.edema

[IMG SURVIVOR]

A 59-year-old woman with a 10-year history of type 2 diabetes mellitus is noted by her physician to have bilateral pitting edema of the ankles and feet. No erythema is noted. On questioning, the patient also reports shortness of breath on exertion and states that she has been using 3 pillows at night in order to sleep comfortably.

An increase in which of the following is the most likely explanation for the edema in her legs?
/ A. Interstitial colloid osmotic pressure
/ B. Lymph flow
/ C. PIasma colloid osmotic pressure
/ D. Right atrial pressure
/ E. Stroke volume

[IMG SURVIVOR]

The correct answer is D. Right atrial pressure rises in congestive heart failure, which elevates venous pressure throughout the body. This increase in venous pressure can cause excessive fluid loss from the microcirculation and the development of peripheral edema.
Fluid loss from the capillaries washes protein molecules from the interstitial compartment and thereby decreases interstitial colloid osmotic pressure (choice A).
Increased lymph flow (choice B) is a consequence rather than a cause of the edema.
Increased plasma colloid osmotic pressure (choice C) would tend to decrease the development of edema.
Stroke volume (choice E) has no effect on the formation of peripheral edema.