Nephro

What are the kidney's functions and how is renal function assessed in children?

The kidney has six main functions: filtering water-soluble salts and ions from blood (without filtering large molecules); reabsorbing necessary filtered small molecules (glucose, amino acids); diluting or concentrating urine to optimize fluid balance; regulating blood pressure; metabolizing vitamin D; and regulating acid-base balance. Assessment variables include: Plasma creatinine (product of muscle breakdown) — used to monitor renal function; normal range increases throughout childhood with muscle mass; does not become abnormally high until renal function is markedly reduced. Plasma urea — rises in AKI and CKD, and rises before creatinine; less specific (also rises in dehydration, catabolic states, high protein diet, GI bleeding); may cause nausea, vomiting, headaches. eGFR — more accurate; formula: eGFR = 31 × height (cm) / creatinine (μmol/L); GFR is very low in premature infants (only 10% of term GFR at 28 weeks); term infant corrected GFR (20–30 ml/min/1.73 m²) rises rapidly to adult rate of 80–120 ml/min/1.73 m² by 1–2 years. Formal GFR measurement — uses inulin clearance; reserved for pre-chemotherapy or research. Urinary protein loss — occurs before GFR falls in CKD. Urine osmolality — indicator of concentrating ability and therefore renal function.

What are the radiological investigations used for the kidneys and urinary tract in children, and what are their specific uses, advantages, and disadvantages?

Ultrasound: standard first-line imaging; provides anatomical assessment but not function; excellent for visualizing dilatation, stones, and nephrocalcinosis; non-invasive and mobile; disadvantages: operator-dependent, may miss renal scars. Micturating Cystourethrogram (MCUG): contrast introduced via urethral catheter; visualizes bladder and urethral anatomy; detects VUR and urethral obstruction; disadvantages: invasive and unpleasant (especially beyond infancy), high radiation dose, can introduce infection. CT scan: accurately identifies position of kidney stones; IV urograms are not performed in children. Plain abdominal X-ray: identifies unsuspected spinal abnormalities; may identify renal stones but poor at showing nephrocalcinosis. DMSA scan (⁹⁹ᵐTc dimercaptosuccinic acid): static scan of renal cortex; detects functional defects (scars, non-functioning tissue); must wait at least 2 months after UTI to avoid false 'scars'. MAG3 renogram: dynamic scan measuring drainage; furosemide given to maximize urine flow; in cooperative children >4 years, can identify VUR (indirect cystogram). Bladder flow urodynamics: assesses bladder emptying and flow rates; detects bladder abnormalities contributing to recurrent UTIs.

What are the main congenital anomalies of the kidneys and urinary tract (CAKUT) detectable on antenatal ultrasound, and why are they clinically important?

CAKUT is identified in 1 in 1000 births; antenatal ultrasound now detects most significant anomalies prospectively. Clinical importance: may be associated with abnormal renal development/function (CKD); predispose to UTI; may involve obstruction requiring surgery; may be associated with non-renal congenital anomalies. Specific anomalies: Bilateral renal agenesis — amniotic fluid is mainly fetal urine, so bilateral agenesis → severe oligohydramnios → Potter sequence (pulmonary hypoplasia, fatal respiratory failure, limb deformities, characteristic facies: low-set ears, beaked nose, epicanthic folds). Multicystic dysplastic kidney (MCDK) — failure of union of ureteric bud and nephrogenic mesenchyme; non-functioning structure with large fluid-filled cysts; no connection to bladder; half involute by 2 years; nephrectomy only if very large or hypertension develops; bilateral MCDK → Potter sequence. Polycystic kidney disease: ARPKD — diffuse bilateral enlargement, presents in childhood/neonates; ADPKD (1 in 1000) — bilateral separate cysts between normal parenchyma; main childhood symptom is hypertension; progresses to CKD requiring renal replacement in late adulthood; associated with liver/pancreatic cysts, cerebral aneurysms, mitral valve prolapse. Horseshoe kidney / pelvic kidney — abnormal caudal migration; predispose to infection or obstruction. Duplex kidney — may cause reflux into lower pole, ectopic ureter to urethra/vagina, or ureterocele with upper pole obstruction. Prune-belly syndrome — absence/severe deficiency of anterior abdominal wall muscles with megacystis-megaureter and cryptorchidism. Bladder exstrophy — failure of fusion of infraumbilical midline structures.

