This year’s milk powder incident triggered a nationwide kidney screening for elementary-aged children, and many children were found to have positive urine occult blood during the examination, and further examination revealed submicroscopic hematuria, but the children usually have no uncomfortable symptoms. Many parents and friends are very anxious, what is the cause of hematuria in such a young child? What should I do if I have hematuria?
The relationship between occult blood in urine and hematuria was introduced in the previous article, and the most likely causes of hematuria in children are briefly described here to help parents understand this.
I. What does hematuria mean?
In normal people, there are no red blood cells in the urine, or a small number of red blood cells after exercise. However, if there is an increase in red blood cells in the urine above the normal amount it is what we call hematuria. To determine hematuria: Take 10 ml of clean fresh middle urine and centrifuge it at 1500 rpm for 5 minutes and take the urine sediment for microscopic examination. If ≥3 red blood cells per high magnification field of view in centrifuged sedimented urine, or more than 1 in non-centrifuged urine or more than 100,000 in 1 hour urine red blood cell count, or more than 500,000 in 12 hour urine sediment count, all indicate an abnormal increase in red blood cells in urine, then it is called hematuria. In mild cases, only increased red blood cells are found under the microscope, which is called microscopic hematuria; in severe cases, the appearance is washed water-like or contains blood clots, which is called sarcoid hematuria. Usually when there is 1mL of blood per liter of urine, it is visible to the naked eye and the urine is red or washed like water.
Second, what are the causes of hematuria?
A normal person has two kidneys, plus the ureter, bladder and urethra connected to the kidneys, which make up the urinary system of the human body, and the main function is to excrete the metabolic waste from the body through urine. The kidneys are made up of many glomeruli and tubules. The glomeruli are like a sieve through which the blood flows, leaving the useful substances in the body and leaking out the useless wastes, which are not excreted together with the formed urine. If this sieve is changed for various reasons, some useful substances will also be excreted out of the body with the urine, such as proteins and red blood cells, which will cause what is clinically known as proteinuria or hematuria. Of course, in addition to lesions of the glomerulus, bleeding from the kidney to any part of the ureter, bladder, or urethra can also cause an increase in red blood cells in the urine, resulting in hematuria.
There are many causes of hematuria, about 98% are caused by urological diseases themselves, and only 2% are caused by systemic or adjacent organ lesions of the urinary tract. When we examine the red blood cells in urine, when there are various morphological changes of different sizes and loss of hemoglobin, that is, when deformed red blood cells are predominant (polymorphic type), it is glomerular hematuria. If the morphology of urine red blood cells is basically normal and homogeneous (homogeneous type), it is non-glomerular hematuria. The examination of urinary red blood cell morphology helps us to initially determine the site of the hematuria.
Glomerular hematuria: refers to hematuria originating from the glomerulus and is seen in
Various primary glomerular diseases: such as acute, chronic and prolonged glomerulonephritis, acute progressive nephritis, nephrotic syndrome, IgA nephropathy.
secondary glomerular diseases: e.g., systemic lupus erythematosus, purpura nephritis, hepatitis B-associated nephritis.
hereditary glomerular diseases: e.g. hereditary nephritis (Alport syndrome), thin basement membrane nephropathy (familial benign hematuria).
Transient hematuria caused after strenuous exercise.
In the case of hematuria presenting in this screening, because there are no previous specific symptoms and no history of other diseases, the key exclusions are acute nephritis, IgA nephropathy, and familial benign recurrent hematuria. In addition to observing hematuria, attention should be paid to the presence of proteinuria, i.e., whether the protein in the urine exceeds the standard. Generally speaking, if the protein in the urine is normal, it is only microscopic hematuria, which usually has little effect on the human body. You can review the urinalysis regularly and observe it for 3~6 months to see the change of hematuria before deciding whether further examination and treatment are needed. However, if there is proteinuria at the same time or proteinuria appears during observation, or if the hematuria worsens in the form of hematuria visible to the naked eye, further examination is needed in a timely manner.
