Paediatrics: Kidneys, urinary tract and hormones in children

🧪 Kidneys, urinary tract and hormones in children -UTIs are common and easily missed in babies (who have no specific symptoms), and repeated infections can scar the kidneys. Type 1 diabetes is often diagnosed late -around a quarter of children present in DKA, which kills through cerebral oedema. Think "4 Ts": Toilet, Thirsty, Tired, Thinner -and check a finger-prick glucose the same day.
Your four questions for every child: Could this be a UTI (test the urine in any unwell child without a clear cause)? Could this be diabetes (check glucose and ketones)? Is the child growing and developing normally? Is there a risk of adrenal crisis (CAH, steroids)?

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Urinary Tract Infection

• Features by age:
  • Babies under 3 months -fever, vomiting, lethargy, irritability, poor feeding, faltering growth, jaundice, sepsis.
  • Toddlers -fever, vomiting, abdominal pain, poor feeding, smelly urine.
  • Older children -frequency, dysuria, wetting, abdominal or loin pain, fever.
• Who to test -any infant or child with symptoms suggesting UTI, unexplained fever of 38 °C or more (test within 24 hours), or an alternative infection not responding.
• Collecting urine -clean-catch sample is best; urine collection pads if not possible; catheter or suprapubic aspiration if needed (unwell infants).
• Testing (NICE NG224):
  • Under 3 months -refer immediately to paediatrics; urgent microscopy and culture; IV antibiotics.
  • 3 months to 3 years -urgent microscopy and culture (dipstick less reliable); treat if microscopy positive for bacteria (or clinically likely).
  • 3 years and over -dipstick:
    • Nitrite positive (with or without leucocytes) -treat; send culture.
    • Leucocytes only -send culture; treat if there's clinical evidence of UTI.
    • Both negative -UTI unlikely.
• Upper UTI (pyelonephritis) -fever of 38 °C or more with bacteriuria, or loin pain or tenderness. Higher risk of kidney scarring.
• Treatment (NICE NG224):
  • Lower UTI (over 3 months) -oral trimethoprim or nitrofurantoin for 3 days (or per sensitivities); amoxicillin if known sensitive.
  • Upper UTI -oral cefalexin or co-amoxiclav for 7–10 days; IV (e.g. co-amoxiclav, cefuroxime, ceftriaxone or gentamicin) if severe, under 3 months, or unable to take oral.
  • Review if no improvement within 48 hours.
  • Fluids; paracetamol or ibuprofen; treat constipation (common contributor).
• Prevention -good fluid intake, regular voiding, treat constipation, avoid bubble baths; antibiotic prophylaxis only in selected children with recurrent UTIs (specialist).

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Imaging After a UTI

• Atypical UTI -seriously ill or septicaemic, poor urine flow, abdominal or bladder mass, raised creatinine, no response to antibiotics within 48 hours, infection with a non-E. coli organism.
• Recurrent UTI -two or more upper UTIs; or one upper and one or more lower; or three or more lower UTIs.

Age	Imaging (NICE CG54)
Under 6 months	Responds within 48 hours -ultrasound within 6 weeks. Atypical -ultrasound during the infection, DMSA scan at 4–6 months, and MCUG. Recurrent -ultrasound within 6 weeks, DMSA and MCUG.
6 months to 3 years	Responds -no routine imaging. Atypical -ultrasound during the infection and DMSA. Recurrent -ultrasound within 6 weeks and DMSA. (MCUG only in some -e.g. dilatation, poor flow, family history of VUR.)
3 years and over	Responds -no routine imaging. Atypical -ultrasound during the infection. Recurrent -ultrasound within 6 weeks and DMSA.

• Ultrasound -kidney size, hydronephrosis, bladder.
• DMSA scan -shows renal scarring (done 4–6 months after infection).
• MCUG (micturating cystourethrogram) -shows vesicoureteric reflux and posterior urethral valves (needs a catheter; antibiotic cover).