What is urinary tract obstruction in children, where can it occur, and what are the causes and consequences?

Obstruction to urine flow can occur at: Pelviureteric junction (PUJ) → unilateral hydronephrosis. Vesicoureteric junction (VUJ) → unilateral hydronephrosis with hydroureter. Bladder neck (e.g. neuropathic bladder) → bilateral hydronephrosis. Posterior urethral valves (PUV) — mucosal folds or membrane in the posterior urethra in boys → bilateral hydronephrosis, thickened trabeculated bladder wall, dilated posterior urethra; always requires urological intervention (cystoscopic ablation); bilateral hydronephrosis in a male infant requires URGENT MCUG to exclude PUV. Consequences: at worst, a dysplastic poorly-functioning kidney with cysts; in severe bilateral cases → Potter sequence. Postnatal management protocol: bilateral hydronephrosis + dilated lower urinary tract in a male → ultrasound within 48 hours to exclude PUV; unilateral hydronephrosis or any anomaly in a female → ultrasound at 4–6 weeks; prophylactic antibiotics started at birth. MAG3 renogram with furosemide is used to measure drainage; delayed excretion curve confirms PUJ obstruction.

What is vesicoureteric reflux (VUR), how does it cause kidney damage, and what are its grades and management?

VUR is a developmental anomaly of vesicoureteric junctions — ureters are displaced laterally and enter directly into the bladder rather than at an angle, with a shortened/absent intramural course, allowing urine to flow back from bladder to ureters/kidneys during voiding. It is familial in 30–50% of first-degree relatives; may also occur temporarily after UTI or with bladder pathology (neuropathic bladder, urethral obstruction). Severity ranges from reflux into ureter only to gross dilatation of ureter, renal pelvis, and calyces (predisposing to intrarenal reflux and scarring). Consequences: incomplete bladder emptying → encourages infection; pyelonephritis if reflux reaches the kidney; high voiding pressures transmitted to renal papillae → renal damage; reflux nephropathy (scarred, shrunken, poorly functioning kidney) → if bilateral and severe → progressive CKD; up to 10% risk of hypertension in childhood or early adult life. Management: prophylactic antibiotics (particularly in children under 2–3 years with congenital abnormality, after upper UTI, or severe reflux until out of nappies); low-dose trimethoprim most often used; circumcision in boys may reduce UTI incidence; bladder urodynamics if incomplete bladder emptying suspected; anti-VUR surgery if progression of scarring with ongoing high-grade VUR; annual blood pressure monitoring; urinalysis for proteinuria; regular renal growth and function assessment if bilateral defects.

What are the epidemiology, clinical features, and diagnosis of urinary tract infection (UTI) in children?

About 3–7% of girls and 1–2% of boys have at least one symptomatic UTI before age 6; 12–30% have a recurrence within a year. UTI is important because up to half have a structural urinary tract abnormality, and pyelonephritis may damage the growing kidney by forming scars → hypertension and CKD. Clinical features vary with age: In infants — non-specific (fever, vomiting, lethargy, irritability, poor feeding, faltering growth, jaundice, septicaemia, offensive urine, febrile seizure). In children — dysuria, frequency, urgency, abdominal/loin pain, fever ± rigors, lethargy, anorexia, vomiting, diarrhoea, haematuria, offensive/cloudy urine, recurrence of enuresis. Upper UTI (pyelonephritis) = bacteriuria + fever >38°C, or loin pain/tenderness. Lower UTI (cystitis) = bacteriuria + dysuria/frequency without systemic features. Diagnosis: clean-catch sample is the recommended method in nappy-wearing children (Quick-wee technique: gentle rubbing of lower abdomen with cold-wet gauze); midstream urine in older children; catheter or suprapubic aspiration if urgently needed. Culture criteria: >10⁵ CFU/ml of a single organism in clean-catch/MSU = 90% probability of infection; same result in second sample = 95%; any growth of single organism in catheter or SPA sample is diagnostic. Dipstick: if both leukocyte esterase AND nitrite are negative, UTI is unlikely; culture still required if clinical suspicion exists. Test urine in all infants with unexplained fever >38°C.

What are the organisms causing UTI in children, the host factors predisposing to infection, and the investigations indicated?