If the child is tested for hematuria, the parents also need to have a urine test, and if one parent has an abnormality, the siblings of the abnormal party need to be tested to find out if the hematuria is familial. Familial benign recurrent hematuria usually has a good outcome, and there is no need to worry too much about it.
If the hematuria examined is non-glomerular :Hematuria originating from the urinary system below the glomerulus is seen in
Acute or chronic infection of the urinary tract.
Stones in the renal pelvis, ureter and bladder.
Tuberculosis.
Idiopathic hypercalciuria.
Idiopathic renal hemorrhage (in the phenomenon of compression of the renal vein or hu-pick clips).
congenital urogenital malformations such as renal cysts, hydrocele, bladder diverticula.
congenital renal vascular malformations such as arteriovenous fistulas, hemangiomas.
drug-induced renal and bladder injuries such as cyclophosphamide, sulfonamide, gentamicin.
Tumors, trauma and foreign bodies.
Renal venous thrombosis.
Bleeding due to systemic diseases such as thrombocytopenic purpura, hemophilia.
If it is homogeneous, in the child focus on checking whether it is due to infection, stones, hypercalciuria, etc.
Third, the discovery of hematuria usually need to do what tests
1.If it is determined to be non-glomerular hematuria
1）Midstream urine culture to look for evidence of urinary tract infection.
2）Send urinalysis for urine biochemical analysis, and measure 24-hour urine calcium if the urine calcium/creatinine ratio is >0.21; to detect hypercalciuria.
3) Relevant blood tests such as platelets and prothrombin time are required when systemic bleeding disorders are suspected.
4) Blood sedimentation, PPD and X-ray should be done when tuberculosis is suspected.
(5) Ultrasound should be done routinely to observe the kidney morphology, whether there are stones, malformations, masses, left renal vein compression and renal vein thrombosis, etc.
(6) Abdominal plain film can observe opaque X-ray stones and calcified foci, and intravenous pyelogram, voiding cystogram and retrograde urography are used as needed.
(7) CT is highly sensitive in diagnosing occupying lesions, but it is rarely used because pediatric hematuria is rarely caused by tumors and the cost is high.
(8) Digital subtraction angiography can be used if renal arteriography is needed, which can clarify the presence of arteriovenous fistula, hemangioma and thrombosis.
(9) Although cystoscopy can directly observe which side of the kidney or bladder the hematuria comes from, the site, scope and nature of the lesion, and take the tissue for pathological examination, because it is an invasive examination, it is done only when there are strict indications.
2.If glomerular hematuria is identified
(1) Urine microprotein test (urine immunization), 24-hour urine protein quantification to clarify the presence of proteinuria, if present, blood albumin/globulin and lipids should also be checked.
2) Blood ASO, complement C3, antinuclear antibody, hepatitis B-related antigen, etc. may help diagnose which nephritis is possible.
3) Blood BUN, Cr and Ccr to determine the degree of kidney damage.
4) Ultrasound observation of kidney size and internal echogenicity, etc. can help determine the degree of kidney damage.
5) Kidney biopsy is helpful to clarify the cause of glomerular hematuria, guide treatment and determine prognosis, and may be considered with the following indications.
Persistent microscopic hematuria or episodes of carnitic hematuria > 6 months.
Those with significant proteinuria and post-streptococcal infection nephritis has been excluded; those with hypertension and azotemia.
with persistent hypocomplementemia.
Those with a family history of nephritis or deafness.
It is worth mentioning that the amount of hematuria does not indicate the site of the lesion, and the severity of hematuria does not exactly correspond to the severity of the primary disease. In about 5% of patients with hematuria, the cause cannot be identified after various tests, and their primary diseases are mostly microscopic kidney stones, minor focal kidney infections, early polycystic kidney, lesions of the renal vascular system and hidden glomerular disorders. For these patients with hematuria, regular follow-up and review are recommended.