A third of urinary tract infections are said to be associated with hematuria though usually this is microscopic rather than overt macroscopic hematuria. However, some children with bacterial urine infections present with macroscopic hematuria and urinary infection is the commonest cause of macroscopic hematuria, accounting for 49 percent of cases of macroscopic hematuria in children.
As with all urine infections, other symptoms and signs may be negligible. It is conventional to diagnose urinary tract infection only if more than 100,000 organisms per ml in urine culture, but it is becoming increasingly recognized that lesser growth of an organism may cause trouble for some children.
Viruses are not often considered to be a cause of urine infection, but an important cause of hematuria is acute hemorrhagic cystitis particularly associated with adenovirus type 11 and type 21, which causes a short self-limiting disease characterized by gross hematuria and symptoms of bladder inflammation.
Usually the macroscopic hematuria has gone by the fifth day, though microscopic hematuria may persist for 2 or 3 days more. TB is a most rare cause of hematuria in Western countries but common in developing country like the Philippines.
Schistosomiasis (bilharziasis) is an important cause of hematuria especially in the Philippines like Davao, the ova causing a granulomatous inflammatory reaction of the bladder and the lower urinary tract.
Trauma due to accidents sufficient to cause hematuria will usually be associated with an obvious history of a damaging event and also with bruising or other signs of external injury.
Glomerulonephritis is an easy diagnosis when associated with other symptoms and signs of an acute nephritic syndrome, but a vast number of subclinical cases of glomerulonephritis present merely with hematuria.
Calculi are uncommon in children but they may present with hematuria alone and usually they do not even complain of abdominal pain.
Conversely, the occurrence of pain at the time of hematuria does not necessarily mean the presence of a renal stone because profuse bleeding can cause colic from the clots of blood passing down the ureter and some of the other causes of hematuria are themselves associated with pain.
Idiopathic hypercalciuria without stone formation is another possible cause of macroscopic hematuria. The relative frequency of this entity in patients with microscopic hematuria is not known but it should be easily identified by measurement of urinary calcium excretion.
Vascular causes are rare and usually the cause is apparent from the rest of the history: thus the striking picture of renal vascular thromboses in a neonate or of arteritis associated with a multi system disorder.
Urinary tract tumors are uncommon. A third of children with nephroblastoma (Wilms' tumour) have microscopic hematuria, but macroscopic hematuria is rare.
It must be exceedingly uncommon for a tumor to be diagnosed as a result of a child presenting with hematuria. Similarly, although children with bleeding disorders such as thrombocytopenia (decreased platelet) like Dengue Fever or hemophilia, may develop hematuria it is extremely an uncommon initial presentation.
Some cause the hematuria by affecting coagulation, others by direct renal damage and others by irritation of the bladder. The cytotoxic drug cyclophosphamide is particularly notorious for causing a chemical cystitis which may progress to severely inflamed and ulcerated bladder mucosa. This is more likely to happen if the child is not passing much urine because of low fluid intake.
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Note: Many other drugs, poisons and ingested substances may occasionally cause hematuria. Thus, whenever hematuria is being investigated and the child may have ingested a drug or poison, that substance should be checked carefully. (To be concluded)
