Table-1. Causes of Hematuria (From ref. no. 1)

Confirmation of hematuria

A child with red- or cola-coloured is labeled to be having gross hematuria only when routine urinalysis reveals presence of RBCs (>5/hpf in the sediment of 10ml of centrifuged fresh specimen of urine). If the microscopic examination does not reveal RBCs, dipstick test for heme is done to detect whether there is pigmenturia. Accordingly, following conditions are considered in the differential diagnosis:
If the dipstick test is positive (i.e., there is either hemoglobinuria or myoglobinuria):

If the dipstick test is negative:

Further Evaluation
History and physical examination
Once hematuria is confirmed, thorough history and physical examination is done to narrow down differential diagnosis. The key features of clinical evaluation are:
Age: It is helpful as certain conditions are more common in certain age-groups. E.g., Post streptococcal glomerulonephritis (PSGN) is more common in 5-15 years age-group; IgA nephropathy is more common in children older than 10 years of age.
Colour of urine: Bright red urine (with or without clots) indicates that source of urine is in lower urinary tract; brown/ tea-coloured urine indicates that of renal origin.
Identify whether it is “total”, “initial” or “terminal” hematuria: Total hematuria (most common) indicates the lesion to be above the bladder neck. Initial hematuria (only during initial part of micturition) is indicative of source of bleeding along the urethra. It is occasionally seen in children following trauma to urethra. In terminal hematuria, the areas last to be emptied of urine (trigone, bladder neck or prostate) are the source f bleeding. It is rare in children. Spotting of blood on the undergarments indicates that the blood is coming from urethra distal to the sphincter.
Ascertain whether gross hematuria occurred in the past: Recurrent, usually painless, gross hematuria narrows down the differential diagnosis to a few clinical conditions: idiopathic benign familial hematuria, IgA nephropathy, Alport’s syndrome and hypercalciuria/ hyperuricosuria.
History of other associated symptoms:
Renal symptoms: (a) Dysuria, urgency and frequency of urination: It suggests UTI/ trauma/ meatal ulceration/ hypercalciuria
(b) Colicky pain abdomen, vomiting, fever, graveluria: Hypercalciuria, urolithiasis
                        (c) Oliguria, edema, headache: Acute glomerulonephritis (AGN)
                        (d) Flank mass: Hydronephrosis, cystic disease, renal vein thrombosis, tumour
                        (e) Anasarca: Non-minimal change nephritic syndrome
Systemic symptoms:
                        (a) Symptoms suggestive of Koch’s disease
(b) Eye/ ear anomalies: May be associated with Alport’s syndrome
                        (c) Sudden onset of pallor, lassitude, and Oliguria:    Hemolytic uremic syndrome
                        (d) Bleeding from any other site: Any such history would obviously indicate presence of coagulopathy, thrombocytopenia or ingestion of anti-coagulants.
                        (e) Menstrual history: It is important in a pubertal girl, as “hematuria” may actually be contamination with menstrual blood.

Ask history of key clinical events preceding the episode of hematuria:
URI: PSGN may be precipitated by streptococcal pharyngitis 7-14 days before the onset of symptoms. Episodes of gross hematuria in IgA nephropathy and Alport’s syndrome are immediately preceded by URI.
Pyoderma: PSGN may be preceded by streptococcal Pyoderma 2-4 weeks before onset of symptoms.
GI infection: Post-infective glomerulonephritis, hemolytic-uremic syndrome and renal vein thrombosis in a newborn may be preceded by gastrointestinal infection.
Trauma:Blunt trauma on abdomen/ back/ pelvis, insertion of foreign bodies in urethra in young children, sexual abuse and cathertization/ invasive procedure can lead to hematuria.
Drug ingestion:  Taking drug history is very important. Various medications can result in hematuria due to various mechanisms like alteration in coagulation system (heparins, warfarin, and aspirin), tubule-interstitial damage (penicillins, sulfonamides, cyclosporine, diuretics, heavy metals) and hemorrhagic cystitis (cyclophosphamide).

Family history: Family history of hematuria, urolithiasis, renal anomalies, deafness and renal failure helps in clinching the diagnosis.

Physical examination should specifically include:
Features of renal disease: Fever, Hypertension, edema, unexplained pallor, bony abnormalities, abdominal mass, renal angle tenderness and assessment of growth
Thorough examination of perineum and urethra: It may show meatal ulceration, signs of child abuse/ trauma or foul smelling purulent discharge.

Investigations
The only lab test that is required in all patients with gross hematuria is urinalysis with microscopic examination. The rest of the laboratory evaluation is tailored according to the patient history, physical examination and findings of urinalysis.

Urine tests
Routine urinalysis confirms presence of hematuria and also helps in detecting/ ruling out proteinuria/ bacteruria/ crystalluria.
Urine C/S is done if UTI is suspected. It may be sterile if the patient has hemorrhagic viral cystitis, anterior uretheritis (2º to trauma) and renal tuberculosis. Sample is sent for AFB culture only if renal tuberculosis is suspected.
Urinary calcium/ creatinine ratio is done to detect hypercalciuria, a common cause of recurrent gross hematuria. If > 0.2, then hypercalciuria is confirmed by 24-hour urinary calcium excretion (>4 mg/kg/day).
Urinary excretion of oxalate/ urate/ citrate/ cysteine is occasionally done in case of urolithiasis to detect underlying etiology.

Blood tests
Complete blood count may reveal degree of anemia, leucocytosis (in UTI/ AGN/ urolithiasis) or reticulocytosis (in hemolysis).
Renal function testsdetect/ rule out renal derangement.   
C3 level is also done in all the cases of hematuria. A low level of C3 narrows down the differential diagnosis to a few clinical conditions: PSGN, lupus nephropathy, Membranoproliferative glomerulonephritis (MPGN) and chronic infections (shunt nephritis/ bacterial endocarditis.
Sickling test or Hb electrophoresis is done in most cases in our country to rule out sickle cell anemia as the cause of hematuria.
Serological evidence of streptococcal infection (ASLO/ DNAse B/ Streptozyme test) is done when PSGN is suspected clinically.
Serum IgA level is done when IgA nephropathy is in differential diagnosis: it is increased in IgA nephropathy.
Blood coagulation studies are done if suggested by personal/ family history.

Imaging studies
Ultrasound (KUB) is done when renal anomalies or urolithiasis is suspected.
Cystography/ retrograde urethrography are occasionally required when lesion of lower urinary tract is suspected.
CT scan/ spiral CT scan is the investigation of choice in assessing renal injury following abdominal trauma and to assess need for surgery.
Other imaging techniques like MRI, pelvic angiography and venography may be required in rare cases like nutcracker syndrome and AV malformations.

Renal biopsy
In a case of gross hematuria, renal biopsy is indicated only in specific circumstances:

References

-Puneet Kumar, Kumar Child Clinic, New Delhi

(Please refer to algorithm)