1. Micturating Cystourethrogram (MCU / VCUG).
2. Posterior Urethral Valves (PUV) (showing dilated, elongated posterior urethra with abrupt caliber change at valve level, hypertrophied bladder neck, trabeculated bladder, and secondary vesicoureteral reflux).
3. Further nuclear renograms:
   • ${}^{99\text{m}}\text{Tc}$-DTPA or ${}^{99\text{m}}\text{Tc}$-MAG3 scan (Dynamic renogram to evaluate GFR, differential renal function, and drainage/obstruction).
   • ${}^{99\text{m}}\text{Tc}$-DMSA scan (Static cortical scan to detect renal parenchymal scarring and dysplasia).

1. Prune-Belly Syndrome (Eagle-Barrett Syndrome / Triad Syndrome).
2. Clinical components:
   • Partial or complete absence/deficiency of abdominal wall musculature (wrinkled "prune-like" abdominal wall)
   • Bilateral intra-abdominal cryptorchidism (undescended testes)
   • Complex urinary tract anomalies (massive bilateral hydroureteronephrosis, megacystis, dilated prostatic urethra, VUR)
   • Secondary oligohydramnios-related pulmonary hypoplasia.
3. Prognostic factors:
   • Severity of pulmonary hypoplasia at birth (leading cause of neonatal mortality)
   • Degree of underlying renal dysplasia and progression to End-Stage Renal Disease (ESRD).

1. Modified Schwartz Formula:
   $\text{eGFR }({\text{mL/min/1.73 m}}^2)=\frac{k\times \text{Height (cm)}}{\text{Serum Creatinine (mg/dL)}}$
   Where $k$ values are:

   • $0.33$ for low-birth-weight preterm infants $<1$ year
   • $0.45$ for full-term infants $<1$ year
   • $0.55$ for children and adolescent females
   • $0.70$ for adolescent males (or standard bedside constant $k=0.413$ with enzymatic IDMS-traceable creatinine assay).

2. Stage 2 CKD: $\text{GFR }60–89{\text{ mL/min/1.73 m}}^2$ with evidence of kidney damage.

CKD Stage	Description	GFR (${\text{mL/min/1.73 m}}^2$)
Stage 1	Kidney damage with normal or $\uparrow$ GFR	$\ge 90$
Stage 2	Kidney damage with mild $\downarrow$ GFR	$60–89$
Stage 3	Moderate $\downarrow$ GFR	$30–59$
Stage 4	Severe $\downarrow$ GFR	$15–29$
Stage 5	Kidney Failure / ESRD	$<15$ (or on dialysis)

3. True/False:
   i. True (rGH improves linear growth velocity in children with CKD).
   ii. False (Anemia of CKD is primarily due to Erythropoietin deficiency by peritubular interstitial cells).
   iii. True (Secondary hyperparathyroidism leads to high-turnover osteitis fibrosa cystica).

(Answers: i-True, ii-False, iii-True)

1. Acute Post-Streptococcal Glomerulonephritis (APSGN).
2. Confirmatory investigations:
   • Evidence of streptococcal infection: Elevated ASO titer (post-pharyngitis) or Anti-DNase B titer (post-impetigo).
   • Serum Complement: Markedly decreased Serum C3 (with normal C4); normalizes within 6–8 weeks.
   • Urinalysis: Dysmorphic RBCs, microscopic/gross hematuria, RBC casts, and subnephrotic proteinuria.
   • Renal function tests (elevated BUN and serum creatinine).
3. First-line antihypertensive: Loop diuretics (IV Furosemide $1–2\text{ mg/kg}$) to manage hypervolemia, hypertension, and pulmonary edema; add Calcium Channel Blockers (Amlodipine/Nifedipine) if BP remains elevated.

