Abdominal percussion: differential diagnosis
The primary diagnostic goal of abdominal percussion is to determine the true causes of its enlargement. The clinician must differentiate what is causing the volumetric change: gas accumulation, free fluid, or solid masses.
- Excess gas (meteorism): Percussion of the anterior abdominal wall reveals a pronounced, loud tympanic sound.
- Free fluid (ascites): The accumulation of fluid in the abdominal cavity is characterized by clear dullness to percussion in the areas where it is localized.
Abdominal auscultation: assessment of bowel sounds
The auscultatory pattern of the abdominal cavity directly depends on the motor function of the gastrointestinal tract. Normally, sound phenomena reflecting natural peristalsis occur regularly, every 5–10 seconds, although these intervals can be quite variable.
Special attention is paid to the dynamics of bowel sounds when intestinal obstruction is suspected.
Phases of mechanical (obstructive) obstruction:
- Early stage: peristaltic sounds are significantly amplified due to the intestine's attempts to overcome the obstacle.
- Late stage: sound phenomena gradually diminish as compensatory mechanisms become exhausted.
Important: The initial absence of sounds (the so-called "grave silence") most often indicates a paralytic form of obstruction and is regarded as an extremely ominous clinical sign.
Auscultation of vascular bruits
In addition to assessing the intestinal tract, auscultation is used to examine the abdominal vasculature.
The main auscultation points include the projections of the abdominal aorta and renal arteries. The diagnostic significance of this step lies in identifying stenosis (narrowing) of major vessels. The appearance of a pathological vascular bruit at these points indicates a disturbance in laminar blood flow due to an obstruction.
Related examination: digital rectal examination
An additional yet essential method of physical examination is the digital rectal examination (per rectum). The technique involves inserting the clinician's index finger through the patient's anus.
Diagnostic goals of the examination:
- Detection of intraluminal pathologies of the bowel itself (presence of hemorrhoids, rectal tumors).
- Assessment of the state of adjacent organs and tissues. In men, the prostate gland is palpated in this manner, and in women, the uterus and ovaries.
- Diagnosis of abdominal infiltrates that localize or extend down into the pelvic cavity.
Briefly: answers to topical questions
At which specific anatomical points are bruits over the abdominal aorta and renal arteries auscultated?
Auscultation of the renal arteries is performed just above the umbilicus, to the left and right of the midline. Specific anatomical landmarks for the abdominal aorta are not detailed; auscultation is performed over the projection area of the vessel.
- Renal arteries — projection above the umbilicus, lateral (left and right) to the midline.
- Abdominal aorta — the projection area of the abdominal aorta.
How is topographic percussion performed to determine liver span according to Kurlov?
Topographic percussion of the liver according to Kurlov is based on measuring three linear dimensions between borders found by percussion.
- First dimension — along the right midclavicular line: the lower point is determined by percussion from the umbilicus upward until dullness appears, and the upper point by percussion from clear lung resonance downward until dullness appears.
- Second dimension — along the midline: the lower point is determined by percussion from the umbilicus upward until dullness appears; the upper point is conventional, found by drawing a horizontal line from the upper point of the first dimension to the midline.
- Third dimension — along the left costal margin: percussion is performed along the edge of the left costal margin, starting approximately from the anterior axillary line; the upper point corresponds to the upper point of the second dimension, and the lower point is determined by percussion.
To remember the phases of mechanical obstruction: "First a STORM (increased sounds), then a CALM (diminished sounds), and in paralysis, immediate SILENCE."
Class and exam questions
What percussion sound is characteristic of ascites?
In ascites (the presence of free fluid in the abdominal cavity), the percussion sound becomes dull.
What is the normal frequency of bowel sounds?
Normally, peristaltic sound phenomena are auscultated every 5–10 seconds, although intervals between them may vary.
What does the disappearance of peristaltic sounds indicate?
Complete disappearance of sounds is an ominous sign of intestinal obstruction (typically the paralytic form).
What is the purpose of renal artery auscultation?
Auscultation over the projection of the renal arteries and aorta is performed to detect pathological bruits indicating stenosis (narrowing) of these blood vessels.
What else to study on this topic
- Detailed palpation of pelvic infiltrates during rectal examination
- Differentiation of rectal tumors from hemorrhoids
- Mechanisms of tympanic sound formation in meteorism
- Pathophysiology of paralytic and mechanical intestinal obstruction
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