What Is Edema of the Kidney?

The kidney is the main organ for the body to discharge water. When the kidney is sick, the water cannot be excreted from the body and is retained in the body, which is called renal edema. Edema is the most common symptom of kidney disease. Eyelids and facial edema are mild, and systemic edema or pleural fluid and ascites are present in severe cases. The degree of edema can be mild or severe, with no visible swelling, only weight gain or slight swelling of the eyelids in the early morning. Severe cases can be markedly edema throughout the body, even pleural and abdominal effusion, causing weight gain of tens of kilograms (severe edema). The most common one is referred to as concave edema, that is, you will see depressions when you press down with your fingers.

Nephrotic edema

Overview of nephrotic edema

The causes of renal edema are generally divided into two categories: one is that the glomerular filtration is reduced, and the renal tubules reabsorb water and sodium well, which causes water and sodium to slip. At this time, it is often accompanied by increased capillary permeability throughout the body, so the tissue gap The water is slippery, which is more common in nephritis. Another reason is that plasma protein is too low due to a large amount of proteinuria.

Systemic edema caused by primary kidney disease is called renal edema. Renal edema is not only the main manifestation of kidney disease but also an important clue for the diagnosis of nephritis. According to its mechanism, it can be divided into nephritis edema and nephrotic edema.

Causes of nephrotic edema

The glomerular filtration rate is reduced and water and sodium retention.

The capillary permeability of the whole body is increased, so that the liquid can easily enter the tissue space from the blood vessel.

The decrease of plasma protein level, especially the decrease of albumin level, causes the plasma colloid osmotic pressure to decrease, and the water easily moves to the interstitial space.

The decrease of effective blood volume leads to the increase of secondary aldosterone, which aggravates water and sodium retention.

Nephrotic Edema Pathology

The mechanism of nephritic edema is mainly caused by sodium-water retention caused by bulb-tube imbalance. The essence is a significant decrease in glomerular filtration rate without a corresponding decrease in renal tubular reabsorption. Swelling and proliferation due to glomerular vascular endothelial cells and interstitial cells. The exudation of inflammatory cells and the accumulation of fibrin and stuffing the sac cavity make the latter narrow, so that the blood flow through the glomerulus is greatly reduced, and the effective filtration area of the glomerulus is significantly reduced. As a result, the kidney Pellet sodium water filtration decreased significantly. However, at this time, the intact renal tubule still reabsorbs sodium and water at a normal rate, so it produces hypertonic oliguria or even anuria. A large amount of sodium water stagnates in the body, causing a marked increase in plasma volume and extravascular extracellular fluid volume. As a result, the interstitial fluid increases and cannot be compensated by lymphatic reflux, so systemic edema occurs. The glomerular capillary wall has increased permeability due to inflammation, so proteinuria may occur, but hypoproteinemia is not obvious. Of course, sodium retention can dilute plasma proteins, but this factor causes secondary effects.

The apparent decrease in normal nephrons significantly reduces the total filtration area;

Persistent renal hypertension exacerbates the burden on the left heart and leads to heart failure in severe cases;

hypoproteinemia caused by long-term proteinuria.

Classification of nephrotic edema

Nephrotic edema

Is one of the four characteristics of nephrotic syndrome. Due to the low content of interstitial protein, edema usually starts from the lower extremity.

Due to the long-term, large amount of proteinuria caused by hypoalbuminemia caused by the decrease in plasma colloid osmotic pressure, the fluid penetrates into the interstitial space from the blood vessel, resulting in edema, which is the central part of its pathogenesis.

The sodium water retention secondary to the decrease in effective circulating blood volume will also play an important role in the development of nephrotic edema. In addition, some patients have decreased effective blood volume, stimulated increased renin-angiotensin-aldosterone system activity, and increased antidiuretic hormone secretion, which can further increase water retention and edema.

Nephropathy edema Nephritis edema

Mainly seen in acute glomerulonephritis. Due to the high content of interstitial protein, edema usually starts from the eyelid and face.

Pathogenesis: At the same time that the glomerular filtration rate has decreased significantly, the reabsorption of the renal tubules has not decreased correspondingly, and some have increased. As a result, severe bulb-tube imbalances have occurred, and the glomerular filtration fraction (the glomerular filtration rate / Renal plasma flow) decreased, resulting in sodium water retention. In nephritic edema, blood volume is often dilated, with renin-angiotensin-aldosterone system activity inhibition, decreased antidiuretic hormone secretion, and edema persistence and exacerbation due to factors such as hypertension and increased capillary permeability.

Mechanism of nephrogenic edema

Chronic glomerulitis may also be accompanied by edema, but it is not as obvious as acute glomerulonephritis. The residual nephrons can compensate to some extent. If edema occurs, the pathogenesis is related to the following factors: The significant reduction in normal nephrons significantly reduces the total filtration area; Persistent renal hypertension increases the burden on the left heart and leads to heart failure in severe cases; Caused by hypoproteinemia.

Nephrogenic edema diet

Renal edema is characterized by: it first occurs in loose tissue sites, such as the eyelids or face, feet and ankles, which is obvious in the morning, and in severe cases can involve the lower limbs and the whole body. The nature of renal edema is soft and easy to move, and clinically presents depression edema, that is, depression on the local skin with fingers can occur.

If there is edema, pay attention to the following aspects of the diet:

Limit water, sodium and protein intake

1. Protein intake

Patients with severe edema and hypoproteinemia can be given 1g of protein per kilogram of body weight per day, of which more than 60% is high-quality protein, and mild to moderate edema of 0.5 to 0.6 g of protein per kilogram of body weight per day. Adequate calorie intake, 125.5 146.4kJ / kg (30 35kcal / kg) per day.

2. Water and salt intake

Mild edema, urine output & gt; 1000ml / d, do not restrict water excessively, sodium salt is limited to 3g / d, including sodium-containing food and beverages. The daily water intake of severe edema with oliguria should be limited to 1000ml, and a salt-free diet should be given (sodium content in main and non-staple foods daily <700mg).