A previously healthy 16-year-old woman was admitted to hospital for fever and dysuria for 1 day, and worsening of intermittent pain in the left costovertebral area and left lower quadrant of abdomen for the last 3 days.The patient denied urinary frequency, urgency, nausea, or vomiting. There was no history or family history of kidney stones.On physical examination, the patient was noted to be an overweight adolescent with Tmax 102.9 F and mild left costovertebral angle tenderness noted on abdomen examination.Laboratory results showed a white blood cell count of 12,700 cells/ml, erythrocyte sedimentation rate of 67 mm/hr, C-reactive protein level .18 mg/dl, and serum creatinine of 1 mg/dl.Urinalysis demonstrated moderate ketones and leukocyte esterase, negative nitrites, numerous white blood cells, and 11 bacteria. Blood and urine cultures were negative throughout hospital stay. Computed tomography scan of abdomen and pelvis (Figure 1A) revealed a wedge-shaped reduction in contrast enhancement consistent with pyelonephritis, and a 6 mm stone obstructing the upper pole, leftcollecting system. Intravenous ceftriaxone was administered for pyelonephritis, and the placement of percutaneous left nephrostomy tube drainage was done.The patient was diagnosed with a urinothorax, which is defined as an accumulation of urine in the pleural space, and can be diagnosed by pleural fluid assessment and imaging. The pleural effusion in a urinothorax is straw colored, transudative, and has a urine odor. The pleural fluid to serum creatinine ratio is .1.0, with elevated pleural fluid lactate dehydrogenase. The fluid pH can be either acid or alkaline (1,2).A urinothorax is usually secondary to obstructive uropathy and post renal and ureteral intervention procedures (3). It can also be seen after blunt kidney trauma, kidney biopsy, kidney transplantation,