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Vesicoureteric Reflux and Congenital Anomalies

• Vesicoureteric reflux (VUR) -urine flows back up from the bladder into the ureters and kidneys:
  • Graded I (into the ureter only) to V (gross dilatation).
  • Runs in families; often found after a UTI or antenatal hydronephrosis.
  • With infection, can cause renal scarring (reflux nephropathy) -hypertension and CKD later.
  • Management -most mild reflux resolves with growth; prompt treatment of UTIs; antibiotic prophylaxis in selected children; surgery (endoscopic injection or reimplantation) for severe reflux with breakthrough infections.
• Antenatal hydronephrosis -common finding on scans; most mild and resolve. Postnatal ultrasound; consider antibiotic prophylaxis for significant dilatation.
• Posterior urethral valves -the commonest cause of urinary obstruction in boys:
  • Antenatal -bilateral hydronephrosis, thick-walled bladder, oligohydramnios (pulmonary hypoplasia in severe cases).
  • After birth -poor urine stream, palpable bladder, UTI, AKI.
  • Urgent catheter; endoscopic valve ablation; long-term kidney follow-up (CKD risk).
• Pelviureteric junction obstruction -hydronephrosis without ureteric dilatation; MAG3 renogram; pyeloplasty if function is falling.
• Multicystic dysplastic kidney -a non-functioning kidney of cysts; usually shrinks; check the other kidney.
• Other -duplex kidneys, horseshoe kidney (Turner syndrome), renal agenesis, polycystic kidney disease (ARPKD, ADPKD), bladder exstrophy.

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Nephrotic Syndrome

• Definition -heavy proteinuria (urine protein:creatinine ratio over 200 mg/mmol, or 3+ on dipstick), low albumin (under 25 g/L) and oedema.
• Who -mostly children aged 2–5; boys more than girls; more common in South Asian children.
• Cause -about 90% of children have minimal change disease, which is usually steroid-sensitive.
• Features:
  • Periorbital swelling (often first, worse in the mornings -mistaken for allergy).
  • Swollen legs, scrotum or labia; ascites; pleural effusions.
  • Frothy urine.
  • Weight gain; reduced urine output; abdominal pain.
• Tests -urine dipstick and PCR; albumin; U&E; FBC; lipids (raised); complement; varicella serology; BP; hepatitis B and C, HIV in some.
• Treatment (steroid-sensitive nephrotic syndrome):
  • Oral prednisolone 60 mg/m² daily (maximum 60 mg) for 4 weeks, then 40 mg/m² on alternate days (maximum 40 mg) for 4 weeks, then stop.
  • Most respond (protein-free urine) within 2 weeks.
  • Salt restriction; fluid restriction only if severe oedema; diuretics with care (risk of hypovolaemia).
  • Penicillin V prophylaxis while nephrotic (pneumococcal infection risk).
  • Pneumococcal vaccine; check varicella immunity (chickenpox can be severe on steroids).
  • Monitor urine at home with dipsticks to detect relapses.
• Complications:
  • Infection -spontaneous bacterial peritonitis (pneumococcus), cellulitis, sepsis (loss of immunoglobulins, steroids).
  • Hypovolaemia -despite oedema: abdominal pain, cold peripheries, tachycardia, raised haematocrit -albumin infusion.
  • Thrombosis -loss of anticoagulant proteins (renal vein, cerebral venous sinus, DVT).
  • High cholesterol; AKI; steroid side effects (behaviour, weight, BP, growth).
• Relapses are common (about 80%) -repeat steroid course. Frequent relapses or steroid dependence -steroid-sparing drugs (levamisole, mycophenolate, tacrolimus, cyclophosphamide, rituximab).
• Refer for biopsy (atypical) if -under 1 or over 12, steroid-resistant (no response after 4 weeks), haematuria, hypertension, low complement, raised creatinine -consider FSGS, membranous, MPGN, lupus.
• Congenital nephrotic syndrome (under 3 months) -genetic (e.g. Finnish type).

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Nephritis and Haematuria

• Nephritic syndrome -haematuria (often cola-coloured), proteinuria, hypertension, oedema, reduced urine output and rising creatinine.
• Causes in children:
  • Post-streptococcal glomerulonephritis -1–3 weeks after a sore throat (or 3–6 weeks after impetigo); low C3, raised ASOT; supportive care (fluid and salt restriction, diuretics, BP control); good prognosis.
  • IgA vasculitis (HSP) nephritis -after the rash; monitor BP and urine for 6 months.
  • IgA nephropathy -visible haematuria 1–2 days after a sore throat.
  • Lupus nephritis; ANCA vasculitis; HUS; Alport syndrome.
• Haematuria -other causes -UTI, trauma, stones (hypercalciuria), sickle cell, coagulopathy, Wilms tumour, exercise, thin basement membrane disease; red urine without blood -beetroot, rifampicin, myoglobin.
• Refer -haematuria with proteinuria, hypertension, raised creatinine, or persistent invisible haematuria.
• See the Glomerular Disease chapter.

