Edema is swelling of soft tissues due to increased interstitial fluid. The fluid is predominantly water, but protein and cell-rich fluid can accumulate if there is infection or lymphatic obstruction.
Edema may be generalized or local (eg, limited to a single extremity or part of an extremity). It sometimes appears abruptly; patients complain that an extremity suddenly swells. More often, edema develops insidiously, beginning with weight gain, puffy eyes at awakening in the morning, and tight shoes at the end of the day. Slowly developing edema may become massive before patients seek medical care.
Edema itself causes few symptoms other than occasionally a feeling of tightness or fullness; other symptoms are usually related to the underlying disorder. Patients with edema due to heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular failure causes shortness of breath and fatigue, and right ventricular failure causes peripheral and abdominal fluid... read more (a common cause) often have dyspnea during exertion, orthopnea, and paroxysmal nocturnal dyspnea. Patients with edema due to deep venous thrombosis Deep Venous Thrombosis (DVT) Deep venous thrombosis (DVT) is clotting of blood in a deep vein of an extremity (usually calf or thigh) or the pelvis. DVT is the primary cause of pulmonary embolism. DVT results from conditions... read more (DVT) often have leg pain.
Edema due to extracellular fluid volume expansion is often dependent. Thus, in ambulatory patients, edema is in the feet and lower legs; patients requiring bed rest develop edema in the buttocks, genitals, and posterior thighs. Women who lie on only one side may develop edema in the dependent breast. Lymphatic obstruction causes edema distal to the site of obstruction.
Pathophysiology of Edema
Edema results from increased movement of fluid from the intravascular to the interstitial space or decreased movement of water from the interstitium into the capillaries or lymphatic vessels. The mechanism involves one or more of the following:
Increased capillary hydrostatic pressure
Decreased plasma oncotic pressure
Increased capillary permeability
Obstruction of the lymphatic system
As fluid shifts into the interstitial space, intravascular volume is depleted. Intravascular volume depletion activates the renin-angiotensin-aldosterone-vasopressin (ADH) system, resulting in renal sodium retention. By increasing osmolality, renal sodium retention triggers water retention by the kidneys and helps maintain plasma volume. Increased renal sodium retention also may be a primary cause of fluid overload Volume Overload Volume overload generally refers to expansion of the extracellular fluid (ECF) volume. ECF volume expansion typically occurs in heart failure, kidney failure, nephrotic syndrome, and cirrhosis... read more and hence edema. Excessive exogenous sodium intake may also contribute.
Less often, edema results from decreased movement of fluid out of the interstitial space into the capillaries due to lack of adequate plasma oncotic pressure as in nephrotic syndrome, protein-losing enteropathy, liver failure, or starvation.
Increased capilliary permeability occurs in infections or as the result of toxin or inflammatory damage to the capillary walls. In angioedema Angioedema Angioedema is edema of the deep dermis and subcutaneous tissues. It is usually an acute mast cell–mediated reaction caused by exposure to drug, venom, dietary, pollen, or animal dander allergens... read more , mediators, including mast cell–derived mediators (eg, histamine, leukotrienes, prostaglandins) and bradykinin and complement-derived mediators, cause focal edema.
The lymphatic system is responsible for removing protein and white blood cells (along with some water) from the interstitium. Lymphatic obstruction allows these substances to accumulate in the interstitium.
Etiology of Edema
Generalized edema is most commonly caused by
Localized edema is most commonly caused by
DVT Deep Venous Thrombosis (DVT) Deep venous thrombosis (DVT) is clotting of blood in a deep vein of an extremity (usually calf or thigh) or the pelvis. DVT is the primary cause of pulmonary embolism. DVT results from conditions... read more or another venous disorder or venous obstruction (eg, by tumor)
Chronic venous insufficiency Chronic Venous Insufficiency and Postphlebitic Syndrome Chronic venous insufficiency is impaired venous return, sometimes causing lower extremity discomfort, edema, and skin changes. Postphlebitic (postthrombotic) syndrome is symptomatic chronic... read more may involve one or both legs.
Evaluation of Edema
History of present illness should include location and duration of edema and presence and degree of pain or discomfort. Female patients should be asked whether they are pregnant and whether edema seems related to menstrual periods. Having patients with chronic edema keep a log of weight gain or loss is valuable.
Review of systems should include symptoms of causative disorders, including dyspnea during exertion, orthopnea, and paroxysmal nocturnal dyspnea (heart failure); alcohol or hepatotoxin exposure, jaundice, and easy bruising (a liver disorder); malaise and anorexia (cancer or a liver or kidney disorder); and immobilization, extremity injury, or recent surgery (DVT).
Past medical history should include any disorders known to cause edema, including heart, liver, and kidney disorders and cancer (including any related surgery or radiation therapy). The history should also include predisposing conditions for these causes, including streptococcal infection, recent viral infection (eg, hepatitis), chronic alcohol abuse, and hypercoagulable disorders. Drug history should include specific questions about drugs known to cause edema (see table Some Causes of Edema Some Causes of Edema ). Patients are asked about the amount of sodium used in cooking and at the table.
The area of edema is identified and examined for extent, warmth, erythema, and tenderness; symmetry or lack of it is noted. Presence and degree of pitting (visible and palpable depressions caused by pressure from the examiner’s fingers on the edematous area, which displaces the interstitial fluid) are noted.
