Urinothorax – Etiology, Clinical features and Management

Urinothorax refers to presence of urine within the pleural space


  • Urinothorax occurs secondary to obstructive uropathy (blockage to flow of urine)
    • Urinary stones
    • Blunt trauma
    • Urinary tract surgeries

Mechanism of development of urinothorax:

  • Blockage to urine flow results in leakage of urine into the retroperitoneal space forming a urinoma
  • Urine then passes through the diaphragmatic lymphatics or defects in the diaphragm into the pleural space

Clinical features:

  • Urinothorax causes accumulation of urine in the pleural space
  • The side affected will correspond to the side where urinary obstruction is present – bilateral cases are rare
  • But the classical features of pleural effusion may not be present
  • Clinical examination reveals decreased respiratory movements, stony dullness on percussion and decreased/absent breath sounds


  • Pleural fluid aspiration shows a straw coloured fluid
  • Light’s criteria for transudate is fulfilled
  • Confirmation is by finding a pleural fluid to serum creatinine ratio more than 1 (usually it is more than 10)


  • Urinothorax usually resolves after the cause of urinary obstruction is removed

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