Organisms: Most common is Escherichia coli; followed by Klebsiella, Proteus, Pseudomonas, Enterococcus faecalis. Proteus is more common in boys (present under prepuce); splits urea to ammonia → alkaline urine → phosphate stones. Pseudomonas may indicate a structural abnormality or presence of catheters/stents. Host factors increasing infection risk: antenally diagnosed renal/urinary tract abnormality including VUR; incomplete bladder emptying from constipation, infrequent voiding, neuropathic bladder, or VUR. Investigations: All infants with first UTI → renal ultrasound (to identify serious structural abnormalities and obstruction). Further investigations only for atypical features: seriously ill or septicaemia; poor urine flow; abdominal or bladder mass; raised creatinine; failure to respond to antibiotics within 48 hours; infection with atypical (non-E. coli) organisms. If urethral obstruction suspected on ultrasound (abnormal bladder in a boy) → MCUG promptly. Functional scans (DMSA or MAG3) → defer 3 months after UTI to avoid false-positive results. Extensive investigation of all children with UTIs is no longer recommended as evidence that investigation improves outcome (without obstruction) is lacking.

What is the complete management of UTI in children, including treatment and prevention strategies?

Treatment: Infants under 3 months with suspected UTI or seriously ill → hospital admission; IV antibiotics (e.g. co-amoxiclav) for at least 5–7 days followed by oral prophylaxis. Infants >3 months and children with acute pyelonephritis/upper UTI → IV antibiotics if concern about sepsis, or oral antibiotics (e.g. trimethoprim for 7 days); if IV used, switch to oral after 2–4 days for total 7–10 days; choice adjusted by culture sensitivities (Enterococcus often resistant to cephalosporins). Children with cystitis/lower UTI → oral antibiotics (trimethoprim or nitrofurantoin) for 5 days. Prevention: High fluid intake for high urine output; regular voiding; double voiding (try again after 1–2 minutes to empty residual or refluxed urine); treat/prevent constipation; good perineal hygiene; Lactobacillus acidophilus probiotic to reduce pathogenic gut flora; antibiotic prophylaxis (controversial; used in children under 2–3 years with congenital urinary tract abnormality, after upper UTI, or severe reflux; low-dose trimethoprim most often; nitrofurantoin or cephalexin alternatives; avoid broad-spectrum poorly absorbed antibiotics like amoxicillin). Follow-up if recurrent UTIs/renal scarring/reflux: dipstick urine with any non-specific illness; consider prophylactic antibiotics; circumcision in boys; bladder urodynamics; anti-VUR surgery if indicated; annual blood pressure; urinalysis for proteinuria; regular renal growth and function monitoring.

What are the causes of daytime enuresis and secondary nocturnal enuresis, and how are they investigated and managed?

Daytime enuresis (lack of bladder control during day in a child >3–5 years): Causes — lack of attention to bladder sensation (developmental/behavioural, even in normal children absorbed in play); detrusor instability (sudden urgent urge from sudden bladder contractions); bladder neck weakness; neuropathic bladder (large, fails to empty, irregular thick wall; associated with spina bifida); UTI (rarely without other symptoms); constipation; ectopic ureter (causes constant dribbling — child is always damp; girls dry at night but wet on getting up suggest ectopic ureter opening into vagina). Examination: look for neuropathic bladder (distended bladder, abnormal perineal sensation, altered anal tone, abnormal leg reflexes and gait; sensory loss in S2–S4 dermatomes). Investigation: urine dipstick + culture; ultrasound (bladder pathology, incomplete emptying, wall thickening); urodynamic studies; spine X-ray for vertebral anomaly; MRI to exclude cord tethering. Management: star charts, bladder training, pelvic floor exercises; treat constipation; portable urine alarm (activated by urine in pants) for attention-related enuresis; oxybutynin (anticholinergic) to dampen bladder contractions if other measures fail. Secondary (onset) nocturnal enuresis (loss of previously achieved continence): Causes — emotional upset (most common); UTI; polyuria from osmotic diuresis (diabetes mellitus), renal concentrating disorder (sickle cell disease, CKD, nephrogenic diabetes insipidus — central or nephrogenic). Investigation: urine dipstick (infection, glycosuria, proteinuria); early morning urine osmolality; water deprivation test if concentrating defect suspected; renal ultrasound.

What are the causes of proteinuria in children, and what is orthostatic proteinuria?

