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An Unusual Case of Metabolic Alkalosis

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eMediNexus    19 September 2020

The Case

A case of an 80-year-old woman who presented with chronic metabolic alkalosis and hypokalemia secondary to exogenous alkali exposure from baking soda as a toothpaste additive.

History

The patient had a past medical history of long-standing hypertension leading to chronic kidney disease stage G3bA1 (baseline serum creatinine 1.4-1.78 mg/dL [123.7-157.35 µmol/L], eGFR 33-45 mL/min), hyperlipidemia, atrial fibrillation and gastroesophageal reflux disease.

She was referred to Nephrology clinic by her primary care provider for assessment of chronic metabolic alkalosis. Initially, patient informed about her decreased appetite and poor oral intake with resultant 5-pound weight loss over a period of 6 weeks. She denied any nausea, vomiting or diarrhoea. Her medications included metoprolol 50 mg twice daily, pravastatin 10 mg daily, pantoprazole 40 mg daily, rivaroxaban 15 mg daily and calcium carbonate 600 mg daily. She denied taking any additional medications.

Physical Examination

The patient had a body mass index (BMI) of 17.2 kg/m2, blood pressure of 160/80 mmHg and heart rate of 80 beats/minute.

She was clinically euvolemic on examination, especially when there was no peripheral edema.

Laboratory Examination

Notably, her serum bicarbonate was elevated to 44 mmol/L, urinalysis was unremarkable, with no proteinuria or active urine sediment, and urine pH of 6.0, which was somewhat lower than expected for her degree of metabolic alkalosis. Spot urine electrolytes revealed urine sodium of 41 mmol/L (fractional excretion of 0.3%), potassium 13.0 mmol/L (fractional excretion of 3.87%) and chloride 48 mmol/L (fractional excretion of 0.5%), with a urine creatinine of 128 mg/dL.

Her urine chloride level was >20 mmol/L.

Radiological Investigation

A computed tomography (CT) scan of her abdomen was obtained and showed normal-appearing adrenal glands. Further, renal vascular ultrasound was unremarkable with no evidence of renal artery stenosis.

Questions

  1. How would you assess and diagnose the patient?
  2. What will be your treatment strategy?

Read the full case report here:

Cervantes CE, Menez S, Jaar BG, et al. An unusual cause of metabolic alkalosis: hiding in plain sight. BMC Nephrol. 2020;21:296. https://doi.org/10.1186/s12882-020-01967-7

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