A 54-year-old man comes to the physician because of edema of his right ankle. He reports heaviness and cramping in the same leg that is worse after a long day at work. The swelling is usually reduced significantly when he wakes up in the morning and worsens progressively throughout the day. He denies any other symptoms. He has no significant medical problems except hypertension, for which he takes atenolol. His temperature is 36.7° C (98° F), blood pressure is 120/76 mm Hg, pulse is 80/min and respirations are 16/min. JVP is normal. Lungs are clear to auscultation. There are no murmurs. There is no hepatosplenomegaly. Examination shows edema of the right ankle. Doppler examination of the leg shows no evidence of thrombosis. Which of the following is the most likely cause of his edema?
The patient described is experiencing unilateral lower extremity edema that worsens when the leg is dependent (i.e. while the patient is at work) and improves with leg elevation (i.e. when the patient is sleeping). There are many potential causes of lower extremity edema. Indeed, all of the above mentioned conditions may cause edema of the legs, but in the clinical scenario provided, venous valvular incompetence is the most likely cause. Venous insufficiency is the most common cause of lower extremity edema; it affects approximately 2% of the population at large. Failure of venous valves allows blood to pool in dependent areas such as the legs resulting in an increase in capillary hydrostatic pressure. This increased pressure favors increased filtration of fluid out of the capillaries into the interstitial tissue. This process causes a decrease in intravascular volume, which stimulates the kidneys to retain water and salt ultimately leading to further progression of edema.
(Choice A) Lymphatic obstruction is an uncommon cause of edema. It may result from malignant obstruction of lymph nodes, lymph node resection, trauma and filariasis. It classically affects the dorsa of the feet and causes marked thickening and rigidity of the skin.
(Choices B & C) Impaired cardiac contraction and reduced diastolic filling of the heart may cause bilateral lower extremity edema due to pooling of blood in the venous circulation causing increased capillary hydrostatic pressure. However, respiratory symptoms and crackles on examination are common.
(Choices D & F) Increased urinary loss of protein and decreased liver protein synthesis causes decreased plasma oncotic pressure, which results in decreased reabsorption of interstitial fluid in distal capillaries and edema. Urinary protein loss occurs in nephrotic syndromes as well as in most cases of nephritis. Failure of liver protein synthesis typically occurs in the setting of cirrhosis or other forms of liver failure where the synthetic function of the liver is impaired. Other signs of liver failure and nephrotic syndrome are usually evident.
(Choice G) Arterial occlusion causes pain, pallor, paresthesias, pulselessness and coolness to the touch in affected extremities.
Educational objective:
Venous insufficiency (valvular incompetence) is the most common cause of lower extremity edema. It classically worsens throughout the day and resolves overnight when the patient is recumbent.