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Haemolytic Uraemic Syndrome

• What it is: A thrombotic microangiopathy -triad of microangiopathic haemolytic anaemia, low platelets and AKI.
• Cause -usually Shiga toxin-producing E. coli (STEC, O157) -from undercooked beef, petting farms, contaminated food; mostly children under 5. Rarely pneumococcal or atypical (complement) HUS.
• Features:
  • Bloody diarrhoea and abdominal pain, then 5–10 days later:
  • Pallor, tiredness, irritability.
  • Reduced urine output, oedema, hypertension.
  • Bruising, petechiae.
  • Seizures, confusion, stroke (CNS involvement).
• Tests -FBC (anaemia, low platelets), blood film (schistocytes), raised LDH, low haptoglobin, negative DAT, U&E (AKI), stool culture and STEC PCR.
• Management:
  • Supportive -careful fluid balance, electrolytes, BP control, blood transfusion (avoid platelets unless bleeding).
  • Dialysis in about half.
  • Avoid antibiotics and antimotility drugs in STEC diarrhoea (may increase toxin release).
  • Eculizumab for atypical HUS.
  • Notify UKHSA; exclude from nursery until two negative stools.
• Outcome -most recover; some develop CKD and hypertension (follow-up).

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AKI and CKD in Children

• AKI causes -dehydration (gastroenteritis), sepsis, HUS, nephrotoxic drugs (NSAIDs, aminoglycosides), glomerulonephritis, obstruction (posterior urethral valves), after cardiac surgery.
• AKI management -restore fluid status, stop nephrotoxins, treat hyperkalaemia, dialysis if needed (see the AKI chapter -doses by weight).
• CKD causes in children -congenital anomalies of the kidney and urinary tract (CAKUT) -the commonest (dysplasia, obstruction, reflux nephropathy); glomerular disease (FSGS); inherited (polycystic kidneys, cystinosis, nephronophthisis, Alport).
• CKD effects in children -poor growth (growth hormone may help), anaemia, renal bone disease (rickets), hypertension, developmental and school problems, acidosis; transplant is the best treatment for kidney failure.
• Hypertension in children -usually secondary in young children (renal parenchymal disease, renal artery stenosis, coarctation, endocrine); measure with the right cuff size and use centile charts.

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Bedwetting and Daytime Wetting

• Nocturnal enuresis (bedwetting) -common: about 1 in 6 five-year-olds, 1 in 20 ten-year-olds. Usually not treated under 5. More common in boys; strong family history.
• Primary (never been dry for 6 months) -usually from a combination of large night-time urine volumes, small bladder capacity, and not waking to the sensation of a full bladder.
• Secondary (wetting after 6 months of dryness) -look for a cause:
  • UTI; constipation (very common).
  • Diabetes mellitus (check urine glucose); diabetes insipidus.
  • Emotional stress -new sibling, school, family breakdown; abuse.
  • Obstructive sleep apnoea; neurological problems (spinal).
• Assessment (NICE CG111) -pattern, daytime symptoms, fluid intake, toileting, bowel habit, emotional factors; urine dipstick (glucose, infection); examine the spine, genitalia and abdomen; bladder diary.
• Management:
  • Reassure -common and not the child's fault; avoid punishment.
  • Fluids -adequate during the day (6–8 drinks), avoid caffeine and fizzy drinks, reduce drinks in the hour before bed.
  • Toilet regularly in the day and just before bed; easy access at night.
  • Reward systems for agreed behaviours (drinking well, using the toilet before bed) -not for dry nights.
  • Treat constipation.
  • Enuresis alarm -first-line treatment for motivated children and families (from about 5–7) -works within 4 weeks; continue until 2 weeks of dry nights.
  • Desmopressin -if an alarm is unsuitable or hasn't worked, or for short-term control (sleepovers, school trips) in children over 5. Restrict fluids from 1 hour before to 8 hours after the dose (risk of hyponatraemia).
  • Combination or anticholinergics (oxybutynin) in specialist care.
• Daytime wetting -overactive bladder (urgency, holding manoeuvres), voiding postponement, constipation, UTI, giggle incontinence; constant wetting in a girl with normal voiding suggests an ectopic ureter. Refer if persistent.

