A. Do you know the location, size and structure of the kidneys?
The human body has two kidneys on the left and right, located on either side of the lumbar spine. The kidneys are shaped like broad beans, with a raised outer edge and a depression in the middle of the inner edge. Each kidney is about 9-12 cm long, 5-6 cm wide, 3-4 cm thick, and weighs 120-150 grams. Both kidneys are roughly similar in shape, size and weight, with the left kidney being slightly larger than the right.
The major structures of the kidney include.
(1) Glomerulus: completes the filtration function of the kidney and removes metabolites and toxins from the body.
(2) renal tubules: reabsorb useful substances (sugar, amino acids, small molecules of protein and minerals, etc.) filtered out by the glomerulus, locally secrete certain regulatory factors, secrete certain metabolites and drugs for their removal, and regulate the acid-base and water balance of the body.
(3) the collecting duct and renal pelvis: urine discharge pipeline, participate in the body’s water balance regulation.
Second, what are the main functions of the human kidney?
1, generate urine, maintain the water balance: the glomerulus is like a sieve, when the blood flows through the glomerulus, the volume of large components, such as red blood cells, white blood cells, platelets, proteins, etc. can not pass through the sieve, so can not be filtered out from the glomerulus, still remain in the blood vessels; and small volume of components, such as water, sodium, chloride, urea, sugar, etc., can pass through the sieve, filtered out by the glomerulus, flowing into the renal tubules, these fluids are called “proto-urine”. When the original urine flows through the renal tubules on the way, the renal tubules have a reabsorption function, 99% of the water is absorbed back into the body, and almost all of the nutrients are reabsorbed; at this time, only the body’s metabolic waste and very little water is left, and urine is formed (called “final urine”). Each kidney in the human body has about 1.3 million glomeruli, which filter out 180 liters of raw urine every day, forming about 1.8 liters of urine. When there is too much or too little water in the body, the kidneys regulate the volume of urine to maintain the balance of water in the body.
2.Discharge the metabolites and toxic substances of human body: When human body carries out metabolism, it will produce some metabolic wastes, such as urea, uric acid and creatinine, etc. Through glomerular filtration and renal tubular secretion, the kidneys discharge these wastes from urine to maintain normal physiological activities. In acute and chronic renal insufficiency, the glomerular filtration function is reduced, and the accumulation of metabolic waste in the body will occur, causing disorders of normal physiological functions of the body.
3, regulation of electrolytes and acid-base balance: the kidney through the glomerular filtration, renal tubular reabsorption and secretion function, excretion of excess water in the body, regulation of electrolytes and acid-base balance, maintaining the stability of the internal environment.
4.Secretion of erythropoietin (EPO): promote bone marrow hematopoiesis and generate red blood cells; when renal insufficiency, erythropoietin synthesis is reduced, it will cause anemia.
5.Produce active vitamin D: convert 25(OH)2 vitamin D3 into 1,25(OH)2 vitamin D3, regulate calcium and phosphorus metabolism in the body, maintain the normal structure and function of bones, and also participate in the regulation of immune function. Insufficient active vitamin D is caused by renal insufficiency.
6, secretion of vasoactive substances: secretion of renin, angiotensin, prostaglandins, etc., play an important role in the regulation of blood pressure. In chronic kidney disease, the above vasoactive substances can become dysregulated, causing an increase in blood pressure.
7. Degradation and inactivation of hormones: The kidney is also the site of degradation and inactivation of many hormones, such as insulin, parathyroid hormone, glucagon, calcitonin and many other hormones, which are degraded in the proximal tubular cells of the kidney. When renal insufficiency occurs, the biological half-life of these hormones is significantly prolonged, leading to accumulation in the body and causing metabolic disorders.
In addition, the kidney secretes a variety of cytokines-growth factors, which play an important role in regulating life activities.
What is glomerular filtration function? How to measure it?
Glomerular filtration function refers to the function of circulating blood passing through the glomerular capillaries, when water and solutes of different molecular sizes in the plasma are filtered into the renal capsule to form ultrafiltrate (primary urine), i.e., the function of the kidney to remove metabolites, toxic substances and excess water from the body. Evaluation of glomerular filtration function is mainly to detect glomerular filtration rate (GFR), which is commonly used clinically, including the following methods.
1, serum creatinine concentration (sCr): early morning fasting blood sampling assay. Normal value: 0.6 to 1.2 mg/dl (mg/dl) or 53 to 106 micromol/l (mmol/L) for men and 0.5 to 1.0 mg/dl (mg/dl) or 44 to 88 micromol/l (mmol/L) for women.
Creatinine is a metabolite of muscle tissue in the body and reaches the kidneys via the blood circulation, where it is filtered from the glomerulus and then excreted in the urine. When the glomerular filtration function decreases significantly (often by about 50%), the blood creatinine concentration will begin to rise. Because serum creatinine concentration is influenced by muscle volume in the body, serum creatinine levels vary greatly among individuals. For example, serum creatinine concentration is relatively high in young and strong men, athletes, manual laborers with developed muscles, or those who eat a lot of lean meat; while serum creatinine is low in women, bedridden people, elderly people, people with little physical activity and muscle atrophy. Therefore, in elderly, thin and bedridden people, although the blood creatinine level is still in the normal range, the actual kidney function may have been slightly reduced.
