The Nephrology Quiz and Questionnaire (NQQ) continues to be the most popular of the 2-hr Clinical Nephrology Conferences held at our annual Renal Week. Our faculty presented eight puzzling cases that prompted some lively discussions at the recent Philadelphia meeting. As most of you know, each of the four faculty is charged with developing two cases, each of which involve some controversial aspect of diagnosis, management, or pathophysiology related to a renal or an electrolyte disorder. One or two questions follow each case. Before Renal Week, we e-mail these cases and multiple-choice questions to all our members and ask them to send us their answers. At the meeting, the collated answers to each question are presented by the faculty, and they discuss their “correct” answer to each question. The responses from the Nephrology Training Program Directors and those from all other nephrologists are assessed and presented separately. In years past, we have e-mailed the answers to the membership after the Renal Week meeting. CJASN will now be the new home for the discussions of NQQ cases. We hope that this “distillate from Philadelphia” will serve as a good review for those of you who were at the session and will provide fresh insights for those of you who missed the Clinical Nephrology Conferences. Two days ago, a 24-yr-old, healthy, 50-kg man developed profuse diarrhea (“rice water” consistency) after drinking contaminated water. On physical examination, he appeared very ill and cyanotic. His BP was 90/60 mmHg, his heart rate was 110 beats/min, and his jugular venous column height was below the sternal angle. The remainder of the examination was not relevant. Laboratory studies on admission included serum electrolytes (in mM) Na 140, HCO3 24, K 4.6, Cl 95; pH 7.39, Pco2 (arterial) 39 mmHg, glucose 72 mg/dl (4.0 mM), …