Something You Need to Know about Edema in Kidney Disease

Edema is a main symptom among the patients with Nephrotic Syndrome. For most of the patients, the onset of kidney disease is marked with the appearance of edema-edema of lower limbs, face, eyelids, etc. That makes lots of patients have a fear for edema, and they are afraid of that the more serious edema presents, the more serious nephropathy is. Is it rational?
First of all, let’s figure out what are the main causes of edema in Nephrotic Syndrome?
There are two main causes accounting for it:
● The filtration rate of glomerulus declines, while the capability of renal tubules remains normal. It refers to that, when the kidney is damaged, or specifically, the glomerulus is damaged, the excess water which is much more than the normal standard will be filtrated out by the glomerulus. However, the renal tubules still keep a normal capability of reabsorption, so the excess water will be reabsorbed. Consequently, it leads to the retention of water in the body, and then the edema occurs.
● As is known to all, proteinuria is a characteristic symptom of Nephrotic Syndrome. The loss of large amounts of protein in blood leads to the unbalanced pressure between outside-inside of vessels, resulting in the movement of the water from blood vessels to tissue space, finally inducing edema.
For those patients with Nephrotic Syndrome whose kidneys are damaged not very seriously, due to the causes above, they will present with severe edema. It makes them look like a big “water bag”, and some may even suffer from hydrothorax, ascites, and hydropericardium. However, in fact, their pathological changes are mainly confined to minimal change disease and the damage of glomerulus is comparably slight. When treated with hormones and medicine against proteinuria, the patient’s condition will get better soon.
In contrast, as to the patients with chronic kidney disease, though the damage of glomerulus is very serious, the reabsorption capability of tubules declines more severely. In that case, the glomerular filtration rate has dropped dramatically, and the renal tubules can hardly reabsorb water and other nutrition. As a result, there is no retention of water and sodium, thereby, the patients may have no edema or slight edema.

Thus, we can draw a conclusion from that, the basis of edema in Nephrotic Syndrome are retention of sodium and water and the water’s movement to tissue space. Once satisfying the conditions, the patients will present with edema. However, the conditions have no inevitable association with the severity of kidney disease. In another word, there is no direct relation between the extent of edema and the severity of nephropathy.