The definition of microscopic haematuria is based on urine microscopic examination findings of red blood cells (RBCs) of more than 5/µL in a fresh un-centrifuged midstream urine specimen or more than 3 RBCs/high-power field (HPF) in the centrifuged sediment from 10 mL of freshly voided midstream urine. However, considerable controversy still exists about the number of RBCs required for diagnosis of microscopic haematuria. Some investigators have used a definition of greater than 2 RBCs/HPF in 12 mL of a midstream urine specimen spun at 1500 rpm for 5 min. Regardless of the criterion used important cofactors to consider when a child has haematuria include the presence of proteinuria, urinary casts, hypertension and a family history of renal disease.

Macroscopic haematuria has an estimated incidence of 1.3 per 1,000. The incidence of microscopic haematuria in school children was estimated at 0.41% when four urine samples per child were collected and 0.32% in girls and 0.14% in boys when five consecutive urine specimens were analysed over 5 years. Overall haematuria is present in about 5-6% of the general population and 4% of school children. In the majority of children, follow-up urinalyses are normal. In most people, the haematuria emanates from the lower urinary tract, especially in the conditions affecting the urethra, bladder and prostate. Less than 10% of haematuria is caused by glomerular bleeding.

RBCs in urine may originate from the renal tissue (glomeruli, renal tubules and interstitial), or urinary tract (collecting systems, ureters, bladder and urethra). The urine dipsticks that are commonly employed to detect microscopic haematuria are very sensitive. When used correctly, urine dipsticks have a sensitivity of 100 and a specificity of 99 to detect 1-5 RBCs/HPF, which translates to 5-10 RBCs/µL of urine. False-positive results can be seen with haemoglobin, myoglobin or hypochlorite in the urine and false-negative results can be seen when the urine specific gravity is high or there are reducing agents like ascorbic acid in the urine. In children, the source of bleeding is more often from glomeruli than from the urinary tract; however, distinction may be made by careful microscopy of the urine, with glomerular haematuria being characterized by deformed, misshapen RBCs. Red cell casts and proteinuria also point to a glomerular origin, but a urologic disorder, particularly tumour, hydro-nephritis, or stone, must always be ruled out by careful ultrasound examination, even if there is obvious evidence of glomerular disease. The renal papillae are susceptible to necrotic injury from micro thrombi and anoxia in patients with a hemoglobinopathy or in those exposed to toxins. Patients with renal parenchymal lesions may have episodes of transient microscopic or macroscopic haematuria during systemic infections or after moderate exercise.

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The way of presentation and the colour of urine may give the clue to probable diagnosis. Tea-colour, brown-colour or cola-colour urine includes differentials like post-infectious glomerulonephritis, membrane-proliferative glomerulonephritis, rapidly progressive glomerulonephritis, IgA nephropathy, HSP and haemolytic-uremic syndrome. These conditions are usually associated with proteinuria and RBC casts along with life-threatening hypertension or oliguria/anuria. Bright red- or pink-colour urine is indicative of bleeding from the urinary tract, away from the glomerulus. The differential diagnosis includes calculus, tumour, trauma, hydro-nephritis, cystitis, urinary tract infection, schistosomiasis, tuberculosis, sickle cell trait, vascular anomalies, polyps, coagulopathy, renal artery or renal vein thrombosis, terminal haematuria (urethrorrhagia), or polycystic kidney disease.

In systematically ill patients or in asymptomatic patients, it is imperative to repeat the urine dipstick test and microscopic urinalysis twice within 2 weeks following the initial result. If the haematuria resolves, no further tests are required. If microscopic haematuria persists on at least two of the three consecutive samples, then further evaluation is required. Increased use of the urine dipstick test to screen for urinary tract infection in a febrile child or in children during routine school health examinations in many countries has resulted in the detection of asymptomatic microscopic haematuria. However, because microscopic haematuria and mild proteinuria may appear transiently during fever, illness, or extreme exertion, it is not practical or cost-effective to extensively investigate every child to find the cause of microscopic haematuria. Common illnesses in children with persistent microscopic haematuria without proteinuria are benign familial haematuria, idiopathic hyper-calciuria, IgA nephropathy and Alport’s syndrome. Benign familial haematuria, also known as thin basement membrane nephropathy (TBMN), is the most common cause of persistent microscopic haematuria in children.

Journal of Nephrology and Urology is an Open Access peer-reviewed publication that discusses current research and advancements in diagnosis and management of kidney disorders as well as related epidemiology, pathophysiology and molecular genetics.

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Regards
Maya Wilson
Editorial Assistant
Journal of Nephrology and Urology