Concentration test

The concentration test is an examination method to check whether the glomerular acidification function is normal. The principle is that the renal tubules have a good urine concentration and dilution function under normal conditions. Changes in plasma osmotic pressure (Posm) can cause an increase or decrease in the secretion of antidiuretic hormone (ADH), while ADH regulates the reabsorption of water by distal tubules, followed by urine volume, urine specific gravity, and urine osmotic pressure (Uosm). change. When water intake decreases, Posm increases, ADH secretion increases, distal tubules reabsorb water increases, urine output decreases, and Uosm and urine specific gravity increase, and when water intake increases, the opposite changes occur. This is the concentration-diluting function of the renal tubules. When the tubule-interstitial is damaged, there is no response or decreased reactivity to ADH, and the concentration-diluting effect on urine is weakened, regardless of the change in Posm, and the urine volume and urine specific gravity are relatively constant with Uosm. Basic Information Specialist classification: urinary examination classification: urine / kidney function test Applicable gender: whether men and women apply fasting: not fasting Tips: Patients with severe renal failure and uremia (no water can aggravate the condition) are not suitable for this examination. Normal value At least once in normal urine, the specific gravity is between 1.022 and 1.032, Uosm should be >650mOsm/kg, H2O-700mOsm/kg, H2O; Uosm/Posm should be >2.0-2.2. Below the above value is positive. CH2O/normal is -15ml/h--100ml/h. The normal person's ratio of day and night urine volume is 3-41, the night urine volume should not exceed 750ml, the highest urine specific gravity is >1.020, and the difference between the highest and lowest urine specific gravity should be >0.009. Clinical significance Abnormal results: 1. Nocturnal urine volume > 750ml, often an early manifestation of renal insufficiency. 2. The amount of urine in each day is similar, with the highest proportion of 1.018, suggesting that the kidney is not fully functional. 3. The specific gravity of urine is fixed at around 1.010, suggesting that kidney function is seriously impaired. Found in chronic nephritis, renal arteriosclerosis, hypertension, kidney disease and other advanced. People who need to be examined: renal insufficiency and diabetes insipidus of various causes. Precautions Taboo before the test: maintain a normal diet and sleep. Requirements for inspection: 1. The specific gravity of urine is easily affected by many factors, such as urine protein, sugar and other macromolecular substances, renal blood flow and endocrine function status. The high specific gravity of the high protein diet increased; the low protein, less salt diet, the proportion of malnutrition urine decreased. Urine osmotic pressure is less interfered by the above factors. The specific gravity of the urine is measured at 15 °C, the urine temperature is ±3 °C, the specific gravity reading should be ±0.003; the urine protein is +10 g/L, and the specific gravity reading should be -0.003. 2. Chronic heart failure and cirrhosis have an effect on the ratio of CH2O and Uosm/Posm. Uosm and CH2O may be affected by age, sex, season, ambient temperature, water restriction time, and certain drugs, but they are mild. Inspection process Improved Fishberg method: 1. Eat a high-protein, low-liquid diet at 18:00 on the 1st of the test, the liquid content is 200ml, and then fast until the end of the test. 2. All night urine is discarded. 3. The bladder was evacuated from the morning of the test, the urine was discarded, and the bed was continued. After that, the urine was urished once a day for 3 times. The urine specimens were placed in the containers, and the urine volume, specific gravity and osmotic pressure were measured. The venous blood can be simultaneously measured for Posm. 4. Calculate the Uosm/Posm ratio, free water removal rate (CH2) or pure water removal rate of each urine, and calculate the formula and steps: V=CH2O+Cosm; CH2O=V-Cosm; Cosm=(Uosm/Posm) · V; CH2O = VV · (Uosm / Posm); = V · (1-Uosm / Posm); where V = urine volume (ml / h), composed of two parts of CH2O and osmotic concentration clearance (Cosm). Not suitable for the crowd Inappropriate people: severe renal failure, uremia (no water can aggravate the condition). Adverse reactions and risks No related complications or hazards.