Urine collection

Cite this article as:
Andrew Tagg. Urine collection, Don't Forget the Bubbles, 2017. Available at:
https://doi.org/10.31440/DFTB.10888

Urine, the other amber nectar, is something we seem to want to check in nearly every unwell appearing child.  But what do you do if they just don’t want to go?  You’ve filled them up with icy poles or dilute apple juice and you are just waiting for a sample to be produced.  As a doctor (and as a parent) I have been urinated on (by children) more times than I dare to recall (in fact it happened to me just this morning) but how do we make sure we get a sample when we need it? With 4 hour targets to meet it’s worth considering any means of speeding up the process.

Paediatric Blunt Trauma and Microhaematuria

Cite this article as:
Taylan Gurgenci. Paediatric Blunt Trauma and Microhaematuria, Don't Forget the Bubbles, 2016. Available at:
https://doi.org/10.31440/DFTB.8785

Bottom line pearls:

  • Gross haematuria must be taken seriously as it raises the likelihood of finding significant renal pathology
  • Microhaematuria of any degree is most useful when serial urinalyses are performed.  Seeing a downward trend in the degree of microhaematuria is much more useful than the actual number.
  • The received wisdom suggesting a microhaematuria of 50RBC/HPF is the dividing line between trivial and significant haematuria is not supported by much evidence.
  • Microhaematuria in a child with a possible renal injury is best managed by serial examination, serial FBC, and serial urinalysis.  Discharge is safe if the examination remains stable, the FBC is stable, and the microhaematuria resolves.
  • There is no role for the urine dipstick in suspected renal injury.
  • Adult imaging protocols may be applied to paediatric blunt trauma though with some important provisos.

Microscopic haematuria

Cite this article as:
Ben Lawton. Microscopic haematuria, Don't Forget the Bubbles, 2013. Available at:
https://doi.org/10.31440/DFTB.2916

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?

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.

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 more sensitive/specific investigation.

 

So the history, exam and urine microscopy was normal, can I forget about the 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 and 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 for real.

 

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.