Transient proteinuria occurs during febrile illnesses or after exercise — does not require investigation.
Persistent proteinuria is significant; quantified by urine protein-to-creatinine ratio in an early morning sample (normal <20 mg/mmol).

Causes: Orthostatic (postural) proteinuria — proteinuria only when upright during the day; diagnosed by measuring protein-to-creatinine ratio in a series of early morning samples (should be normal); excellent prognosis, no further investigation needed.
Glomerular abnormalities: nephrotic syndrome; glomerulonephritis; abnormal glomerular basement membrane. Increased glomerular filtration pressure. Reduced renal mass in CKD. Hypertension. Tubular proteinuria (low molecular weight proteins not reabsorbed in tubule). Investigations for non-orthostatic proteinuria: urine microscopy; plasma urea, electrolytes, creatinine, albumin; complement levels; renal ultrasound; and depending on findings, renal biopsy.

What are the clinical features, investigations, and management of nephrotic syndrome in children, including its complications?

Nephrotic syndrome = heavy proteinuria → low plasma albumin → oedema. Most primary childhood nephrotic syndrome has an unknown cause; secondary causes include Henoch–Schönlein purpura, vasculitis (SLE), infections (malaria), or allergens (bee sting).

Clinical signs: periorbital oedema (especially on waking — often the earliest sign, frequently misdiagnosed as allergy/conjunctivitis); scrotal or vulval, leg, and ankle oedema; ascites; breathlessness from pleural effusions and abdominal distension; infection (peritonitis, septic arthritis, sepsis from urinary immunoglobulin loss).

Investigations at presentation:
urine dipstick (≥3+ protein); FBC (high Hb suggests intravascular depletion); urea/electrolytes/creatinine/albumin (hyponatraemia common; high urea/creatinine → intravascular depletion);
complement C3, C4 (low C3 in post-infectious GN; low C3 and C4 in SLE); ASO/anti-DNAse B titres and throat swab;
urinary sodium (<10 mmol/L in hypovolaemia); hepatitis B and C screen; malaria screen if recent travel.

Complications:
Hypovolaemia — abdominal pain, faintness, peripheral vasoconstriction, urinary sodium retention;
treat with IV 0.9% saline or 4.5% albumin;
severe oedema →
IV 20% albumin + furosemide
Thrombosis — hypercoagulable state from urinary loss of antithrombin III, thrombocytosis (exacerbated by steroids), increased clotting factor synthesis, raised haematocrit; may affect lungs, brain, limbs, splanchnic circulation.
Infection — susceptibility to capsulated bacteria (especially Pneumococcus); spontaneous peritonitis may occur; pneumococcal and seasonal influenza vaccination recommended;
penicillin prophylaxis while in relapse;
chickenpox/shingles → aciclovir.
Hypercholesterolaemia — inversely correlates with serum albumin.

What are the features of steroid-sensitive nephrotic syndrome, its management protocol, and clinical course?

Steroid-sensitive nephrotic syndrome (SSNS) accounts for 85–90% of childhood nephrotic syndrome — proteinuria resolves with corticosteroids; these children do NOT progress to CKD.

More common in boys than girls and in Asian than Caucasian children; associated with atopy; often precipitated by respiratory infections.

Features suggesting SSNS: age 1–10 years; no macroscopic haematuria; normal blood pressure; normal complement levels; normal renal function. Histology: minimal change disease — normal on light microscopy but fusion of podocytes (specialized epithelial cells investing glomerular capillaries) seen on electron microscopy.

Management: oral prednisolone 60 mg/m²/day for 4 weeks, then 40 mg/m² on alternate days for 4 weeks, then weaned/stopped; median time for urine to become protein-free is 11 days; extending corticosteroid duration does not reduce relapse rate.

Children not responding to 4–6 weeks of steroids or with atypical features → renal biopsy. Clinical course: 50% resolve directly; 30% have infrequent relapses; 20% have frequent relapses/steroid dependence.

Frequent relapses → refer to paediatric nephrologist; steroid-sparing agents: levamisole (immunomodulator), mycophenolate mofetil, calcineurin inhibitors (tacrolimus), rituximab (anti-CD20 B-cell monoclonal antibody) for difficult cases.

What is steroid-resistant nephrotic syndrome and congenital nephrotic syndrome, and how are they managed?

