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Urinothorax: Case report and systematic review of the literature

Urinothorax, the presence of urine in the pleural space, is a rare cause of pleural effusion, usually associated with obstructive uropathy, or urinary trauma. We present the case of a 3 year-old boy and a systematic review of the literature of the 44 cases encountered. After resection of a Wilm’s tumour in the right kidney our patient presented acute respiratory distress associated with radiographically confirmed pleural effusion. With the initial diagnosis of pneumonia or malignant pleural effusion, a closed thoracotomy was performed. The liquid obtained suggested urine, which was confirmed by the laboratory. Cystoscopy with retrograde pyelography detected a fistula on the posterior wall of the right kidney. The report of cases worldwide is low, probably due to its low incidence but also to underdiagnosis. Respiratory symptoms are not always present and urological symptoms usually predominate. Diagnosis requires a high degree of clinical suspicion and is confirmed by the main biochemical marker: The ratio >1.0 pleural fluid creatinine and creatinine serum.


INTRODUCTION
Urinothorax is a rare cause of pleural effusion in patients with obstructive or traumatic uropathy. [1][2][3][4][5] It has been reported in patients with blunt trauma or after abdominal surgical procedures. [6] Disruption of the urinary tract leads to accumulation of urine in the retroperitoneal space that leaks into the pleural space. [5,7] It is usually ipsilateral to the lesion side. [8,9] Diagnosis can be done with renal scintigraphy with a radioactive tracer, [10,11] or measuring creatinine levels in pleural fluids. [12] Frequently reported in adults; we present the case of a 3-year-old boy and a systematic review of the literature.

CASE REPORT
A 3-year-old boy was admitted for surgical treatment of Wilm's tumor in the right kidney. The patient had a history of chronic kidney disease, secondary hypertension and had undergone a left nephrectomy 2 years before due to the same condition. The surgical procedure, partial nephrectomy with total resection of the tumor and suture of the renal pelvis, was uneventful. Central venous and peritoneal catheters were placed. On postoperative day 3 the patient developed acute respiratory distress, and a chest X-ray revealed right pleural effusion, which affected two-thirds of the right hemithorax [ Figure 1]. Diagnoses of pneumonia and parapneumonic effusion were considered. A thoracostomy was performed, and 1,050 ml of yellowish color liquid were drained during the following 20 h, during which he also developed oliguria and fever. He received treatment with antibiotics (meropenem and vancomycin). The aspect and particularly, the smell of pleural liquid oriented the diagnosis of urinothorax. The ratio of creatinine levels in pleural fluid and blood was 4.8, which was highly suggestive of urine. Excretory urography was not performed due to the high risk of inducing renal failure.
Cystoscopy with retrograde pyelography showed a low flow fistula on the posterior wall of the right renal calyx. A ureteral catheter was placed during the surgical closure of the fistula, and nutritional support was initiated, 3 days after thoracotomy pleural effusions disappeared. Pathology confirmed contralateral Wilm's tumor (grade 5). He remained with the ureteral catheter 6 months until achieving complete closure of the fistula and was asymptomatic on last clinical control, 3 months later.

METHODS
We performed a systematic review of the literature, following a standard methodology [13] in three databases (PubMed, Scopus and Scielo, a Latin American database), using "pleural effusion" and "urine" as free terms, with no language or time limits. A thorough review process ended up with a total of 752 references [ Figure 2], 23 of which were published before 1998 (of which only 9 were located and retrieved full-text). [14][15][16][17][18][19][20][21][22] Of the 57 articles in full-text, ten were excluded because they were not cases of urinothorax.

DISCUSSION
Urinothorax should be included in the differential diagnosis of pleural effusions in patients of any age subjected to gynecological, urological surgical procedures as well as resections of intraperitoneal tumors. [19,23,31] Most of the case reports reviewed emphasize urinothorax as an unexpected surprise. Despite being a rare condition, most large adult or pediatric urological departments should expect to see one of these cases.
Respiratory symptoms are evident in some patients but are not always present, and may be wrongly attributed to atelectasis or  pneumonia. [8] Biochemical testing is useful, and the ratio of creatinine and biochemical analysis of pleural fluid confirms the diagnosis. [5,19] Diagnostic imaging, renal scan, X-ray, contrast-enhanced computed tomography or pyelogram are essential to establish the anatomical location of the defect causing urine leakage. [24,36] In our case, contrast means were not indicated, given that the patient had renal failure, but cystoscopy plus pyelogram in the operating room showed the atomic location of the fistula.
Initial management of urinothorax is with toracocentesisis or thoracostomy [37] but detecting the origin of the leakage and performing surgical repair is essential. As a conclusion, urinothorax is a rare complication, but should be held in mind, since an early diagnosis will improve the patient's outcome.

Article Year Gender Age (years) Etiology Underlying condition
Firedland et al. [14] 1971 M 3 weeks old Obstructions of urinary tract Hydro ureteronephrosis Lahiry et al. [15] 1978 F 19 Right nephrectomy Car accident Leung et al. [16] 1981 M 65 Obstruction of the distal portion of the left ureter