2.Creatinine clearance (Ccr): Normal value: 90 ±10(80-100)ml/min. Ccr can reflect the degree of glomerular filtration impairment earlier. In most adults, serum creatinine begins to rise only when Ccr decreases by about 50%. However, due to the large individual differences in serum creatinine levels and the fact that various methods of calculating Ccr may have certain errors, most of them tend to be low, so the kidney function cannot be evaluated by only one Ccr result.
3.Isotope method to measure GFR: According to the nuclear kidney dynamic imaging, the GFR of each bilateral kidney can be measured, but the results are affected by the isotope attenuation and the experience of the operator, and there are also some limitations. Normal values are generally 90 – 100 ml/min
4. serum urea nitrogen concentration (BUN): normal value 6-20mg/dl (2.9-7.5mmol/L). bun has a certain reference value in reflecting glomerular filtration function, but there are many influencing factors, so you cannot judge the kidney function of patients only by the blood BUN concentration.
What diseases are included in chronic kidney disease?
Chronic kidney diseases include glomerulonephritis, tubulointerstitial diseases, renal vascular diseases and hereditary kidney diseases. At present, primary glomerulonephritis is still common in China (especially IgA nephropathy is the most common), followed by hypertensive renal arteriosclerosis, diabetic nephropathy, chronic interstitial nephritis and polycystic kidney, etc. However, in recent years, along with the aging of the population and changes in people’s lifestyle, the incidence of diabetic nephropathy and hypertensive renal arteriosclerosis has increased significantly.
V. Why has the number of patients with chronic kidney disease increased year by year over the past 30 years?
Epidemiological survey shows that chronic kidney disease has become one of the major diseases threatening public health all over the world in the past 30 years or so. From the statistics in recent years, in developed countries (such as the United States and the Netherlands), about 6.5% to 10% of the general population suffer from kidney disease of varying degrees, of which the number of kidney disease patients in the United States has exceeded 20 million, and the number of patients with kidney disease admitted to hospitals each year is up to more than 1 million, and the number of people who have not sought medical attention for kidney disease is much larger than the number of patients admitted. There is no detailed epidemiological survey data of chronic kidney disease in China, the preliminary results show that the prevalence of chronic kidney disease in people over 40 years old is about 8% to 9%, the results are alarming.
Why is the prevalence of chronic kidney disease high and the number of patients increasing year by year?
The main reason is that with the improvement of material life and working conditions, people’s lifestyle has undergone some unreasonable changes, such as excessive consumption of certain nutrients (carbohydrates, fats, salt, etc.) and too little physical activity; at the same time, due to increased work pressure, high mental tension, lack of sleep, as well as smoking, alcohol abuse, various environmental pollution and other factors, making diabetes, hypertension, hyperlipidemia, hyperuricemia, obesity and other metabolic diseases. The prevalence of metabolic diseases such as diabetes, hypertension, hyperlipidemia, hyperuricemia, obesity, and chronic kidney disease secondary to these metabolic diseases is increasing.
Secondly, the prevalence of various infections (hepatitis, tuberculosis, AIDS, schistosomiasis, etc.), immune-mediated primary or secondary nephropathies remains high, especially in developing countries.
In addition to the above-mentioned causes, drug-related kidney damage due to drug abuse or irregular drug use is another reason for the yearly increase of kidney disease that should not be taken lightly, such as painkillers and aristolochic drugs.
Of course, with the development of society, the extension of human life expectancy, the aging of the population is becoming more and more obvious, the elderly (> 65 years old) organ function with age and gradually show a degenerative trend, so that the elderly, especially the elderly (> 80 years old) in the population with a significantly higher prevalence of kidney disease.
Who are more likely to get chronic kidney disease? What are the risk factors?
The onset of chronic kidney disease is caused by a combination of factors, and its pathogenesis is also very complex, but the incidence of the following risk factors is significantly higher in the population, should be highly alert.
First, people with diabetes, hypertension, cardiovascular disease and family history of kidney disease are more likely to get chronic kidney disease, followed by metabolic diseases (obesity, hyperlipidemia, hyperuric acid), long-term use of nephrotoxic drugs (NSAIDs, antimicrobials, etc.), chronic urinary tract infections, urinary tract obstruction, hypercoagulable state, autoimmune diseases (lupus erythematosus, etc.), high protein diet, smoking, excessive alcohol consumption, low Chronic kidney disease is also likely to develop in people with low birth weight and age over 65 years.
Do you know whether your kidneys are healthy or not? Why is chronic kidney disease not easily detected early or even missed?
