Category Archives: Renal

Fabry’s disease

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



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.


So needs thorough history and examination, including:

  • Fundi
  • Bruits, radiofemoral delay
  • Neck for goitre


Consider then end organ effects –

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


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

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


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


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.


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

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:

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.

Autosomal dominant polycystic kidney disease

ADPKD – previously Adult PCKD but now recognized as having manifestations in childhood.  Cf Autosomal recessive disease, severe, renal failure in infancy.

1 in 400 to 1,000 live births, making it the most common monogenic cause of renal failure. The typical age of onset is in middle life, but the range is from infancy to 80 years.  Associated with liver cysts (asymptomatic) and intracranial aneurysms. 10-25% do not have family history (de novo mutations, missing records or mosaicism).

Possible presenting symptoms of renal disease in children with ADPKD are frequency, nocturia and/or, hematuria, urinary tract infection(s) and back, flank or abdominal pain. Often, the earliest symptoms are polyuria and polydipsia, from decreased urinary concentrating ability.

Extrarenal manifestations seen esp hypertension (renin angiotensin system, sodium retention, endothelial dysfunction), also liver cysts (asymptomatic), intracranial cysts and valvular defects but these are only seen in adults. 25% of children are hypertensive by the time they reach adolescence.  (GFR stays stable until around 40yrs, then rapid decline, about 50% have ESRF by 60yrs).

Importantly, children who were diagnosed in utero or within their first 18 months of life, the so-called VEO group, represent a particularly high-risk group of ADPKD patients and should be managed accordingly.  Diagnostic imaging criteria not validated under 15yrs, genetic testing also challenging.

Recommendation from Kidney Disease Improving Global Outcomes (KDIGO) Consortium against screening children for APCKD.  [Also highlight variety of different cystic disorders in children, so recommend thorough clinical assessment for extrarenal manifestations in case syndrome eg Von Hippel Lindau, USS of parents and/or grandparents if negative family history, and USS to look for dysplastic kidneys, glomerulocystic disease, and tuberous sclerosis complex].[Kidney international 2015]

Increasing evidence that hypertension, left ventricular hypertrophy (even between 75th and 95th centile for BP) and increased kidney volume predates symptoms in affected children.  A study of early use of ACE inhibitor halted progression of LVH and fall in renal function.  Adding pravastatin reduced progression of structural kidney disease.  Disease modifying drugs in development.  [BMJ 2016;353:i2957 Editorial, GOS, Birmingham, Evelina].  “We propose an urgent national debate on an improved inclusive approach involving patients and their families and a range of clinicians, ethicists, and commissioners. A few pounds spent now on screening and early intervention could save many thousands later by delaying hypertensive complications and chronic kidney disease.”

Potential for pre-implantation genetic diagnosis.  See Ethics.

Only one drug known to have moderate effect on disease progression in adult ADPKD patients, vasopressin V2 receptor antagonist tolvaptan (recent Cochrane review).  But timing of use unclear.

Psychological impact of having genetic disease that can be passed on to children very common in adult patients.  But a benefit of diagnosis is potential to target modifiable risk factors  – children with normal BP have slower cyst growth.  And knowledge can give sense of control over life decisions, esp reproductive decisions.

Posterior urethral valves

1 in 5000 births.  Mostly failure of Wolffian duct development, rarely failure of urethral canalisation.

2/3 detected antenatally, with distended bladder. If missed, then present with urinary tract infection, abnormal voiding (dribble rather than fountain!) else incontinence (if toilet trained, of course).

Later detrusor failure, tubular dysfunction, renal failure.

Renal investigations


Renal uss image anotated

Incomplete bladder emptying cannot be diagnosed on a single post-void residual urine on ultrasound, due to significant intra-individual variability. Two post-void residual urine tests are recommended; larger volumes are seen if the bladder has been over distended (eg initial volume greater than 115% of expected), and in younger children. Greater than 20 ml is more specific than 10% bladder capacity. [J urology 2009 (182):1933]

Bladder capacity is = (Age +1) x 30 (ml) max 390ml.



In a study of 342 kids with asymptomatic microscopic haematuria, no cause was found in the large majority of patients. The most common cause discovered was hypercalciuria (16% of patients) followed by post–streptococcal glomerulonephritis (1%). No evidence for value of early detection of hypercalciuria (may be at long-term risk for nephrolithiasis and bone demineralization).  The children with asymptomatic post–streptococcal glomerulonephritis all improved spontaneously and without complication.  None had evidence of urinary tract infection! Clinically insignificant abnormalities in the upper urinary tracts of 5 children and grade 3 reflux in 1  [Arch Pediatr Adolesc Med. 2005;159(4):353-355. doi:10.1001/archpedi.159.4.353]

Asympt recurrent can be monitored for 5yr!