1. Alport Syndrome (Hereditary Nephritis, defect in Type IV collagen $\alpha -3,\alpha -4,\alpha -5$ chains).
2. Extrarenal manifestations:
   • Bilateral sensorineural hearing loss (SNHL) (high-frequency; progressive)
   • Ocular abnormalities: Anterior lenticonus (pathognomonic), perimacular retinal flecks, corneal endothelial vesicles / recurrent corneal erosions
   • Diffuse Leiomyomatosis of the esophagus, tracheobronchial tree, and female genitalia (in deletion involving COL4A5 and COL4A6).
3. Inheritance patterns:
   • X-linked dominant (85%): COL4A5 gene mutation on chromosome Xq22 (severe in males).
   • Autosomal recessive (10–15%): COL4A3 or COL4A4 on chromosome 2q36.
   • Autosomal dominant (~5%): Heterozygous COL4A3 or COL4A4.

1. Distal Renal Tubular Acidosis (Type 1 RTA / Classic dRTA) with bilateral Nephrocalcinosis (due to failure of distal $\alpha$-intercalated cells to secrete ${\text{H}}^{+}$ ions, causing urine $\text{pH}>5.5$ despite systemic metabolic acidosis).
2. Classification of RTA:
   • Type 1 (Distal RTA): Impaired distal ${\text{H}}^{+}$ excretion ($\text{urine pH}>5.5$, hypokalemia, nephrocalcinosis).
   • Type 2 (Proximal RTA): Impaired proximal ${\text{HCO}}_3^{-}$ reabsorption (hypokalemia, associated Fanconi syndrome).
   • Type 3 (Mixed RTA): Rare variant with combined proximal and distal defects (Carbonic anhydrase II deficiency with osteopetrosis).
   • Type 4 (Hyperkalemic RTA): Aldosterone deficiency or distal tubular resistance (Hyperkalemia, urine $\text{pH}<5.5$).
3. Secondary causes of Distal RTA:
   • Autoimmune: Systemic Lupus Erythematosus (SLE), Sjögren syndrome
   • Hereditary: Sickle cell nephropathy, Ehlers-Danlos syndrome, Wilson disease
   • Obstructive uropathy / chronic pyelonephritis / medullary sponge kidney
   • Drugs/toxins: Amphotericin B, Lithium, Toluene inhalation.
4. Management:
   • Oral alkali therapy: Sodium bicarbonate or Potassium citrate (Bicitra/Polycitra) at $2–4\text{ mEq/kg/day}$ in 3–4 divided doses to maintain normal serum bicarbonate.
   • Potassium supplementation (Potassium citrate prevents hypokalemia and alkalinizes urine to dissolve/prevent nephrocalcinosis).
   • Adequate hydration and nutritional rehabilitation for catch-up growth.

1. Differential diagnoses: Wilms' Tumor (Nephroblastoma) and Neuroblastoma.
2. Mechanism of hypertension:
   • In Wilms' Tumor: Renal ischemia induced by tumoral compression of the adjacent renal parenchyma and renal artery, leading to activation of the Renin-Angiotensin-Aldosterone System (RAAS) and hyperreninism.
   • In Neuroblastoma: Hypersecretion of Catecholamines (Epinephrine, Norepinephrine, and Dopamine) by tumor chromaffin neuroblasts causing systemic vasoconstriction.
3. Common metastatic sites:
   • For Wilms' Tumor: Lungs (most common, 85%) and liver.
   • For Neuroblastoma: Cortical bones, Bone Marrow, orbit ("raccoon eyes"), and liver.

1. MCU findings: Marked dilatation and elongation of the posterior urethra, narrow thread-like anterior urethral stream with caliber transition, hypertrophied bladder neck, heavily trabeculated "Christmas tree" bladder with multiple pseudodiverticula, and secondary high-grade Vesicoureteral Reflux (VUR).
2. Indication: Suspicion of Posterior Urethral Valves (PUV) (antenatal bilateral hydronephrosis with distended bladder, poor urinary stream, or palpable bladder/renal masses).
3. Antenatal intervention: Ultrasound-guided Fetal Vesicoamniotic Shunting (Harrison catheter) or fetal cystoscopy/valve ablation in select cases with oligohydramnios and preserved fetal renal cortical function.
4. Risk of CKD: $25–35\mathrm{\%}$ of affected children progress to ESRD by adolescence/young adulthood despite successful valve ablation (due to congenital renal dysplasia and "valve bladder" syndrome).
5. Surgical procedures:
   • Primary endoscopic transurethral Valve Ablation / Fulguration (treatment of choice)
   • Cutaneous Vesicostomy (in small preterms $<2\text{ kg}$ where scope cannot be negotiated)
   • High diverting ureterostomy / pyelostomy (for persistent severe upper tract obstruction).

