Edema Formation

Question 1

Elevated capillary hydrostatic pressure

Answer 1

• results in increased net plasma filtration into the interstitium, particularly in dependent tissues.
• can occur due to abnormal arteriolar dilation (eg, use of dihydropyridine calcium channel blockers)
• or impairments in venous return (eg, venous thrombosis and right-sided heart failure).

Question 2

Decreased plasma oncotic pressure

Answer 2

• reduces the amount of interstitial fluid returning to the circulation via the capillary bed venules
• Oncotic pressure is generated by plasma proteins, especially albumin.
• Edema develops in conditions with decreased albumin levels, including nephrotic syndrome, severe liver disease, and malnutrition.

Question 3

Sodium and water retention

Answer 3

• leads to an increase in intravascular volume, which acts to raise capillary hydrostatic pressure and decrease plasma oncotic pressure by diluting plasma proteins
• can occur with acute kidney injury, chronic kidney disease, and congestive heart failure.

Question 4

Lymphatic obstruction

Answer 4

• causes edema by impairing the removal of excess interstitial fluid
• Common causes of lymphatic obstruction include filariasis, invasive malignancies, and iatrogenic etiologies (eg, surgical lymph node dissection and radiation therapy).