Below is a detailed paediatrics exam-oriented explanation of Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD). I organized it in a clear structured format used in paediatric nephrology notes and exams (MBBS / MD / DNB). No images included as requested.

Acute Kidney Injury (AKI) in Paediatrics

Definition

Acute Kidney Injury (AKI) is a sudden decline in kidney function occurring over hours to days, resulting in inability of the kidneys to maintain fluid, electrolyte, and acid–base balance, with accumulation of nitrogenous waste (urea and creatinine). ([Medscape eMedicine][1])

It is diagnosed mainly by rise in serum creatinine and/or decrease in urine output according to KDIGO criteria. ([Chikd][2])

Epidemiology

• Occurs in 5–10% of hospitalized children
• Up to 30% of children in PICU
• Neonates have highest risk. ([cps.ca][3])

Etiology / Causes

AKI in children is classified into three major categories:

1. Prerenal AKI (Most common)

Due to reduced renal perfusion

Examples

• Dehydration
• Shock
• Sepsis
• Severe burns
• Heart failure
• Hemorrhage
• Severe diarrhea

2. Intrinsic Renal AKI

Glomerular causes

• Acute glomerulonephritis
• Lupus nephritis

Tubular causes

• Acute tubular necrosis (ATN)
• Drugs (aminoglycosides, NSAIDs)
• Ischemia

Interstitial causes

• Acute interstitial nephritis
• Drugs (penicillin, sulfonamides)

Vascular causes

• Hemolytic uremic syndrome (HUS)
• Vasculitis

HUS is one of the most common intrinsic renal causes of AKI in children. ([infoKID][4])

3. Postrenal AKI

Due to urinary tract obstruction

Examples

• Posterior urethral valve
• Ureteric obstruction
• Kidney stones
• Tumors
• Neurogenic bladder

Pathophysiology

AKI involves three major mechanisms:

1. Reduced renal perfusion
2. Tubular cell injury
3. Obstruction of urine flow

Consequences:

• Reduced GFR
• Accumulation of urea and creatinine
• Fluid overload
• Electrolyte imbalance
• Metabolic acidosis

Stages of AKI (KDIGO)

Stage 1

• Creatinine ↑ ≥0.3 mg/dL

OR

• 1.5–1.9 × baseline

OR

• Urine output <0.5 ml/kg/hr for 6–12 hr

Stage 2

• Creatinine 2–2.9 × baseline

OR

• Urine output <0.5 ml/kg/hr for ≥12 hr

Stage 3

• Creatinine ≥3 × baseline

OR

• Creatinine ≥4 mg/dL

OR

• Dialysis required

Clinical Features

Symptoms depend on cause.

Early symptoms

• Reduced urine output (oliguria)
• Vomiting
• Poor feeding
• Lethargy
• Edema

Severe symptoms

• Hypertension
• Pulmonary edema
• Hyperkalemia
• Metabolic acidosis
• Seizures
• Encephalopathy

Investigations

Blood tests

• Serum creatinine
• Blood urea nitrogen
• Electrolytes (Na, K, bicarbonate)
• ABG
• CBC
• Complement levels

Urine tests

• Urinalysis
• Urine sodium
• Fractional excretion of sodium (FeNa)

Imaging

• Ultrasound kidney and bladder

Other tests

• Renal biopsy (if intrinsic disease suspected)

Complications

• Hyperkalemia
• Metabolic acidosis
• Fluid overload
• Hypertension
• Uremia
• CKD later in life

AKI can predispose children to future chronic kidney disease. ([PMC][5])

Management

1. Treat underlying cause

Examples:

• Rehydration for dehydration
• Antibiotics for sepsis
• Stop nephrotoxic drugs

2. Fluid management

Careful balance:

If hypovolemic:

• IV isotonic saline bolus

If fluid overloaded:

• Fluid restriction
• Diuretics (Furosemide)

Drug: Furosemide

Class: Loop diuretic

Mechanism

• Inhibits Na-K-2Cl transporter in loop of Henle

Dose

• 1–2 mg/kg IV or oral

Adverse effects

• Hypokalemia
• Dehydration
• Ototoxicity

3. Electrolyte correction

Hyperkalemia treatment

1. Calcium gluconate
2. Insulin + glucose
3. Sodium bicarbonate
4. Salbutamol
5. Dialysis if severe

4. Nutrition

• Restrict potassium
• Restrict phosphate
• Adequate calories

5. Dialysis (Renal Replacement Therapy)

Indications (AEIOU):

A — Acidosis

E — Electrolyte imbalance (hyperkalemia)

I — Intoxication

O — Overload (fluid)

U — Uremia

Types in children:

• Peritoneal dialysis
• Hemodialysis
• Continuous renal replacement therapy (CRRT)

Prognosis

Depends on:

• Cause
• Severity
• Early treatment

Most children recover kidney function, but some develop CKD later.

