We have been friends for more than 20 years and he has never come to me for any health challenge all this while until lately. Suffice it to say that I have managed his children for illnesses varying from acute febrile conditions to minor surgical interventions. On this day when he came to my office, he was very agitated and almost cursing. I was initially taken aback and wanted to know why he was in such terrible mood. He merely pointed at his legs and said:” Dr., I am not comfortable with this thing.”
When I had a look at his legs two things were obvious, swelling of both legs and an in growing toe nail of the middle toe of the right leg. He had tried to impress it on me that the infection in growing toe nail had led to the swelling. Of course, I didn’t buy that. I made him to understand that if that was the case, the swelling would have been only on the affected leg. And being a diabetic he would have been a lot sicker than the way he looked.
My good friend had bilateral pitting pedal oedema or edema. By definition, oedema is abnormal accumulation of fluid in the interstitium beneath the skin and the cavities in the body. This usually manifests as a swelling that may lead to discomfort in some cases. The interstitium is contiguous fluid-filled space that exists between a structural barrier such as cell wall or the skin and internal structures such as organs including muscles and the circulatory system. This space is awash with water and solutes known as interstitial fluid. This fluid is eventually channeled through the lymphatic system of drainage. There are basically two types of oedema in clinical practice. The first is the very common type known as the pitting type and the non-pitting type.
In pitting oedema, when a finger is placed on the swelling and depressed, on removing the finger the indentation produced by the finger persists. This type of oedema is usually caused by water retention resulting from systemic diseases, pregnancy, and heart failure. There are other localised health challenges that could result in oedema of the lower extremities like inflammation of the veins as a result of blockage by blood clot known as thrombophlebitis, abnormal dilatation of the veins due to incompetent valves known as varicose veins and inflammation of the skin from infection known as cellulitis or dermatitis if the deeper layer of the skin is involved.
In non-pitting on the removal of a finger placed at the site, no indentation is left afterwards. And this type of oedema is common where there is lymphatic drainage obstruction caused by infection by worms like Wuchereria bancrofty. A classic example is elephantiasis. Lymphedema can also be a complication from the treatment of cancer, especially when lymph nodes are lost during surgery and radiotherapy. Lipedema results from a disorder that leads to abnormal distribution of fat. Lately we have been seeing this in some patients on anti-retro viral therapy for acquired immune deficiency syndrome. Myxedema is a designation commonly used for the type of swellings or oedema associated with hypothyroidism and hyperthyroidism or Grave’s disease.
Under normal circumstances the maintenance of a healthy interstitial fluid balance or homeostasis depends on two forces; the water hydrostatic pressure and oncotic/osmotic or colloidal pressure. Other factors would include blood vessel wall permeability especially during inflammatory process. With an increase in hydrostatic pressure there is extravasation of fluid and low molecular weight solutes into the interstitial space. This in turn leaves the distal portion of the vessel with relatively higher molecular weight substances concentrated there. The consequence of this is an increase in osmotic pressure in the intravascular compartment. The effect of this would be the drawing back of fluids into the blood vessels. This phenomenon happens mainly at the venules and capillary end of the circulatory system. This way the homeostasis of the interstitial space is maintained with the vascular wall serving as semi-permeable membrane.
This phenomenon is often referred to as Starlings equation. The formation of oedema would depend on the discrepancies in the balance between the osmotic and hydrostatic pressures after factoring in the permeability of the blood vessel. Thus an increase in hydrostatic pressure with reduction in oncotic pressure would result in oedema formation. Similarly a decrease in oncotic pressure would also result in oedema formation. This is commonplace in situations like nephrotic syndrome where proteins especially albumin is lost in urine and in chronic liver disease due to poor synthesis and production of proteins. An increase in colloidal pressure in the tissues would also lead to the drawing in of fluids into the interstitial compartment. For completion, the commonest mechanism of oedema formation is when there is increased permeability of blood vessels as seen in inflammation.
Obstruction of lymphatic drainage commonly results n non-pitting oedema. This usually results from extravasations of fluids from the lymph as a result of buildup of pressure from lymph that must have accumulated over a period of time. This situation is commonly experienced after treatment of certain cancers especially Breast and in certain worm infection. This may also be the outcome if lymph nodes are removed by surgeons during dissections. Finally there are conditions during which the water retaining properties of cells and tissues are altered as seen in some auto-immune disorders that result in swelling.
By and large oedema helps to tell a story but on its own is not the story. For instance it could be generalized in which case the clinician would refer to it as anarsaca. At this point one is compelled to make references to two important organs in the body where if oedema is not promptly treated could be life threatening. And these organs are the lungs and the brain. With regards to the lungs n acute inflammation as seen in pneumonia alveoli air spaces could be filled with inflammatory fluid and n the process making it difficult for life sustain gas exchanges to take place. Due to the improvement of antibiotics administration these days the incidence of such oedema with inflammatory consolidation is on the decline.
One of the common causes of pulmonary or lung oedema is when the left ventricle of the heart fails to adequately pump out the blood that is coming from the lungs after oxygenation. This leads to increased hydrostatic pressure from damming and extravasations of fluid into the alveolar space. Finally in the brain, cerebral oedema usually is caused by toxic materials and some metabolic states. This is a known cause of the loss of consciousness as seen in diabetic ketoacidosis.
• To be concluded.