I. General Description.
Urine sediment examination is a test performed on the sediment of urine after the supernatant has been discarded by centrifugation. It includes cytological components (red blood cells, white blood cells, epithelial cells)
The urine sediment examination includes cytological components (erythrocytes, leukocytes, epithelial cells), tubular forms and crystals. Because of the convenience of specimen retrieval and low operating cost, it is a very popular test for clinical application, and some people call it liquid kidney biopsy, “non-invasive kidney biopsy”, “in vitro second kidney biopsy”, which shows the importance of urinalysis for the diagnosis and monitoring of kidney patients. The importance of urinalysis for the diagnosis and monitoring of kidney patients.
History of urine sedimentation
One thousand years ago, Ismail, a famous Persian doctor, already made observations on the color, consistency, transparency, volume, odor, foam and sediment of urine. After the invention of the microscope, Bright first discovered the presence of tubular patterns in protein urine of patients with nephritis in 1827, after which Bird in 1854 and Purdy in 1900, further demonstrated the clinical value of urine sediment examination. quantitative examination of urine sediment established by Addis was used in 1948 for the observation of the course of kidney diseases [2]. In recent years, Brody used phase contrast microscopy to identify red blood cells with fat droplets, etc. Haber used interference microscopy to carefully observe the composition of the sediment from three directions.Rutecki et al. used immunofluorescence technique to determine plasma proteins in the granular tubular form. It is believed that some of the tubular particles are aggregates of multiple plasma proteins. Some scholars used polarized light microscopy to identify crystals in urine. linder et al. combined immunofluorescence technique, acid phosphatase staining and scanning electron microscopy to typify the granular tubular pattern. Many scholars applied Pap stain or Sternheimer-Malbin(SM) stain to observe urinary tubular pattern, exfoliated cells, etc. In recent years, flow cytometry technology has entered a new era of examination without centrifugation.
Three, urine sediment examination classification
(A) Red blood cells
1.1, urine erythrocyte morphological classification urine erythrocyte examination is the most important item in urine sediment examination, which has an important role in guiding the diagnosis and treatment of kidney diseases. According to its morphological characteristics, red blood cells are divided into three types:
①Homogeneous type: the red blood cell morphology is basically normal, the size and hemoglobin content is the same, the cell membrane is normal, the microscopic observation of red blood cells can be seen in the same size and shape of the shadow red blood cells and spiny cells;
②Polymorphic type: erythrocytes with various morphologies, including blistering, pseudopod type, uneven cytoplasm, bagel-like, target-shaped, intra-membrane vacuole, wreath-like, etc., which vary in size and hemoglobin content, and various cell membrane changes such as granular aggregation of the cell membrane, rupture, cell remnants, etc;
③Mixed type: homogeneous and polymorphic cells each accounted for about 50%.
The morphological classification of urine red blood cells is A. Homogeneous hematuria; B. Mixed hematuria; C. Polymorphic hematuria Red blood cell morphology: ① target-shaped, ② uneven cytoplasm, ③ spiny, ④ wreath-shaped,
⑤Bread-ring-like
Clinically, hematuria is divided into visual hematuria and microscopic hematuria, and further etiological diagnosis is needed after the determination of hematuria.
1.2 The morphological analysis of urine sediment erythrocytes has been used since the 1980s when Australian scholar Fairley came to China and introduced the application of differential hematology.
Since the Australian scholar Fairley came to China in the 1980s, he introduced the application of phase contrast microscopy to distinguish the morphology of red blood cells to classify hematuria into glomerulogenic and non-glomerulogenic, and most hospitals in China have been carrying out this technique for more than 20 years and have accumulated rich experience. Glomerulogenic hematuria is also called polymorphic/
endogenous hematuria, and non-glomerular hematuria, also known as homogeneous/surgical hematuria.