Everyone wants to know whether their kidneys are healthy or not. But how to determine whether the kidneys are healthy or not? Doctors need to take into account your past medical history, family history, symptoms, signs, and necessary laboratory tests to make a comprehensive judgment. In other words, to know whether your kidneys are healthy or not, you must go to the hospital for regular medical checkups instead of relying on your self-perception.
Chronic kidney disease is often not easily detected early, or even missed. Why is this the case?
First of all, chronic kidney disease can have no symptoms at all or the symptoms are not obvious, which cannot attract enough attention from patients and their families. The compensatory function of the kidney is extremely strong, even if more than 50% of the patients with chronic kidney disease whose kidney function has been lost still may not have any symptoms.
Second, many routine physical examinations or unit checkups often do not do kidney function tests, and thus it is easy to miss chronic kidney disease.
Third, some doctors lack the awareness of routine urine and kidney function tests for patients, especially those at high risk. For patients with hypertension and diabetes mellitus who are first diagnosed, some doctors only treat them with antihypertensive drugs and hypoglycemic drugs, but fail to implement routine urine and kidney function tests in a timely manner.
Fourthly, various methods of checking kidney function have certain limitations and lack early sensitive indicators, which cannot diagnose chronic kidney disease earlier.
In addition, the popularization of kidney disease in China is relatively weak, and the general public cannot fully understand the knowledge of kidney disease prevention in time. Moreover, the problem of “difficulty in seeing a doctor” still exists, which makes it not rare that some patients fail to seek timely medical treatment or are unwilling to actively seek medical treatment, which is also an important reason why chronic kidney disease is not easily detected at an early stage.
Eight, what are the main symptoms of chronic kidney disease?
Most patients with chronic kidney disease may have no symptoms or fewer symptoms in the early stage; as the disease progresses, various symptoms of different degrees may gradually appear. In the early stage, it can be manifested as frequent fatigue, weakness, eyelids, face, lower limbs (especially ankles), large amount of foam in the urine, abnormal urine color, pain or difficulty in urination, and an increase in the number of urination at night.
When renal insufficiency appears, various symptoms of chronic kidney disease gradually become obvious, with manifestations such as fatigue, loss of appetite, nausea and vomiting, lumbago, increased nocturnal urination, generalized edema, elevated blood pressure with urine odor on exhalation, bone pain, skin itching, muscle tremor, numbness in hands and feet, drowsiness, and unresponsiveness. Laboratory tests may reveal anemia, elevated serum creatinine and urea nitrogen concentrations, etc. When entering the advanced stage of uremia, the above-mentioned symptoms continue to worsen, leading to multiple organ failure such as heart, liver and lung, with a high mortality rate.
What tests are commonly used to screen for chronic kidney disease?
Most patients with chronic kidney disease have no symptoms or mild symptoms in the early stage, therefore, early laboratory tests are very important. To achieve early detection, the key is to insist on regular screening every year. Even if there are no symptoms, it is usually necessary to screen urine routine and kidney function once a year. If you have high blood pressure, diabetes, etc., you should regularly check urine routine, kidney function and other items twice or more per year (depending on the condition); if you already have certain symptoms, you should go to the hospital as soon as possible to do a more comprehensive examination.
1, urinary routine: urinary routine is the most simple examination of the urinary system for the presence of lesions, the nature and extent of lesions. Among them.
Urine protein (Pro): Positive urine protein is often caused by kidney disease, but excessive plasma protein, strenuous exercise, fever, heart failure, pericardial effusion and drugs may also cause positive urine protein.
Glucose (Glu): Positive urine glucose indicates decreased renal tubular reabsorption or diabetes mellitus. When blood glucose is normal and urine glucose is positive, it is called “renal diabetes”, which indicates abnormal renal tubular reabsorption of glucose (glucose leaks out of the renal tubules), not diabetes.
Erythrocytes (Ery): Positive urine red blood cells is called “hematuria”. In mild cases, hematuria cannot be detected by the naked eye and can only be determined by microscopic examination, called “microscopic hematuria”; in heavy cases, the urine is the color of washed water or even blood, called “carnal hematuria”. “Hematuria is commonly seen in glomerulonephritis, urinary tract infection, urinary stones, and sometimes in tumors, cysts, malformations, and trauma of the urinary tract.
Leukocytes (LEU): The presence of leukocytes (1+~4+) in fresh mid-stage urine examination is often indicative of urinary tract infection, and sometimes may also indicate non-infectious tubulointerstitial lesions.
Other influencing factors: drugs or food can change the color and pH of urine; urine dilution after drinking a lot of water can affect urine specific gravity and other items; urine test during menstruation and within 2-3 days before and after menstruation in female patients can affect urine results.
2, urine red blood cell morphology examination: if urine anomalous red blood cells > 80% are found, hematuria should be considered to come from the glomerulus.
3.Serum creatinine concentration (sCr): see above.
4.Myohepatic clearance (Ccr): see above.
5.24-hour urine protein quantification: normal value.