In normal people, the number of red blood cells in urine is only 0 to 2 per high-powered field of view, mostly from the lower urethra. Hematuria is a condition in which the number of red blood cells in the urine exceeds the normal level and is divided into microscopic hematuria and visual hematuria.
Microscopic hematuria is called microscopic hematuria when only increased red blood cells are found under the microscope. When the number of red blood cells is ≥3 per high magnification field, microscopic hematuria is considered to be microscopic and has pathological significance only when it is more than 3 times.
If the urine is “flesh-water” colored or blood-like, it is called carnal hematuria. 1000ml of urine containing 0.5ml of blood can show carnal hematuria. The color of carnal hematuria is related to the pH of the urine, neutral or weakly alkaline urine is bright red or meat wash-like; acidic urine is strong tea-like or sooty water-like.
At present, the common urine analyzer (test paper method) to detect urine occult blood its principle is to use the oxidation of hemoglobin and the color reaction of the test paper to carry out semi-quantitative analysis. However, when there are reducing substances in the urine (such as vitamin C > 50mg/L), it can be a false negative; if there is free hemoglobin, myoglobin and peroxidase substances in the urine can present a false positive. And 1.8% to 5.8% of healthy people have positive urine analysis of occult blood, so urine occult blood and microscopic examination are often not parallel, can not be used as a basis for the diagnosis of hematuria, can only be used as a screening, hematuria diagnosis still needs to rely on microscopic examination.
A. Etiology of hematuria:
Patients with hematuria may present clinically with either carnal hematuria or microscopic hematuria, with or without proteinuria. The management of simple (isolated) microscopic hematuria is the most difficult.
1.Glomerular hematuria
Hematuria with edema, hypertension, tubular and proteinuria found in urine or systemic symptoms should be considered primary or secondary glomerular disease
Glomerulogenic microscopic hematuria is most commonly caused by IgA nephropathy, followed by thin basement membrane nephropathy and a few hereditary nephropathies, as revealed by renal biopsy. The following diseases should be considered if hematuria is the main manifestation.
(1) IgA nephropathy.
(2) Familial recurrent hematuria: also known as thin basement membrane disease.
(3) Hereditary nephritis.
(4) Isolated hematuria (simple hematuria): also known as asymptomatic hematuria, manifested as persistent microscopic and/or intermittent carnal glomerular hematuria, which can be clinically diagnosed as isolated hematuria after hereditary nephritis and familial recurrent hematuria are excluded.
(5) Recovery period of glomerular disease
Acute nephritis, acute nephritis and allergic purpura nephritis can be recovered with a small amount of microscopic hematuria, so it is important to follow up the symptoms and signs of the acute period. Most of these diseases can be clearly diagnosed after the medical history is taken.
2.Non-glomerular hematuria
Non-glomerular source microscopic hematuria, bleeding can come from the kidney and upper urinary tract, including neoplastic, nephrolithiasis, cystic diseases such as polycystic kidney and medullary sponge kidney, renal papillary necrosis and metabolic defects such as hypercalcemia or hyperuricemia; bleeding can also come from the lower urinary tract including bladder, urethra and prostate.
If the hematuria is not accompanied by systemic or systemic symptoms, the following diseases can be considered.
(1) Urinary tract abnormalities.
(2) Nutcracker phenomenon: also known as left renal vein compression syndrome.
(3) Idiopathic hypercalciuria.
(4) Oxalate nephropathy.
(5) Urological tumors: Urological tumors are mainly bladder and prostate cancer, accounting for about 5% of the causes of microscopic hematuria, and the incidence of bladder cancer increases significantly after 65 years of age.
(6) Other: rare causes include ruptured renal hemangioma, renal pelvic vein pelvic fistula and spontaneous (or due to renal puncture) arteriovenous fistula bleeding, etc. Hematuria comes from one kidney and is quite serious; minor renal contusion and renal arteriovenous embolism can also cause hematuria.