The former has a variety of red blood cell morphology and size. In the former, the red blood cells are of various morphology and size, and the hemoglobin in the cells is not uniformly distributed; in the latter, the red blood cells are of flat disc shape and similar size, and the hemoglobin in the cells is uniformly distributed. However, it should be emphasized that this test can only be used as a primary screening of the source of hematuria, providing clues for further examination, but not as a basis for confirming the diagnosis. Because the accuracy of morphological observation is related to the experience of the examiner, it has been found in recent years that the use of urinary echinococytes > 5% (3%)
(3-8%) as a basis for diagnosing glomerulogenic hematuria than polymorphic erythrocytes > 80
It is more sensitive to differentiate glomerulogenic hematuria because the echinocytes are easy to identify. However, as a clinician, consideration of the cause of hematuria should be integrated with the morphology of red blood cells, the presence or absence of proteinuria, the tubular shape of red blood cells, special crystals, etc., as well as with the medical history and physical examination for a comprehensive analysis.
1.3 Clinical significance of urine red blood cell examination The morphology of red blood cells can provide the following direct information for diagnosis:
① The nature of the kidney disease. Most of the glomerular diseases and some tubular diseases (lesions involving above the superior branch of medullary collaterals) are often manifested as polymorphic hematuria, while hematuria caused by stones, tumors and trauma is often homogeneous. In addition, homogeneous hematuria can also be caused by drugs (contrast agents, diuretics, etc.), and it is worth mentioning that homogeneous hematuria can also occur in some severe glomerular diseases (such as crescentic nephritis, severe purpura nephritis and systemic vasculitis, etc.) and when renal function is drastically reduced. Therefore, the significance of hematuria must be analyzed in the context of clinical manifestations and renal function;
②Localization of urinary tract infection. The hematuria of urinary tract infection is generally homogeneous, but when polymorphic or mixed hematuria occurs, it indicates that the infection has involved the interstitial tubules of the kidney and is no longer a lower urinary tract infection;
(3) The red blood cell count in the urine sediment can be used to assess the activity and severity of the disease and to monitor whether the disease recurs. Therefore, by observing the morphological characteristics of red blood cells in urine, the site of kidney disease can be clarified. In addition, the number of erythrocytes is also helpful for diagnosis. The presence of a large number of polymorphic erythrocytes in urine is often indicative of a heavy glomerular inflammatory response, and should be highly considered for thylakoid lesions or vasculitic lesions involving the thylakoid membrane, such as IgA nephropathy, membranoproliferative nephritis, endothelial thylakoid proliferative nephritis, and other congenital or secondary renal damage. It has been suggested that when urine red blood cells >
106 /ml,
Crescent formation is seen in 90% of kidney biopsy specimens. The combination of a large number of red blood cells or hemoglobin tubular pattern is even more suggestive of crescentic nephritis. Another important point is that not all patients with glomerulonephritis have polymorphic erythrocyte urine, but when renal disease is combined with severe interstitial tubular damage (e.g., crescentic nephritis, acute nephritis)
When renal disease is combined with severe interstitial tubular damage (e.g., crescentic nephritis, acute nephritis), red blood cells in the urine can be homogeneous or the proportion of homogeneous cells increases significantly. Sometimes some vascular inflammatory diseases, such as purpura nephritis, polyarteritis nodosa, etc., may also show homogeneous red blood cells due to bleeding in the interstitium and other parts of the body caused by the disease involving small blood vessels. Therefore, when patients with glomerular disease repeatedly have homogeneous erythrocyte urine, or when the proportion of homogeneous erythrocytes increases gradually, we should be highly alert to interstitial tubular damage, and should search for the cause (drugs, contrast, dehydration, etc.).
The cause should be investigated (drugs, contrast, dehydration, etc.). In addition, the use of diuretics before urine specimen collection may also disrupt the hypotonic environment of the renal tubules, resulting in homogeneous erythrocyte morphology.
1.5 Factors affecting erythrocyte count and morphology Our previous studies have shown [ 4 ] that a variety of factors in the body can affect urine erythrocyte count and morphology:
(1) A small number of deformed red blood cells (< 10,000/ml) can occasionally be detected in the urine of healthy people
Thus, the difference between “healthy” and “glomerular disease” not only lies in the number of red blood cells, but also in the recurrence of the disease; (2) exercise and hypertension increase urinary red blood cells by affecting glomerular hemodynamics (mean urinary red blood cell counts of 5,151 and 11,160,000/ml, respectively). 5,151 and 11,160,000/ml, respectively)
(3) Injury to the renal parenchyma (e.g., after renal biopsy) may result in a change in the composition of the hematuria, which may recover after a few days;
④After oral administration of diuretics, urine red blood cells are significantly reduced and the morphology of urine red blood cells also changes significantly.
