Visual changes (abdominal inspection)
Initial physical diagnosis begins with a thorough inspection of the patient. When free fluid accumulates, noticeable changes in the shape and overall volume of the abdomen occur—it becomes visibly enlarged.
Special attention should be paid to the condition of the umbilicus. If the patient develops tense ascites (a condition where a truly large amount of fluid accumulates), intra-abdominal pressure increases significantly. This picture leads to characteristic eversion of the umbilicus. As a result of this pressure, an umbilical hernia is formed, which serves as a striking visual marker of massive fluid accumulation in the abdominal cavity.
Percussion and determining the nature of the sound
Percussion allows for an accurate assessment of fluid and gas distribution. Detecting ascites is based on the laws of physics: fluid always tends to occupy the most dependent areas due to gravity.
Assessment in the supine position When the patient lies on their back, free fluid accumulates in the dependent (lateral) parts of the abdominal cavity—the flanks. The percussion sound pattern appears as follows:
- An absolute dull percussion note is determined in the flanks (lateral regions).
- In the middle of the abdomen, the sound becomes tympanic. This occurs because the intestinal loops, containing gas inside, are lighter and naturally "float" upward, ending up directly beneath the anterior abdominal wall in the center.
Positional change method To confirm that the dullness is indeed due to free rather than loculated fluid, the method of eliciting shifting dullness is used. The physician asks the patient to turn onto their side. At this moment, the fluid shifts to the dependent parts of the abdominal cavity.
- Result: At the bottom (closer to the couch surface), the percussion note becomes dull.
- At the top (on the side that is now higher up), the sound changes to tympanic, as the floating intestinal loops move there.
Testing for fluid thrill (fluid thrill sign)
The main goal of this method is the definitive confirmation of free fluid using the physician's tactile senses.
Technique for performing the maneuver:
- The physician places the palm of one hand firmly against the lateral surface of the patient's abdomen.
- With the fingers of the other hand, the physician delivers short, light tapping blows to the opposite lateral side of the abdomen.
- If fluid is indeed present in the abdominal cavity, the physician's left hand clearly feels the transmission of mechanical vibrations—the so-called fluid wave.
Important nuance: exclusion of a false wave Tapping blows can be transmitted not only through the fluid but also through the subcutaneous adipose tissue of the anterior abdominal wall, creating the illusion of a fluid thrill (a false wave). Assistance is required to prevent the transmission of these superficial vibrations. The patient themselves or an assistant must firmly press the edge of their hand along the midline of the abdomen. This action creates a reliable mechanical barrier to superficial vibration through the adipose tissue, allowing the physician to isolate and assess specifically the intra-abdominal fluid vibrations.
Briefly: answers to topical questions
In what diseases does ascites most commonly develop?
The primary cause of ascites is portal hypertension, primarily due to liver cirrhosis; ascites can also be associated with portal vein thrombosis.
Free fluid in the abdominal cavity can accumulate in other conditions:
- Heart failure — congestive circulatory nature.
- Hypoproteinemia syndromes — nephrotic syndrome, malabsorption syndrome, protein-losing enteropathy.
- Infectious and inflammatory processes — polyserositis, peritonitis, pancreatitis.
- Oncological pathology — primary liver cancer, tumors of the gastrointestinal tract and pelvic organs, lymphomas, peritoneal mesothelioma.
What instrumental methods are used to confirm ascites?
For the instrumental confirmation of free fluid in the abdominal cavity, sources indicate ultrasonography (ultrasound). Ultrasound allows for the detection of ascites and the assessment of signs of portal hypertension.
Depending on the severity, the following grades are distinguished:
| Grade of ascites | Characteristic |
|---|---|
| Degree 1 | Fluid is detected exclusively on ultrasound |
| Degree 2 | Symmetrical abdominal enlargement |
| Degree 3 | Tense ascites |
To remember percussion in ascites: "Heavy water sinks, light gas floats." Lying on the back — water in the flanks (dullness), intestines in the center (tympany). On the side — water flows down.
Class and exam questions
Why does the patient turn onto their side during percussion?
This is the positional change method for detecting shifting dullness. Upon turning, free fluid flows downward, and a dull sound appears there, while a tympanic sound appears at the top.
How to distinguish a true fluid thrill from a false wave?
A false wave is transmitted through the subcutaneous adipose tissue. To exclude it, an assistant presses the edge of their hand against the midline of the abdomen, creating a barrier.
What else to study on this topic
- Technique for performing percussion in the flanks
- Differentiation of tense ascites from other causes of abdominal enlargement
- Mechanism of vibration transmission during the fluid thrill sign
- Technique for correctly creating a barrier for a false wave
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