Edema
Synonyms and keywords: oedema or dema

# Overview
Edema (American English), formerly known as dropsy or hydropsy, is the increase of interstitial fluid in any organ  swelling. Generally, the amount of interstitial fluid is in the balance of homeostasis. Increased secretion of fluid into the interstitium or impaired removal of this fluid may cause edema.  Cutaneous edema is referred to as "pitting" when, after pressure is applied to a small area, the indentation persists after the release of the pressure.

# Classification
Edema can be classified into pitting edema and non piting edema. Peripheral pitting edema is the more common type, resulting from water retention. It can be caused by systemic diseases, pregnancy in some women, either directly or as a result of heart failure, or local conditions such as varicose veins, thrombophlebitis, insect bites, and dermatitis.  Non-pitting edema is observed when the indentation does not persist. It is associated with such conditions as lymphedema, lipedema, and myxedema.

# Pathophysiology
Generation of interstitial fluid is regulated by the Starling equation of tissue fluid which states that it depends on the balance of osmotic pressure and of hydrostatic pressure which act in opposite directions across the semipermeable capillary walls.  Consequently, anything that increases oncotic pressure outside blood vessels (for example inflammation), or reduces oncotic pressure in the blood (states of low plasma osmolality, for example cirrhosis) will cause edema. Increased hydrostatic pressure inside the blood vessel (for example in heart failure) will have the same effect.  If the permeability of the capillary walls increases, more fluid will tend to escape out of the capillary, as can happen when there is inflammation.

# Causes
Causes of edema can be grouped by its extension as generalized and localized edema. Other way to classify it is by its primary mechanism: Increased capillary hydraulic pressure, hypoalbuminemia, increased capillary permeability, lymphatic obstruction or increased interstitial oncotic pressure.

## Life Threatening Causes
Life threatening causes of edema are:
- Acute kidney failure
- Acute pulmonary edema
- Adult respiratory distress syndrome
- Anaphylaxis
- Anthrax
- Burns
- Eclampsia
- Ischemic heart disease
- Sepsis

## Common Causes
- Cirrhosis
- Drugs
- Heart failure
- Nephrotic syndrome and other forms of renal disease
- Pregnancy
- Premenstrual edema
- Venous insufficiency

