Q & A: Hypokalemic Nephropathy

Q: A patient I follow who suffers from long-standing anorexia nervosa (AN) with binge-eating and purging has developed serious renal disease. Her internist and nephrologist have told her that her renal disease may be related to her long history of purging. I’ve never heard of this relationship. Is this a well-known complication of AN? (D.F., Baltimore)

A: Associations of renal disease and AN have been recorded for many years. A German case series published in 1978 of 23 patients with AN who had been hypokalemic for an average of 6.5 years reported that histological findings in nine patients showed chronic abacterial interstitial nephritis, and that two patients developed terminal renal failure. Because of the association with low serum potassium, they used the term “chronic kaliopenic nephropathy” to describe these cases (Klin Wochenschr; 1978; 56 Suppl 1:91-6.) Subsequently, cases of “hypokalemic nephropathy” have been regularly reported, in relation to AN binge eating/purging subtype (CMAJ, published on line, June 13, 2011) sometimes in association with laxative abuse, bulimia nervosa (Int J Eat Disord; 2005 Dec; 38(4):383-5), and sometimes in association with excessive licorice ingestion (Int J Eat Disord; 1999 Jul;26(1):111-4.).

Chronic diuretic abuse with untreated hypokalemia may also result in this syndrome. If caught early enough, treatment with potassium replacement may help reverse the disorder, but if hypokalemia persists untreated for a long time the condition may become irreversible. Although eating disorders are present in around 30% to 40% of patients with hypokalemic nephropathy, the prevalence of hypokalemic nephropathy in people with eating disorders is unknown. The take-home message is that patients who are frequent purgers, laxative abusers, and diuretic abusers require frequent monitoring of their serum potassium levels. When hypokalemia is found, replacement treatment should be instituted and maintained as long as the eating disorder symptoms persist.

— JY