of renopleural fistula.
2. Discussion
Urinothorax is a rare cause of pleural effusion that is typically classified as having either an obstructive or traumatic/iatrogenic etiology (Table 1).1, 2 Urinothorax secondary to obstructive uropathy usually results in bilateral effusions, while traumatic causes of urinothorax usually lead to a unilateral effusion. A history of obstructive renal or bladder disease or potential trauma or injury to the kidney and urine collection system should increase the suspicion for urinothorax. Pleural fluid analysis can help confirm the diagnosis. A fluid:serum ratio of creatinine>1 has been suggested as an indicator of urinothorax, although this ratio may not reliably exclude other causes of pleural effusion.3, 4 In our patient, the initial pleural fluid:serum ratio of creatinine was >2.5, but ranged from 1.1 to 8 on repeat analyses in spite of his persistent urinothorax. Though a very high ratio is certainly suggestive of urinothorax, there appears to be a degree of variability in pleural fluid creatinine level in urinothorax that may complicate interpretation. Urinothorax is typically associated low protein levels and high LDH levels.4 Low pH and glucose levels have been reported as well, but do not serve as reliable indicators of the presence or absence of urinothorax. Findings on CT scan may include renal or bladder pathology, the presence of perirenal urinomas, or the extravasation of contrast-enhanced urine into the retroperitoneum or pleural space. Renal scan may be a better indicator of the presence of urinopleural fistula, however, as CT scans may show only the presence of a large effusion. Tc-99m labeled diethylenetriamine pentaacetic acid (DTPA) renal scan has been used in the past, though MAG-3 scans provide better resolution, employ less radiation, and are the preferred study today.5 More invasive studies, such as retrograde pyelogram and endoscopy of the renal collecting system, should be used when the possibility of a therapeutic intervention exists.
Table 1. Various etiologies of urinothorax.
| Obstructive | Iatrogenic/traumatic |
|---|---|
| Vesicoureteral reflux | Extracorporeal shock wave lithotripsy |
| Posterior urethral valves | Percutaneous nephrostomy |
| Benign prostatic hypertrophy | Renal transplantation |
| Retroperitoneal fibrosis | Ileal conduit surgery |
| Malignancy | Renal biopsy |
| Nephrolithiasis | Blunt trauma |
The treatment of urinothorax involves relieving urinary obstruction if present, and draining the effusion with simple tube thoracostomy if the patient is symptomatic. If the patient is minimally symptomatic or asymptomatic from a respiratory perspective, it is reasonable to forgo pleural drainage, as in some patients, the urinothorax will resolve by relieving the urinary obstruction alone. As our case demonstrates, the failure of an urinothorax to resolve likely indicates an inadequately drained renal collecting system that should be studied further and treated aggressively. There have been no reports to our knowledge of persistent urinothorax requiring operative management involving the diaphragm or thoracic cavity; the threshold for referring a patient for video-assisted thoracoscopic surgery (VATS) to identify and repair a renopleural fistula should therefore be high. An urologist should be consulted in the treatment of these patients; surgical correction of injuries or tears in the urinary system and even nephrectomy may be required if the urinothorax fails to respond to tube thoracostomy and relief of urinary obstruction.
Conflict of interest statement
None of the authors have a conflict of interest to declare in relation to this work.
References
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PII: S1755-0017(09)00008-6
doi:10.1016/j.rmedc.2009.01.009
© 2009 Elsevier Ltd. All rights reserved.
