There is a type of hematuria that cannot be distinguished by the naked eye, called microscopic hematuria, and there is also a term called urinary occult blood or urinary occult blood that is often seen in outpatient clinics.
Microscopic hematuria
Although microscopic hematuria is not visible to the naked eye, it is not necessarily not a problem. The first thing to know is whether it is symptomatic or asymptomatic.
Symptomatic microscopic hematuria: there is usually an underlying problem; symptoms are mostly atypical, such as fever and malaise; symptoms are often diagnostically oriented, such as abdominal pain (stones), swelling (kidney disease), and oliguria (acute nephritis).
Asymptomatic microscopic hematuria: rarely combined with obvious kidney disease, often transient; a simple exclusion test, without overly complex tests, is necessary, but close follow-up observation is necessary. Microscopic hematuria is not uncommon in renal disease.
The patient’s family history is important for stratifying the patient with microscopic hematuria: is there a family history of hematuria or nephrotic damage? Is there a family history of hearing or vision abnormalities? Note whether there is a combination of proteinuria, even in the absence of any other symptoms. Microscopic hematuria combined with proteinuria should raise concern for the glomerulus.
Possible causes of microscopic hematuria.
Dr. Zhang Yi used to divide hematuria into surgical and medical. The so-called surgical hematuria mainly occurs in lesions of the urinary tract, such as kidney stones, infections, tumors, congenital malformations and other factors. Internal hematuria, on the other hand, occurs within the renal parenchyma, i.e., the glomerulus in the renal unit. Microscopic hematuria is less frequent in surgical disorders and more frequent in internal factors, such as intense exercise (possibly with sports trauma or red blood cell rupture), drugs (aspirin, penicillin, heparin, etc., which can cause hematuria), urinary tract infections (the occurrence of infection can trigger inflammation of the urinary tract, mucosal congestion or bleeding, and there may also be fever and back pain), genetic disorders (such as polycystic kidney, sickle cell anemia and Alport syndrome – Alport: glomerulonephritis, renal failure, hearing loss, etc.), acute and chronic glomerulonephritis, etc.
Treatment of microscopic hematuria
In the same way as surgical hematuria, treatment of medical hematuria should be directed at the cause. If it is excessive exercise and rest without special treatment, hematuria usually heals in a few days; if it is a urinary tract infection, choose antibiotic treatment; if it is a drug cause, the patient needs to stop using it immediately. Note: If hematuria occurs, it is crucial to try to find the cause of the hematuria and treat it early.
A study of microscopic hematuria
In the elderly, recent significant carnal hematuria is a strong indication of a urinary tract tumor. Painless sarcoid hematuria + >50 years of age was associated with a 16.3% likelihood of urothelial malignancy. Other high-risk factors for painless hematuria are male, smoking, etc.
The current AMAO recommendation is that anyone with >3 red blood cells per high-powered view in urine and >35 years of age should initiate a full workup including cystoscopy, CT, etc. to rule out the possibility of malignancy. The definitions of hematuria and age are very broad here! Of course the inclusion of a larger scope can avoid missed diagnoses, but how do you weigh the pros and cons of including invasive tests?
In fact, microscopic hematuria is a very unreliable predictor, not uncommon in the overall adult population but not uncommon in urothelial malignancies. The incidence of urothelial neoplasia in patients with microscopic hematuria was recently found (2013) to be 0.43% over a two-year period, and diagnostic guidelines from urologic specialty institutions are not yet satisfactory for identifying these potential patients. Therefore, in order to find other more reliable criteria, the investigators analyzed patients with microscopic hematuria using the “KaiserPermanente’s” comprehensive electronic health database. “Based on the study, the chance of urinary tract malignancy in adults younger than 50 years old without a history of sarcohematuria was almost zero. patients younger than 50 years old with microscopic hematuria, but without sarcohematuria, had no significant clinical benefit from initiating a comprehensive examination and should therefore avoid radiation exposure and invasive endoscopy.”
The country has opened the era of big data, and the tendency to make decisions calculated in the data environment is crying out for attention. Almost all hospitals are applying electronic medical records to record patient data, and health screening and insurance agencies have long used electronic health records. Once the boundaries of the data system are opened, the operational or computing system automatically decision aids based on patient symptoms, such as microscopic hematuria. If the current medical recommendations are not modified, many patients are subjected to comprehensive, including invasive, examinations. However, medical recommendations are also based on a lot of evidence and the scientific validity of the above study has yet to be further validated, so it is normal that different options will arise during a patient’s visit to the doctor.
Urinary occult blood
Some people call it urinary occult blood or occult hematuria, which is represented by OB (occult blood) or BLO in a formal routine urinalysis. In outpatient clinics, such patients encounter a lot of such patients, often with OB+~++ in the routine urine report of the physical examination and then suggested by the medical institution to come for follow-up.
Since we are talking about blood, it is divided into intact red blood cells (red blood cells) and red blood cell components (hemoglobin and its products, etc.). They are all shown as OB positive in the urine test paper test, from +~++++, the more + signs represent the more serious the situation. After a positive urine test paper test, the regular laboratory will usually perform another microscopic examination to see if there are red blood cells and also to observe the morphology of the red blood cells. These are very helpful for diagnosis. However, most hospitals or medical institutions currently use instruments to replace manual testing, so the lack of microscopic results in the lab report makes it difficult for clinicians to judge.
OB positivity is not uncommon in the health screening population (2.8-16%) and is 2-3 times higher than the rate of proteinuria positivity. It is more common in women and may be due to a high chance of infection or contamination of the urine with menstrual blood. OB positivity is also higher in people with systemic diseases, such as hypertension, diabetes, gout, autoimmune diseases, etc. Cortical lesions of the kidney (glomerulonephritis, nephropathy, renal cell carcinoma, etc.) and diseases of the urinary system (stones, infections, prostate hypertrophy, uroepithelial tumors, etc.) are also contributors to OB positivity, sometimes directly constituting carnal hematuria. Another type of problem that can cause OB positivity is caused by blood cells or intracellular components of muscle entering the urine.
The intense training of competitive athletes can cause blood cells to squeeze into the filtration membrane of the renal unit, break down and enter the urine, and sometimes even red blood cells can leak through.
Some clinical emergencies occur with acute hemolysis or rhabdomyolysis, where a large number of red blood cells or myocytes rupture and are discharged through the kidneys, which can lead to serious conditions including acute renal failure. There is also the impact on the hematological system after radiotherapy for tumors that can also lead to positive OB or even hematuria.
However, most of the positive urine occult blood is not clinically significant. However, it should not be overlooked that many of those who are told that they are OB positive are still very worried, and appropriate retesting and ultrasound and other tests as well as psychological counseling are necessary. The vast majority of simple OB+ found in physical examinations of healthy people have no lesions after nephrology or urology. However, people with high-risk factors, such as being older than 40-50 years old, having systemic diseases, recurrent, smoking, etc., are recommended to be retested in cycles of 3-6 months even if no problems are found.