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Venous hum clinical features

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.
Situation in which we search for abdominal venous hum ?
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.
(B) In the upper chest (left side) :
  •  Patent ductus arteriosus.