Secondary kidney disease

　　Secondary nephropathy is a group of diseases that occur in the process of many diseases, causing damage to the permeability of the glomerular capillary filtration membrane and resulting in a group of diseases. Common causes of secondary nephropathy include:
　　Diabetic nephropathy
　　Diabetes often occurs in patients with diabetes for more than 10 years, especially in those with diabetes type 1 who have not been controlled satisfactorily. There is a large amount of proteinuria and nephrotic syndrome, fundus examination often shows micro-arteriolar aneurysms, early kidney volume increases, renal plasma flow and glomerular filtration rate increase or remain normal, and kidney function deteriorates in the later stage.

　　Systemic lupus erythematosus
　　Lupus nephritis is common in women aged 20 to 40, of whom 20% to 50% present with clinical manifestations of nephrotic syndrome. Patients often have fever, rash, and joint pain, especially the butterfly-shaped rash on the face is of diagnostic value. Serum antinuclear antibody, antidsDNA, and antiSm antibody are positive, complement C3 decreases, and serum protein electrophoresis a2 and gamma globulin increase. The main results of immunoglobulin examination are increased IgG. Renal biopsy under light microscopy shows lesions with diverse characteristics in addition to mesangial proliferation.

　　Amyloidosis
　　Amyloidosis nephropathy has primary and secondary types, the latter often secondary to chronic infection (such as tuberculosis, leprosy, or chronic pulmonary empyema, etc.), tumor, multiple myeloma, and rheumatoid arthritis. Most patients have myocardial hypertrophy, arrhythmias, and heart failure, liver and spleen enlargement, macroglossia, and skin with lichenoid mucinous edema. The early stage of amyloidosis nephropathy only has proteinuria, and generally nephrotic syndrome appears within 3 to 5 years, with increased serum gamma globulin, and hyperlipidemia is not obvious. The diagnosis is not difficult with the combination of heart, liver, and spleen enlargement. Diagnosis depends on renal biopsy.

　　Malignant tumors
　　All kinds of malignant tumors can cause nephrotic syndrome, even with nephrotic syndrome as the early clinical manifestation. For example, breast cancer, lung cancer, gastric cancer, colon cancer, and lymphoproliferative diseases often occur nephrotic syndrome. Therefore, comprehensive examinations should be performed on patients with nephrotic syndrome, and if systemic lymphadenopathy and abdominal masses are found, secondary kidney disease caused by tumors should be considered, and the diagnosis of the primary tumor should be actively confirmed.

　　Purpura nephritis
　　It is common in adolescents, and the clinical manifestation is nephrotic syndrome, with extrarenal manifestations mainly including purpura at the distal ends of the limbs, abdominal pain, and joint pain, etc.

　　During the development of secondary kidney disease, it can cause varying degrees of hypertension, edema, and in severe cases, it can cause ascites and pleural effusion; it often complicates diabetic retinopathy; chronic interstitial nephritis can complicate renal glycosuria, even Fanconi syndrome; it can complicate tubular acidosis, leading to uremia; it can also complicate renal anemia and hypertension; acute interstitial nephritis can complicate acute renal failure; when patients have symptoms such as decreased appetite, nausea and vomiting, anemia, and others, it indicates that chronic renal insufficiency has appeared.

　　The main clinical manifestations of secondary kidney disease are massive proteinuria, hypoalbuminemia, edema, hyperlipidemia, and changes in other protein concentrations in the blood. Clinical symptoms include symptoms of the primary disease, and patients can have no symptoms or only mild discomfort such as fatigue, lower back pain, and increased nocturia; a few patients may have decreased appetite, metabolic acidosis, and mild anemia.

　　In addition to actively treating primary diseases that may cause kidney disease in life, pay attention to the following details in daily life:
　　1. Pay attention to diet
　　People's diet is very important for their bodies, and they should pay attention to a light diet. If a large amount of animal and plant protein is consumed, the final metabolic products such as uric acid and urea nitrogen all need to be excreted by the kidneys, so excessive drinking and eating will increase the burden on the kidneys, which is not conducive to the prevention of secondary kidney disease.
　　2. Do not hold urine
　　The harm of holding urine has been recognized by everyone. Urine in the bladder for too long can easily breed bacteria, and bacteria may cause kidney infection through the ureter. Drinking enough water and urinating regularly every day can prevent the occurrence of secondary kidney disease.
　　3. Strengthen physical fitness
　　Strengthening physical fitness can effectively prevent various diseases. Having a planned physical activity and sports every day, controlling weight, and avoiding colds are the basis for preventing secondary kidney disease.
　　4. Prevent infection
　　Try to prevent infections. If laryngitis or tonsillitis occurs, antibiotics should be used thoroughly under the guidance of a doctor immediately, otherwise streptococcal infection is likely to induce kidney disease, which is a cause of many types of kidney diseases, and it must be controlled.
　　5. Use drugs with caution
　　Many drugs have certain side effects on the body, and it should be avoided to misuse drugs; various drugs, chemical toxins, and long-term or excessive use of analgesics, inappropriate use of aminoglycoside antibiotics, and long-term or excessive use of traditional Chinese herbs containing aristolochic acid can all gradually cause kidney function damage, making it difficult to prevent secondary kidney disease.