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Type 1 Diabetes in Children

• The commonest form of diabetes in children in the UK; autoimmune destruction of insulin-producing beta cells. Peak onset at 5–7 years and around puberty.
• Symptoms -the "4 Ts":
  • Toilet -passing lots of urine, new bedwetting, heavy nappies.
  • Thirsty.
  • Tired.
  • Thinner -weight loss.
  • Also -recurrent infections (thrush), blurred vision, behaviour change.
• DKA features -vomiting, abdominal pain, deep sighing breathing (Kussmaul), ketotic breath, dehydration, drowsiness.
• Diagnosis -a child with symptoms and a random glucose over 11 mmol/L. Check a finger-prick glucose the same day and refer the same day to the paediatric diabetes team (don't wait for a fasting test or HbA1c).
• Tests -glucose, blood ketones, venous gas, U&E, HbA1c; autoantibodies (GAD, IA-2, ZnT8); coeliac serology and TFTs (associated autoimmune diseases).
• Treatment (NICE NG18):
  • Insulin -multiple daily injections (basal–bolus: long-acting once daily plus rapid-acting with meals) or an insulin pump.
  • Hybrid closed-loop systems (pump plus continuous glucose monitor with an algorithm) -recommended by NICE for children and young people with type 1 diabetes.
  • Continuous glucose monitoring (CGM) for all.
  • Carbohydrate counting to match insulin to meals.
  • HbA1c target 48 mmol/mol or lower (as long as it doesn't cause problematic hypoglycaemia); time in range on CGM.
  • Education -child, family and school; multidisciplinary team (nurse, dietitian, psychologist).

⚠️ Safety Pearl: A child who is drinking more, wetting the bed again, and losing weight needs a finger-prick glucose today. Delayed diagnosis leads to DKA -refer the same day, don't send for a fasting test.

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Living With Type 1 Diabetes

• Hypoglycaemia (glucose under 4 mmol/L):
  • Symptoms -shaky, sweaty, pale, hungry, irritable, poor concentration, behaviour change; then confusion, seizures, unconsciousness.
  • Mild -fast-acting glucose (e.g. 0.3 g/kg -glucose tablets, juice), recheck in 15 minutes, then a longer-acting snack.
  • Severe (can't swallow safely) -glucagon IM or SC (or nasal glucagon); in hospital -IV 10% glucose 2 mL/kg.
• Sick day rules -never stop insulin; check glucose and blood ketones more often; extra rapid-acting insulin if ketones raised; fluids; seek help if vomiting or ketones over 3 mmol/L.
• Exercise -check glucose before, during and after; extra carbohydrate or reduced insulin; delayed hypoglycaemia overnight.
• School -individual healthcare plan; trained staff; access to snacks, glucose testing and insulin.
• Annual screening -thyroid function, coeliac serology, retinopathy (from 12), urine ACR (from 12), BP, growth and puberty, foot and injection site checks.
• Adolescence -insulin resistance in puberty, risk-taking, alcohol (delayed hypoglycaemia), eating disorders (insulin omission for weight loss), mental health, driving rules; transition to adult services.
• Psychological support -depression, anxiety and "diabetes distress" are common.

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Diabetic Ketoacidosis in Children

• Diagnosis (BSPED) -acidosis (venous pH under 7.3 or bicarbonate under 15 mmol/L) plus ketonaemia (blood ketones over 3 mmol/L) or ketonuria, in a child with diabetes (glucose usually over 11).
• Severity -mild (pH 7.2–7.29), moderate (7.1–7.19), severe (under 7.1).
• Management (follow the BSPED DKA guideline and calculator):
  • ABC; senior help; weigh the child.
  • Shocked (poor perfusion, low BP) -10 mL/kg 0.9% saline bolus over 15 minutes, repeated if needed (up to 40 mL/kg) -discuss with PICU.
  • Not shocked -a 10 mL/kg bolus over 60 minutes may be given; then calculate fluids:
    • Deficit -5% of body weight (pH 7.1 or above) or 10% (pH under 7.1), replaced slowly over 48 hours, plus maintenance.
    • Fluid -0.9% sodium chloride with potassium chloride 40 mmol/L (unless anuric or high potassium); add glucose (5–10%) when glucose falls below 14 mmol/L.
  • Insulin -IV infusion of soluble insulin at 0.05–0.1 units/kg/hour, started 1–2 hours after IV fluids begin. No insulin bolus. Continue long-acting insulin if already on it.
  • Monitoring -hourly glucose, observations, neurological state and fluid balance; blood ketones and gas 1–2 hourly; U&E and potassium regularly; ECG monitoring.
  • Avoid bicarbonate (except in specific cardiac arrest situations).
  • Look for and treat the trigger (missed insulin, infection).
  • Switch to subcutaneous insulin when ketones under 1 mmol/L, pH normal, and eating and drinking.
• Cerebral oedema -the main cause of death in childhood DKA (higher risk in young children, new diagnosis, severe acidosis, low CO2, rapid fluid or insulin, a falling sodium):
  • Warning signs -headache, irritability, confusion, slowing heart rate, rising BP, falling GCS, abnormal breathing, incontinence, pupil changes.
  • Treat immediately -hypertonic saline (2.7% or 3%, 2.5–5 mL/kg) or mannitol (0.5–1 g/kg) over 15 minutes; reduce fluids; raise the head of the bed; PICU; CT after treatment.
• Other complications -hypokalaemia, hypoglycaemia, aspiration, VTE (especially with central lines).

