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 effusions, is the most common respiratory symptom.[4] Other symptoms include abdominal pain, chest pain, and reduced urination.[3] It typically occurs within hours of the causative condition.[5]

It is usually caused by obstructive uropathy. The obstructive uropathy may be at the bladder or urethral level.[6] 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 cal be on both sides or on the opposite side of the urinoma.[7] It can also be caused by kidney biopsy, kidney transplant, 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] The fluid has the smell of urine.[5] The urine arrives in the pleural space either retroperitoneally (under the peritoneum) under the posterior diaphragm, or via the retro peritoneal lymphatics.[8] Urine can reach the pleural space either directly or indirectly. It can reach directly, by going though pores in the diaphragm due to a pressure gradient, or by a rupture of a urinoma releasing the contents into the pleural space. 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]

CT scan showing nephrostomy tube placement in a case of urinothorax being treated.jpg

Due to the main symptoms typically being urological rather than respiratory, the condition requires a high amount of suspicion to diagnose.[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 is mostly mononuclear and has a nucleated cell count ranging between 50-1500.[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 LDH content.[10] Low glucose levels and acidity are also described, but 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 99Tc that translocates into the pleural space from the genitourinary tract.[4]

Chest X-ray showing urinothorax disappearing after treatment.

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] Also ineffective is pleurodesis.[11]

Urinothoraces typically resolve spontaneously without recurring after the underlying urinary tract disorder is treated.[12]

Urinothorax remains a rare, possibly under-diagnosed, differential in the case of transudative pleural effusion.[8] There have only been 58 reported cases until January 2006.[9]