Urinothorax

The characteristics of people affected by urinothorax are poorly defined. Urological symptoms tend to occur, while the respiratory symptoms are typically nonexistent or mild.^[3] Difficulty breathing, occurring in moderate to large pleural effusions, is the most common respiratory symptom.^[4] Other symptoms include fever, abdominal pain, chest pain, and reduced urination.^[3] It typically occurs within hours of the causative condition.^[5]

Urinothorax is usually caused by obstructive uropathy. The obstructive uropathy may be at the urinary bladder or urethral level.^[6] Obstructive causes have been caused by prostate disease, kidney cyst, retroperitoneal fibrosis, and supernumerary kidney.^[3] Traumatic cases tend to occur on one side, while obstructive cases tend to be bilateral.^[2] In cases caused by urinoma, the urinothorax is usually on the same side of it. Rarely, it can be on both sides or on the opposite side of the urinoma.^[7] It can also be caused by renal biopsy, kidney transplantation, lithotripsy, failed tube nephrostomy, or cancer of the urinary tract.^[6]

Injury to the urinary tract can result in collections of fluid known as a urinoma.^[4] It has the smell of normal urine.^[5] The urine arrives in the pleural space either retroperitoneally (under the peritoneum), or via the retroperitoneal lymphatics.^[8] Urine can reach the pleural space either directly or indirectly. It can reach directly, by going through pores in the thoracic diaphragm due to a pressure gradient, or by a rupture of a urinoma releasing the contents into the pleural space.^[4] It can also reach indirectly, when a urinoma drains into the pleural space via linkage between the lymphatics of the retroperitoneal and pleural regions.^[4]

Due to the main symptoms typically being urological rather than respiratory, the condition requires exclusion of other conditions and the identification of specific symptoms before diagnosis.^[7] Pleural fluid analysis is one way to diagnose the condition. The pleural fluid is most often straw-colored, and it has a distinct smell like ammonia. The fluid usually has a nucleated cell count between 50 and 1500 per cm³.^[4] The pH of the fluid is usually between 5 and 7.^[9] Primary factors for diagnosing urinothorax by pleural fluid include low protein and high lactate dehydrogenase content.^[10] Low glucose levels and acidity are also described, but are not reliable ways to diagnose or rule out urinothorax.^[2] The most important chemical diagnostic factor of the fluid is that the ratio of creatinine to serum is more than 1 and usually more than 10.^[10]

Abdominal ultrasonography and CT scan can help diagnose the underlying condition of the genitourinary tract. If other methods prove inconclusive, an accurate diagnosis can be made by a technetium-99m kidney scan, which shows albumin labeled with 99Tc that translocates into the pleural space from the genitourinary tract.^[4]

Treatment mainly consists of treating the underlying disorder of the genitourinary tract.^[2] It requires a multidisciplinary team that includes a pulmonologist and urologist. A nephrostomy tube or Foley catheter can be used to relieve any underlying obstruction. Any injuries are repaired.^[11] When the underlying disorder is addressed, the urinothorax rapidly resolves. Thoracic surgery is usually not needed,^[4] especially if respiratory symptoms are minimal or nonexistent.^[2] Pleurodesis is also ineffective.^[11] A chest tube can be used to drain urine from the pleural cavity.^[12]

Urinothoraces typically resolve spontaneously without recurring after the underlying urinary tract disorder is treated.^[11]

Urinothorax remains a rare, possibly under-diagnosed, differential in the case of transudative pleural effusion. There were only 58 reported cases up until January 2006. In the literature, there are under 100 reported cases.^[8]

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