  • frank blood,
  • protein,
  • hypertension,
  • other features (joints, rash, wt loss)

Haematuria defined as persistent dipstick positive on at least 3 occasions for at least 3 months. Else as >2rbc per HPF (not same as flow cytometry). Then consider:

  • Red cells or not?
    • myoglobinuria = haemolysis
    • beetroot!
    • Porphyrins, other unusual pigments
  • Proteinuria or not?

If spot urine abnormal, repeat on early morning urine and then proceed to 12-14hr collection. Urine calcium/creatinine has age specific normals, high at birth (up to 1.5 in toddlers) falling to adult max of 0.7 at age 7. High levels especially significant in the presence of a normal plasma calcium

Investigations – only do bloods if macroscopic or nephritis suspected:

  • Do urine culture and microscopy.
  • Do PCR if proteinuria.
  • If macroscopic, do FBC, U&Es, LFTs, Coag.
  • Renal USS
  • Screen family members with urinalysis
  • Spot urine calcium/creatinine
  • If acute nephritis, do C3/4, ASOT, immunoglobulins, ANCA, anti GBM as below.
  • If stones suspected, do 2 sets of spot urine Ca/creat, Oxalate/creat, Urate, amino & organic acids, pH, KUB.

Differential is:

  • Tumour – bladder (colour changes during voiding, dysuria with sterile culture) or kidney
  • IgA nephropathy – persistent, progressive in 30%, diagnosis on biopsy
  • Alports – usually X dominant, deafness in minority, cataracts in 10%
  • Sickle cell – 1% macroscopic, 16% microscopic. Papillary necrosis, usually painless, episodic. May progress to sickle nephropathy.
  • Venous thrombosis – esp neonates, nephrotics.
  • Vascular – AVM, Nutcracker syndrome (compression of the left renal vein between the abdominal aorta and SMA)
  • Nail-patella syndrome (BM disorder, like Alports)
  • Polycystic Kidney Disease

Biopsy if persistent high grade microscopic, or microscopic with proteinuria (>150 mg/24 hr)/hypertension/impaired renal function, or 2 episodes of gross haematuria. Cystoscopy for bladder problem.

Atypical HUS

Most Haemolytic Uraemic Syndrome is associated with a diarrhoeal illness (D+ HUS), esp E coli O157.

Atypical HUS is a bad name for HUS that develops in certain individuals due to a genetic, complement disorder.  Disease is typically triggered by infection, esp respiratory tract, else diarrheal illness in 80% of pediatric forms.

Consider in young infants (less than 5% of D+HUS cases occur before the age of 6 mo), severe cases, non-colitis.

The penetrance of the disease among carriers of mutations in CFH, CFI and MCP genes is approximately 50%-60%.

Low C3 levels are a clue (seen with mutations in CFH, CFI and MCP).  In almost all cases of aHUS C4 levels are normal. Normal C3 levels do not however exclude a mutation.  Check factor H and factor I too.


Measure CFH, CFI and MCP levels using radio-immune-diffusion assay (RIDA) or FACS. This however fails to detect low protein levels in 25%-75% of mutations, so genetic analysis also needed.

Check ADAMTS13 activity (as seen in thrombotic thrombocytopaenic Purpura, TTP) as part of differential.

Make sure you have enough blood samples before plasma exchange!

In neonates, screen for defective cobalamin metabolism (excess homocystine and methylmalonate in urine ).  These babies have high mortality from multiorgan failure, a prompt diagnosis and B12 supplementation is their only hope.

Haemolytic Uraemic Syndrome

Or HUS for short.  Mainly caused by VTEC (Verocytotoxin producing E coli), esp serotype O157.  But note also:

  • Occasionally Pneumococcal
  • Atypical HUS – not infective, but a genetic complement disorder
  • D- HUS is the shorthand for HUS which manifests in absence of diarrhoeal illness.  Still worth looking for E coli O157, but need to look at other possibilities.


What it says on the tin!

  • Haemolysis
  • Uraemia

Mechanism is Thrombotic Microangiopathy, with microthrombi circulating that affect not just kidneys (producing uraemia) but also:

  • Thrombocytopenia,
  • MI/stroke/infarction
  • Encephalopathy


  • Acute dysentery eg campylobacter, shigella
  • Intussusception
  • Atypical HUS
  • Acute colitis (Ulcerative Colitis)

Although atypical HUS has a genetic cause, it is typically triggered by infection, esp respiratory tract, else diarrheal illness in 80% of kids, so may be difficult to exclude.  Consider in young infants, severe cases, non-colitis. Low C3 levels are a clue.