　　Examination methods for secondary kidney disease:
　　1. Urine glucose test is a simple method for screening diabetes, but it can appear false-negative or false-positive in diabetic nephropathy, so blood glucose measurement is the main basis for diagnosis.
　　2. Urinary albumin excretion rate (UAE) is 20 to 200μg/min, which is an important indicator for diagnosing early diabetic nephropathy; when UAE is continuously greater than 200μg/min or routine urine protein test is positive (urinary protein quantification is greater than 0.5g/24h), it is diagnosed as diabetic nephropathy. Urinary sediment generally does not change significantly, and an increased number of leukocytes suggests urinary tract infection; a large number of red blood cells suggest possible hematuria due to other causes.
　　3. In the late stage of diabetic nephropathy, the clearance rate of endogenous creatinine decreases and blood urea nitrogen and creatinine levels increase.
　　4. Increased glomerular filtration rate (GFR) and increased renal volume measured by B-ultrasound are consistent with early diabetic nephropathy. In uremia, GFR decreases significantly, but the renal volume often does not shrink明显.
　　5. Fundus examination: Fluorescein fundus angiography may be performed when necessary, showing microaneurysms and other diabetic fundus lesions.

　　Patients with secondary kidney disease usually need to choose a diet low in fat, salt, and high-quality low-protein diet, with a recommended protein content of 0.6-0.8g/kg/d (for nephrotic syndrome, it can be appropriately increased by 0.8-1.0g/kg/d); avoid consuming alcohol and spicy foods, and eat less greasy foods. Different kidney diseases have different dietary plans.

　　Normal adults should consume about 5 to 6 grams of salt per day, and salt is sodium chloride. Excessive salt intake can easily cause water retention in the body, leading to edema. Therefore, for patients with edema, the intake of salt should be controlled, and 2 to 3 grams of salt per person is sufficient. A salt-free diet is also not scientific, and prolonged use can easily lead to fatigue, dizziness, and other symptoms. For patients without edema, they can consume salt like normal people, but in moderation.

　　The normal urine volume of a healthy person is generally 1500-2000ml per day. For patients with acute nephritis, acute renal failure oliguria phase, nephrotic syndrome, and chronic renal failure with oliguria and edema, it is necessary to control the intake of water (including water intake, water content in food, and the volume of intravenous medication). Because what is ingested cannot be excreted, water retention in the human body aggravates edema and is also prone to aggravate hypertension. At this time, the water intake should be 500ml more than the urine output. After the urine output increases, the water intake can be relaxed. While patients with normal urine output can drink water normally. In addition, for patients with urinary tract infections such as acute pyelonephritis, urethritis, cystitis, etc., drinking more water and urinating more are very beneficial to the recovery of the disease, in addition to timely medical treatment.

　　Treatment methods for secondary kidney diseases:
　　1. There is no effective treatment for diabetic nephropathy. The vast majority of patients with nephrotic syndrome should not use glucocorticoids, cytotoxic drugs, or tripterygium wilfordii hooker treatment, as there is no significant efficacy.
　　2. Actively control blood sugar, including dietary treatment, oral hypoglycemic agents, and insulin application. When azotemia occurs, adjust the dose and type of insulin and oral hypoglycemic agents in a timely manner based on blood sugar levels.
　　3. Limit protein intake. Add essential amino acids or α-ketoglutaric acid treatment when necessary.
　　4. For patients with hypertension or edema but normal renal function, small-dose thiazide diuretics can be selected. For patients with renal insufficiency, loop diuretics or indapamide tablets should be used; for patients with severe edema, in addition to strictly limiting sodium intake, appropriate fluid expansion and diuresis should be performed; if blood pressure is too high or there is heart failure, and the condition does not improve after active fluid expansion and diuresis, dialysis treatment can be considered.
　　5. Actively lower blood pressure below 18.6Kpa. It is recommended to choose ACEI first, which can improve GFR and reduce the excretion rate of urinary albumin while lowering blood pressure, but it is necessary to prevent the decrease of functional GFR; use diuretics, calcium channel blockers, cardiac selective β-receptor blockers, and angiotensin II receptor antagonists as appropriate.
　　6. Actively treat hyperlipidemia and hyperuricemia.
　　7. Apply drugs that inhibit platelet aggregation and adhesion, such as dipyridamole, clopidogrel, aspirin, or heparin, etc. Correctly use traditional Chinese medicine based on syndrome differentiation, which has a good effect on controlling blood sugar and improving microvascular lesions, especially.