💡 Clinical Pearl: Children with DKA are dehydrated, but rehydration is slow (over 48 hours) and insulin is started 1–2 hours after fluids -both to reduce the risk of cerebral oedema. Headache or a slowing pulse during treatment is cerebral oedema until proven otherwise.

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Hypoglycaemia in Children

• In children without diabetes, low glucose (under 3.0 mmol/L) needs investigation.
• Causes:
  • Ketotic hypoglycaemia -the commonest: thin young children (18 months to 5 years) after a period of fasting or illness; ketones high; resolves with age. Avoid long fasts; bedtime snacks.
  • Adrenal insufficiency (CAH, Addison's, steroid withdrawal); growth hormone deficiency; hypopituitarism.
  • Metabolic disorders -MCADD (fatty acid oxidation -low ketones; screened at birth), glycogen storage diseases (large liver), galactosaemia.
  • Hyperinsulinism -congenital, insulinoma, factitious (insulin given by a carer -low C-peptide).
  • Poisoning -alcohol, beta-blockers, sulfonylureas, salicylates.
  • Sepsis; liver failure; malnutrition.
• Hypo screen -take blood during the hypoglycaemia (before treatment if possible): glucose, ketones, insulin, C-peptide, cortisol, growth hormone, lactate, ammonia, free fatty acids, acylcarnitines, plus the first urine (organic acids, ketones, toxicology).
• Treatment -oral glucose if alert; IV 10% glucose 2 mL/kg then an infusion if not; glucagon IM (not in adrenal insufficiency or fatty acid oxidation disorders where it may not work); hydrocortisone if adrenal insufficiency suspected.

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Type 2 and Other Diabetes

• Type 2 diabetes -increasing with childhood obesity; more common in South Asian and Black children, girls, family history; acanthosis nigricans; PCOS. Treatment -lifestyle, metformin, then insulin or GLP-1 agonists; screen for complications at diagnosis (higher early complication rates than type 1).
• MODY (maturity-onset diabetes of the young) -autosomal dominant, strong family history, onset under 25, non-obese, no autoantibodies, low insulin needs; HNF1A MODY responds to sulfonylureas; GCK MODY (mild stable hyperglycaemia) needs no treatment.
• Neonatal diabetes (under 6 months) -genetic (e.g. KCNJ11 -treat with sulfonylureas); always test genetics.
• Cystic fibrosis-related diabetes; steroid-induced diabetes; diabetes after pancreatitis.

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Thyroid Disorders

• Congenital hypothyroidism:
  • About 1 in 2,500 babies; usually thyroid dysgenesis (absent, small or ectopic gland) or dyshormonogenesis.
  • Detected by newborn blood spot screening (raised TSH).
  • Untreated -prolonged jaundice, poor feeding, constipation, large tongue, umbilical hernia, hoarse cry, dry skin, hypotonia, delayed development and learning disability.
  • Start levothyroxine within the first 2 weeks -normal development if treated early.
• Acquired hypothyroidism -usually autoimmune (Hashimoto's); more common in girls, Down syndrome, Turner syndrome, type 1 diabetes: slowing growth (with weight gain), tiredness, constipation, declining school performance, goitre, delayed (or sometimes early) puberty. Levothyroxine.
• Hyperthyroidism -usually Graves' disease in teenagers: weight loss, tremor, anxiety, poor sleep, heat intolerance, tall stature, goitre, eye signs, falling school performance. Carbimazole (block-and-replace), beta-blocker; radioiodine or surgery later.
• Neonatal thyrotoxicosis -from maternal TSH-receptor antibodies (Graves'): irritability, tachycardia, poor weight gain; temporary.