Acute colitis will usually have more extensive history or other clues.  The emphasis on managing these cases is on identifying toxic megacolon, and surgical intervention if necessary.  Antibiotics are recommended if high risk of infection (eg signs of sepsis) and/or immediately pre-surgery.


Features of established disease are:

  • Microangiopathic haemolysis
    • Falling Hb, Plts – clinically pallor, petechiae and bruising
    • Fragmented rbc’s on film
    • High LDH
    • Blood/protein on urinalysis (if there’s any urine being produced to collect)
  • Rising Urea/Creatinine

But ideally you get the diagnosis early, before too much damage has been done.  Clues are:

  • Rising LDH
  • Falling Plts
  • Oliguria
  • Blood/protein on urinalysis

Stool results, to confirm E coli O157, take 24-48hrs (culture and toxin test). Discuss with microbiology if stool culture negative, consider gene PCR, serology.

[Pediatr Int. 2009 Apr;51(2):216-9 PMID 19405919]


But not everyone who gets E coli O157 gets HUS. Some people get diarrhoea without progressing to colitis (prob the majority), some get colitis without progressing to HUS (only a minority).  Predictors of progression to HUS are:

  • Fever (usually not at presentation, but in history – not very specific)
  • WCC >11
    • Normal WBC provides reliable reassurance against progression to HUS in 9/10
    • WCC>11 predicts progression to HUS in 70–90% of children
  • Raised CRP

[Ikeda, Epid infection 2000; 124:343.  Archimedes, Arch Dis Child 2007]

Ikeda proposes scoring system of 2+ features of fever, high CRP and WCC – 32% sens cf 98% spec.

Public Health

Preventing further cases is as important as managing your case.  About 20% of cases in outbreaks are secondary, but this increases to over 50% of cases in under 6yrs.  Interestingly, secondary cases are usually other children in the nursery (but rarely adults) if pre-school, but family members if primary/secondary school age!  [BMC Infect Dis. 2009 Aug 28;9:144. doi: 10.1186/1471-2334-9-144] Notify Health Protection team on suspicion of E. coli O157 syndrome.


Controversial.  Would be considered for other infective dysenteries viz Clarithro for campylobacter, Cipro/cef for salmonella, Azithro for shigella.

But do they precipitate HUS in E coli O157? “Exposure to antibiotics (aOR 3.62; 95% CI, 1.23–10.6) in 1st week independently associated with development of HUS” [Wong 2012].  Current 2011 UK guidance states “The use of antibiotics should, therefore, be governed by good paediatric practice as indicated by needs other than the suspicion of enteric VTEC infection”.

Fluids etc

Loperamide has traditionally been associated with toxic megacolon in acute dysentery so is not advised.

Pain – can be significant with colitis.  Opiates, NSAIDs contraindicated given potential for megacolon or nephropathy.

IV fluid volume and sodium during E coli O157:H7 infections, esp in first 4 days of illness, associated with oligoanuric HUS:

  • 1.6x more likely to become oligoanuric if no IV fluids were given during the first 4 pre-HUS days

[Christina Hickey (St Louis) and Jim Beattie, prospective study Arch Pediatr Adolesc Med. 2011;165(10):884-889. doi:10.1001/archpediatrics.2011.152]

Hence, seems reasonable to:

  • Give 20ml/kg at presentation
  • Rehydrate aggressively eg correct over 6-8hrs
  • Repeat boluses if urine output reduces


Since onset of HUS is from 5 to a maximum of 13 days into diarrhoea illness, there is a need to monitor those with suspected or proven E coli O157 without HUS viz repeat bloods at 5-7 days or earlier if symptoms worsen.  Consider admission if significant infection control issues eg young children/siblings.

Advanced Measures

  • Renal replacement therapy
  • Plasmapheresis (not done in Glasgow)
  • Eculizumab – drug of choice for aHUS, recommended for children in whom plasma exchange is technically difficult
  • Monoclonal antibodies vs STX1/2

Eculizumab = Recombinant monoclonal anti-C5 antibody. Orphan drug.  No good evidence from Germany, but they had good results from plasma exchange anyway.  Evidence from severe TTP that it is effective in cases resistant to immunosuppression and plasma exchange.