Abstract Introduction Urinothorax is a rare cause of unilateral pleural effusion, defined by the accumulation of urine within the pleural space. It occurs secondary to genitourinary interventions (iatrogenic), trauma, or obstructive uropathy. This case highlights a rare postoperative complication of nephrolithotomy, underscoring the importance of considering urinothorax in the differential diagnosis of acute pleural effusion, particularly in patients with recent urologic procedures. Case Description A 59-year-old woman with a history of recurrent nephrolithiasis, cystectomy with ileal conduit diversion urostomy, was admitted for elective nephrostomy and nephrolithotomy for bilateral staghorn calculi causing worsening flank pain. On postoperative day one, she developed hypoxemia with respiratory distress. Chest radiography revealed complete opacification of the left hemithorax. She was transferred to the ICU for emergent bedside thoracentesis followed by chest tube placement, draining serosanguinous fluid. Pleural fluid analysis demonstrated a pleural fluid-to-serum creatinine ratio of 2.2, confirming urinothorax. Cultures grew Providencia rettgeri, an organism commonly associated with urinary tract infections. She was treated with intravenous ceftriaxone, with clinical improvement and discharge. Discussion Clinical presentation of urinothorax ranges from mild dyspnea to hypoxemic respiratory failure, often accompanied by pleuritic chest pain, palpitations, fever, or fatigue. A temporal relationship to recent urologic intervention aids early suspicion. Imaging usually shows a unilateral, uncomplicated pleural effusion, although loculated effusions can occur. The most widely accepted mechanism is extravasation of urine or urine-contaminated fluid through diaphragmatic pores into the pleural cavity. Characteristic pleural fluid findings include acidic pH (7.40) and a pleural fluid-to-serum creatinine ratio (PFA) 1.0. Our patient demonstrated these features, with a PFA of 2.33 and pleural fluid pH of 7.15. Notably, up to 24% of cases may present with a pH greater than 7.4. CT urogram, PET-CT, or technetium-99m renal scintigraphy may help in uncertain cases. Management includes thoracentesis for symptom relief and correction of the underlying urological cause, which facilitates definitive treatment. Chest tube drainage is often required for large or recurrent effusions as it promotes faster recovery. Secondary infections may occur, occasionally necessitating antibiotics or surgical intervention such as VATS or fibrinolytic therapy. In conclusion, Urinothorax is a rare, underrecognized cause of pleural effusion. Early diagnosis and prompt management of the underlying pathology lead to favorable outcomes. This abstract is funded by: None
Manne et al. (Fri,) studied this question.