Stenosis

Stenosis means abnormal narrowing of a tubular body structure (from Greek stenos, “narrow”). The clinical consequence depends on which structure is narrowed, the degree of narrowing, and whether it developed congenitally or was acquired through disease.

Types of Stenosis in Dogs

Cardiac Valve Stenosis

• Subaortic stenosis (SAS): narrowing below the aortic valve, creating obstruction to left ventricular outflow. One of the most common congenital heart defects in dogs, particularly in Newfoundlands, Golden Retrievers, Rottweilers, and Boxers. Severe SAS can cause exercise intolerance, syncope, and sudden death.
• Pulmonic stenosis (PS): narrowing of or below the pulmonic valve, obstructing right ventricular outflow. Common in English Bulldogs, Beagles, and terrier breeds. Balloon valvuloplasty can improve outcomes in moderate-to-severe cases.
• Aortic stenosis: narrowing at or near the aortic valve.

Spinal Stenosis

• Degenerative lumbosacral stenosis: narrowing of the spinal canal at the L7-S1 junction, compressing the cauda equina nerve bundle. Common in German Shepherds and other large breeds.
• Cervical vertebral stenosis: narrowing of the cervical spinal canal, associated with wobbler syndrome in Great Danes and Doberman Pinschers.

Airway Stenosis

• Nasopharyngeal stenosis: abnormal narrowing of the nasopharyngeal passage
• Tracheal stenosis: narrowing of the tracheal lumen, which can occur post-trauma or post-intubation
• Brachycephalic syndrome: functional airway stenosis from stenotic nares, elongated soft palate, and other conformational narrowing

Vascular Stenosis

• Renal artery stenosis: narrowing of the renal arteries, potentially contributing to hypertension
• Portal vein stenosis: can occur post-surgical or with chronic hepatic fibrosis

Clinical Consequences

The clinical impact of stenosis follows a general principle: as narrowing increases, the effort required to move fluid (blood, air, cerebrospinal fluid) through the constriction increases. This creates:

• Increased pressure upstream of the narrowing (e.g., ventricular hypertrophy in cardiac stenosis)
• Reduced flow downstream (e.g., reduced organ perfusion, reduced airflow)
• Turbulence at the narrowing point (produces heart murmurs in cardiac stenosis, stridor in airway stenosis)
• Compensatory changes that may eventually fail

The severity classification typically ranges from mild (hemodynamically insignificant) to severe (causing clinical signs and requiring intervention). Regular monitoring of stenotic conditions guides the timing of treatment decisions.