Steroid-resistant nephrotic syndrome (SRNS): failure to respond to 4–6 weeks of corticosteroids or presence of atypical features → renal biopsy and genetic testing indicated; refer to paediatric nephrologist.

Main causes:
Focal segmental glomerulosclerosis (FSGS) — most common SRNS; familial or idiopathic; 30% progress to stage 5 CKD; 20% respond to tacrolimus or rituximab; common recurrence post-transplant.
Mesangiocapillary (membranoproliferative) GN — more common in older children; haematuria and low complement; decline over many years; treat with ACE inhibitors ± mycophenolate mofetil.
Membranous nephropathy — associated with hepatitis B; may precede SLE; most remit spontaneously within 5 years.

Management of oedema in SRNS: diuretics, salt restriction, ACE inhibitors, and sometimes NSAIDs (may reduce proteinuria).

Congenital nephrotic syndrome: presents in first 3 months of life; rare; most common type is autosomal recessive (Finnish type); more common in consanguineous families in the UK; >70% have an underlying genetic defect → genetic testing recommended.
Albuminuria so severe that unilateral nephrectomy may be necessary → dialysis → renal transplantation once child is old enough and is no longer nephrotic; some children have milder disease and may not need renal replacement in childhood.

What are the causes of haematuria in children, how is it investigated, and when is renal biopsy indicated?

Red urine or positive urine dipstick for haemoglobin must be confirmed with microscopy (>10 red blood cells per high-power field). Glomerular haematuria: brown urine, dysmorphic red cells, casts, often with proteinuria; occurs throughout urinary stream. Lower urinary tract haematuria: red urine, beginning or end of stream, no proteinuria (unusual in children). UTI is the most common cause of haematuria. Non-glomerular causes: infection (bacterial, viral, TB, schistosomiasis), trauma, stones, tumours, sickle cell disease, bleeding disorders, renal vein thrombosis, hypercalciuria. Glomerular causes: post-infectious GN, Henoch–Schönlein purpura and other vasculitides, IgA nephropathy, genetic basement membrane disorders (Alport syndrome, thin basement membrane disease). Investigation in all patients: urine microscopy (with phase contrast) and culture; urinary protein:creatinine and calcium:creatinine ratios; renal ultrasound; plasma urea, electrolytes, creatinine, calcium, phosphate, albumin; FBC, coagulation screen, sickle cell screen. If glomerular haematuria suspected, add: ESR, complement levels, anti-double-stranded DNA; throat swab and ASO/anti-DNAse B; hepatitis B and C screen; test family for haematuria; hearing test (if Alport syndrome suspected). Renal biopsy indicated if: significant persistent proteinuria; recurrent macroscopic haematuria; abnormal renal function; persistently abnormal complement levels.

What is acute glomerulonephritis — its causes, pathophysiology, clinical features, and management?

Causes: postinfectious (most commonly post-streptococcal); vasculitis (Henoch–Schönlein purpura; rarely SLE, microscopic polyarteritis, granulomatosis with polyangiitis); IgA nephropathy; mesangiocapillary GN; antiglomerular basement membrane disease (Goodpasture syndrome — very rare). Pathophysiology: increased glomerular cellularity restricts glomerular blood flow → decreased GFR → decreased urine output and volume overload → hypertension (may cause seizures) → oedema (characteristically initially periorbital) → haematuria and proteinuria.

Post-streptococcal GN: follows streptococcal sore throat or skin infection; evidence of recent streptococcal infection (culture, raised ASO/anti-DNAse B titres); low complement C3 levels returning to normal after 3–4 weeks; long-term prognosis is good.

Rapidly progressive GN: may occur with any cause; if left untreated → irreversible CKD over weeks/months → requires renal biopsy + immunosuppression + plasma exchange. Management: attention to water and electrolyte balance; diuretics when necessary; monitor for rapid deterioration in renal function.

What is Henoch–Schönlein Purpura (HSP) — its epidemiology, pathophysiology, clinical features, renal involvement, and management?

HSP is the most common vasculitis in childhood, occurring mainly between 3 and 10 years; twice as common in boys; peaks in winter; often preceded by an upper respiratory infection.

Pathophysiology: genetic predisposition + antigen exposure → increased circulating IgA levels + disrupted IgG synthesis → IgA/IgG complexes activate complement → deposited in affected organs → inflammatory vasculitis.

