Hematuria being an important clue for the diagnosis of kidney disease and the main reason leading patients to the nephrology department, it is crucial to train a complete and strict logical diagnostic thinking. First, it must first be confirmed whether it is true hematuria (excluding contamination with vaginal or rectal blood) or a change in urine color such as brown, coffee, or red urine due to different causes. Avoid retaining urine during menstruation or when there is vaginal bleeding, which can exclude contamination by vaginal blood. Asking whether there are hemorrhoids or colitis, dysentery and other diseases and teaching the patient the correct way to retain urine can avoid contamination of rectal blood. If the two are inconsistent, we need to analyze the reason carefully and repeat the examination if necessary. Second, after it is clear that it is true hematuria, the next thing that needs to be clarified is the site of bleeding and to distinguish nephrogenic hematuria or non-nephrogenic hematuria. The urine 3 cups test can roughly understand the site of hematuria production, anterior segment hematuria (the first cup of urine, the beginning of urination appears hematuria or pus urine, the last two cups clear) suggests lesions in the anterior urethra, urethritis, etc.; terminal hematuria (the first cup of urine and the second cup of urine clear, the third cup of urine appears red cells) suggests lesions in the bladder neck and triangle or posterior urethra, etc. See bladder stones or tumors, prostate lesions, etc. If the whole hematuria or pus urine is in the upper urinary tract or bladder, renal hematuria is mostly the whole hematuria. The urine three-cup test is only a rough diagnosis, and its accuracy is affected by many factors. Therefore, further observation of red blood cell morphology in urine with phase contrast microscopy is needed to distinguish glomerulogenic from non-glomerulogenic hematuria. Due to the extrusion of red blood cells through the glomerular basement membrane, resulting in breakage, and the existence of osmotic gradient in normal renal tubules, especially the hypotonic concentration of tubular fluid in the thick segment of the outer branch of the medullary loop, the red blood cells in the urine of patients with glomerular disease without interstitial tubular damage are deformed red blood cells. In the case of non-glomerular hematuria, the morphology and size of red blood cells in isotonic or hypertonic urine are mostly normal, and only a small percentage of them are aberrant red blood cells. Therefore, observing the morphology of urine red blood cells through phase contrast microscopy and calculating the ratio of deformed red blood cells has a greater diagnostic value to determine whether it is glomerulogenic hematuria, and it is generally believed that if the rate of deformed red blood cells is above 75-80%, glomerulogenic hematuria is more likely. However, in clinical practice, we also found that sometimes relying on urine red blood cell morphology can also encounter some rather confusing problems, such as red blood cells. When the number is small, the calculation of urinary deformed red blood cell ratio often has a large variation and is not of high diagnostic value, or sometimes the urinary red blood cell anisotropy rate is slightly lower than the diagnostic criteria but much greater than those with non-glomerular-derived hematuria, and in other cases, the results of multiple tests in the same patient vary greatly, etc. In addition, in special cases when the condition of nephrogenic hematuria is severe and the amount of hematuria is large, the urinary red blood cell morphological anisotropy rate also decreases to a certain extent, such as when a patient with IgA nephropathy diagnosed by renal biopsy in the first episode shows carnal hematuria, the urinary red blood cell anisotropy rate is surprisingly only 50%. In view of the above, Prof. Gao Jining believes that although urine red blood cell bite-image examination is indeed an effective diagnostic tool to clarify the source of hematuria, it should never be used in an overly superstitious or simple mechanical manner, and it is always very important to integrate the clinical manifestations and various microscopic findings. In addition, proteinuria of moderate amount or more often indicates glomerular disease, so when hematuria is accompanied by proteinuria, the possibility of glomerulonephritic hematuria increases significantly. Third, after the above diagnostic process, we can initially determine whether it is renal hematuria. If it is renal hematuria, the primary disease leading to glomerulogenic hematuria should be further clarified without intravenous pyelogram, cystoscopy, retrograde imaging, CT, MRI and other examinations, which not only have no clinical significance but also bring unnecessary pain and economic burden to the patient or even delay the diagnosis. In this case, the specific type of glomerular disease needs to be further defined based on the medical history and clinical manifestations. If it is non-glomerular origin hematuria, it is not necessary to perform renal biopsy, but to clarify the site of bleeding and primary disease through abdominal plain film, intravenous pyelogram, B ultrasound, CT, cystoscopy and retrograde pyelogram, renal arteriogram, etc. At this time, it is very important to consult with urology.