A bit more on babies’ stooling habits this month, NICE’s update on the epilepsies and glycosuria. Also the annual round up of useful blogs to get newcomers off to a good start in their paediatric practice. Please do leave comments below:
www.lifeinthefastlane.com has a great article describing the components of the humble urine dipstick and what we might learn from it. It is available here and I am going to borrow extensively from Dr Mike Cadogan’s work over the next few months but try to put a paediatric slant on it.
1) SPECIFIC GRAVITY (SG) – measures concentration of urine
Normal range varies by lab but roughly 1.005 to 1.030
< 1.005 – diabetes insipidus, fluid overload, pyelonephritis
> 1.030 – dehydration, glycosuria, SIADH
Falsely high in proteinuria, falsely low in alkaline urine
Glomerular filtrate has a pH of about 7.4 which is acidified to about 6 by the time it is passed as urine.
Causes of alkaline urine (⇑pH)
Causes of acidic urine (⇓pH)
Old sample, vegetarian diet, salicylate
overdose, UTI, citrus fruit ++, low carb diet
Metabolic/respiratory acidosis, diarrhoea, high
protein diet, DKA, cranberries, malabsorption
Nitrites on a dipstick test has a positive predictive value of 96% ie. it is highly likely that the child has a UTI. But the test’s negative predictive value is not so good (around 70%) ie. some children still have a UTI even though they have no nitrites in their urine. Why?
- 󠇫 only gram -ive bacteria convert nitrates to nitrites in urine; E coli, Proteus and Klebsiella are gram -ive, Enterococcus is not
- Can take 4 hours for this conversion to take place. Babies don’t hold urine in their bladder for that long.
The current NICE UTI guideline recommends microscopy and culture to rule out UTI in children younger than 3 but suggests that dipstick urinalysis is enough in older children. They are currently looking at new evidence to see if the dipstick result (leucocytes and nitrites) can be “trusted” in younger children. Update due to be published this year.
- Determines the presence of whole or lysed white cells in the urine (pyuria) by detecting leucocyte esterase activity.
- A positive leucocyte esterase test correlates well with pyuria. BUT, pyuria does not necessarily indicate a UTI. The white cells may be increased because of infection elsewhere. NICE “do not do recommendation”: Do not test urine if the infant or child has an obvious alternative source of infection.
- Conversely, a UTI diagnosis may be missed if a negative urinalysis dipstick is used to exclude UTI. Especially true in children less than 3 years old. NICE recommendation: if you suspect a UTI clinically, send urine for MC&S and do not rely on the dipstick result alone; we are supposed to diagnose a UTI if there is bacteriuria on microscopy, even without pyuria. Click here for further information on diagnosing UTI in children; it’s not quite as straight forward as you would hope.
- Red or brown urine does not always mean blood
- High false positive rate (eg. haemoglobinuria, myoglobinuria, concentrated urine, menstrual blood in the urine sample, rigorous exercise) so dipstick positive blood needs to be looked at under the microscope to accurately diagnose haematuria
- False negative possible if specific gravity is < 1007
- Significant haematuria is defined as ≥ 10 red blood cells (≥ 3 in adults) per high-power field in a properly collected and centrifuged urine specimen
- Isolated microscopic haematuria in a well child only really needs further investigation after 3 positive samples over a period of a few months
- Concomitant proteinuria, high BP or a palpable abdominal mass should be investigated promptly
- Possible causes of haematuria in children:
• Viral infections
• Post streptococcal glomerulonephritis
• Henoch Schonlein Purpura
• Wilm’s tumour (median age 3.5 years)
- The Royal Children’s Hospital in Melbourne has a sensible, easy-to-follow guideline for the management of children with haematuria
- Normal daily protein excretion ≤ 150mg/24 hours or 10mg/100mL. In nephrotic syndrome >3.5g/day is excreted. “Trace” positive results = 10 mg/100 ml or about 150 mg/24 hours (the upper limit of normal).
