Q J Med 2004; 97:167–178 doi:10.1093/qjmed/hch031 Masterclasses in medicine Anorexia nervosa and chronic renal insufficiency: a prescription for disaster M. LUTHRA 1 , M.R. DAVIDS 2 , M.A. SHAFIEE 1 and M.L. HALPERIN 1 From the 1 Division of Nephrology, St. Michael’s Hospital, University of Toronto, Toronto, Canada, and 2 Nephrology Unit and Department of Internal Medicine, Stellenbosch University, Cape Town, South Africa Summary Our imaginary consultant, Professor McCance, is asked to explain the basis for four major acute electrolyte abnormalities in a young woman with long-standing anorexia nervosa. She has a severe degree of hypokalaemia (2.0 mmol/l) with renal potassium wasting, a contracted extracellular fluid volume with renal NaCl wasting, hyponatraemia (118 mmol/l) while excreting hypoosmolar urine, and metabolic acidosis with a normal plasma anion gap (pH 7.20, bicarbonate 9 mmol/l). McCance begins his discussion by considering the basis for hypokalaemia, as this electrolyte disorder is poten- tially life-threatening. Its pathophysiology is linked to the other major findings, using principles of integrative physiology together with a deductive and quantitative analysis. Nevertheless, to reach his final diagnosis, he requires information about newer molecular discoveries. Not only is he able to suggest a likely diagnosis, but he also devises a novel long- term plan for therapy. Introduction In our continuing series on applying integrative physiology at the bedside, we present another problem in the fluid, electrolyte, acid–base, and/or energy metabolism area. Once again, we are guided by our imaginary consultant, the integrative physiol- ogist Professor McCance, whom we transport to the present to help with the management of an actual case. As always, he begins with an analysis of the most pressing abnormality—his emphasis is on concepts rather than details. Facts are revealed only when they advance the understanding of key issues. Elements that could contribute to the diagnosis and treatment become evident once the issues are considered from the perspective of whole-body physiology. When Professor McCance is made aware of recent molecular discoveries, he suggests an unanticipated diagnosis, and suggests a novel form of therapy. The consultation On the morning post-intake ward round, Professor McCance was shown a 37-year-old woman with four similar hospital admissions in the past 6 months. On each admission, there had been a period of one week where she became progressively ill. She was not febrile, and her respirations were neither rapid nor deep. Although her blood pressure was 110/70 mmHg and her pulse rate 80 bpm lying Address correspondence to Professor M.L. Halperin, University of Toronto, St. Michael’s Hospital Annex, Lab #1, Research Wing, 38 Shuter Street, Toronto, Ontario, M5B 1A6, Canada. e-mail: mitchell.halperin@ utoronto.ca QJM vol. 97 no. 3 ! Association of Physicians 2004; all rights reserved. Downloaded from https://academic.oup.com/qjmed/article/97/3/167/1577550 by guest on 22 January 2023