Sounds Heard on Percussion

1. Resonant (Normal)

• Quality: Hollow, low-pitched, moderately loud, long duration
• Heard over: Normal air-containing lung tissue
• Clinical significance: Normal finding over the lung fields
• Percussion of the thorax over normal air-containing lung produces a resonant note. (Murray & Nadel's Textbook of Respiratory Medicine)

2. Hyperresonant

• Quality: Louder, lower-pitched, and more "booming" than normal resonance - like tapping an empty box
• Heard over: Hyperinflated or air-filled spaces
• Clinical causes:
  • Emphysema (widespread hyperresonance)
  • Pneumothorax (circumscribed hyperresonance over the affected side)
  • Large bulla
  • Tension pneumothorax (tympanitic quality develops)

3. Tympanitic

• Quality: High-pitched, drum-like, musical tone
• Heard over: Hollow, gas-filled viscera
• Clinical causes:
  • Tension pneumothorax (extreme hyperresonance becomes tympanitic)
  • Normal gastric air bubble (left lower anterior chest)
  • Dilated loops of bowel overlying a mass
  • Gastric tympany used historically to locate stomach/cardiac situs

4. Dull

• Quality: Low-intensity, short duration, high-pitched, with feeble carrying power
• Heard over: Solid or fluid-filled structures replacing air
• Clinical causes:
  • Consolidation (lobar pneumonia)
  • Atelectasis
  • Pleural effusion (dullness in the middle zone of a large effusion)
  • Pleural thickening
  • Large mass at the lung surface
  • Normal liver dullness in the right lower chest
  • Cardiac dullness on the left
• When percussing a large pleural effusion, three zones are found: resonance above the fluid, dullness in the middle, and flatness below. (Murray & Nadel's)

5. Stony Dull (Flat)

• Quality: Absolute absence of resonance - the "deadest" sound, like percussing a solid muscle
• Heard over: Very dense, airless tissue or large fluid collections
• Clinical causes:
  • Massive pleural effusion (below the fluid level)
  • Thick pleural thickening
  • Normal: percussing the thigh (used as a reference for "flat")
• Defined as the non-resonant sound obtained by percussing over the liver. (Murray & Nadel's)

Summary Table

Clinical Tips

• Move from resonant to dull when mapping out organ borders or fluid - this is the most sensitive technique (Bailey & Love's Short Practice of Surgery)
• Shifting dullness on abdominal percussion indicates free peritoneal fluid (ascites)
• Percussion over a pneumothorax may obliterate normal liver dullness (right-sided) or cardiac dullness (left-sided) (S. Das Manual on Clinical Surgery)
• The percussion note is primarily felt as vibration in the pleximeter finger, not just heard (Murray & Nadel's)

Abdominal Percussion - Sounds & Their Significance

Normal Findings on Abdominal Percussion

Initial cursory light percussion across the upper, mid, and lower abdomen is useful to denote areas of dullness and tympany as well as to elicit unanticipated areas of pain or tenderness before palpation. (Goldman-Cecil Medicine)

1. Tympanitic Note

• Quality: Drum-like, high-pitched, hollow
• Normal over: Gas-filled bowel loops (throughout the central abdomen)
• Abnormal causes of increased tympany:
  • Intestinal obstruction - loud, generalized tympany
  • Bowel perforation - free air in the peritoneum
  • Gaseous distension (aerophagia, ileus)
  • Overlying distended caecum or pelvic colon may give tympanicity even over a solid mass (S. Das)

2. Dull Note

• Quality: Short, soft, high-pitched, no resonance
• Normal over: Liver (RUQ), spleen (LUQ), full bladder, uterus
• Pathological dullness:
  • Hepatomegaly - dullness extends below the normal liver border (below 2 cm from right costal margin in the midclavicular line)
  • Splenomegaly - dullness between the 9th and 11th ribs in the left midaxillary line
  • Ascites - dullness in the flanks
  • Abdominal mass (solid tumour, abscess, full bladder)
  • Ovarian cyst - dullness centrally with resonance in the flanks (opposite pattern to ascites)

Liver Percussion (Span):

• Percuss from resonance (lung) downward to dullness (upper liver border), then from tympany (bowel) upward to dullness (lower liver border)
• Normal liver span: 6-12 cm in the midclavicular line (Goldman-Cecil Medicine)
• Diminished span = cirrhosis; increased span = hepatomegaly (heart failure, fatty liver, hepatitis)

Spleen Percussion:

• Percuss in the left midaxillary line near the 10th rib
• Dullness distinct from gastric/colonic tympany suggests splenomegaly (Goldman-Cecil Medicine)

3. Shifting Dullness (Ascites Sign)

1. Patient lies supine - percuss from midline outward toward the flanks
2. Note where the note changes from tympanitic (central, over floating bowel) to dull (flank, over fluid)
3. Keep the finger at the dullness point - ask the patient to roll toward you
4. Wait ~1 minute for fluid to gravitate, then percuss again
5. If now tympanitic - shifting dullness is positive (free fluid/ascites confirmed)

Shifting dullness results from movement of ascites to the most dependent portion of the abdomen. A change from a tympanic sound to a dull sound signifies a change from air to fluid. (Goldman-Cecil Medicine)

• Even becomes positive when the quantity of fluid is comparatively small (S. Das)
• When ascites is very large, shifting dullness may be absent - use fluid thrill instead

4. Ascites vs. Ovarian Cyst - Percussion Distinction

5. Obliteration of Liver Dullness (Surgical Emergency Sign)

• Technique: Percuss along the right midaxillary line from above downward
• Normally: resonant (lung) → dull (liver)
• Abnormal: If the liver dullness is replaced by resonance = free gas under the diaphragm
• Cause: Perforation of a hollow viscus (perforated peptic ulcer, perforated appendix, etc.)
• Absence of this sign does NOT exclude perforation - it is only present with sufficient air leakage (S. Das)
• Fallacy: Gross intestinal distension or pulmonary emphysema can mimic this sign

6. Percussion Tenderness (Peritonitis)

• Sharp pain on gentle percussion = peritoneal irritation
• Preferred over deep palpation and rebound testing - less painful, equally informative
• Percussion is the best way to localize the area of maximum tenderness before palpation (Yamada's Gastroenterology)
• Diffuse percussion tenderness = generalized peritonitis
• Localized tenderness (e.g., RIF on percussion) = appendicitis, localized peritonitis

Quick Summary Table