Dynamic changes in chest tube output after weaning from invasive mechanical ventilation: a case report of traumatic urinothorax

Abstract Introduction Urinothorax is an uncommon cause of pleural effusion that is frequently undiagnosed. Existing literature consists predominantly of sporadic case reports, mostly in male patients with obstructive uropathy or iatrogenic injury. This case reports a right-sided urinothorax in an elderly female following a traumatic motor vehicle accident, resulting from concurrent ureteral rupture and diaphragmatic injury. Key symptoms and clinical findings A 70-year-old female developed a persistent large right-sided pleural effusion after trauma. During mechanical ventilation (MV), chest tube output showed substantial variability and an overall decrease. After liberation from invasive MV and extubation, output generally remained high at approximately 800–2,500 mL/day, except during periods of documented catheter obstruction. Pleural fluid transitioned from an initial hemorrhagic exudate-like to a clear transudate-like. Renal function and urine output were normal. Pleural fluid was acidic (pH 5.0), with a creatinine level of 1,466 µmol/L versus serum creatinine of 45 µmol/L at the time of paired pleural fluid analysis, yielding a pleural fluid-to-serum creatinine ratio > 32. Main diagnosis, therapeutic interventions, and outcomes The diagnosis of urinothorax was supported by a pleural fluid-to-serum creatinine ratio > 1.0 and acidic pH, and was further corroborated by CT urography demonstrating the urinary leakage pathway into the right-sided pleural cavity. The patient underwent laparoscopic pyeloureterostomy, laparoscopic pyeloplasty, and ureteral stent placement under direct vision. Postoperatively, the pleural effusion rapidly resolved with no recurrence. Conclusion Traumatic urinothorax should be considered in patients with persistent or recurrent pleural effusion after major trauma, even when renal function and urine output remain preserved. In this patient, chest tube output decreased during positive-pressure ventilation and increased after extubation, but this nonspecific temporal pattern may have been influenced by changes in intrathoracic pressure and should not be interpreted as an independent diagnostic sign. The diagnosis was based on the integration of serial pleural fluid findings, a markedly elevated pleural fluid-to-serum creatinine ratio, and CT urography demonstrating the urinary leakage pathway. Resolution after repair of the ureteral injury further supported the diagnosis and highlights the importance of correcting the underlying urinary tract lesion.