Clinical features: Rash (most obvious, cornerstone of clinical diagnosis, present as first feature in 50%):
symmetrically distributed on buttocks, extensor surfaces of arms and legs, ankles; trunk usually spared; initially urticarial → maculopapular → purpuric; palpable; may recur over weeks.

Joints (2/3 of patients): knees and ankles most common; periarticular oedema; no long-term joint damage; resolves before rash.

Abdomen: colicky abdominal pain (treat with corticosteroids if severe);
GI involvement → haematemesis and melaena; intussusception (difficult to diagnose in this setting); rare: ileus, protein-losing enteropathy, orchitis, CNS involvement.

Renal involvement (common but rarely first symptom): >80% have microscopic/macroscopic haematuria or mild proteinuria → usually complete recovery; heavy proteinuria → nephrotic syndrome; risk factors for progressive CKD: heavy proteinuria, oedema, hypertension, deteriorating renal function → renal biopsy.

Follow-up: all children with HSP should be followed for 1 year to detect persistent haematuria/proteinuria (5–10%); those with persistent renal involvement require long-term follow-up (hypertension and CKD may develop after years).

What are IgA nephropathy, Alport syndrome, and the renal vasculitides — their features, investigations, and management?

IgA nephropathy: presents with episodes of macroscopic haematuria, commonly during upper respiratory tract infections; histological findings and management same as HSP nephritis; may be a variant of the same pathological process limited to the kidney; prognosis in children better than in adults. Alport syndrome and thin basement membrane disease: caused by genetic abnormalities of collagen in glomerular basement membrane. Most common form of Alport syndrome is X-linked recessive (COL4A5 mutation): progresses to severe CKD by early adult life in males; associated with nerve deafness and ocular defects; also autosomal dominant and recessive forms. Thin basement membrane disease causes milder phenotype; requires long-term follow-up; ACE inhibitors slow CKD progression if proteinuria develops. Renal vasculitides (rarer): polyarteritis nodosa, microscopic polyarteritis, granulomatosis with polyangiitis (GPA, formerly Wegener): fever, malaise, weight loss, skin rash, arthropathy; prominent respiratory tract involvement in GPA; ANCA (antineutrophil cytoplasm antibodies) present and diagnostic; renal angiogram may show aneurysms in polyarteritis nodosa; renal involvement may be rapidly progressive. Treatment: corticosteroids, plasma exchange, IV cyclophosphamide, and increasingly biological monoclonal antibody therapy. SLE: predominantly female teenagers/young adults; more common in Asian and Afro-Caribbean groups; characterized by multiple autoantibodies including anti-dsDNA; low C3 and C4 during active disease; haematuria and proteinuria → renal biopsy → immunosuppression (intensity depends on severity of renal involvement).

What are the causes, presentation, and management of hypertension in children?

Hypertension in children is defined as blood pressure above the 95th percentile for age, height, and gender (plotted on centile chart). Children who are overweight or obese are at increased risk. Symptomatic hypertension in children is usually secondary to renal, cardiac, or endocrine causes: Renal — renal parenchymal disease; renovascular (renal artery stenosis); polycystic kidney disease (ARPKD and ADPKD); renal tumours. Cardiac — coarctation of the aorta. Catecholamine excess — phaeochromocytoma (also causes paroxysmal palpitations, sweating); neuroblastoma. Endocrine — congenital adrenal hyperplasia; Cushing syndrome or corticosteroid therapy; hyperthyroidism. Essential hypertension — diagnosis of exclusion in children; increasingly common especially with obesity and obstructive sleep apnoea. Presentation: vomiting, headaches, facial palsy, hypertensive retinopathy, seizures, proteinuria; in infants: faltering growth and cardiac failure most common. Management: Some causes are correctable — nephrectomy for unilateral scarring; angioplasty for renal artery stenosis; surgical repair of coarctation; resection of phaeochromocytoma. Most cases require antihypertensive medication: calcium channel blockers, ACE inhibitors, or angiotensin II receptor blockers (ARBs). All children with renal tract abnormality should have annual blood pressure checks throughout life. Family history of essential hypertension → salt restriction, avoid obesity, regular BP monitoring.

What are renal calculi in children — their types, presentations, predisposing causes, and management?