1.6 Classification of hematuria and diagnostic procedures
Hematuria is clinically common and is usually detected by visual observation, test strip or microscopic examination. The causes of hematuria are complex, mainly caused by diseases of the urinary tract itself, and the common causes include glomerular diseases (IgA
The common causes include glomerular diseases (IgA nephropathy, thin basement membrane nephropathy and Alport syndrome, other primary and secondary glomerular diseases)
interstitial disease (allergic interstitial nephritis, painkiller nephropathy, cystic kidney disease, acute pyelonephritis, renal tuberculosis, and rejection of transplanted kidneys)
Blood and vascular diseases (coagulation abnormalities, excessive anticoagulation, small artery thromboembolism, arteriovenous malformations, renal vein thrombosis, lumbago-hematuria syndrome, nutcracker syndrome), urinary tract diseases (malignancy, trauma, inflammation, stones, parasitic diseases)
and other unexplained diseases.
1.7. Diagnostic procedures for hematuria
(II) Proteinuria
1.1. Proteinuria is the most common and important sign of kidney disease, which is often detected early through urine protein screening to enable patients to receive timely treatment. The analysis of urine protein quantity and quality can help identify glomerular and tubular diseases and serve as a basis for treatment and prognosis of the disease. The detection of some specific proteins in urine can be used as auxiliary diagnostic indicators, such as retinol-binding protein, which is one of the diagnostic indicators of reflux nephropathy in children;
Retinol-binding protein and NAG appear earlier than albumin in the urine of type 1 diabetic patients; urinary Ben-Hur protein indicates multiple myelopathy.
The urinary Ben-Hur protein indicates multiple myeloma, and the light chain protein indicates light chain disease. Therefore, it is essential for clinicians to understand the methods and significance of urine protein testing. 2. 1 Proteinuria testing indicators and procedure (1)
The urine protein is determined by taking the morning urine or any random urine, and then using the test strip method or other methods for qualitative examination.
In children, morning urine should be rechecked to exclude upright proteinuria. Persistent proteinuria is pathological and requires further examination.
1.2 Urine protein quantification: Urine protein quantification in healthy adults is 30-130 mg/24 h, with an upper limit of 150-200 mg/24 h. Albumin 3.0 or 3.5 mg/24 h is equivalent to urine protein quantification >3.
mg is equivalent to urine protein quantification > 3. 0 g/ 24 h or 3. 5 g/ 24 h; ratio < 0. 2 mg/ mg is equivalent to urine protein 0. 50
The ratio < 0. 2 mg/mg corresponds to urinary protein 0. 50. Usually, selective proteinuria is seen in microscopic nephropathy and responds well to corticosteroid therapy, but the selective and nonselective nature of glomerular proteinuria does not allow for systematic sensitivity and specificity in glomerular diseases of different etiologies, and the test itself is cumbersome and expensive, limiting the clinical use of this test. It has been reported that urinary IgG
excretion fraction or IgG excretion or IgM excretion has been reported to be a good predictor of chronic progression of primary glomerulonephritis, while α1-microglobulin is a widely used indicator for assessing tubular injury.
1.4. Clinical outcome of proteinuria Glomerular disease leads to increased permeability of the glomerular filtration membrane, resulting in proteinuria, hypoalbuminemia, hyperlipidemia, and subsequent edema and lipiduria due to plasma protein filtration; plasma protein filtration also results in loss of hormones, trace elements, vitamins, and enzymes, leading to decreased resistance to infection, increased metabolic disorders, and thromboembolism and other comorbidities. The more important effect is that a large amount of protein is reabsorbed in the renal tubules, causing a large amount of protein accumulation and rupture in the lysosomes and endoplasmic reticulum of the proximal tubular epithelial cells, stimulating the production of inflammatory factors, vasoactive substances, chemokines, activation of nuclear transcription factors and fibroblast phenotype transformation, increased production and accumulation of extracellular matrix, renal fibrosis and decreased renal function, which is commonly known as proteinuria itself nephrotoxic effect. This is the nephrotoxic effect of proteinuria itself. Several clinical trials have demonstrated that the amount and duration of urinary protein correlates with the rate of progression of kidney disease. For example, the REIN
trial found a decrease in urine protein (0. 39 ± 0. 58) g/24 h, GFR (0. 13 ± 0. 21) ml – 1・min – 1・mo – 1・1. 73
m2 , renal survival/year 97%; urine protein (6. 74 ± 2. 04) g/ 24 h, GFR decreased (0. 90 ± 0. 37) ml – 1・min – 1・1.