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Congenital Adrenal Hyperplasia

• What it is: An autosomal recessive enzyme deficiency in cortisol production -over 90% 21-hydroxylase deficiency. Low cortisol (and often low aldosterone) drives high ACTH, so the adrenals overproduce androgens.
• Presentation:
  • Girls -ambiguous (virilised) genitalia at birth (enlarged clitoris, fused labia) with a normal womb and ovaries (46,XX).
  • Boys -normal genitalia, so often missed until a salt-wasting crisis at 1–3 weeks: vomiting, poor feeding, weight loss, dehydration, collapse.
  • Salt-wasting crisis bloods -low sodium, high potassium, low glucose, metabolic acidosis.
  • Non-salt-wasting (simple virilising) -early pubic hair, rapid growth, advanced bone age, enlarged penis or clitoris in childhood.
  • Non-classical CAH -later presentation: early pubarche, hirsutism, irregular periods (mimics PCOS).
• Diagnosis -raised 17-hydroxyprogesterone; electrolytes; karyotype; pelvic ultrasound.
• Treatment:
  • Hydrocortisone (glucocorticoid replacement, and suppression of ACTH and androgens).
  • Fludrocortisone (mineralocorticoid) and salt supplements in infancy (salt-wasting).
  • Salt-wasting crisis -IV fluids (0.9% saline with glucose), IV or IM hydrocortisone, treat hyperkalaemia and hypoglycaemia.
  • Sick day rules -double or triple hydrocortisone during illness; emergency IM hydrocortisone injection kit; steroid emergency card.
  • Monitor growth, bone age, 17-OHP and androgens.
  • Multidisciplinary care for genitalia (surgery decisions are complex).

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Adrenal Insufficiency

• Causes in children:
  • CAH (the commonest primary cause).
  • Long-term steroids (including high-dose inhaled steroids) -suppression of the adrenals; risk on sudden stopping or during illness.
  • Autoimmune Addison's disease (with other autoimmune conditions), adrenoleukodystrophy (boys -with neurological decline), adrenal haemorrhage (meningococcal sepsis -Waterhouse–Friderichsen).
  • Hypopituitarism (craniopharyngioma, after brain tumour treatment).
• Features -tiredness, poor weight gain, vomiting, abdominal pain, hypoglycaemia, low BP; hyperpigmentation (primary); adrenal crisis with illness (shock, low sodium, high potassium, low glucose).
• Emergency treatment -IM or IV hydrocortisone -under 1 year 25 mg, 1–5 years 50 mg, 6 years and over 100 mg; IV fluids and glucose.
• Sick day rules -double or triple the usual hydrocortisone during fever or illness; IM injection if vomiting; steroid emergency card; extra cover for surgery.

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Disorders of Sex Development

• What they are: Conditions where chromosomal, gonadal or anatomical sex is atypical -e.g. ambiguous genitalia at birth.
• Causes:
  • 46,XX -CAH (the commonest cause of ambiguous genitalia), maternal androgens.
  • 46,XY -androgen insensitivity syndrome (complete -female appearance; partial -ambiguous), 5-alpha reductase deficiency, testicular dysgenesis.
  • Sex chromosome DSD -Turner (45,X), Klinefelter (47,XXY), 45,X/46,XY mosaicism.
• Signs at the newborn examination -ambiguous genitalia, bilateral impalpable testes, severe hypospadias with undescended testes, clitoral enlargement, labial fusion.
• Management:
  • Urgent specialist assessment -a medical priority (exclude salt-wasting CAH -check electrolytes and glucose).
  • Don't guess the baby's sex; explain that tests are needed; support parents (birth registration can be delayed).
  • Tests -karyotype (rapid), 17-OHP, electrolytes, hormones, pelvic ultrasound.
  • Multidisciplinary team (endocrinology, urology, genetics, psychology).

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Thirst and Passing Lots of Urine

• Causes:
  • Diabetes mellitus -always check glucose first.
  • Habitual (psychogenic) polydipsia -toddlers who drink lots of juice or water; concentrate urine overnight.
  • Diabetes insipidus:
    • Cranial -brain tumours (craniopharyngioma, germinoma), Langerhans cell histiocytosis, head injury, after neurosurgery.
    • Nephrogenic -genetic (X-linked, boys), lithium, hypercalcaemia, hypokalaemia.
  • CKD (poor concentrating ability); renal tubular disorders (Fanconi, Bartter).
  • Hypercalcaemia; hypokalaemia.
  • UTI (frequency rather than polyuria).
• Tests -glucose, U&E, calcium, plasma and urine osmolality (early-morning sample); water deprivation test (specialist); MRI pituitary if cranial DI.