Renal stones are uncommon in childhood. When they occur, predisposing causes must be sought: UTI (most common, especially Proteus which alkalinizes urine by splitting urea to ammonia → phosphate stones); structural urinary tract anomalies; metabolic abnormalities. Specific stone types: Calcium-containing stones — most common metabolic cause is idiopathic hypercalciuria; also with increased urinary urate and oxalate. Phosphate stones — associated with Proteus infection. Cystine and xanthine stones — rare. Nephrocalcinosis (calcium deposition in renal parenchyma) — occurs with hypercalciuria, hyperoxaluria, and distal renal tubular acidosis (type I); may also be a complication of furosemide therapy in neonates. Presentation: haematuria; loin or abdominal pain; UTI; passage of a stone. Investigation: ultrasound (shows stones and nephrocalcinosis); CT scan for precise stone localization; metabolic screen (calcium, phosphate, urate, oxalate, cystine in blood and urine). Management: high fluid intake in all affected children; stones not passed spontaneously → lithotripsy or surgery; repair structural anomaly if present; specific therapy for metabolic cause if identified (e.g. thiazides for hypercalciuria, alkalization for uric acid stones).

What is Fanconi syndrome, what are its causes, cardinal features, and clinical presentation?

Fanconi syndrome is generalized proximal tubular dysfunction — proximal tubule cells are among the most metabolically active in the body and therefore especially vulnerable to cellular damage. Cardinal features: excessive urinary loss of amino acids, glucose, phosphate, bicarbonate, sodium, calcium, potassium, and magnesium (all normally reabsorbed in the proximal tubule). Causes: Idiopathic. Inborn errors of metabolism — cystinosis (autosomal recessive, intracellular cystine accumulation; most common cause in children), glycogen storage disorders, Lowe syndrome (oculocerebrorenal dystrophy), galactosaemia, fructose intolerance, tyrosinaemia, Wilson disease. Acquired — drugs and toxins (gentamicin, amphotericin), heavy metals. Clinical presentation: polydipsia and polyuria; salt depletion and dehydration; hyperchloraemic metabolic acidosis; rickets (phosphate loss); faltering or poor growth. Specific tubular defects (not Fanconi): Glycosuria (glucose transport defect, asymptomatic); cystinuria (cystine + dibasic amino acid transport defect → renal calculi); phosphate wasting → vitamin D-resistant rickets; bicarbonate wasting → renal tubular acidosis type II; distal RTA type I (hydrogen ion secretion defect → metabolic acidosis, alkaline urine, nephrocalcinosis, faltering growth); nephrogenic diabetes insipidus (water reabsorption defect → polydipsia, polyuria, fever, faltering growth); Bartter syndrome (loop of Henle chloride transport defect → hypokalaemic metabolic alkalosis, hypercalciuria, normal blood pressure with high renin, polydipsia, polyuria, faltering growth).

What is acute kidney injury (AKI) in children — its causes, classification, and management?

AKI is a sudden, potentially reversible, reduction in renal function; oliguria (

What is Haemolytic Uraemic Syndrome (HUS) — its triad, causes, pathophysiology, and management?

HUS is a triad of: 1) Acute kidney injury; 2) Microangiopathic haemolytic anaemia (low Hb, high LDH from red cell damage in occluded microcirculation); 3) Thrombocytopenia (platelets consumed in intravascular thrombogenesis). Typical (diarrhoea-associated) HUS: caused by Shiga/verocytotoxin-producing E. coli O157:H7 (acquired from farm animals or uncooked beef) or less often Shigella; follows a prodrome of bloody diarrhoea. Pathophysiology: toxin enters GI mucosa → localizes to renal endothelial cells → intravascular thrombogenesis → coagulation cascade activated (but coagulation normal, unlike DIC); platelets consumed; microangiopathic haemolytic anaemia from RBC damage in occluded microcirculation; other organs (brain, pancreas, heart) may also be involved. Management: early supportive therapy including dialysis; typical HUS usually has good prognosis; long-term follow-up necessary for persistent proteinuria, hypertension, and progressive CKD. Atypical HUS: no diarrhoeal prodrome; may be genetic; may relapse frequently. Treatment: eculizumab (monoclonal anti-terminal complement complex antibody) has greatly improved prognosis of atypical HUS, which previously had high risk of hypertension, progressive CKD, and mortality; however, it is very expensive and duration of treatment is unknown.

What are the five stages of chronic kidney disease (CKD) in children, its causes, and clinical features?