1. mo – 1. 1. 73 m2 , renal survival rate/year 78. 5%, while patients with urine protein >4 g/24 h and less than 1 year entered dialysis treatment. Two other reports reported 840
Another two reports of 840 patients with various chronic kidney diseases found that urine protein 3 g/24 h, GFR decreased < 0. 57 ml - 1 min - 1 mo - 1. 1. 73 m2 .
In 389 cases with microscopic nephropathy, the average observation period was 9.4 years. 35 % of patients with massive proteinuria lasting for 6 months despite 8 weeks of regular hormonal treatment were found to have end-stage renal disease.
The average time to end-stage renal disease was 35.0% after 8 weeks of regular hormonal treatment. Therefore, clinicians are very aggressive in the management of proteinuria and usually measure the treatment effect and prognosis by the dynamic change of protein amount.
Chu reported that the sensitivity and specificity of G1 ≥5% for the diagnosis of glomerulonephritis were 73% and 100%, but in acidic concentrated urine, the sensitivity and specificity were up to 99.2% and 100%.
The sensitivity and specificity were 99.2% and 100% in acidic concentrated urine. In China, Dong Xiuqing et al. reported that the sensitivity and specificity of morning urine or fresh urine with G1 ≥5% for the diagnosis of glomerulonephritis were 82.2% and 100%, and in acidic concentrated urine, the sensitivity and specificity were 90.6% and 100% [1 ].
and 100% [1 ]. Our results showed that the sensitivity and specificity of G1 ≥ 5% for the diagnosis of glomerulonephritis were 76% and 100%, and in acidic concentrated urine, the sensitivity and specificity were 89% and 100%.
The sensitivity and specificity were 89% and 100% in acidic concentrated urine. This is consistent with the literature. In non-glomerular hematuria, urinary pH and specific gravity did not affect the presence of G1.
G1 cells have a specific morphology and are easy to recognize, which reduces the error of the examiner in determining the morphology of aberrant red blood cells.
G1 ≥5% can be used as a strong evidence of glomerular hematuria, and a new and correct criterion for the diagnosis of glomerular hematuria and non-glomerular hematuria.
(C) Leukocytes
Leukocytes are usually not found in the urine of patients with nephritis. If they appear, first of all, urinary tract infectious diseases such as pyelonephritis, urethritis, cystitis and prostatitis need to be excluded. If leukocyturia is accompanied by ___ red blood cells and various cell types, often clinically referred to as “kaleidoscopic” changes, it is the most characteristic change in the urine of acute post-streptococcal nephritis, lupus nephritis, membranoproliferative nephritis and acute interstitial nephritis and other renal pathologies. If leukocyturia or pus cell urine persists repeatedly, further careful examination is needed to exclude reflux nephropathy. In addition, abnormal numbers of leukocytes can be seen in the urine when the urine is contaminated by tumors or inflammation of the tissues adjacent to the urinary tract, or leukorrhea in women.