1. Microangiopathic Hemolytic Anemia (MAHA): Fragmented red blood cells (Schistocytes, helmet cells, burr cells, microspherocytes), polychromasia, and thrombocytopenia with reduced large platelets.
2. Differential diagnoses: Hemolytic Uremic Syndrome (HUS) and Renal Vein Thrombosis (RVT).
3. Diagnostic modality: Renal Doppler Ultrasonography (demonstrates absent flow in renal vein in RVT; intact flow in HUS).
4. Streptococcus pneumoniae-associated HUS (SP-HUS / Neuraminidase-induced HUS): Bacterial neuraminidase cleaves sialic acid from RBC/platelet/glomerular membranes, exposing the hidden Thomsen-Friedenreich (T) antigen. Transfusion of plasma (FFP) containing normal donor anti-T IgM antibodies triggers massive complement-mediated hemolysis and worsening renal failure.
5. Indications for corticosteroids: Not indicated in typical STEC-D+ HUS; used only in atypical HUS associated with autoimmune diseases (SLE, secondary vasculitis).
6. Other MAHA conditions: Thrombotic Thrombocytopenic Purpura (TTP), Disseminated Intravascular Coagulation (DIC), Malignant hypertension, Systemic sclerosis (renal crisis).

1. Granulomatosis with Polyangiitis (GPA / Wegener's Granulomatosis).
2. Serological marker: c-ANCA (Cytoplasmic antineutrophil cytoplasmic antibody) / Anti-Proteinase 3 (Anti-PR3) antibodies (positive in $>90\mathrm{\%}$).
3. Induction treatment options:
   • IV Pulse Methylprednisolone followed by oral Prednisolone PLUS Rituximab (Anti-CD20 monoclonal antibody) OR
   • High-dose Corticosteroids PLUS IV / Oral Cyclophosphamide
   • Therapeutic Plasma Exchange (Plasmapheresis) in severe rapidly progressive crescentic glomerulonephritis or diffuse alveolar hemorrhage.
4. Other ANCA-associated vasculitides:
   • Microscopic Polyangiitis (MPA - p-ANCA / anti-MPO)
   • Eosinophilic Granulomatosis with Polyangiitis (EGPA / Churg-Strauss syndrome).

1. Neonatal Renal Vein Thrombosis (RVT) (precipitated by polycythemia, hyperviscosity, dehydration, and infant of diabetic mother status).
2. Differential diagnoses:
   • Congenital hydronephrosis / PUV
   • Autosomal Recessive Polycystic Kidney Disease (ARPKD)
   • Bilateral Wilms' tumor / Congenital mesoblastic nephroma
   • Hemolytic Uremic Syndrome (HUS).
3. Diagnostic modality: Renal Color Doppler Ultrasonography (demonstrates absence of venous Doppler signal in main renal vein, reversal of diastolic arterial flow, and enlarged echogenic kidney).
4. Management:
   • Aggressive correction of dehydration, electrolyte imbalance, and partial exchange transfusion if hematocrit $>65–70\mathrm{\%}$.
   • Systemic anticoagulation with Low-Molecular-Weight Heparin (LMWH - Enoxaparin) or unfractionated heparin (for bilateral RVT or extension into IVC).
   • Thrombolysis (rTPA) reserved for bilateral occlusion with acute anuric renal failure.
5. Long-term complications: Renal parenchymal atrophy / scarring, chronic hypertension, renal tubular dysfunction, and CKD.

