Urinary tract disruption or obstruction -> urine accumulates in retroperitoneum -> dissects through fascial planes or travels through lymphatics into the pleural space
Diagnosis
Pleural fluid:
Appearance: like urine
pH: low (urinothorax is the only transudate with a low pH)
LDH ratio: low
Total protein ratio: low
Pleural: Serum creatinine ratio: >1.0 (diagnostic of urinothorax)