(D) Epithelial cells
There can be a small number of epithelial cells in normal urine, but when the urinary system is diseased, there can be a large number of epithelial cells. Observation of the morphology of epithelial cells can help determine the site of tubular lesions. Small round epithelial cells: slightly larger than leukocytes, round or polygonal, with large, round nuclei and clear nuclear membranes, sometimes indistinguishable from monocytes and lymphocytes. If a large number of these cells appear in the urine, we should be alert to various causes of proximal tubular damage; if a large number of epithelial cells adhere to the tubular type, especially when accompanied by granular debris, it is highly suggestive of acute tubular necrosis; if the cytoplasm of these cells is full of fat droplets, it indicates heavy proteinuria, the risk of interstitial tubular damage is great, and we should be alert to the nephrotoxicity of various drugs; when the urine appears in heaps of tubular epithelial cells,
When there are heaps of renal tubular epithelial cells in the urine, drug-related renal damage should be considered. In addition, patients with these changes after renal transplantation should be alerted to rejection and drug toxicity. Flat epithelial cells (squamous epithelial cells)
Large, flat cells with small nuclei, which may increase in bladder and urethral lesions. (iii) caudate epithelial cells: they are more common in renal pelvis, ureter and bladder neck lesions.
(E) Tubular pattern
Tubular pattern is a column formed by protein coagulation in the renal tubules, and its shape is related to the formation site. Therefore, by observing the morphology of the tubular pattern, it can also help to determine the nature and location of renal lesions. ①Transparent tubular pattern: It can appear in normal people, especially in dehydrated state such as strenuous exercise and high fever, and sometimes in cardiac insufficiency. ②Cellular tubular pattern: It is the embedding of cellular components in the tubular pattern. According to the embedded cellular components, they are divided into erythrocyte tubular, leukocyte tubular, and epithelial cell tubular. These cell types are often closely related to the primary disease. The erythrocyte tubular pattern indicates that the hematuria originates from renal parenchymal lesions, especially in primary or secondary nephritis such as post-streptococcal infection, acute nephritis, lupus nephritis, vasculitis and infective endocarditis; if the red blood cells have disintegrated, the tubular pattern is homogeneous red-brown, which is also called blood or hemoglobin tubular pattern. The leukocyte tubular pattern is usually seen in acute pyelonephritis, interstitial nephritis and renal vascular inflammatory disease; the epithelial cell tubular pattern is formed by embedding the epithelial cells of the renal tubules, which can appear when there is a large amount of proteinuria combined with interstitial tubular damage; sometimes there are multiple cellular components in the tubular pattern, which is called “mixed cellular pattern”; when the cells disintegrate to form granules and Once this type of tubular pattern appears in the urine, it indicates acute inflammatory reaction or degeneration of the glomerulus and tubular interstitium, such as acute glomerulonephritis, acute nephritis, etc., and requires active measures. (3) Waxy tubular pattern: It is caused by the long-term retention of various tubular types in the renal tubules or the lysis of amyloid degenerated renal tubular epithelial cells, which mostly indicates serious damage to the renal tubules, often appearing in the late stage of chronic glomerulonephritis, renal insufficiency or renal amyloid degeneration. Fatty tubular pattern: Fat droplets enter the tubular matrix. It is often seen in patients with large amounts of proteinuria. (5) Giant tubular pattern or tubular pattern of renal failure: The tubular pattern formed by the collecting ducts is named because its morphology is several times larger than the normal tubular pattern, and is usually seen in chronic renal insufficiency. Crystals The diagnosis of salt crystals in urine is not significant. Crystalized urine is the basis for stone production, and examination of crystalized urine can help in the diagnosis of stones, which can be reduced with effective treatment. If uric acid, calcium oxalate, and phosphate are frequently present in fresh urine and are accompanied by a high number of red blood cells, the possibility of stones should be suspected. If cystine crystals are detected, cystinuria can be identified. If crystals of sulfa drugs appear in the urine, it has a reference value for clinical use.
(vi), PH
Normal urine is weakly acidic, about 6.0, and the range of PH changes from 4.5 to 8.0 due to different foods. the judgment of PH measurement results is more difficult than that of other experimental results because the fluctuation of urine PH is large and fast, and there is no significant difference between the PH of normal urine and the patient’s urine, so PH alone is not very meaningful. However, when analyzed in conjunction with other clinical information, it can be an important information.
(vii) Urine specific gravity
Measurement of urine specific gravity allows estimation of renal concentration function. Since the specific gravity of urine is also affected by age, water consumption, sweating and other factors, it can better reflect the concentrated function of the kidney than a single measurement.
