Edema

I. Background
Edema is defined as a clinically apparent increase in the interstitial fluid volume that may expand by several liters before the abnormality is evident (1).
II. Pathophysiology
A. Etiology
The etiology is multifactorial, revolving around the intricate balance of capillary blood and oncotic pressures, tissue pressures, capillary permeability, and lymphatic flow. A change in any of these factors can offset the extravascular fluid balance and result in edema formation (2).
B. Epidemiology
The epidemiology of edema in the United States is unknown.
III. Evaluation
A. History
The following factors are pertinent to the establishment of the etiology of edema.
  • Onset: gradual or sudden
  • Site of the edema
  • History of recurrence or chronicity
  • Color, warmth, induration, sensitivity, and/or pain
  • Associated dyspnea or orthopnea
  • Associated fever or chills
  • Medications such as nonsteroidal antiinflammatories, calcium channel blockers, α-blockers and β-blockers, corticosteroids
  • Endocrine diseases: hypothyroidism, Cushing's disease
  • Prolonged dependent position
  • Pregnancy
  • Increased sodium chloride intake
  • Trauma: ecchymosis, abrasions
B. Physical examination
A complete or focused examination should be performed, depending on information obtained from the history. Special attention should be paid to whether the edema is generalized or localized (see Table 2.3.1). Vital signs should be noted with special attention to an elevated temperature, decreased oxygen saturation, tachypnea, and/or tachycardia. Mental status changes reported by the patient or the patient's family should be noted. Neck vein distension should be evaluated. It is necessary to listen carefully for a gallop in the heart rhythm. Crackles in the lungs should also be noted. Ascites and hepatosplenomegaly should evaluated. It should be noted whether the edema is generalized or localized, whether it is pitting or nonpitting, and whether there is coloration if a painful sensation is present. The findings on physical examination should be very helpful in determining the etiology of the edema.
TABLE 2.3.1 Causes of Localized Edema
  • Injury
  • Local allergic reactions
  • Arthritis/joint inflammations
  • Insect stings/venomations
  • Venous thrombosis or occlusion
  • Surgical interruption of veins or lymphitis
  • Angioedema
  • Idiopathic
  • Physiologic (e.g., dependent pedal edema)
  • Infections
TABLE 2.3.2 Drugs Associated with Edema
Nonsteroidal anti-inflammatory drugs
Antihypertensive agents
Direct arterial/arteriolar vasodilators
   Minoxidil
   Hydralazine
   Clonidine
   Methyldopa
   Guanethidine
Calcium channel antagonists
   Adrenergic antagonists
Steroid hormones
   Glucocorticoids
   Anabolic steroids
   Estrogens
   Progestins
Cyclosporine
Growth hormone
Immunotherapies
   Interleukin-2
   OKT3 monoclonal antibody
From Braunwald E, ed. Edema. In: Harrison's principles of internal medicine, 15th ed. New York, NY: McGraw Hill; 2001:217 - 222.
C. Testing
The following tests should be entertained and/or ordered depending on the history and physical examination: complete blood count, urinalysis, thyroid-stimulating hormone, comprehensive metabolic profile including albumin and liver function tests, congestive heart failure peptide, chest x-ray, electrocardiogram, computed tomography, magnetic resonance imaging, venous Doppler study, and venograms.
IV. Diagnosis
For the differential diagnosis of drug-induced edema, see Table 2.3.2.
References
1. Braunwald E, ed. Edema. In: Harrison's principles of internal medicine, 15th ed. New York, NY: McGraw-Hill, 2001:217 - 222.
2. Terry, M., O'Brien, S., Kerstein, MD. Lower-extremity edema: evaluation and diagnosis. Wounds 10(4):11 - 124:1998.