In the general examination, the skin is inspected for jaundice, bruising, and spider angiomas (suggesting a liver disorder).
Lungs are examined for dullness to percussion, reduced or exaggerated breath sounds, crackles, rhonchi, and a pleural friction rub.
The internal jugular vein height, waveform, and reflux are noted.
The heart is palpated for thrills, thrust, parasternal lift, and asynchronous abnormal systolic bulge. Auscultation for loud pulmonic component of 2nd heart sound (P2), 3rd (S3) or 4th (S4) heart sounds, murmurs, and pericardial rub or knock is done; all suggest cardiac origin.
The abdomen is inspected, palpated, and percussed for ascites, hepatomegaly, and splenomegaly to check for a liver disorder or heart failure. The kidneys are palpated, and the bladder is percussed. An abnormal abdominal mass, if present, should be palpated.
Certain findings raise suspicion of a more serious etiology of edema:
Shortness of breath
History of a heart disorder or an abnormal cardiac examination
Hemoptysis, dyspnea, or pleural friction rub
Hepatomegaly, jaundice, ascites, splenomegaly, or hematemesis
Unilateral leg swelling with tenderness
Interpretation of findings
Potential acute life threats, which typically manifest with sudden onset of focal edema, must be identified. Such a presentation suggests acute DVT Deep Venous Thrombosis (DVT) Deep venous thrombosis (DVT) is clotting of blood in a deep vein of an extremity (usually calf or thigh) or the pelvis. DVT is the primary cause of pulmonary embolism. DVT results from conditions... read more , soft-tissue infection, or angioedema. Acute DVT may lead to pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in the large veins of the legs or pelvis. Risk factors for pulmonary embolism are... read more (PE), which can be fatal. Soft-tissue infections range from minor to life threatening, depending on the infecting organism and the patient’s health. Acute angioedema sometimes progresses to involve the airway, with serious consequences.
Dyspnea may occur with edema due to heart failure, DVT if PE has occurred, acute respiratory distress syndrome, or angioedema that involves the airways.
Generalized, slowly developing edema suggests a chronic heart, kidney, or liver disorder. Although these disorders can also be life threatening, complications tend to take much longer to develop.
For most patients with generalized edema, testing should include complete blood count (CBC), serum electrolytes, blood urea nitrogen (BUN), creatinine, liver tests Laboratory Tests of the Liver and Gallbladder Laboratory tests are generally effective for the following: Detecting hepatic dysfunction Assessing the severity of liver injury Monitoring the course of liver diseases and the response to treatment... read more , serum protein, and urinalysis (particularly noting the presence of protein and microscopic hematuria). Other tests should be done based on the suspected cause (see table Some Causes of Edema Some Causes of Edema )—eg, brain natriuretic peptide (BNP) for suspected heart failure or D-dimer for suspected pulmonary embolism.
Patients with isolated lower-extremity swelling should usually have venous obstruction excluded by ultrasonography.
Treatment of Edema
Specific causes are treated.
Patients with sodium retention often benefit from restriction of dietary sodium. Patients with heart failure should eliminate salt in cooking and at the table and avoid prepared foods with added salt.
Patients with advanced cirrhosis or nephrotic syndrome often require more severe sodium restriction (≤ 1 g/day). Potassium salts are often substituted for sodium salts to make sodium restriction tolerable; however, care should be taken, especially in patients receiving potassium-sparing diuretics, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin II receptor blockers (ARBs) and in those with a kidney disorder because potentially fatal hyperkalemia Hyperkalemia Hyperkalemia is a serum potassium concentration > 5.5 mEq/L (> 5.5 mmol/L), usually resulting from decreased renal potassium excretion or abnormal movement of potassium out of cells. There... read more can result.
People with conditions involving sodium retention may also benefit from loop or thiazide diuretics. However, diuretics should not be given only to improve the appearance caused by edema. When diuretics are used, potassium wasting can be dangerous in some patients; potassium-sparing diuretics (eg, amiloride, triamterene, spironolactone, eplerenone) inhibit sodium reabsorption in the distal nephron and collecting duct. When used alone, they modestly increase sodium excretion. Both triamterene and amiloride have been combined with a thiazide to prevent potassium wasting. An ACE inhibitor–thiazide combination also reduces potassium wasting.
In older people, use of drugs that treat causes of edema (particularly heart failure) requires special caution, such as the following:
Starting doses low and evaluating patients thoroughly when the dose is changed
Monitoring for orthostatic hypotension if diuretics, ACE inhibitors, angiotensin II receptor blockers, or beta-blockers are used
Evaluating for bradycardia or heart block if digoxin, rate-limiting calcium channel blockers, or beta-blockers are used
Frequently testing for hypokalemia or hyperkalemia
Not stopping calcium channel blockers because of pedal edema, which is benign
Logging daily weight helps in monitoring clinical improvement or deterioration immensely.
Edema may result from a generalized or local process.
Main causes of generalized edema are chronic heart, liver, and kidney disorders.
Sudden onset should trigger prompt evaluation.
Edema may occur anywhere in the body in.
Not all edema is harmful; consequences depend mainly on the cause.