Kidney Disease Popular Science | Edema - The signs of nephrotic syndrome you can see

Aunt Zhang developed eyelid edema one month ago, but she did not go to the hospital because she was usually healthy. One month later, the edema not only did not subside but became more severe, and her lower limbs also gradually became swollen. She also felt bloating and loss of appetite, so she went to the hospital for treatment. After the doctor examined Aunt Zhang, he told her that she had "nephrotic syndrome." So, what kind of disease is nephrotic syndrome?

Nephrotic syndrome is actually the sum of a group of clinical and laboratory tests. It is mainly characterized by "three highs and one low": 1. Large amounts of proteinuria (urine protein ≥ 3.5 g/day). 2. Hypoalbuminemia (serum albumin < 30 g/L). 3. Severe edema (edema of the eyelids and lower limbs, even pleural effusion and ascites) 4. Hyperlipidemia. The first two of these must be present to diagnose this disease.

What are the symptoms of nephrotic syndrome?

The most common and prominent symptom is edema, which is more common in the face at first, and gradually spreads to the lower limbs and the whole body. In severe cases, the patient's eyelids will be highly swollen, so that he cannot open his eyes. The skin of the limbs is tight, thin and translucent, and water seeps from the places where the needles are inserted or the skin is damaged. The scrotum of male patients can swell like a ball. The patient may even have pleural effusion and ascites, leading to abdominal distension, poor appetite, chest tightness, shortness of breath, and difficulty breathing. The degree of edema is generally consistent with the degree of decrease in serum albumin, and is often accompanied by a decrease in urine output.
Patients with secondary nephrotic syndrome will also experience different symptoms due to the characteristics of their primary disease. Let us briefly understand them.

1. Henoch-Schonlein purpura nephritis

First of all, what is purpura? Purpura is a hemorrhagic rash. The size of the rash varies from the tip of a needle to the size of a soybean. When there are many, they can merge into a patch. It is mainly distributed on the limbs, and is most common on the extensor side of the lower leg. It is red at first, then gradually darkens, does not fade when pressed, and occasionally it itches. It often appears in batches.

Secondly, what is Henoch-Schonlein purpura? Henoch-Schonlein purpura is a disease caused by the body's allergy to certain substances (such as drugs, food, vaccines, etc.). Some substances attack small blood vessels throughout the body, causing vascular inflammation. Therefore, in addition to purpura, joint swelling, heat and pain, abdominal pain, blood in the stool and kidney damage may also occur.

About 1/3 of patients develop renal damage, namely Henoch-Schonlein purpura nephritis, which is more common in children and adolescents. It often occurs within 4 weeks of the onset of purpura and can be clinically manifested as hematuria (dysmorphic hematuria), proteinuria, edema, hypertension, and even abnormal renal function (elevated creatinine).

2. Systemic lupus erythematosus nephritis

First of all, what is systemic lupus erythematosus? Systemic lupus erythematosus is an autoimmune disease. The attack of multiple autoantibodies (such as antinuclear antibodies, anti-dsDNA antibodies, anti-Sm antibodies, etc.) causes damage to multiple organs throughout the body. Clinical manifestations include skin damage (facial rash, butterfly rash), fever, oral ulcers, hair loss, vasculitis and visceral damage (damage to the kidneys, blood system, heart, nervous system, etc.).

Secondly, what is lupus nephritis? Lupus nephritis is caused by systemic lupus erythematosus invading the kidneys. The invasion rate is almost 100%. It is more common in young and middle-aged women, with a male to female ratio of 1:9. According to its 6 pathological types (Ⅰ～Ⅵ), from mild to severe, it manifests as varying degrees of proteinuria, edema, hypertension, and even renal dysfunction.

3. Diabetic nephropathy

First of all, what is diabetes? Diabetes is a chronic systemic metabolic disease with a very high incidence rate, characterized by elevated blood sugar, and is mainly divided into type 1 and type 2.

Secondly, what is diabetic nephropathy? If diabetes is not well controlled for a long time, the kidney complications caused by diabetic nephropathy are diabetic nephropathy. About 1/4 of diabetic patients have renal damage, which is more common in middle-aged and elderly people. From mild to severe, it manifests as microalbuminuria, macroalbuminuria, edema, hypertension, abnormal renal function, and eventually progresses to uremia.

The formation of the "four major characteristics" of nephrotic syndrome

1. Heavy proteinuria

The glomerular filtration membrane normally acts like a fence, not allowing albumin to leak out of the urine. However, when it becomes diseased, the barrier function of this fence is destroyed. At this time, the permeability of the glomerular filtration membrane to plasma proteins (mainly albumin) increases, causing excessive protein to leak out of the urine. When the amount exceeds the reabsorption capacity of the proximal tubule, a large amount of proteinuria is formed.

2. Decreased plasma albumin

The body's albumin is mainly synthesized in the liver. When a large amount of albumin leaks out of the urine, the liver's synthesis of albumin increases accordingly. When the increased synthesis still cannot meet the amount leaking out of the urine, hypoalbuminemia occurs. In addition, patients often have poor appetite due to gastrointestinal mucosal edema, low protein intake, and poor absorption, which can also aggravate hypoalbuminemia.

3. Edema

Plasma albumin in the human body is like a "water-absorbing sponge", firmly absorbing water in the blood vessels. When a large amount of proteinuria leaks out and causes a decrease in plasma albumin, water will enter the interstitial space from the blood vessels, especially the loose and drooping parts. Therefore, we will see edema in the eyelids and lower limbs of patients.

4. Hyperlipidemia

Patients with nephrotic syndrome often suffer from hyperlipidemia, including hypercholesterolemia and/or hypertriglyceridemia. The mechanism of hyperlipidemia is related to the increased compensatory lipoprotein synthesis and weakened lipoprotein decomposition in the liver during hypoproteinemia.