- Causes: transient or orthostatic (most common and benign), click here for summary of causes in children
- False Positive: Concentrated or alkaline urine (pH >7.5), trace residue of bleach, NaHCO3, cephalosporins
- False Negative: Dilute urine or acidic urine (pH <5) Use spot, early morning urine testing for a protein/creatinine ratio if the urine dipstick test result is 1+ protein or more. A 24 hour collection is impractical
|Dipstick protein reading||Protein excretion gm/24 hours||Protein excretion mg/dL|
|1+ (and above is abnormal)||0.2-0.5||30|
Ketones are not normally found in the urine. Produced by the liver as intermediate products of fatty acid metabolism, in normal states they will be completely metabolised. In “starvation” states eg. DKA or vomiting and reduced intake, fever, extreme cold and extreme exercise, the body metabolises increased fat to get the energy it needs to keep functioning. This results in ketonuria. ≥ ++ is abnormal. We often see ketones in the urine of unwell children in the ED. When glucose is present at the same time in the urine, diabetic ketoacidosis is the likely diagnosis.
We welcome back Dr Marilyn Emedo for a series on pooing and constipation throughout infancy. First Installment: What is Normal?
BREASTFED newborn babies stool anywhere between 7 times a day and once every 7-10 days. Stool is commonly “loose” in consistency and yellow in colour resembling “mustard seeds”. A reduction in frequency is typically seen from the 2nd month of life. 1
BOTTLE FED babies tend to open their bowels fewer times per day.
In 90% of normal term babies, meconium (intestinal epithelial cells, lanugo, mucus, amniotic fluid, bile, and water) is passed within 24 hours of birth and by 48 hours in nearly all normal babies.2
Preterm infants may take longer than this to first open their bowels; one study reported only 37% of preterm infants (25 -36 weeks gestation) open their bowels in the first 24 hours, and 32% are delayed over 48 hours. The ongoing frequency of stool output, and expected colour and consistency thereafter depends largely on what the baby is being fed.
Haematuria this month with links to an algorithmic Australian guideline on how to manage it in children, assessing paediatric hypertension, postural orthostatic tachycardia syndrome and the last for the time being in the “decoding the FBC” series – MCHC.
Please do leave comments below:
It stands for Postural Orthostatic Tachycardia Syndrome, an autonomic disturbance
leading to light-headedness, sweating, tremor, palpitations and near syncope in the upright position1
- Heart rate >120bpm on standing
- HR increase > 40bpm after 10 minutes of standing (if aged 12-19 yrs. >30bpm if older)2
- Despite our traditional concern with lying and standing blood pressures, it
is the persistent tachycardia that characterises this health condition. Blood
pressure may not change at all.
- Recognised in age group 12 – 50, female to male ratio of 5:1
- Can be primary (eg. adolescence) or secondary (eg. diabetes, hypermobility)
- Different types and some are associated with a particular gene mutation
- Can be diagnosed on tilt table or active stand test if necessary
- Reassurance, a healthy lifestyle with sufficient aerobic exercise and fluid
intake will help with symptoms and most adolescents grow out of it
Prevalence of HTN in children aged 8-17 years was approximately 2.2% between 2011 and 2014. Compare this with asthma prevalence of 9%, autism 1%, epilepsy 1%, and yet these all get much more air time than hypertension. Up to 30% of newly diagnosed hypertensive children and young people already have end organ damage, left ventricular hypertrophy in particular. 1
Hypertension: important points in the history:
- Symptoms: lethargy, visual disturbances, headache, nausea, vomiting, failure to thrive
- Past medical history: prematurity, central lines, UTIs, congenital heart disease
- Family history: essential hypertension, polycystic kidneys, early CVS disease
BP measurement in babies and children is a skill which is often not done well:
- Cuff size – you need a range of sizes. The bladder width needs to be at least 40% of the child’s arm circumference between olecranon and acromion and 80-100% of the circumference. A small cuff leads to an erroneously high BP measurement. Take BP in the arm, not leg (both if doing 4-limb BP obviously). At birth, BP measured in the legs is often lower than in the arms, equalises at 8/52 of age and after that leg blood pressure tends to be higher than in the arm.
- Position – the child should ideally be lying down, relaxed, their limb at the same level as their heart.
- Equipment – centile charts are put together using auscultation and a sphygmomanometer. Mechanical oscillometric devices are easy to use (be sure to still ensure correct cuff size) but are not as accurate which is why nephrologists always insist on a “manual reading”.