How should a 50‑year‑old patient with severe hyponatraemia (serum sodium 121 mmol/L) and hyperkalaemia (serum potassium 5.5 mmol/L) presenting with a urinary tract infection and obstructive ureteric calculi be managed?

Management of Severe Hyponatremia and Hyperkalemia in Obstructive Ureteric Calculi with UTI

This patient requires immediate urinary tract decompression via percutaneous nephrostomy or ureteral stenting, followed by urgent treatment of hyperkalemia with IV calcium and insulin/glucose, while addressing hyponatremia cautiously to avoid overcorrection.

Immediate Priorities (First Hour)

1. Urgent Urinary Decompression

• Perform immediate decompression via percutaneous nephrostomy or ureteral stenting for the obstructed kidney with UTI, as this is the primary driver of the electrolyte abnormalities 1.
• Collect urine for culture and antibiogram testing before and after decompression 1.
• Start broad-spectrum antibiotics immediately, adjusting based on culture results 1.
• The obstructive uropathy combined with UTI is likely causing secondary pseudohypoaldosteronism, explaining both the hyponatremia and hyperkalemia 2, 3.

2. Hyperkalemia Management (K+ 5.5 mmol/L)

• Administer IV calcium gluconate 10 mL of 10% solution to stabilize cardiac membranes within 1-3 minutes 1.
• Obtain immediate ECG to assess for hyperkalemia-related changes (peaked T waves, widened QRS) 1, 4.
• Give IV insulin 10 units with 50 mL dextrose to shift potassium intracellularly within 30-60 minutes 1.
• Consider nebulized salbutamol 20 mg in 4 mL to augment intracellular potassium shift 1.
• Monitor glucose closely to prevent hypoglycemia from insulin therapy 1.

3. Hyponatremia Assessment (Na+ 121 mmol/L)

• Assess symptom severity: look specifically for confusion, seizures, altered consciousness, or severe headache 5, 6.
• This is moderate hyponatremia (125-129 mmol/L range) bordering on severe (<125 mmol/L) 5.
• Determine volume status: likely hypovolemic given UTI, obstruction, and probable poor oral intake 5, 6.

Hyponatremia Treatment Strategy

If Severely Symptomatic (seizures, coma, obtundation)

• Give 100-150 mL bolus of 3% hypertonic saline to increase sodium by 4-6 mEq/L within 1-2 hours 6, 7, 8.
• Do not exceed 10 mEq/L correction in first 24 hours to avoid osmotic demyelination syndrome 6, 7, 9.
• Recheck sodium every 2-4 hours during active correction 6, 8.

If Mildly Symptomatic or Asymptomatic

• Administer normal saline (0.9% NaCl) for hypovolemic hyponatremia, which is most likely given the clinical context 5, 6.
• Correct underlying cause (relief of obstruction will resolve the secondary pseudohypoaldosteronism) 2, 3.
• Monitor sodium every 4-6 hours initially 8.
• Target correction rate of 6-8 mEq/L per 24 hours, not exceeding 10 mEq/L 6, 7, 9.

Critical Monitoring Parameters

First 24 Hours

• Serum sodium every 2-4 hours during active correction to prevent overcorrection 8, 9.
• Serum potassium every 2-4 hours until stable below 5.5 mmol/L 1.
• Continuous cardiac monitoring for hyperkalemia-related arrhythmias 1, 4.
• Blood glucose monitoring every 1-2 hours after insulin administration 1.
• Urine output monitoring (should improve after decompression) 1.

Ongoing Management

• Definitive stone treatment should be delayed until sepsis resolves and electrolytes stabilize 1.
• Re-evaluate antibiotic regimen based on culture results 1.
• The electrolyte abnormalities should resolve once obstruction is relieved and infection treated, as the mechanism is transient aldosterone resistance from severe pyelonephritis 2, 3.

Common Pitfalls to Avoid

• Do not correct sodium too rapidly: overcorrection beyond 10 mEq/L in 24 hours risks osmotic demyelination syndrome, which can cause irreversible neurological damage 6, 7, 9.
• Do not delay urinary decompression: the obstruction with infection is the root cause and can rapidly progress to septic shock 1.
• Do not forget glucose with insulin: insulin without glucose causes severe hypoglycemia 1.
• Do not attempt stone removal acutely: definitive stone treatment must wait until infection clears 1.
• Have desmopressin available: if sodium rises too quickly, desmopressin can prevent further increase 8, 9.

Expected Clinical Course

Once the obstruction is relieved and infection treated, the secondary pseudohypoaldosteronism should resolve within days, with normalization of both sodium and potassium levels 2, 3. The severe renal inflammation causing transient aldosterone resistance will improve as the infection clears 2.