Venous hum is synonymous with murmur heard in arteries. This may be called as venous murmur. It is produced as a result of enormous blood flow through the veins.
What are the common sites for venous hum ?
Sometimes, it is heard above either clavicle in a child and during pregnancy (physiological).
Commonly heard as a continuous humming sound over prominent veins seen in the epigastrium or
dilated veins seen around the umbilicus (pathological).
Pathological venous hum-It is often audible in hyperkinetic circulatory states eg. severe anaemia, thyrotoxicosis etc.
What are the characteristics of venous hum ?
- Soft and low pitched.
- Often continuous with early diastolic accentuation.
- Best heard in sitting or erect position.
- Best audible in inspiration.
- Disappears on pressing the bell of stethoscope (so. place the bell lightly over a prominent vein),
- and after Valsalva manoeuvre. It is accentuated by exercise.
- Thrill may be associated with and disappear by application of light pressure.
In the presence of dilated abdominal veins, we should search for venous hum.
The combination of dilated abdominal wall veins (caput medusae) and a venous hum at the umbilicus with normal liver is called Cruveilhier-Baumgarten syndrome. This syndrome may originate due to congenital patency of umbilical vein but more usually to a well-compensated cirrhosis.
Differential diagnosis of venous hum :
(A) In the epigastrium :
- Arterial murmur of alcoholic hepatitis (heard over liver).
- Arterial murmur heard over liver In hepatoma.
- Continuous murmur produced due to coarctation of aorta.
- Patent ductus arteriosus.
