Pediatric emergency medicine trisk 0554 0554
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CHAPTER 25 ■ EDEMA
JAMES F. LEONI, ELAINE K. FIELDER
INTRODUCTION
Edema is defined as the abnormal swelling of tissues from the accumulation of
fluid in the extravascular space. This fluid may appear as generalized or localized
swelling. Frequently in pediatrics, edema occurs as a localized response to injury
or inflammation and, in this setting, is often benign and self-limited. However, it
is important to recognize that edema may be the result of a variety of causes and
the initial presentation of generalized edema may be quite subtle. When
significant edema is present, collections of fluid may be visualized as pericardial
or pleural effusions, or as ascites. When edema is profound and generalized, the
patient is described as having anasarca. The completion of a careful history and a
thorough physical examination will not only help to identify these patients early,
but may also lead to a definitive diagnosis in some cases.
PATHOPHYSIOLOGY
The occurrence of edema in healthy individuals is usually prevented by the
balance of oncotic and hydrostatic pressures between the intravascular and
interstitial spaces, as well as the normal function of the lymphatic system. Any
imbalance in this system may lead to increased interstitial fluid and eventual
tissue swelling. Edema may occur as a result of decreased intravascular oncotic
pressure, increased vascular permeability, increased hydrostatic pressure,
lymphatic dysfunction, or a combination of these factors.
Tightly controlled levels of circulating proteins, especially albumin, maintain
normal intravascular oncotic pressure. Hypoalbuminemia may arise from the
decreased production of proteins caused by hepatic disease, as a result of protein
malnutrition or, more commonly, from losses of protein through gastrointestinal,
renal, or dermal conditions. When the albumin level decreases, the oncotic
pressure in the vascular space is reduced and fluid can begin to move freely into
the soft tissues. If not corrected, generalized edema may result.
Edema can also result from changes in vascular (capillary) permeability,
mediated by mast cell release of histamines, IgE, and compliment cascade. This is
seen most commonly in patients with burns, sepsis, or hypersensitivity reactions.
In certain cases, the swelling may be rapid, localized, and potentially lifethreatening. In patients with a severe allergic reaction, such as that associated