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Calcium Problems

• Hypocalcaemia:
  • Neonates -prematurity, infant of a diabetic mother, maternal vitamin D deficiency, DiGeorge syndrome (22q11 -with heart defects, cleft palate, immune problems).
  • Older children -vitamin D deficiency (rickets), hypoparathyroidism, CKD, pseudohypoparathyroidism (short fourth metacarpals).
  • Features -jitteriness, tetany, carpopedal spasm, seizures, laryngospasm, long QT.
  • Treatment -IV calcium gluconate (slowly, with ECG monitoring) for symptoms; oral calcium and vitamin D (or alfacalcidol).
• Hypercalcaemia -rare: Williams syndrome (infants), immobilisation, malignancy, vitamin D excess, hyperparathyroidism; vomiting, constipation, polyuria.
• Rickets -see the Growth, Development and Nutrition chapter.

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Drug Reference Table

Drug	Key points
Trimethoprim / nitrofurantoin	Lower UTI over 3 months -3 days.
Cefalexin / co-amoxiclav	Upper UTI -7–10 days oral; IV options if severe.
Prednisolone 60 mg/m² then 40 mg/m² alternate days	Steroid-sensitive nephrotic syndrome -4 weeks each; relapses common.
Penicillin V	Prophylaxis while nephrotic (pneumococcus).
Desmopressin	Nocturnal enuresis (short term or if alarm unsuitable) -fluid restriction for hyponatraemia; cranial DI.
Basal–bolus insulin / insulin pump	Type 1 diabetes; hybrid closed-loop systems for children and young people.
Glucagon IM/SC or nasal	Severe hypoglycaemia in type 1 diabetes.
Glucose 10% IV 2 mL/kg	Hypoglycaemia in hospital.
Soluble insulin infusion 0.05–0.1 units/kg/hour	DKA -start 1–2 hours after fluids; no bolus.
0.9% sodium chloride + KCl 40 mmol/L	DKA rehydration over 48 hours.
Hypertonic saline 2.7–3% / mannitol	Cerebral oedema in DKA.
Metformin	Type 2 diabetes in children.
Levothyroxine	Congenital (start within 2 weeks) and acquired hypothyroidism.
Carbimazole	Graves' disease; agranulocytosis -sore throat warning.
Hydrocortisone (oral / IM / IV)	CAH and adrenal insufficiency; emergency doses 25 mg (under 1), 50 mg (1–5), 100 mg (6+).
Fludrocortisone + sodium chloride	Salt-wasting CAH.
Eculizumab	Atypical HUS.

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Spot the Diagnosis

Clue	Diagnosis
Feverish 8-week-old with no focus and a positive urine culture	UTI -needs IV antibiotics and ultrasound
Fever, loin pain and nitrites in a 6-year-old	Pyelonephritis
Newborn boy with a poor stream, palpable bladder and bilateral hydronephrosis	Posterior urethral valves
Scarring on DMSA after recurrent UTIs	Reflux nephropathy
3-year-old with puffy eyes, frothy urine, albumin 16, normal BP	Nephrotic syndrome (minimal change)
Nephrotic child with fever and abdominal pain	Spontaneous bacterial peritonitis
Cola urine and high BP 2 weeks after tonsillitis	Post-streptococcal glomerulonephritis
Pallor, low platelets and AKI a week after bloody diarrhoea	HUS
7-year-old who has never been dry at night, otherwise well	Primary nocturnal enuresis -alarm
Bedwetting again after a year dry, with thirst and weight loss	Type 1 diabetes
Girl constantly damp despite normal voiding	Ectopic ureter
Vomiting, deep breathing, glucose 28, pH 7.08, ketones 5	Severe DKA
Headache and falling heart rate 6 hours into DKA treatment	Cerebral oedema -hypertonic saline or mannitol
Thin toddler with low glucose and high ketones after missing breakfast	Ketotic hypoglycaemia
Hypoglycaemia with low ketones after a long fast	Fatty acid oxidation disorder (MCADD) or hyperinsulinism
2-week-old boy vomiting with sodium 124, potassium 7.2	Salt-wasting CAH
Virilised genitalia in a 46,XX baby with high 17-OHP	CAH
Teenager with slowing growth, weight gain and falling school grades	Acquired hypothyroidism
Polyuria and visual field loss with calcification on scan	Craniopharyngioma with cranial DI
Neonatal seizures, low calcium, cleft palate and a heart defect	DiGeorge syndrome (22q11)

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Exam-style Scenarios

1. A 4-month-old has a fever of 39 °C for 2 days with no focus. A catheter urine shows many white cells and Gram-negative rods. She responds to IV antibiotics within 24 hours.
Answer: Upper UTI in an infant under 6 months, responding well.

• Complete 7–10 days (switch to oral when well).
• Renal ultrasound within 6 weeks.
• If atypical or recurrent -ultrasound during illness, DMSA and MCUG.

