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You are seeing a 17 year old boy with left flank pain, nausea, and vomiting. There has been no fever, dysuria, hematuria, or urinary frequency. The pain did start after the patient drank a large caffeinated frappuccino and had a brisk diuresis. The patient reports similar pains in the past that self resolved, but never this severe. Urinalysis has 0-2 wbc, 0-2 rbc, no bacteria, and is nitrite negative. Suspecting nephrolithiasis, you obtain a renal US that shows severe left hydronephrosis but no evidence of stone. You then obtain a CT non-contrast that confirms no stone is present.