INTRODUCTION: Urinothorax can be challenging to diagnose and needs a high index of suspicion particularly when complicated by co-existing pulmonary pathology.
CASE PRESENTATION: A 60 year old woman with hypertension, diabetes mellitus type 2, obesity, and smoking history was admitted to stroke ICU after she developed left sided weakness following surgical intervention. Patient was initially diagnosed with right staghorn calculus following repeated urinary tract infections with Escherichia coli. She underwent an elective nephrostolithotomy, which was complicated by renal pelvis perforation requiring placement of Malecot percutaneous nephrostomy tube. Post-operatively on day one patient developed stroke and MRI demonstrated acute ischemia in right frontoparietal region. Carotid ultrasound revealed bilateral carotid artery stenosis. Right sided crackles with a new right perihilar infiltrate on X-ray were also noted. She was started on appropriate therapy for stroke along with antibiotics. Patient developed shortness of breath on day two with decreased breath sounds on left side and complete opacification of left hemithorax suggesting atelectasis, which improved with aggressive pulmonary toilet. Patient improved subsequently and was about to undergo urinary stent placement with removal of nephrostomy tube on day eight. Procedure was abandoned secondary to dyspnea requiring oxygen. Physical examination showed absent breath sounds in both bases along with bilateral diffuse crackles and right sided rhonchi. X-ray demonstrated worsening infiltrates and bilateral pleural effusions (right greater than left). The WBC count was trending down (12.0 X 10*9/L compared to 23.8 X 10*9 on admission) and pro-BNP was 3960. Thoracocentesis yielded red turbid pleural fluid that was exudative by LDH criteria. Patient’s dyspnea improved, only to get worse in four days requiring oxygen through non-rebreather. Recurrence of right pleural effusion on chest X-ray raised suspicion of parapneumonic effusion with volume overload vs. urinothorax. A repeat thoracocentesis yielded one liter of cloudy reddish fluid, also an exudate making urinothorax less likely (pleural fluid to serum creatinine ratio 0.92). CT chest showed infiltrates in lower lobes with bilateral effusions. On day thirteen, nephrostomy tube is downsized and a urinary stent was placed without complications. Recurrence of dyspnea warranted another pleural tap within three days which showed a pleural fluid to serum creatinine ratio of 1.16. Urinothorax was reconsidered prompting further investigation with a Tc99m-DTPA renal scan, which confirmed bilateral urinothorax. A nephropleural fistula was identified at the time of percutaneous nephrostomy tube removal. Our patient had a prolonged hospital course due to recurrent pleural effusions secondary to persistent fistula requiring bilateral chest tubes and ultimately surgical pleurodesis. She was discharged in stable condition.
DISCUSSION: Urinothorax is defined as presence of urine in pleural space secondary to multiple etiologies and was reviewed in detail(1). Clinically urinothorax is suspected when pleural fluid analysis reveals a transudative effusion with pleural to serum creatinine ratio greater than one. However, the creatinine ratio is neither specific nor sensitive. It could be lower than one as transpired in our case. Nine percent of effusions were reported to have a ratio greater than one with most frequent being malignant and parapneumonic effusions. Patients with urinothorax have low pH and glucose and high LDH levels in pleural effusions resulting in misclassification as an exudate by Light’s criteria1. Nuclear renal scan is definitive test for diagnosing urinothorax(2). Contralateral or bilateral urinothorax is an unusal occurrence but not entirely unexpected, considering various channels of communication across diaphragm and between pleural spaces(2). Once the urinary tract injury is addressed and appropriately treated, urinothorax often resolves spontaneously unlike in our patient.
CONCLUSIONS: Our experience suggests the importance of having a high degree of suspicion towards urinothorax in patients with pleural effusion following urological procedures. Furthermore, our study highlights the use of Tc99m-DTPA renal scan for the diagnosis of urinothorax.
Reference #1 Garcia-Pachon E, Romero S. Urinothorax: a new approach. Curr Opin Pulm Med 2006; 12:259-263
Reference #2 Mora RB, Silvente CM, Nieto JM, et al. Urinothorax: presentation of a new case as pleural exudate. South Med J 2010; 103:931-933
DISCLOSURE: The following authors have nothing to disclose: Anthony Arauz, Lina Mackelaite, Eleanor Lederer, Almothana Shanaah, Bashar Alhariri, Rodrigo Cavallazzi, Michael Rice, Muralidhar Kondapaneni
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