2. A 4-year-old has had puffy eyes for a week and swollen legs. Urine protein 4+, albumin 14 g/L, BP normal, no haematuria.
Answer: Nephrotic syndrome, probably minimal change disease.

• Prednisolone 60 mg/m² for 4 weeks, then 40 mg/m² on alternate days for 4 weeks.
• Penicillin V prophylaxis; salt restriction; check varicella immunity; pneumococcal vaccine.
• Watch for hypovolaemia, infection and thrombosis; home urine dipsticks for relapse.

3. A 9-year-old has been drinking a lot and wetting the bed for 3 weeks, and has lost 3 kg. Finger-prick glucose 21 mmol/L; blood ketones 1.2.
Answer: New type 1 diabetes without DKA.

• Same-day referral to the paediatric diabetes team.
• Start subcutaneous insulin; education; CGM.
• Coeliac serology and TFTs.

4. A 6-year-old with new diabetes is in DKA (pH 7.05, bicarbonate 6, ketones 6). She weighs 20 kg and is not shocked.
Answer: Severe DKA.

• Fluids: 10% deficit (2 L) over 48 hours plus maintenance, with potassium 40 mmol/L (BSPED calculator); possible initial 10 mL/kg bolus over 60 minutes.
• Insulin infusion 0.05–0.1 units/kg/hour started 1–2 hours after fluids; no bolus; no bicarbonate.
• Hourly neurological observations; act immediately on headache or bradycardia (cerebral oedema).

5. A 12-day-old boy has vomited for 2 days and is lethargic. Sodium 122, potassium 7.4, glucose 2.3. His genitals look normal.
Answer: Salt-wasting congenital adrenal hyperplasia (adrenal crisis).

• IV fluids (0.9% saline with glucose); treat hypoglycaemia; IV hydrocortisone 25 mg.
• Bloods for 17-OHP, cortisol and renin before treatment if possible; ECG and treat hyperkalaemia.
• Long term: hydrocortisone, fludrocortisone, salt; sick day rules and emergency kit.

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Key Points

• Test the urine in any unexplained fever; under 3 months -refer immediately.
• Under 3 years -microscopy and culture; 3 and over -dipstick (nitrites are most useful).
• Lower UTI: 3 days of trimethoprim or nitrofurantoin; upper UTI: 7–10 days of cefalexin or co-amoxiclav.
• Imaging after UTI depends on age, atypical features and recurrence (ultrasound, DMSA, MCUG).
• Posterior urethral valves: boys with poor stream and bilateral hydronephrosis -catheterise.
• Nephrotic syndrome in children is usually minimal change and steroid-sensitive; watch for infection, hypovolaemia and clots.
• HUS: bloody diarrhoea then anaemia, low platelets and AKI -supportive care, no antibiotics.
• Enuresis: look for causes if secondary; alarm first line; desmopressin with fluid restriction.
• 4 Ts (Toilet, Thirsty, Tired, Thinner): same-day finger-prick glucose and same-day referral.
• Type 1 diabetes: basal–bolus or pump, CGM, hybrid closed loop; HbA1c 48 or below; never stop insulin when ill.
• Paediatric DKA: slow rehydration over 48 hours, insulin 0.05–0.1 units/kg/hour started 1–2 hours after fluids, no bolus.
• Cerebral oedema (headache, bradycardia, rising BP) -hypertonic saline or mannitol immediately.
• Hypoglycaemia without diabetes: take a hypo screen during the episode.
• Congenital hypothyroidism is screened at birth -start levothyroxine within 2 weeks.
• CAH: virilised girls; boys present with salt-wasting crisis at 1–3 weeks (low sodium, high potassium, low glucose) -hydrocortisone.
• Emergency hydrocortisone: 25 mg under 1, 50 mg aged 1–5, 100 mg aged 6 and over.
• Ambiguous genitalia: urgent assessment; don't guess the sex; check electrolytes.

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Guidelines and Further Reading

• NICE NG224: Urinary tract infection in under 16s -diagnosis and management
• NICE CG54: Urinary tract infection in under 16s (imaging)
• NICE CG111: Bedwetting in under 19s
• NICE NG18: Diabetes (type 1 and type 2) in children and young people
• NICE TA943: Hybrid closed loop systems for managing blood glucose in type 1 diabetes
• BSPED: Guideline for the management of children and young people under 18 with diabetic ketoacidosis
• British Association for Paediatric Nephrology: guidance on nephrotic syndrome
• BSPED: Adrenal insufficiency and CAH guidance (emergency steroid doses)
• BNF for Children -for current doses

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