Bartter, Liddle, and Conn Syndromes

Bartter, Liddle, and Conn Syndromes

A practical comparison of salt-handling disorders causing metabolic alkalosis

Disorders of renal sodium handling are frequently tested and clinically relevant because they present with characteristic patterns of blood pressure, electrolytes, and hormonal changes. Bartter syndrome, Liddle syndrome, and Conn syndrome all cause metabolic alkalosis but differ fundamentally in their mechanisms and clinical profiles.

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Bartter Syndrome

Salt-wasting disorder mimicking chronic loop diuretic use

Bartter syndrome is a hereditary defect of ion transport in the thick ascending limb of the loop of Henle, most commonly involving the Na–K–2Cl cotransporter (NKCC2) or related channels.

Pathophysiology

Impaired sodium reabsorption in the loop of Henle

Renal sodium loss → extracellular volume depletion

Secondary activation of RAAS

Increased distal sodium delivery → potassium and hydrogen ion loss

Key Biochemical Changes

Increased

Renin

Aldosterone

Decreased

Sodium

Blood volume

Potassium

Clinical Features

Normal or low blood pressure (no hypertension despite high aldosterone)

Polyuria, polydipsia

Growth retardation (pediatric cases)

Metabolic alkalosis

Core Concept

> High renin, high aldosterone, no hypertension

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Liddle Syndrome

Pseudohyperaldosteronism

Liddle syndrome is a rare genetic disorder caused by constitutive activation of the epithelial sodium channel (ENaC) in the collecting duct.

Pathophysiology

Excessive sodium reabsorption independent of aldosterone

Volume expansion → suppression of RAAS

Increased potassium and hydrogen ion secretion

Key Biochemical Changes

Increased

Sodium

Blood volume

Blood pressure

Decreased

Renin

Aldosterone

Potassium

Clinical Features

Early-onset hypertension

Hypokalemia

Metabolic alkalosis

Poor response to spironolactone

Treatment Principle

ENaC blockers: amiloride or triamterene

Core Concept

> Hypertension without aldosterone

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Conn Syndrome (Primary Hyperaldosteronism)

True aldosterone excess

Conn syndrome is caused by autonomous aldosterone secretion, usually from an adrenal adenoma or bilateral adrenal hyperplasia.

Pathophysiology

Excess aldosterone → increased sodium reabsorption

Volume expansion → suppressed renin

Increased potassium and hydrogen ion excretion

Key Biochemical Changes

Increased

Sodium

Blood volume

Blood pressure

Aldosterone

Decreased

Renin

Potassium

Clinical Features

Resistant hypertension

Hypokalemia (may be mild or absent)

Metabolic alkalosis

Diagnostic Clue

High aldosterone-to-renin ratio

Core Concept

> Hypertension due to high aldosterone

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Side-by-Side Summary

Feature Bartter Liddle Conn

Primary defect NKCC2 / loop transport ENaC overactivity Aldosterone excess

Blood pressure Normal / low High High

Renin ↑ ↓ ↓

Aldosterone ↑ ↓ ↑

Potassium ↓ ↓ ↓

Acid–base status Metabolic alkalosis Metabolic alkalosis Metabolic alkalosis

Key clue Salt wasting, no HTN HTN without aldosterone HTN with high aldosterone

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Exam Pearls

Bartter = diuretics effect + no hypertension

Liddle = low renin, low aldosterone, hypertension

Conn = low renin, high aldosterone, hypertension

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