Amanda is an 18-year-old with anorexia nervosa. She was recently admitted to an eating disorders clinic with a BMI of 13.9, and although she was a voluntary patient, she was reluctant about the treatment

Question

She was convinced she was overweight because her clothes felt tight on her. She complained that even her hands and feet "were fat." One of her nurses explained that a protein in her blood was low. The nurse further explained that, as difficult as it may be to believe, eating a normal healthy diet would make the "fat hands and feet" go away.

What protein do you suspect the nurse was referring to? How would a deficiency in this protein contribute to edema?

What is the difference between the physiology of pitting and nonpitting edema?

Because of her weakened condition, Amanda was moved around the ward in a wheelchair when she was not on bed rest. How does this affect her edematous tissues?

Answer 1

Amanda was presenting with low serum albumin. Albumin has a low molecular weight and high concentration in the plasma, allowing it to create a strong colloidal osmotic pressure. When albumin levels are decreased, the serum osmotic gradient declines. Fluid therefore leaves the capillaries to the surrounding interstitial space.

Pitting edema is a result of an increased level of interstitial fluid that exceeds the absorptive capacity of the tissue gel. The edema is mobile and can shift with pressure. Nonpitting edema involves the migration of capillary fluid and plasma proteins into the tissue space. The protein coagulates and creates a firm edema that does not move with pressure.

Edema increases the distance between tissue cells and circulation. The diffusion of gases, nutrients, and wastes between tissue cells and capillaries is consequently decreased. Edema can also mechanically compress tissue capillaries. Both situations leave tissues prone to ischemic damage and, when the patient is immobile, pressure ulcers.