CKD is progressive loss of renal function, staged by GFR: Stage 1 (>90 ml/min/1.73 m²): normal function but structural abnormality or persistent haematuria/proteinuria. Stage 2 (60–89): mildly reduced, asymptomatic. Stage 3 (30–59): moderately reduced; renal osteodystrophy begins. Stage 4 (15–29): severely reduced; metabolic derangements and anaemia; plan for RRT. Stage 5 (<15): end-stage renal failure; RRT required. Incidence of stage 5 CKD in children: only 10 per million child population per year. Causes in children: congenital anomalies of kidney and urinary tract (CAKUT) 53%, glomerular disease 19%, familial/hereditary 13%, systemic diseases 4%, tubulointerstitial 5%, miscellaneous (PKD, metabolic) 6%. Clinical features (rarely develop before renal function falls below one-third of normal/stage 4): anorexia and lethargy; polydipsia and polyuria; faltering growth/growth failure; bony deformities from renal osteodystrophy (renal rickets); hypertension; acute-on-chronic renal failure (precipitated by infection or dehydration); incidental proteinuria finding; unexplained normochromic normocytic anaemia.

What is the complete management of chronic kidney disease in children, including nutrition, bone disease, anaemia, hormonal issues, dialysis, and transplantation?

Nutrition: poor appetite, nausea, and vomiting are common; calorie supplements and nasogastric/gastrostomy feeding may be necessary; protein intake must NOT be restricted and must be sufficient to maintain growth and normal albumin; restrict potassium and phosphate under paediatric renal dietician guidance. Renal osteodystrophy prevention: phosphate retention + hypocalcaemia from decreased vitamin D activation → secondary hyperparathyroidism → osteitis fibrosa and osteomalacia; treat with: dietary phosphate restriction (reduce milk products), calcium carbonate as phosphate binder, activated vitamin D supplements. Salt and water balance and acidosis: children with congenital structural CKD have obligatory salt and water loss → need salt supplements and free water access; in steroid-resistant NS or anephric patients → fluid and salt restriction; bicarbonate supplements for acidosis. Anaemia: reduced erythropoietin production + bone marrow toxins → normochromic normocytic anaemia; treat with subcutaneous recombinant human erythropoietin. Hormonal abnormalities: growth hormone resistance (high GH levels but poor growth) → recombinant human growth hormone effective for up to 5 years; delayed puberty and subnormal pubertal growth spurt in stages 4–5. Dialysis and transplantation: renal transplantation is optimum management for stage 5 CKD; minimum weight ~10 kg before transplant (to avoid renal vein thrombosis); living related donor kidneys have higher success (1-year graft survival 97%) than deceased donors (96%); 5-year graft survival: 89% (living related) and 86% (deceased donor); immunosuppression: tacrolimus + mycophenolate mofetil + prednisolone; minimal steroid regimens improve growth. If transplant not immediately available → peritoneal dialysis (continuous cycling overnight or continuous ambulatory peritoneal dialysis by parents at home — less disruptive to family/schooling) or haemodialysis (usually 3–4×/week in hospital; home haemodialysis increasingly adopted).

What are renal masses in children — their causes and key distinguishing features?

An abdominal mass on palpation should be investigated promptly by ultrasound. Causes of palpable kidneys: Unilateral — multicystic dysplastic kidney (MCDK); compensatory hypertrophy of normal kidney; obstructed hydronephrosis; renal tumour (Wilms tumour); renal vein thrombosis. Bilateral — autosomal recessive polycystic kidneys (ARPKD); autosomal dominant polycystic kidneys (ADPKD); tuberous sclerosis; renal vein thrombosis. Key distinction: Bilaterally enlarged kidneys in early life are most frequently due to ARPKD — associated with hypertension, hepatic fibrosis, and progressive CKD. Must be distinguished from ADPKD: more benign prognosis in childhood; progressive CKD onset in adulthood; but hypertension present in at least 30% of affected children. Wilms tumour (nephroblastoma): most common renal tumour in childhood; presents as unilateral abdominal mass; investigated by ultrasound and CT; treated with nephrectomy ± chemotherapy ± radiotherapy depending on stage. Nephrocalcinosis (small multiple calcium deposits within renal parenchyma) is visualized on ultrasound and may be seen in hypercalciuria, hyperoxaluria, distal RTA, and as a complication of furosemide therapy in neonat