Lab Case 94 – Interpretation

Young female with generalised weakness and lethargy1. 5 abnormalities:

pH 7.56 – alkalaemia

high HCO3 – primary metabolic

high CO2 – respiratory compensation

severe hypokalaemia

1of – hyponatraemia, elevated lactate, hypochloraemia

  1. Interpretation

hypokalaemic, hypochloraemic, hyponatraemic primary metabolic alkalosis with appropriate respiratory compensation which classically occurs with renal tubular acidosis/ Barterr’s syndrome (or the variant, which is Gitelman’s syndrome). In an infant or the elderly you must consider gastric outlet obstruction.

  1. DDx:

RTA – Gitelman’s syndrome

Pyloric stenosis/ gastric outlet obstruction

Diuretic abuse – especially thiazides

cyclical vomiting

mineralocorticoid excess

  1. Cause of death – hypokalaemia

Gitelman’s:

Renal salt wasting disorder with urinary loss of Na/ K/ Cl and lack of Cl reabsorption.

Reduced Cl reabsorption leads to reduced Na reabsorption with causes an increase in solute load to the distal tubules.

Increase Na and water loss causes increased renin–>increased ACEII–> increased renal vasoconstriction and increased proximal Na reabsorption which prevents systemic BP abnormalities

high aldosterone causes increased H/K exchange for Na

Both Barterr’s and Gitelman’s are ion chanellopathies in the thick ascending loop of henle or DCT. Mutation is in the NCCT gene.

Complications include failure to thrive, short staure, sensorineural defects in paediatrics and electrolyte abnormalities can cause arrhythmias (sudden death), weakness, lethargy, renal stones.

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