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Microscopic haematuria

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A previously well 3-year-old girl presented to your ED with a history of fever. You have confidently diagnosed otitis media and are just about to discharge the child when the nurse mentions a urine was requested at triage and has come back positive for blood.

The nurse asks you what it means if the girl has blood in her urine…

The Bottom Line

With a urine dipstick that is positive for blood, the first thing to do is establish whether the finding is real (by microscopy)

Remember to look for UTI, hypertension, proteinuria and concerning family history

In the absence of red flags on history and examination, no investigations beyond microscopy are required until the microscopic haematuria has proved to be persistent

What does this finding represent?

Microscopic haematuria is a common finding in the setting of febrile illness. It can be caused by many benign phenomena including adenovirus, ibuprofen, antibiotics including penicillin and indeed by fever itself.

There is always a concern that haematuria represents significant underlying renal pathology but in this circumstance, the risk is extremely small.

What further assessment should you perform and what are you looking for?

Glomerular disease typically doesn’t hurt so loin pain suggests a non-glomerular cause such as UTI or a kidney stone. In the textbooks post-infectious glomerulonephritis is preceded by a sore throat or skin infection 10-14 days. It is classically, but not always, caused by Strep but in real life the history of preceding illness is absent in about 20% of cases. A recent history of diarrhoea, particularly bloody diarrhoea, is concerning for Haemolytic-Uraemic Syndrome. Non-renal symptoms such as rashes, bruising or joint pain may suggest a rheumatological cause like Heinoch-Schonlein Purpura (HSP) or rarely Lupus (SLE). Idiopathic Thrombocytopaenic Purpura (ITP) can present with a petechial rash and haematuria.

Apples often fall close to trees in renal disease so explore the family history carefully. Anyone having been on dialysis is a big red flag, as is deafness (which is associated with Alport’s syndrome). A family history of kidney stones may be the marker of familial hypercalciuria. Other people having been investigated for haematuria without any obvious consequences is reassuring in suggesting benign familial haematuria (aka thin basement membrane disease). Finally ask about holidays, partly because it’s nice to take an interest in your patients, but mostly because schistosomiasis and tuberculosis are important causes of haematuria in some parts of the world and if you don’t look, you won’t find them.

Clinical examination and urine microscopy are sufficient at this stage. The following table outlines the major things you should be looking for. There are more sensitive and specific ways of searching for all these findings but in this context, underlying renal disease is pretty unlikely so clinical assessment alone is good enough for now.

The key things to remember are to check for hypertension, proteinuria, UTI and a family history of renal failure. It;s also worth asking about a history of trauma.

FindingSuggestive of
Failure to thrivechronic disease process
WTU for proteinglomerulonephritis
WTU for leucs/nitriteUTI
FH renal failureany hereditary nephropathy
FH deafnessAlport syndrome
FH renal stonesfamilial hypercalciuria
Hx infection (2 weeks ago)post strep GN
Hx infection (1-2 days ago)TBMN/IgA nephropathy
bruises/bleedingbleeding diathesis
loin massesWilm’s tumour
oedemanephrotic syndrome
hypertensionnephritis

If this is all normal the only investigation required at this stage is urine microscopy and culture to confirm and quantify the presence of blood and determine if the cells are dysmorphic (suggesting a glomerular source of bleeding), This is also the definitive test for a UTI.

Any positive findings from the list above should prompt a more sensitive/specific investigation.

So the history, exam and urine microscopy were normal, can I forget about microscopic haematuria?

No, although significant renal disease is unlikely the child should be referred back to their GP for a repeat urinalysis in 2-4 weeks when they are well. If the haematuria has resolved at that time then no further action is required. Persistent haematuria will require further investigation.

So what proportion of kids with microscopic haematuria actually have significant renal disease?

A large study where urinalysis was performed in asymptomatic school children to evaluate its suitability as a screening tool for occult renal disease found the following:

  • Children screened – 7 million
  • Abnormal UA – 1044
  • Isolated haematuria – 719 (of 1044)
  • Biopsy performed (indications for biopsy = severe proteinuria, hypertension, abnormal renal function of a family history of renal disease) – 52
  • Thin glomerular basement membrane nephropathy (benign condition) on biopsy – 33
  • Other defined pathology on biopsy – 16

In other words of 719 children with isolated haematuria, 16 went on to have proven renal disease that warranted further management.

This was a population of well children. You can imagine that in a population of febrile kids, with the benign reasons for having haematuria outlined above, the proportion of kids with significant renal disease as a cause of their microscopic haematuria would be even smaller.

Does a positive dipstick mean there is definitely blood in the urine?

No, false positives on a dipstick can result from haemoglobinuria (e.g secondary to haemolysis) or myoglobinuria. It is also worth remembering that blood in the urine may originate from the vagina or rectum and some causes (e.g. anal fissure) may not be immediately evident on exam). Several things have been reported to cause a red tinge to the urine that may be mistaken for blood.

The following can all cause the appearance of gross haematuria but they should not cause a dipstick to read positive:

  • Drugs – chloroquine, ibuprofen, iron, sorbitol, nitrofurantoin, phenazopyridine, phenolphthalein
  • Foods – beets, blackberries, food colouring metabolites
  • Other – bile pigments, homogentisic acid, melanin, methemoglobin, porphyrin, tyrosine, urates

Microscopy should be able to confirm that the blood is real. In contrast to microscopic Bloodaematuria that is visible to the naked eye (referred to as “gross” or “macroscopic” haematuria) should have an identifiable cause the majority of the time. The big distinction to make is between glomerular bleeding (i.e that coming from the kidney), and bleeding further down the urinary tract. Urine from glomerular bleeding is classically described as tea or cola coloured. Bleeding occurring further downstream will be more red than brown. More accurate is microscopy of the urine where dysmorphic red cells suggest the kidney is letting them through and normal red cells are more likely to have come from damaged mucosa somewhere on the way out.

References

McTaggart S. Childhood Urinary Conditions. Aust Fam Phys 2005; 34:937-41.

Park YH, Choi JY, Chung HS, et al. Hematuria and proteinuria in a mass school urine screening test. Pediatr Nephrol 2005; 20:1126–1130.

Quigley R. Evaluation of hematuria and proteinuria: how should a pediatrician proceed? Current Opinion in Pediatrics 2008, 20:140–144.

Rees L, et al. Oxford Specialist Handbooks in Paediatrics: Paediatric Nephrology, Oxford University Press. 2007. p18-19

About the authors

  • Ben Lawton is a paediatric emergency physician interested in education, retrieval medicine and simulation. Lives in Brisbane where he enjoys falling off his mountain bike and being outsmarted by his pre-teen children. @paedsem | + Ben Lawton | Ben's DFTB posts

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