Cardiac asthma, renal asthma and uremic lung

 Cardiac asthma

Cardiac asthma is wheezing, cough, and breathlessness caused by left heart failure, especially acute LV failure, rather than primary bronchial asthma.

Mechanism

Left ventricular dysfunction → ↑ left atrial pressure → pulmonary venous congestion → interstitial edema around bronchioles → airway narrowing and reflex bronchoconstriction.

Clinical features

Paroxysmal nocturnal dyspnea

Orthopnea

Wheeze (“cardiac wheeze”)

Basal crackles

Pink frothy sputum in severe pulmonary edema

Often elderly with hypertension/CAD/valvular disease

Renal asthma

Renal asthma is an older clinical term describing paroxysmal dyspnea/wheezing due to pulmonary congestion from renal failure, usually because of:

Fluid overload

Severe hypertension

Heart failure secondary to kidney disease

Essentially, it is a form of cardiogenic pulmonary edema precipitated by renal dysfunction.

Pathophysiology

Renal failure → sodium and water retention → volume overload → pulmonary venous hypertension → pulmonary edema → wheeze and dyspnea.

Typical setting

Advanced CKD

Acute kidney injury with fluid overload

Missed dialysis

Important point

“Renal asthma” is not true asthma; it is pulmonary edema from renal disease.

Uremic lung

Uremic lung refers to pulmonary edema occurring in severe uremia/advanced renal failure, classically before dialysis era.

Pathogenesis

Combination of:

Fluid overload

Increased pulmonary capillary permeability due to uremic toxins

LV dysfunction/hypertension

Reduced oncotic pressure (sometimes)

Pathology

Interstitial and alveolar edema

Fibrinous alveolar exudates may occur

Clinical features

Severe dyspnea

Tachypnea

Hypoxemia

Crackles

Sometimes wheeze

Imaging

Classic chest X-ray:

Bilateral perihilar fluffy opacities

“Bat-wing” or “butterfly” pattern

May resemble cardiogenic pulmonary edema.

Management

Urgent dialysis

Oxygen/NIV if needed

Fluid removal

Treat hypertension and heart failure

Relationship between the three

Cardiac asthma → pulmonary edema from heart failure causing wheeze.

Renal asthma → pulmonary edema from renal disease/volume overload causing wheeze.

Uremic lung → pulmonary edema and lung injury specifically associated with severe uremia.

So, renal asthma and uremic lung overlap substantially, while cardiac asthma emphasizes the wheezing phenotype from heart failure.