A 34-year-old man presents to his primary care physician with concerns of a feeling of heaviness in his legs. He states that this feeling has been getting progressively worse over the past 3 weeks. He also states it seems as if his ankles are getting larger. The patient has not seen a physician in the last 10 years. He has a 12-year history of alcohol abuse, but he has been reducing his alcohol intake over the last year in an attempt to improve his overall health. Past medical history is otherwise negative, and he does not take any medications. Family history is noncontributory. Vital signs are within normal limits. Physical examination reveals normal cardiac and pulmonary findings. On abdominal examination, he has evidence of ascites with a fluid wave. He has bilateral pitting edema in the legs without any erythema.
A) Albumin content in the capillaries
Albumin content in the capillaries has the biggest impact on starling forces in this patient. Starling forces include hydrostatic pressure in the capillaries, oncotic pressure in the interstitial space, hydrostatic pressure in the interstitial space, and oncotic pressure in the capillaries. The first two are forces favoring filtration and the second two are forces opposing filtration. Albumin is the largest contributing factor to oncotic pressure. Since this patient has a 12-year history of alcohol abuse and has lower extremity edema, he likely has a cirrhotic liver. This results in reduced albumin synthesis by the liver. Lower albumin content in the capillaries leads to flow of fluid into the interstitial space.
Answer choice B: Albumin content in the interstitial space, is incorrect. Albumin content in the interstitial space is typically not a major factor contributing to the overall Starling forces. This value typically does not change.
Answer choice C: Capillary permeability, is incorrect. Sepsis is the most common cause of increased capillary permeability. Since this patient does not have a fever or any other symptoms of sepsis, this is not the most likely cause.
Answer choice D: Lymphatic obstruction, is incorrect. Lymphatic obstruction typically causes unilateral edema. This patient exhibits signs of bilateral pitting edema as well as ascites.
Answer choice E: Mucopolysaccharides in the interstitial space, is incorrect. Myxedema results from mucopolysaccharides in the interstitial space and is commonly associated with hypothyroidism. This typically appears in the area of the face and can cause exophthalmos as well as causing lower limb edema.
Key Learning Point
Determining the causes of edema requires knowing which of the normal Starling forces have been disrupted. Cirrhosis leads to decreased albumin levels, thereby decreasing the capillary oncotic pressure. The Starling equation is (Pc+ πi)-(Pi+ πc), where Pc is the capillary hydrostatic pressure, πi is the interstitial oncotic pressure, Pi is the interstitial hydrostatic pressure, and πc is the plasma protein oncotic pressure.
