Aetiology

The differential diagnosis of metabolic alkalosis divides patients into those that have volume depletion (also called chloride-responsive metabolic alkalosis) and those that do not have volume depletion (also called chloride-resistant metabolic alkalosis).

Chloride-resistant metabolic alkalosis

With hypertension:[2][4][5][6][7]​​​

  • Primary hyperaldosteronism

  • Secondary hyperaldosteronism, for example, renin-producing tumour

  • Renal artery stenosis

  • Cushing's syndrome

  • Liquorice ingestion

  • Tobacco chewing

  • Apparent mineralocorticoid excess

  • Liddle's syndrome: autosomal-dominant inheritance, early onset hypertension, hypokalaemic metabolic alkalosis, low plasma renin activity, and suppressed aldosterone secretion.[4]

No hypertension:[8][9][10][11][12][13]

  • Bartter's syndrome: autosomal-recessive inheritance, hypokalaemic metabolic alkalosis, raised plasma renin activity and hyperaldosteronism, normal blood pressure (BP), deranged prostaglandin metabolism, and increased urinary chloride excretion

  • Gitelman's syndrome:  autosomal-recessive inheritance, hypokalaemic metabolic alkalosis, hypocalciuria, and hypomagnesaemia

  • Current loop or thiazide diuretic therapy

  • Profound potassium depletion

  • Hypercalcaemia of non-hyperparathyroid aetiology

  • Post-starvation refeeding syndrome

  • Transfusion of blood products (sodium citrate).

Chloride-responsive metabolic alkalosis

Gastrointestinal causes:[2][5]​​[14]​​[15][16]

  • Vomiting

  • Gastric drainage

  • Villous adenoma of colon (usually leads to normal anion gap metabolic acidosis; however, some of these tumors secrete chloride, leading to metabolic alkalosis)

  • Congenital chloride diarrhoea (rare congenital syndrome due to a defect in large bowel chloride absorption, which leads to chronic diarrhoea with stool fluid rich in chloride)

  • Cystic fibrosis.

Renal causes:[2][5]

  • Post-diuretic therapy

  • Post-hypercapnia.

Exogenous alkali intake:[2][5][17]

  • Bicarbonate administration

  • Milk-alkali syndrome.

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