Focal segmental glomerulosclerosis

　　Focal segmental glomerulosclerosis (FSGS) has various pathogenic factors. Such as toxic injury, humoral immunity, and changes in hemodynamics, all can cause damage to the capillary wall, leading to the production and retention of macromolecular proteins, the deposition of immunoglobulins combined with C1q and C3, and the degeneration of podocytes and their detachment from the basement membrane.
　　Changes in hemodynamics of residual renal units cause compensatory hypertension, hyperperfusion, and hyperfiltration of glomerular capillaries, resulting in damage to epithelial and endothelial cells, abnormal function of mesangial cells, and leading to progressive focal segmental sclerosis. This pathological process can be exacerbated by the intake of a large amount of protein and alleviated by restricting protein intake and antihypertensive treatment. Endothelial cell damage causes platelet aggregation and microthrombosis, further aggravating the progression of the disease. Many cases of FSGS are related to this pathogenesis, such as post-infectious glomerulonephritis after chronic streptococcal infection, chronic transplant kidney rejection, reflux nephropathy, and analgesic nephropathy, etc.

　　Focal segmental glomerulosclerosis can be complicated by various diseases. The common complications in clinical practice are as follows:

　　1. Infectious diseases
　　It is related to protein loss, malnutrition, immune function disorder, and the use of glucocorticoid therapy. Infection is a common complication of nephrotic syndrome, and the clinical manifestations of infection are often not obvious due to the use of glucocorticoids. Although there are many antibiotics available at present, if the treatment is not timely or thorough, infection remains the main cause of recurrence of the disease and poor efficacy, and even leads to death of the patient, which should be highly valued.

　　2. Thrombosis and embolism
　　Due to the increased blood viscosity caused by blood concentration and hyperlipidemia, as well as the loss of certain proteins and the increased compensatory protein synthesis by the liver, which leads to an imbalance in the coagulation, anticoagulation, and fibrinolysis systems of the body, thrombotic and embolic complications are more likely to occur.

　　3. Acute renal failure
　　Patients with nephrotic syndrome may experience a decrease in renal blood flow due to insufficient effective blood volume, which can trigger pre-renal azotemia. Additionally, due to severe interstitial edema that compresses the renal tubules and a large amount of protein casts that block the renal tubules and increase intratubular pressure, there is an indirect reduction in glomerular filtration rate, leading to acute renal failure.

　　4. Disordered protein and fat metabolism
　　Long-term hypoalbuminemia can lead to malnutrition, delayed growth and development in children; decreased immunoglobulins can cause decreased immune function, making infections more likely; the loss of metal-binding proteins can lead to deficiencies in trace elements (such as iron, copper, zinc, etc.); insufficient endocrine-binding proteins can induce endocrine disorders; reduced drug-binding proteins may affect the pharmacokinetics of certain drugs (increasing the concentration of free drugs in plasma and accelerating excretion), affecting drug efficacy. In hyperlipidemia, the increase in blood viscosity promotes the occurrence of thrombotic and embolic complications, and will also increase cardiovascular complications, as well as promote the occurrence of glomerulosclerosis and tubulointerstitial lesions, promoting the chronic progression of renal lesions.

　　Focal segmental glomerulosclerosis (FSGS) mostly occurs in children and adolescents, with a slightly higher incidence in males than in females. A few patients have upper respiratory tract infection or allergic reactions before onset. The most common initial clinical symptom is nephrotic syndrome, with about 2/3 of patients having large amounts of proteinuria and severe edema, with proteinuria ranging from 1 to 30 grams per day. More than 50% of patients have hematuria, with microscopic hematuria being more common. In adults, 30% to 50% of patients have mild persistent hypertension or present as chronic nephritis syndrome.
　　The clinical manifestations of pediatric patients with FSGS are similar to those of adults, mainly manifested as nephrotic syndrome, while the incidence of hypertension and renal insufficiency is lower than that in adults. Most FSGS presents as a chronic progressive course, eventually leading to renal failure. A few patients have a rapid progression of the disease and develop renal failure earlier.

　　The clinical course of focal segmental glomerulosclerosis (FSGS) varies greatly, with different outcomes, so prevention should start with personal health. Avoid overexertion, have a balanced diet, engage in scientific exercise, enhance physical fitness, and improve immune function to prevent the occurrence of diseases. For patients who have the disease or complications, active and effective prevention and treatment of the primary disease and complications should be carried out. If infection is detected, it is necessary to promptly select antibiotics that are sensitive to the pathogen, strong in efficacy, and non-nephrotoxic for treatment. If there is a clear focus of infection, it should be removed as soon as possible. If acute renal failure occurs and is not properly treated, it can be life-threatening. With timely and correct treatment, the majority of patients can expect to recover.

