Q J Med 2004; 97: 167-178
QJM vol. 97 no. 3 (c) Association of Physicians 2004; all rights reserved.
Masterclasses in medicine |
Anorexia nervosa and chronic renal insufficiency: a prescription for disaster
From the 1Division of Nephrology, St. Michael's Hospital, University of Toronto, Toronto, Canada, and 2Nephrology Unit and Department of Internal Medicine, Stellenbosch University, Cape Town, South Africa
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 potentially 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.
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{at}utoronto.ca