(H), nitrite
Under normal conditions, qualitative tests for urinary nitrite are generally negative. When the urinary system is infected, the test result is positive due to bacterial reduction of nitrate to generate nitrite, which is commonly found in urinary system infections caused by Escherichia coli. When the urine nitrite test result is positive, it indicates that the number of bacteria in the urine is more than 100,000/ml.
(ix), glucose.
8.1, physiological diabetes is a transient diabetes, which is temporary and returns to normal after excluding physiological factors. There are three main types: ① dietary diabetes, that is, in a short period of time to take a large amount of sugar, causing excessive blood glucose concentration; ② acute diabetes, in cases of traumatic brain injury, cerebrovascular accident, emotional excitement, strenuous exercise periodic limb paralysis, etc., the delayed brain sugar center is stimulated, so that abnormal secretion of adrenal hormones or insulin, can appear temporary diabetes; ③ diabetes is mostly visible in the middle and late stages of pregnancy.
8.2, pathological diabetes can also be divided into three kinds: ① true diabetes, both the relative or absolute insufficiency of insulin secretion, so that the blood glucose concentration exceeds the renal glucose threshold urine glucose examination can not only diagnose diabetes, but also guide clinicians to decide the amount of insulin, determine the efficacy; ② renal diabetes, that is, renal tubular reabsorption of glucose, the newborn’s proximal tubular function is not perfect can also appear diabetes; ③ Other diabetes, such as excessive growth hormone (acromegaly), excessive thyroid hormone (hyperthyroidism), excessive adrenal hormone (pheochromocytoma), cortisol (Cushing’s syndrome), glucagon, etc. can make the blood glucose concentration higher than the renal sugar threshold and diabetes; in addition, obesity, hypertension may also appear diabetes.
(X), bilirubin, urobilinogen
9.1 The detection of bilirubin has important value for the diagnosis of hepatobiliary system diseases. Urobilinogen is more sensitive to reflect liver function.
9.2 The detection of bilirubin helps to diagnose jaundice. In cases such as sepsis, serum sickness and allogeneic blood transfusion cause massive destruction of red blood cells and produce hemolytic jaundice, when although there is a large increase in bilirubin, most of it is indirect bilirubin, and therefore, urinary bilirubin is still negative.
9.3 The detection of bilirubinogen group can reflect hepatocyte function sensitively. Clinical experience shows that the bilirubinogen group in urine has increased significantly in the early stage of viral hepatitis before jaundice appears. In combination with bilirubin it can provide a basis for diagnosing the type of jaundice. Jaundice can be broadly divided into three categories: ① prehepatic jaundice, or hemolytic jaundice, ② hepatogenic jaundice, or hepatocellular jaundice, which is caused by a large number of lesions of hepatocytes or intrahepatic capillary bile ducts in cases of infection (such as viral hepatitis), poisoning and cirrhosis, resulting in impaired uptake, binding, transport and excretion of bilirubin by hepatocytes; ③ posthepatic jaundice, or obstructive jaundice, due to stones, tumors or congenital (iii) post-hepatic jaundice, or obstructive jaundice, due to stones, tumors or congenital biliary atresia, etc.
(XI), ketone bodies
10.1 Diabetic ketoacidosis. Reduced sugar utilization and excess ketone bodies from lipolysis. The examination of urinary ketone bodies is valuable in the diagnosis of acidosis or coma in uncontrolled or improperly treated diabetes mellitus, and can be distinguished from hypoglycemia, acidosis of heart and brain disease, or hyperglycemic osmotic diabetic coma.
10.2 Infectious diseases (such as pneumonia, typhoid, sepsis, tuberculosis and other febrile periods), severe vomiting, diarrhea, prolonged starvation, fasting, and after general anesthesia, etc. may present with ketonuria. In addition, women can also develop ketonuria during pregnancy due to pregnancy reaction with more vomiting and less eating, and significantly increased body fat metabolism.
10.3 Ketonuria can also occur after chloroform, ether anesthesia, phosphorus poisoning, etc.
10.4 Ketonuria may also occur after taking biguanide hypoglycemic drugs such as hypoglycemic agents, because the drugs inhibit cellular respiration.