　　The diagnosis of focal segmental glomerulosclerosis relies not only on clinical manifestations but also on auxiliary examination, which is an indispensable diagnostic method. The commonly used clinical examinations are as follows:

　　1. Urine examination
　　Microscopic hematuria, proteinuria, often with asymptomatic bacteriuria, glucosuria. Patients with tubular dysfunction have aminoaciduria and phosphaturia, which occur more frequently than other types of NS.

　　2. Blood tests
　　There is significant hypoalbuminemia, plasma albumin is usually below 25g/L, and a few may be below 10g/L. Glomerular filtration rate (GFR) decreases, blood urea nitrogen and creatinine levels increase. Most patients have hyperlipidemia. 10% to 30% of patients have positive circulating immune complexes. A decrease in blood volume can cause an increase in hematocrit and a slight increase in platelets. Water retention can cause a decrease in blood sodium concentration; long-term sodium restriction or acquired adrenal insufficiency can also lead to a decrease in blood sodium concentration; hyperlipidemia can cause pseudo-hypoalbuminemia.

　　3. Renal biopsy examination
　　The typical features of FSGS are focal and segmental glomerular damage. The lesions involve a few glomeruli and part of the glomerular segments, often starting from the deep cortex or perimédullary glomeruli and gradually extending to the renal cortex. The affected glomeruli show segmental sclerosis, the uninvolved glomeruli are normal or the mesangial matrix increases, and amyloid material accumulates beneath the endothelial cells of the damaged capillary loops. Occasionally, foam cells may form in the sclerotic areas, and there is often limited epithelial cell hyperplasia.
　　

　　Focal segmental glomerulosclerosis (FSGS) requires dietary adjustments in addition to routine treatment. The main dietary requirements are as follows:

　　1. Limit protein intake
　　Reducing the protein content in the diet can improve azotemia, alleviate the damage to the kidneys caused by proteinuria, and is also beneficial for lowering blood phosphorus and mitigating acidosis. This is because the intake of protein is often accompanied by the intake of phosphorus and other inorganic acid ions. Generally speaking, 0.6/kg of protein per day can meet the physiological needs of the body, so chronic kidney disease patients only need to supply 30-36g of protein per day. The selection of protein foods should be mainly fish, lean meat, chicken, and milk, and try to eat less plant protein substances such as peanuts, soybeans, and soy products. Because plant proteins contain more non-essential amino acids, excessive consumption does not contribute to nutritional supply and may worsen the phenomenon of proteinuria.

　　2. High calorie intake
　　Consuming sufficient carbohydrates can provide the human body with enough energy, reduce the decomposition of protein to provide energy, improve azotemia, and make full use of amino acids from low-protein diets. The daily energy requirement is about 125.6J/kg, obtained through the intake of staple foods, mainly from carbohydrates-rich grains such as rice, wheat, and corn. In addition, sweet potatoes, taros, potatoes, apples, and lotus roots also contain a lot of carbohydrates, which can be used as supplementary foods to satisfy hunger between meals.

　　3. High vitamin intake
　　Patients with chronic kidney disease often have vitamin deficiencies, which are related to dietary restrictions on one hand and to metabolic abnormalities caused by the disease on the other. Therefore, patients should pay attention to a diet rich in vitamins, especially B vitamins and vitamin C, folic acid, etc. Most of these vitamins are stored in fruits and vegetables, such as tomatoes, rapeseed, chives, oranges, hawthorn, etc., and fresh vegetables and fruits should be added to the daily diet.

　　The treatment of focal segmental glomerulosclerosis is controversial. In the past, it was believed that the efficacy of the disease was poor, the treatment was difficult, and there was no mature and effective treatment method. Patients generally enter the renal failure stage within 5 to 10 years. In recent years, a large number of retrospective studies have shown that active removal and treatment of the causes of the disease, and symptomatic treatment such as diuresis and antihypertensive therapy, can promote the remission, prevention, and delay of the disease. The current treatment methods for patients with this disease are:

　　1. Glucocorticoids should be treated with prednisone (prednisone) in a timely manner before hormone resistance occurs. The average time to achieve complete remission is generally 3 to 4 months. For patients with hormone dependence, resistance, and recurrence, the addition of prednisone and intermittent cyclophosphamide pulse therapy can increase the remission rate.

　　2. After 6 months of treatment with cyclosporine and cyclosporine A, urinary protein can be reduced and remission can be induced, but recurrence often occurs when the dose is reduced or the medication is stopped, so long-term application should be maintained to maintain remission. As the drug has nephrotoxicity, blood creatinine should be monitored during use, and the dose should be adjusted according to the situation. The mechanism of action of cyclosporine A is similar to that of cyclosporine, and it can be used with hormones. It is often used in patients with ineffective or dependent on cyclosporine treatment.

　　3. Cytotoxic drugs (cyclophosphamide and ifosfamide) can be used as a second-line therapy, but their efficacy needs to be confirmed by clinical observation.

　　4. Plasma exchange and protein adsorption therapy can be applied to renal transplant patients with recurrent FSGS. Plasma exchange or protein adsorption can reduce circulating immune factors, temporarily alleviating proteinuria.