VCP 411: Medicine Section

AREAS OF PERCUSSION FOR DIFFERENT ORGANS

Lungs

• This is best carried out using a soft tipped acoustic hammer and pleximeter. The lung area extends from its dorsal extremity at the 11^th intercostals space, across the middle of the 9^th rib to about two-finger breadth above the elbow joint when the foreleg is in a forward stance. On the right side, the posterior border of the lung field extends one or two fingers breadth further back (to about the 12^th rib) at its dorsal extremity compared with the left side, which is compressed slightly in the cranial direction (to about the 11^th rib) by the mass of the fore-stomachs.
• Acoustic percussion of the lung is done in the first stage as horizontal percussion to establish the course of the caudal lung limits. This is best performed on the right side where the lung region is easier to differentiate from the adjacent areas of hepatic and omasal dullness than on the left side here the presence of rumen in the dorsal part of the field produces sonorunous resonance which resembles that of lung apart from booming. Backward extension of thoracic field occurs in pulmonary emphysema and pneumothorax. Restriction of the field from behind may be due to overloading of the fore stomachs, enlarged liver, displacement of the abomasums to the right, severe dilation and displacement of the caecum, ascites, hydroamnion and occasionally the uterus in advanced pregnancy.
• Next stage is the vertical percussion from above to below, commencing at the cranial edge of the thoracic lung field extending backwards at each intercostals space. Special attention should be paid to the air-containing angle just behind the area of cardiac dullness, which becomes noticeably dull when the pericardium is enlarged by inflammation.

Heart

• Percussion is carried out as in figure starting form top to bottom along the edge of the triceps muscle, then in caudoventral, caudal and caudo-dorsal directions in order to establish an area of dullness. In cattle, only the apex lies caudal to the part covered by the shoulder muscles, because the apex is separated from the chest wall by the thin ventral portions of the lung. Percussion in the ventral part of the thoracic lung percussion field normally gives only a relative cardiac dullness and not absolute dullness. On the left side of the healthy cattle, this area is the size of the palm of the hand, while one the right side it is smaller and indistinct. In bulls and fat animals the heart field is quite difficult to percuss. An enlarged heart field is found in pericarditis, hypertrophy and dilatation of the heart giving a damp tone beyond the fifth rib. Pneumonia or other pathological processes in the region of heart can also cause this dampness. In pulmonary emphysema, the area of cardiac dullness is smaller than normal or completely absent on both sides and the same applied to pneumothorax. In some cases of traumatic pericarditis, pericardium will contain gas, giving tympanic tone in the heart region on the upper side. Accumulation of fluid within the pericardial sac produces more pronounced dullness.

Liver

• The normal liver percussion field is the dorsal region of the last intercostals spaces, adjoining the caudal edge of the lung percussion field. In adult cattle it is usually distinguishable from the full lung sound and sub tympanic sound of the dorsal intestinal regions, as areas of complete dullness, 3-4 fingers wide and the length of the palm of the hand. It may be displaced forward by 1-3 finger width by advanced pregnancy and abdominal swellings and the same distance backwards by pulmonary emphysema. Enlargement of liver percussion field to five fingers width is pathological, if this area is also sensitive to pain.

Spleen

• In left side of chest, it extends from the upper end of the last two ribs to the junction between rib and costal cartilage at the 7^th and 8^th ribs. The normal spleen is too thin to produce a detectable dullness on the percussion and dorsally there is only an indistinct transition from the full lung sound to the sub-tympanic visceral sound. Spleenic dullness in cattle is caused by an enlarged spleen at least three times its normal size. Such splenomegaly is usually due to leucocytic neoplasia or an accumulation of pus from a foreign body within the spleen or anthrax. In such cases percussion for sensitivity should be undertaken gently, owing to the risk of rupture in the spleenic capsule.

Rumen

• Rumen is located on the left side in the abdominal cavity. It extends from the diaphragm to the pelvic inlet and goes over to right side, somewhat above right flank fold. Percussion can be conducted in left side over a wide area extending from ribs caudally to the tubercoxae. The percussion area of rumen can be divided in to a) hollow of the flank and b) abdominal wall within the costal arch.
• Acoustic percussion of the rumen in the left abdominal wall normally produces a subtympanic sound in the dorsal part. Ventral to this there is a horizontal zone, the thickness of a hand, of relative damping sound. Lower still is a zone of almost, but not quiet completely, damped sound. This zone becomes completely damped when the rumen is overloaded or contains balls of solid food masses or soil. By contrast the percussion sound has a drum like boom in bloat. An obliquely oval zone of tympanic sound is often present under rib cage in left side abomasal displacement. An excessively loud sound (box sound) may be detected underneath the rumen, close to the xiphoid cartilage. This has been described in fresh cases of traumatic reticulo-peritonitis; after few days the sound extends backwards.