What causes vomiting in a child with Chronic Kidney Disease (CKD)?

Causes of Vomiting in Children with CKD

Vomiting in children with CKD is primarily caused by chronic intravascular volume depletion from sodium and water losses (in polyuric salt-wasting forms), uremic toxin accumulation, electrolyte disturbances, and metabolic acidosis. 1

Primary CKD-Related Causes

Volume Depletion and Sodium Imbalance

• Infants and children with polyuric salt-wasting forms of CKD (especially obstructive uropathy or renal dysplasia) experience vomiting, constipation, and significant growth retardation associated with chronic intravascular volume depletion and negative sodium balance. 1
• This occurs because these children have polyuria, polydipsia, and difficulty conserving sodium chloride, developing a salt-wasting state that requires supplementation. 1
• Normal serum sodium levels do not rule out sodium depletion and the need for supplementation. 1

Uremic Toxin Accumulation

• Uremic toxins accumulate as kidney function declines, leading to nausea and vomiting that may necessitate dialysis initiation. 2, 3
• The production of uremic toxins in CKD patients leads to secretion of proinflammatory cytokines into circulation, contributing to gastrointestinal symptoms. 2
• Refractory periodic vomiting in CKD children may be related to impaired kidney function from congenital anomalies causing uremic toxin buildup. 2

Electrolyte and Acid-Base Disturbances

• Hyperkalemia can develop with GFR below 10-20 mL/min, particularly with medications (ACE inhibitors, ARBs, NSAIDs, aldosterone antagonists), constipation, prolonged fasting, or metabolic acidosis. 4
• Metabolic acidosis (bicarbonate 16-20 mEq/L) is common with GFR below 20 mL/min and contributes to gastrointestinal symptoms. 4
• Hyponatremia from water overload or hypernatremia from inadequate water intake during intercurrent illness can trigger vomiting. 4

Secondary and Medication-Related Causes

Immunosuppressive Medications (Post-Transplant)

• Food-borne illness causing diarrhea and vomiting may lead to dehydration and interfere with absorption of immunosuppressive medications in transplanted children. 1
• Gastric acidity inhibitors given after transplantation increase risk of intestinal infections that manifest with vomiting. 1

Medication Side Effects

• Immunosuppressive agents can cause gastrointestinal side effects including nausea and vomiting in the early post-transplant period. 1

Differential Diagnosis Considerations

Life-Threatening Causes to Exclude

• In infants: congenital intestinal obstruction, malrotation with volvulus, pyloric stenosis, intussusception, hydrocephalus, inborn errors of metabolism, congenital adrenal hypoplasia, obstructive uropathy, sepsis, meningitis. 5
• In older children: appendicitis, intracranial mass lesion, diabetic ketoacidosis, toxic ingestions, uremia, meningitis. 5

Red Flag Signs Requiring Urgent Evaluation

• Bilious or bloody vomiting, altered sensorium, toxic/septic appearance, inconsolable cry, severe dehydration, severe wasting, bent-over posture. 5

Clinical Approach Algorithm

Step 1: Assess Volume Status and Sodium Balance

• Evaluate for polyuria and salt-wasting (common in obstructive uropathy/renal dysplasia). 1
• Check serum sodium, but remember normal levels don't exclude depletion. 1
• If polyuric salt-wasting: supplement with 2-4 mmol sodium/100 mL formula or 1-5 mmol Na/kg/day. 1

Step 2: Evaluate Kidney Function and Uremic Status

• Check GFR/creatinine to assess degree of kidney dysfunction. 2
• Consider uremic toxin accumulation if GFR <15-20 mL/min. 4, 2
• Evaluate need for dialysis initiation if uremic symptoms are refractory. 3

Step 3: Check Electrolytes and Acid-Base Status

• Measure potassium, bicarbonate, and other electrolytes. 4
• Correct hyperkalemia if present (dietary restriction, resins, or dialysis). 4
• Treat metabolic acidosis with sodium bicarbonate 0.5-1 mEq/kg/day targeting bicarbonate 22-24 mmol/L. 4

Step 4: Consider Medication Effects

• Review all medications for those causing hyperkalemia (ACE-I, ARBs, NSAIDs, aldosterone antagonists). 4
• In post-transplant patients, assess immunosuppressive medication side effects and food-borne illness risk. 1

Step 5: Exclude Other Organic Causes

• Rule out surgical emergencies and life-threatening conditions based on age and presentation. 5
• Consider cyclic vomiting syndrome if recurrent episodes with symptom-free intervals. 6

Common Pitfalls to Avoid

• Assuming normal serum sodium excludes sodium depletion in polyuric CKD children—supplementation may still be needed. 1
• Failing to recognize that the most common causes of pediatric CKD (obstructive uropathy, renal dysplasia) are salt-wasting conditions requiring sodium supplementation, not restriction. 1
• Overlooking uremic toxin accumulation as a cause when GFR approaches 10-15 mL/min. 4, 2
• Not checking medications that worsen hyperkalemia, which can contribute to vomiting. 4
• Missing food-borne illness in immunosuppressed post-transplant patients. 1