Bartter's syndrome  (characterised by hypokalaemia, normotension, and elevated renin and aldosterone levels.)

a rare form of renal potassium wasting

primary defect is in chloride reabsorption in the ascending limb, leading to NaCl excessively presented to the distal tubule, with sodium reabsorption in exchange for potassium, resulting in urinary sodium wasting.

occasionally autosomal recessive.

Severe hyper-reninaema with consequent hyperaldosteronism.(characterised by hypokalaemia, normotension, and elevated renin and aldosterone levels.)

BP low or normal

There is secondary stimulation of prostaglandin synthesis, which activates the renin angiotensin aldosterone system which exacerbates the renal potassium wasting.

- Growth failure

- muscle weakness

- constipation

- polyuria and

- dehydration

are typical in younger children; with

- muscle weakness

- cramps or

- carpopedal spasms

present in older children.

The potassium is <2.5mmol/L, there is metabolic alkalosis, and hyperammonaemia with hyperaldosteronism.

There are high levels of urinary potassium and chloride.

The high urinary chloride level is helpful in distinguishing it from similar presentations which have low urinary chloride levels, such as

- liquorice, laxative, or diuretic use

- persistent vomiting or diarrhoea

- pyelonephritis, or

- diabetes insipidus.

Oral potassium and indomethacin may be used.