Chronic Kidney Disease (CKD) in Paediatrics

Definition

Chronic Kidney Disease (CKD) is irreversible kidney damage lasting ≥3 months with structural or functional abnormalities and reduced GFR.

Diagnostic criteria:

• GFR <60 ml/min/1.73 m² for ≥3 months

OR

• Evidence of kidney damage (proteinuria, structural abnormality)

Stages of CKD (based on GFR)

| Stage | GFR |

| ------- | ----------------------------- |

| Stage 1 | ≥90 |

| Stage 2 | 60–89 |

| Stage 3 | 30–59 |

| Stage 4 | 15–29 |

| Stage 5 | <15 (End stage renal disease) |

Causes of CKD in Children

Most common causes

1. Congenital anomalies of kidney and urinary tract (CAKUT)
2. Obstructive uropathy
3. Reflux nephropathy
4. Glomerulonephritis
5. Hemolytic uremic syndrome
6. Polycystic kidney disease
7. Hereditary nephropathies (Alport syndrome)

Pathophysiology

Progressive loss of nephrons leads to:

• Reduced GFR
• Hyperfiltration injury
• Proteinuria
• Tubulointerstitial fibrosis

Consequences:

• Fluid retention
• Electrolyte imbalance
• Hormonal abnormalities

Clinical Features

Early features

• Growth failure
• Polyuria
• Polydipsia
• Anemia

Late features

• Edema
• Hypertension
• Bone disease
• Uremic symptoms

Complications

Major complications:

1. Growth retardation
2. Anemia
3. Renal osteodystrophy
4. Hypertension
5. Electrolyte imbalance
6. Cardiovascular disease

Investigations

Blood

• Serum creatinine
• Urea
• Electrolytes
• Calcium
• Phosphate
• Parathyroid hormone
• Hemoglobin

Urine

• Proteinuria
• Albumin/creatinine ratio

Imaging

• Ultrasound kidney

Others

• Renal biopsy

Management

1. Treat underlying cause

Examples

• Control infection
• Relieve obstruction
• Immunosuppressive therapy for GN

2. Blood pressure control

Drug: Enalapril

Class: ACE inhibitor

Mechanism

• Blocks angiotensin II formation
• Reduces intraglomerular pressure
• Decreases proteinuria

Dose

• 0.1–0.5 mg/kg/day

Adverse effects

• Hyperkalemia
• Hypotension
• Dry cough

3. Anemia management

Drug: Erythropoietin

Mechanism

• Stimulates RBC production

Dose

• 50–100 IU/kg SC 3 times/week

Adverse effects

• Hypertension
• Thrombosis

4. Mineral bone disease management

Drugs

• Calcium carbonate
• Vitamin D (calcitriol)
• Phosphate binders

5. Nutrition

• High calorie diet
• Controlled protein
• Potassium restriction

6. Growth therapy

Recombinant growth hormone

Indication

• Growth failure in CKD

7. Renal replacement therapy

When GFR <15:

Options

• Peritoneal dialysis
• Hemodialysis
• Kidney transplantation (definitive treatment)

Differences Between AKI and CKD (Exam Table)

| Feature | AKI | CKD |

| ------------- | -------------------- | ------------ |

| Onset | Sudden | Gradual |

| Duration | Days–weeks | >3 months |

| Kidney size | Normal | Small |

| Anemia | Usually absent early | Common |

| Bone disease | Absent | Present |

| Reversibility | Often reversible | Irreversible |

If you want, I can also give very important paediatric exam points, MCQs, clinical case questions, or AKI vs CKD flowcharts for quick revision.

[1]: https://emedicine.medscape.com/article/243492-overview?utm_source=chatgpt.com "Acute Kidney Injury (AKI): Practice Essentials, Background, ..."

[2]: https://www.chikd.org/journal/view.php?id=10.3339%2Fjkspn.2020.24.1.19&utm_source=chatgpt.com "Pediatric Acute Kidney Injury: Focusing on Diagnosis and ..."

[3]: https://cps.ca/en/documents/position/acute-kidney-injury?utm_source=chatgpt.com "Recognition and management of acute kidney injury in ..."

[4]: https://infokid.org.uk/conditions/acute-kidney-injury/causes-of-acute-kidney-injury-aki/?utm_source=chatgpt.com "Causes of Acute Kidney Injury (AKI)"

[5]: https://pmc.ncbi.nlm.nih.gov/articles/PMC12337562/?utm_source=chatgpt.com "From acute kidney injury to chronic kidney disease in children"