1. 24-hour Urinary Calcium (or Spot Urine Calcium-to-Creatinine ratio) and Urinary Chloride.
2. Why: To differentiate Gitelman syndrome (Hypocalciuria, Urine $\text{Ca/Cr}<0.1\text{ mg/mg}$) from Bartter syndrome (Hypercalciuria, Urine $\text{Ca/Cr}>0.2\text{ mg/mg}$) and surreptitious diuretic abuse.
3. Causes of hypokalemic metabolic alkalosis with normal BP:
   • Gitelman syndrome
   • Bartter syndrome
   • Surreptitious vomiting / bulimia (low urine chloride $<10\text{ mEq/L}$)
   • Thiazide or loop diuretic abuse.
4. Diagnosis: Gitelman Syndrome (autosomal recessive mutation in SLC12A3 encoding the thiazide-sensitive ${\text{Na}}^{+}{\text{-Cl}}^{-}$ cotransporter in the DCT).
5. Treatment:
   • Oral Potassium chloride supplementation
   • Oral Magnesium salts (Magnesium chloride / pidolate)
   • Potassium-sparing diuretics (Spironolactone, Amiloride, or Eplerenone) $\pm$ NSAIDs (Indomethacin).
6. Plasma Renin and Aldosterone: Elevated (Secondary hyperreninemic hyperaldosteronism).
7. Urinary calcium excretion: Markedly Low (Hypocalciuria).

• Image A: Intravenous Urogram (IVU / IVP) showing Pelviureteric Junction (PUJ) Obstruction (marked hydronephrosis with abrupt cutoff at PUJ).
• Image B: Excretory Urogram showing "Cobra-head" / "Spring-onion" sign characteristic of an intravesical Ureterocele.
• Image C: ${}^{99\text{m}}\text{Tc}$-DMSA cortical renal scintigraphy showing a Horseshoe Kidney (fusion of lower poles across midline).
• Image D: Micturating Cystourethrogram (MCU) demonstrating High-Grade (Grade IV/V) Vesicoureteral Reflux (VUR) with tortuous, dilated ureters and blunted calyces.

1. Partially Compensated Metabolic Alkalosis with hypoxemia absent.
2. Expected respiratory compensation in metabolic alkalosis:
   $\text{Expected }pC{O}_2=40+0.7\times (\text{Actual }HC{O}_3^{-}-24)\pm 2$
   $\text{Expected }pC{O}_2=40+0.7\times (37-24)=40+9.1=49.1\text{ mmHg}$
   Since actual $pC{O}_2$ is 46 mmHg, appropriate respiratory compensation is present.
3. Diagnosis: Gitelman Syndrome.
4. Molecular defect: Inactivating mutation in the SLC12A3 gene on chromosome 16q13 encoding the Thiazide-sensitive ${\text{Na}}^{+}{\text{-Cl}}^{-}$ Cotransporter (NCCT) in the distal convoluted tubule.
5. Associated metabolic abnormalities:
   • Severe Hypokalemia
   • Severe Hypomagnesemia
   • Hypocalciuria (decreased urinary calcium excretion)
   • Secondary hyperreninemic hyperaldosteronism with normal/low blood pressure.

1. Etiologies: Cerebral Salt Wasting (CSW) vs Syndrome of Inappropriate ADH Secretion (SIADH).
2. Differentiating features:

Feature	SIADH	Cerebral Salt Wasting (CSW)
Volume Status	Euvolemic / Hypervolemic	Hypovolemic (Dehydrated)
Urine Output	Normal or Decreased	Profuse Polyuria
Urine Sodium	Elevated ($>20–40\text{ mEq/L}$)	Massively Elevated ($>100–150\text{ mEq/L}$)
Central Venous Pressure (CVP)	Normal / High ($>6–10{\text{ cm H}}_2\text{O}$)	Low ($<5{\text{ cm H}}_2\text{O}$)
Serum Uric Acid / Urea	Low / Diluted	Normal or High (prerenal azotemia)

3. Management:
   • CSW: Volume and sodium replacement using Normal Saline (0.9% NaCl) or 3% Hypertonic Saline plus oral Fludrocortisone ($0.1–0.4\text{ mg/day}$) to enhance renal sodium retention. (Fluid restriction is dangerous and contraindicated in CSW).
   • SIADH: Fluid restriction ($50–70\mathrm{\%}$ of maintenance). Hypertonic (3%) saline reserved only for acute symptomatic seizures.

