Category Archives: Renal

Bartter’s syndrome

General paediatrics, Genetics, Renal

Abnormal renal excretion, leading to low potassium.

Presents in early childhood with failure to thrive. Could also be constipation, muscle cramps and weakness (potassium needed for membrane potential, so these are all neuromuscular) and non-specific dizziness and fatigue.

Characteristic hypokalemic, hypochloremic metabolic alkalosis. High plasma renin activity and high aldosterone concentration seen.

Gitelman syndrome is similar, less severe (distal tubule, rather than ascending limb of loop of Henle) – less failure to thrive, in fact often asymptomatic detected incidentally. Might present with nocturia/polyuria.

Urinary calcium excretion distinguishes the two syndromes. Bartter’s waste calcium (more severe, after all), Gitelman retain.

Treatment is with supplementation.

Decompensation can be precipitated by diarrhoea or vomiting. Acute treatment can include potassium-sparing diuretics (spironolactone), cyclo-oxygenase inhibitors and renin-angiotensin blockers.

Pseudo-Bartter’s is due to CF.

Hypokalaemia

Clinical, General paediatrics, Neurology, Renal

Could be reduced intake but usually excessive losses –

RenalNon-renal
Renal tubular acidosis (type 1 or 2)Vomiting eg pyloric stenosis
Bartters or Gitelmans syndromeDiarrhoea
DiureticsLaxative overuse
Hyperaldosteronism (CAH, tumour)Thyrotoxicosis
Salbutamol
Familial periodic paralysis
Pseudo-Bartter’s
Trauma
Diabetic ketoacidosis

Symptoms depend on severity and how rapidly decrease has happened. Chronic low levels are better tolerated. Since potassium important for membrane potentials, effects are mostly neuromuscular.

  • Cramps, weakness, paralysis
  • Ileus
  • Metabolic acidosis (although underlying cause often produces alkalosis)
  • Arrhythmia, heart failure
  • Rhabdomyolysis

ECG classically shows U waves, T wave flattening, and ST-segment changes. Can be tall wide P waves, can look like long QT if T and U waves merge.

Do urine and blood electrolytes to look at fractional excretion.

[Endocrine connections 2018][Current Treatment Options in Peds 2022]

Hyperkalaemia

Emergency medicine, General paediatrics, Renal

Usually due to renal failure. Causes arrhythmia and death…

Treatment

  • Slow injection of calcium – note calcium chloride and gluconate both available so potential for confusion. Dose is 0.11 mmol/kg, to be given over 5–10 minutes, maximum 4.5 mmol (0.11 mmol/kg is equivalent to 0.5 mL/kg of calcium gluconate 10%). Repeat as necessary if ECG changes do not improve.
  • Bicarbonate indicated if hyperkalaemia due to acidosis or renal failure. 
  • Insulin/dextrose – 10ml/kg 10% dextrose (so 5x usual dose for hypoglycaemia!), plus 0.1u/kg insulin (max 10 units), give over 5 mins. Likely peak action at 30 mins.
  • Dialysis.
  • Hydrocortisone if suspected Addisons. 
  • ECG monitoring
  • Repeated salbutamol nebs

Frusemide and calcium resonium only for asymptomatic!

Urinary tract infection

Common, General paediatrics, Infectious disease, Renal

Upper, lower, atypical, recurrent – all have specific definitions;

Diagnosis is ideally by culture – minimum of 1.25 ml, pref 2.5ml of urine in a 7ml red top boric acid container. White top only acceptable if received at lab on same day or day before, within hospital. Collection method important, ideally clean catch.

But given delay in getting culture result, urinalysis more practical, if less sensitive/specific. Nitrites have high positive predictive value so treatment usually started pending culture. Microscopy (for white cells and bacteria) is routinely done in infants under 3 months but needs to be requested between 3 months and 3 years. Greater than 100 wcc or 1000 organisms considered “numerous”, above 40 wcc or 500 organisms “moderate”.

Renal tubular acidosis

General paediatrics, Renal

Leaky tubules, shedding bicarbonate plus other things, leading to acidosis.

  • Type 1 is distal tubule, which does most of the reabsorbing.
  • Type 2 is proximal tubule, so similar but less severe.
  • Type 3 probably just a mixture of types 1 and 2!
  • Type 4 have high rather than low potassium, so clearly not a leakage issue. Related to aldosterone ineffectiveness.

Types 1 and 2 can present with growth failure, else the effects of hypokalaemia (profound muscle weakness) and acidosis (abdominal pain). Type 1 leads to progressive kidney disease, with the associated bone disease (rickets). May also end up with stones. Associated with sickle cell, Ehlers Danlos.

Type 2 usually Fanconi syndrome so leakage of amino acids, phosphate etc. Can be caused by Cystinosis, Wilson’s, hereditary fructose intolerance, poisoning.

Type 4 often related to drugs, but also Addison’s, urinary tract obstruction.

Proteinuria

General paediatrics, Renal

Dipstick testing is highly sensitive and picks up tiny amounts of protein (and blood) that isn’t necessarily of any concern.

A significant proportion of well people will have one or 2 pluses of protein on dip testing at any one time. More common with intercurrent illness.

Can happen with urine infection. Can happen with exercise.

Large amounts of protein loss can indicate nephrotic syndrome. PCR (or ACR) would typically be above 200.