## Causes by Organ System

## Causes in Alphabetical Order
- Aagenaes syndrome
- Acanthocheilonemiasis
- Acute altitude sickness
- Acute glomerulonephritis
- Acute infantile hemorrhagic oedema
- Acute pulmonary edema
- Acute renal failure
- Adult respiratory distress syndrome
- Aldesleukin
- Alitretinoin
- Allergic reaction
- Alpha1 blockers
- Amlodipine
- Amnion rupture sequence
- Anaphylaxis
- Andersen disease
- Androgens
- Angioimmunoblastic T-cell lymphoma
- Anthrax
- Aorta-pulmonary artery fistula
- Aortic coarctation
- Aplasia cutis congenital - intestinal lymphangiectasia
- Aromatase inhibitors
- Aspirin
- Aspirin
- Autoimmune disease (juvenile idiopathic arthritis & Crohn's disease)
- Azficel-T
- Bicalutamide
- Bone marrow failure
- Boston ivy poisoning
- Bronchogenic carcinoma
- Burns
- C1 esterase inhibitor deficiency
- Cachexia
- Calcium channel blockers
- Capillary leak syndromes
- Carbenoxolone
- Carcinoid tumours and carcinoid syndrome
- Cardiomyopathy - hearing loss, type t-RNA lysine gene mutation
- Cefaclor
- Cetrorelix
- Chagas disease
- Chlordiazepoxide
- Chronic kidney disease
- chronic venous insufficiency - post-thrombotic syndrome
- Cirrhosis
- Cisplatin
- Classical hodgkin disease
- Combined oxidative phosphorylation deficiency 5
- Congenital disorder of glycosylation type 1h
- Conivaptan
- Conjugated estrogens
- Crizotinib
- Cushing disease
- Cystic fibrosis
- Danazol
- Decreased cardiac output
- Deep vein thrombosis
- Deserpidine
- Desmopressin
- Desogestrel and ethinyl estradiol
- Dexamethasone
- Dextrocardia-bronchiectasis-sinusitis
- Diabetes mellitus
- Diazoxide
- Dihydropyridine calcium channel blockers
- Dilated cardiomyopathy
- Diltiazem
- Distichiasis
- Docetaxel
- Early hepatic cirrhosis
- Eclampsia
- Ectodermal dysplasia - arthrogryposis - diabetes mellitus
- Eosinophilic gastroenteritis
- Encephalopathy progressive - optic atrophy
- Eosinophilia-myalgia syndrome
- Eosinophilic enteropathy, pattern II
- Epidemic dropsy
- Erythroderma
- Essential mixed cryoglobulinemia
- Estramustine
- Estrogen dependent hereditary angioedema
- Estrogens
- Ethynodiol diacetate and ethinyl estradiol
- Excessive dieting
- Felbamate
- Felodipine
- Fludrocortisone
- Flurbiprofen
- Fructose-1-phosphate aldolase deficiency, hereditary
- Fungemia
- Gabapentin
- Gallium nitrate
- Gastritis, familial giant hypertrophic
- Gestrinone
- Ginseng overuse
- Glomerular disease
- Glucocorticoids
- Glufosinate
- Gold salts
- Goldberg syndrome
- Goodpasture's syndrome
- Granulomatous lymphangitis
- Heart failure
- Hemangiomatosis, familial pulmonary capillary
- Hemolytic disease of the newborn
- Hepatic failure
- Hepatic venous obstruction
- Hepatitis
- Hepatorenal tyrosinemia
- Hereditary angioedema
- Hydralazine
- Hydrocortisone
- Hydroxyprogesterone caproate
- Hypernatremia
- Hypertensive heart disease
- Hypoproteinaemia
- Hypothyroidism
- Ichthyosis congenita
- Imatinib mesylate
- Indomethacin
- Inflammation or sepsis
- Inherited hemolytic-uremic syndrome
- Insulins
- Interleukin 11
- Interleukin-2 therapy
- Intestinal capillariasis
- Irons-bhan syndrome
- Ischemic heart disease
- Isradipine
- Jacobs syndrome
- Junin virus
- Kawasaki disease
- Kwashiorkor
- Leg injury
- Lenalidomide
- Letterer-siwe disease
- Lidocaine (cream)
- Lidocaine (ointment)
- Lipoprotein glomerulopathy
- Liver disease
- Liver failure
- Lymph node dissection
- Lymphadenitis
- Lymphangiomatosis, pulmonary
- Lymphatic filariasis
- Lymphedema praecox
- Malabsorption syndrome
- Malignant ascites
- Malnutrition
- Mefenamic acid
- Membranoproliferative glomerulonephritis
- Menetrier's disease
- Mesangiocapillary glomerulonephritis type I
- Mesangiocapillary glomerulonephritis type III
- Methysergide
- Microcephaly -- microphthalmos -- blindness
- Milroy's disease
- Minoxidil
- Mitral valve disease
- Mixed cellularity hodgkin's disease
- Monosomy 3p14 p11
- Multiple joint dislocations -- metaphyseal dysplasia
- Nabilone
- Nephritis
- Nephrosis, idiopathic form, familiar
- Nephrotic syndrome
- Neu-laxova syndrome
- Nevus of ota retinitis pigmentosa
- Nifedipine
- Nilutamide
- Nitrendipine
- Nodal enlargement due to malignancy
- Nodular sclerosing hodgkin's lymphoma
- Non-diarrheal (d-) HUS syndrome
- Nondihydropyridine calcium channel blockers
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Noonan syndrome
- Nutritional deficiency
- Obal syndrome
- Opitz-Reynolds-Fitzgerald syndrome
- Ovarian hyperstimulation syndrome
- Oxandrolone
- Oxaprozin
- Palifermin
- Pegaspargase
- Penciclovir
- Pergolide
- Phenylbutazone
- Pimavanserin
- Pinacidil
- Pioglitazone
- Plasmodium malariae
- Plasmodium ovale
- POEMS syndrome
- Polyarteritis nodosa
- Post-streptococcal glomerulonephritis
- Pramipexole
- Prednisolone
- Pre-eclampsia
- Pregabalin
- Pregnancy and premenstrual edema
- Pregnancy
- Primary biliary cirrhosis
- Progestins
- Protein deficiency
- Protein losing enteropathy
- Proximal spinal muscular atrophy
- Pulmonary lymphangiectasia, congenital
- Recurring airway infection
- Refeeding edema
- Renal disease
- Renal failure
- Reserpine
- Rheumatic fever
- Rofecoxib
- Ropinirole
- Sargramostim
- Schneckenbecken dysplasia
- Siltuximab
- Sinecatechins
- Single ventricular heart
- Sleeping sickness (east african)
- Sleeping sickness (west african)
- Sodium overload
- Sodium phenylbutyrate
- Spinal muscular atrophy, type I
- St. Anthony's fire
- Streptozocin
- Sympatholytics
- Tamoxifen
- Tang His Ryu syndrome
- Temsirolimus
- Terconazole
- Testosterone
- Thiamine deficiency
- Thiazolidinediones
- Thyroid disorders
- Tiagabine
- Tolmetin
- Trauma
- Trichinosis
- Tricuspid atresia
- Tricuspid valve diseases
- Turner syndrome
- Type IV glycogen storage disease
- Tyrosinemia
- Uhl anomaly
- Varicose veins
- Vasodilators
- Venous stenosis
- Venous thrombosis
- Vitamin E deficiency
- Von Willebrand factor
- Waldmann disease
- Water intoxication
- Whipple's disease
- X chromosome, duplication xq13 1 q21 1
- X chromosome, monosomy xp22 pter
- X chromosome, monosomy xq28
- X chromosome, trisomy 26-28
- X chromosome, trisomy xp3
- X chromosome, trisomy xpter xq13
- X chromosome, trisomy xq
- X chromosome, trisomy xq25
- Yellow nail syndrome

# Organ-Specific Edema
Edema of specific organs (cerebral edema, pulmonary edema, macular edema, pedal edema) may also occur, each with different specific causes to peripheral edema, but all based on the same principles. Ascites is effectively edema within the peritoneal cavity, as pleural effusions are effectively edema in the pleural cavity. Causes of edema which are generalized to the whole body can cause edema in multiple organs and peripherally. For example, severe heart failure can cause peripheral edema, pulmonary edema, pleural effusions and ascites.
Common and usually harmless appearances of cutaneous edema are observed with mosquito bites and skin contact with certain plants (urticaria).
Edema may be found in the eyes after corrective surgery or procedures of that nature.