• 1. ${}^{99\text{m}}\text{Tc}$-DMSA Scan $\to$ a. Detection of renal parenchymal scarring / acute pyelonephritis
• 2. Plain Abdominal X-ray (KUB) $\to$ d. Radiopaque calcium oxalate/phosphate stones
• 3. Micturating Cystourethrogram (MCU) $\to$ e. Vesicoureteral Reflux (VUR) grading and PUV
• 4. Renal Doppler USG $\to$ f. Renal artery / vein thrombosis and stenosis
• 5. Intravenous Urogram (IVU) $\to$ c. Horseshoe kidney / anatomical duplication
• 6. ${}^{99\text{m}}\text{Tc}$-MAG3 Renogram $\to$ b. Pelviureteric junction (PUJ) obstruction and GFR drainage kinetics

1. ${}^{99\text{m}}\text{Tc}$-MAG3 (Mercaptoacetyltriglycine) Diuretic Dynamic Renogram (Furosemide renogram).
2. Clinical applications:
   • Differentiating mechanical anatomical obstruction from non-obstructive hydronephrosis
   • Evaluation of Pelviureteric Junction (PUJ) obstruction and Vesicoureteric Junction (VUJ) obstruction
   • Measurement of differential (split) renal function and drainage half-time ($T_{1/2}$).
3. Three phases of normal renogram curve:
   • Phase 1 (Vascular / Transit Phase): Rapid initial upstroke (first 30–60 seconds) representing initial arrival and vascular perfusion of tracer.
   • Phase 2 (Parenchymal / Secretory Phase): Gradual upward curve (peaking at 3–5 minutes) reflecting active tubular extraction of tracer from blood.
   • Phase 3 (Elimination / Excretory Phase): Rapid downward descent as tracer washes out of the pelvicalyceal system into the bladder ($T_{1/2}<10\text{ minutes}$).
4. Interpretation in this child: The left kidney shows a continuous rising curve with failure of clearance after Furosemide ($T_{1/2}>20\text{ minutes}$), diagnostic of Left Pelviureteric Junction (PUJ) Mechanical Obstruction.

• 1 $\to$ b. Testicular Torsion (Urological emergency requiring immediate surgical exploration and detorsion within 6 hours).
• 2 $\to$ c. Henoch-Schönlein Purpura (HSP / IgA Vasculitis) (Scrotal vasculitis).
• 3 $\to$ a. Epididymo-orchitis (Bacterial or viral infection treated with targeted antibiotics).

1. ${}^{99\text{m}}\text{Tc}$-DMSA (Dimercaptosuccinic Acid) Static Renal Cortical Scintigraphy.
2. Ectopic Right Kidney (Pelvic Kidney) with normal left orthotopic kidney.
3. Time interval: 2 to 4 hours post-intravenous injection (to allow fixed cortical tubular binding and clearance of background tracer).
4. Indications:
   • Detection of Renal Cortical Scarring secondary to recurrent pyelonephritis / VUR (gold standard)
   • Diagnosis of Acute Pyelonephritis (focal/multifocal photopenic areas of reduced uptake)
   • Accurate measurement of Differential / Split Renal Function
   • Detection of congenital anomalies: Ectopic kidney, Horseshoe kidney, Dysplastic kidney, or Single functioning kidney.

1. ${}^{99\text{m}}\text{Tc}$-DTPA (Diethylenetriaminepentaacetic Acid) Dynamic Renal Scintigraphy (Gates method).
2. Functional parameters obtained:
   • Glomerular Filtration Rate (GFR) measurement (purely filtered by glomerulus without tubular secretion or reabsorption)
   • Renal Perfusion / Blood Flow kinetics
   • Differential (Split) Renal Function
   • Upper urinary tract drainage and clearance dynamics.
3. Timing of imaging: Immediate continuous dynamic sequential imaging starts concurrently with the IV bolus injection (0–60 seconds for perfusion, up to 20–30 minutes for excretion).
4. Indications:
   • Quantitative evaluation of individual and global GFR in CKD / acute kidney injury
   • Evaluation of hydronephrosis and urinary tract obstruction
   • Assessment of renal allograft function and detection of acute tubular necrosis vs graft rejection
   • Captopril renography for screening Renovascular Hypertension (Renal Artery Stenosis).