to the editor: In an otherwise comprehensive review of the causes and treatment of edema in American Family Physician, O’Brien and colleagues1 make no mention of idiopathic edema or sleep apnea. Several years ago, my colleagues and I identified idiopathic edema as the most common cause of bilateral leg edema in the primary care setting.2 More recently, we have shown that idiopathic edema is associated with obstructive sleep apnea in women.3 In addition, treating the obstructive sleep apnea reduces or eliminates the amount of swelling in patients who have obstructive sleep apnea and leg edema.4 This information may or may not have an impact upon the clinical care of patients with edema. The majority of my patients with obstructive sleep apnea and leg edema are not interested in treating the obstructive sleep apnea, primarily because they do not complain of excessive daytime sleepiness. Consequently, I often prescribe a diuretic to treat the leg edema, which is what many physicians do when their patients complain of leg edema with no apparent cause.
in reply: Idiopathic edema (IE) is a perplexing problem that may represent a contradiction in terms. In an extensive review of IE, Kay and Davis1 note that “no consensus has been reached as to underlying causes, management or even existence of IE.” As Blankfield2 and others3 have noted, there are often underlying causes identified that would seem to be at odds with the label “idiopathic.” In the study of bilateral leg edema referenced by Dr. Blankfield,2 IE was noted to be the most common cause of edema. However, there is no evidence that the patients identified met the criteria for IE, and the evaluation of the patients was probably not adequate to rule out all other causes. The number of patients in this study was small, and when no obvious cause was identified, the patients were labeled as having IE. We think it likely that what is identified currently as idiopathic edema, when subjected to extensive evaluation, will have discoverable underlying causes. In many instances, periodic, cyclical edema never reaches a threshold that results in an individual seeking medical help. Yet, many patients present with edema that must be treated. Our review recommended an approach that would address all types of edema, whatever the underlying cause.