A breast fed child presents with hypernatremia (Serum sodium> 170 mg/dL). His urine sodium is 70 mg/dL. Most probable cause in this patient is
A. Diabetes insipidusB. Acute necrosis
C. Severe dehydration
D. Excessive intake of sodium
Ans. D. (Excessive intake of sodium)
1. Hypernatremia due to excess sodium: (e.g., intake of sodium as oral or IV, Hyperaldosteronism, etc).
• In excess sodium intake there will be hypenatremia with raised urinary sodium. But breast-feeding child can not have hypernatremic unless given improperly mixed formula, excess NaHCO3, ingestion of sea water, etc.
2. Hypernatremia due to water deficit: (child with renal water loss, e.g., Diabetes insipidus) Diabetes insipidus: The diagnosis is suggestive in a male infant with polyuria, hypernatremia, and diluted urine (urine Na <20 mg/dL).
3. Hypernatremia due to combined sodium and water deficits: Analysis of the urine differentiates renal and non-renal etiologies.
• When the losses are extra-renal (e.g., from gut and cutaneous losses), the kidney responds to volume depletion with low urine volume, a concentrated urine, and sodium retention (urinary sodium <20 mg/dL) (Therefore severe dehydration can not be an Answer).
•
With renal causes (e.g., Diabetes mellitus, osmotic diuresis, polyuric phase
ofATN, etc), the urine volume is not appropriately low, the urine is not
maximally concentrated, and the urine sodium may be inappropriately elevated. 1. Hypernatremia due to excess sodium: (e.g., intake of sodium as oral or IV, Hyperaldosteronism, etc).
• In excess sodium intake there will be hypenatremia with raised urinary sodium. But breast-feeding child can not have hypernatremic unless given improperly mixed formula, excess NaHCO3, ingestion of sea water, etc.
2. Hypernatremia due to water deficit: (child with renal water loss, e.g., Diabetes insipidus) Diabetes insipidus: The diagnosis is suggestive in a male infant with polyuria, hypernatremia, and diluted urine (urine Na <20 mg/dL).
3. Hypernatremia due to combined sodium and water deficits: Analysis of the urine differentiates renal and non-renal etiologies.
• When the losses are extra-renal (e.g., from gut and cutaneous losses), the kidney responds to volume depletion with low urine volume, a concentrated urine, and sodium retention (urinary sodium <20 mg/dL) (Therefore severe dehydration can not be an Answer).
• Therefore Answer is excessive intake of sodium.
• Acute tubular necrosis could have been answer but child did not have any problem suggesting ATN.. Remember polyuric phase of ATN can also present as hyponatremia.