Rarely PCR can be extremely high, but turns out not to be albumin but Tam Horsfall protein – can be ignored!

Fabry’s disease

Cardiology, General paediatrics, Neurology, Renal

Alpha-galactosidase defect, one of the lysosomal storage disorders, with accumulation in various tissues.

X-linked but females get disease, so not correct to call them carriers.

Classically, “pain attacks”, affecting the extremities. In the abdomen, can mimic appendicitis. Due to accumulation in nerves. Since nothing to really see on examination, easily misdiagnosed as functional.

Other features:

  • Renal impairment and failure.
  • Angiokeratomas – a more specific feature, but not always present, and seen in other lysosomal disorders.
  • Corneal changes
  • Cerebrovascular and cardiac problems

[Omim]

Hypertension

Cardiology, Endocrinology, General paediatrics, OPD, Renal

In children under 10, high BP is usually secondary to an underlying disease or condition. Primary hypertension increasingly recognised in older, obese children.

Do repeated measurements, ideally automated home BP monitoring, before diagnosing hypertension. Check manually as well as with automated device. Beware “white coat effect”, even if not clearly anxious.

Use appropriate cuff size – cuff should cover at least 75% of the upper arm from the acromion to the olecranon (should be sufficient space at the antecubital fossa to apply stethoscope!) .  An inappropriately small cuff will overestimate BP.

Long list of causes, so follow the clues.

Family history important, of course.

Examination

So needs thorough history and examination, including:

  • Fundi
  • Bruits, radiofemoral delay
  • Neck for goitre

Complications

Consider then end organ effects –

  • Proteinuria, high creatinine
  • Retinopathy
  • Left ventricular hypertrophy, cardiac failure
  • Abnormal tone and reflexes, cranial nerve deficits if severe

Management

Depends on how high, whether other risk factors (diabetes, chronic kidney disease), symptoms and evidence of end organ damage.

Initially low salt diet, weight loss (if obese).  Remember other morbidities related to obesity.

Acute hypertension might need frusomide and/or nifedipine.

Long term treatment is only going to be started if no improvement with lifestyle measures. Target BP depends on risk factors, as above.

[2016 European Society for Hypertension guidelines]

Cobalamin related metabolic disorders

General paediatrics, Genetics, Haem/Oncology, Neurology, Renal

Amino acid homocysteine is converted to methionine (“remethylated”) – cobalamin is involved in some of these processes, folate metabolism also important.

Various disorders.

Variety of presentations, at different ages:

  • Neurological (central and peripheral)
    • Feeding difficulties, apnoea in babies
    • Seizures
    • Subacute combined degeneration of spinal cord (peripheral neuropathy, ataxia, incontinence)
    • Acute and/or chronic encephalopathy – hypotonia, regression
    • Neuropsychiatric problems
  • vascular problems (stroke/embolism)
  • bone marrow (megaloblastic anaemia, cytopenia) – folate related
  • Atypical HUS
  • Glomerulopathy

Investigations

  • High homocysteine, usually
  • Vitamin B12 and folate, for differential
  • Methylmalonic acid (in urine)
  • Acylcarnitine
  • Methionine (usually goes low)

Treatment

Start intramuscular B12 (hydroxocobalamin) as soon as samples collected, to prevent end organ damage.

Betaine should be started if high homocysteine with low methionine found, helps push conversion to methionine.

Homocystinuria

Autosomal recessive condition of high homocysteine in blood and urine, causing similar neurological problems, thrombosis, Marfanoid appearance, downward subluxing lenses.

Needs low methionine diet. Betaine supplements help.

Fractional excretion

General paediatrics, Renal,

Used to work out whether biochemical abnormalities are due to renal dysfunction. There is not really a “normal range” for sodium and potassium in the urine, because it depends whether the body is trying to retain or excrete at any given time. So urinary sodium can be undetectable in dehydration, for instance.

Since creatinine is filtered passively, you can compare how much sodium/potassium is being excreted with what you would expect, by calculating:

Sodium excretion (Urinary Na/Plasma Na), divided by creatinine clearance (urinary creatinine/Plasma creatinine). Multiply by 100 to get a percentage.

Note that creatinine in plasma is usually measured in micromoles, and in urine in millimoles. Online calculator here:
https://www.thecalculator.co/health/FENa-Calculator-309.html

If sodium low, you expect the kidneys to retain, so fractional excretion should be less than 1%. For low potassium, fractional excretion should be less than 10%. The opposite is true for high values.

Even where plasma sodium normal, fractional excretion can give you a clue to kidney disease – 1-4% suggests intrinsic renal pathology, over 4% post-renal.

Renal causes of low sodium/potassium include renal tubular acidosis (various forms), Bartter’s syndrome. Non-renal causes include GI losses (eg pyloric stenosis), Pseudo-Bartter’s syndrome (eg CF).

An alternative, possibly simpler method is transtubular potassium gradient (TTKG) :

TTKG = urine potassium/(plasma osmolality/urine osmolality)/serum potassium

For this formula to be accurate urine osmolality should be higher than plasma osmolality and urine sodium should be greater than 25 mEq/L.

Individuals with hyperkalemia should have a TTKG above 10. Values below 7 are consistent with mineralcorticoid deficiency, especially if accompanied by hyponatremia and high urine sodium concentration.

Individuals with hypokalemia should have TTKG values below 2.