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Ascites: John W. Williams, Jr, MD, MHS, discusses the clinical examination for ascites.
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Ascites: John W. Williams, Jr, MD, MHS, discusses the clinical examination for ascites.
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Language: EN.
Segment:0 .
>> I'm Joan Stephenson, Editor of JAMA's Medical News and Perspective section. Today we'll be hearing from Dr. John Williams about ascites, a topic discussed in Chapter 6 of the Rational Clinical Examination. Welcome back to the podcast, Dr. Williams, and please introduce yourself to our listeners. >> Thank you. I'm John Williams. I'm a general internist, Professor of Medicine at Duke University, and I've had a longstanding interest in the clinical evaluation, including history and physical examination findings, for various clinical problems.
>> Dr. Williams, what is ascites? And why is recognizing it by clinical examination important? >> Ascites, very simply, is free fluid in the abdominal cavity. Detecting ascites is important because it may indicate problems like underlying heart failure, liver disease, nephrotic syndrome, or in some cases malignancy. It may also have prognostic significance. For example, in patients with liver disease, those with ascites have lower overall survival.
Another example involves patients with malignancy, and in this instance ascites may signal metastasis. So it's important, both diagnostically, and in some instances prognostically. >> Can you please describe the pathophysiologic basis for ascites? >> Sure. Normally, intravascular and extravascular hydrostatic and colloid osmotic pressures are balanced, and this prevents accumulation of extravascular fluid.
Now any process that disrupts this balance can precipitate ascites. And understanding the basic path of physiology helps clinicians classify ascites into three major categories. They are elevated hydrostatic pressure, decreased osmotic pressure, and fluid production that exceeds resorptive capacity. An example of elevated hydrostatic pressure is cirrhosis, and cirrhosis fibrotic restriction of the hepatic sinusoids leads to increased venous hydrostatic pressure and ultimately to ascites by forcing lymphatic drainage into the abdomen through the hepatic capsule.
The second major category, decreased osmotic pressure, is caused by conditions that lead to protein loss, such as nephrotic syndrome, protein losing enteropathy, and malnutrition. Because of the protein loss, osmotic pressure is decreased and transudative fluid moves from the intravascular space into the abdominal cavity to balance hydrostatic and osmotic forces. The final category is represented by infections, such as tuberculosis, and malignancies.
And this is where inflammatory exudates or malignant effusions are produced in the abdominal extravascular space faster than they can be resorbed. >> What information should clinicians gather when conducting a medical history and physical examination for ascites? >> The clinical evaluation, that is, the history and physical exam, are useful both to detect ascites and to determine the etiology. The gold standard for determining ascites is ultrasonography, although other imaging modalities, such as abdominal CT are also useful but have the downside of radiation exposure.
For diagnosis, I'd recommend to ask about typical symptoms of IM overload, such as ankle edema, weight change, change in abdominal girth. And of these symptoms, increased abdominal girth has the highest likelihood ratio positive. So the likelihood ratio positive for increased abdominal girth is 4.2, and therefore, when present it increases the probability of ascites the most of these various history symptoms.
In contrast, ankle edema has the best likelihood of ration negative. The likelihood ratio is 0.17, and so when ankle edema is absent, it decreases substantially the probability of ascites. The examiner should also ask about potential causes of ascites or volume overload, such as a history of liver disease or congestive heart failure. These questions are more useful for determining the etiology than determining the presence or absence of ascites. >> How can clinicians use percussion techniques to detect ascites?
>> Percussion techniques are interesting, and they're important both historically and for modern diagnosis. So let me start with a percussion technique that is of historical interest only, and that is the puddle sign. The puddle sign is difficult to perform and it discriminates poorly between those with and without ascites. For listeners who are interested in historical artifacts like this, there are descriptions and videos of the puddle sign readily available on the internet. Two percussion techniques that we recommend for use are percussion for flank dullness and percussion for shifting dullness.
And let me take a moment and describe the approach to determine flank dullness and shifting dullness. You should start with the patient recumbent, so on their back, and in that position gas-filled loose bowel will characteristically float on top of the ascites, making the percussion note tympanitic at the umbilicus and dull beyond the fluid meniscus into the flanks. The examiner can confirm this pattern by progressively percussing the abdomen, beginning at the umbilicus and moving to the flanks, listening for the transition from tympani to dullness when the meniscus is reached.
Having identified a marked transition, further evidence for ascites can be obtained by testing for shifting dullness. And this is done by rolling the patient away from the examiner and repeating the percussion. With ascites, the area of dullness shifts to the dependent side and the area of tympani shifts toward the top. Both of these techniques are reasonably sensitive, detecting roughly 8 out of 10 patients with ascites. And it's a technique that you can practice.
You can practice percussing for tympani by puffing out your cheek and percussing your cheek, and you should get a tympanitic sound, or a drum-like percussion note. >> What other techniques or signs are potentially useful in determining if a patient has ascites? >> There are a couple of other methods to consider. So simple inspection for bulging flanks is quick and has some diagnostic utility. Bulging flanks occur when the weight of the abdominal free fluid is sufficient to push the flanks outward.
However, it's sometimes difficult to distinguish between bulging flanks caused by ascites and bulging flanks caused by obesity. Another potentially useful sign is the fluid wave. The fluid wave is performed by having the patient, or an assistant, place the medial edges of both hands firmly down the midline of the abdomen to block transmission of a wave through subcutaneous fat. And then the examiner taps one flank sharply while using the fingertips of their other hand to feel for an impulse on the opposite flank.
When ascites is present, an impulse may be felt in the receiving hand after a short lag. This test has high specificity, meaning the examiner is unlikely to detect a fluid wave in patients without ascites. Highly specific signs, like the fluid wave, are useful for ruling in the condition, in this case ascites, when the sign is positive. >> Is there anything else you would like to tell our readers about the clinical examination for ascites?
>> Yes, a couple of things. First, ascites is uncommon, occurring in less than 1% of patients in the general primary care population. Given its very low prevalence, patients should only be evaluated for ascites when there's a reason to suspect the condition, such as in patients with a history of cirrhosis, neoplastic disorders, or systemic infectious diseases. Second, the clinical evaluation is most useful for determining moderate or larger amounts of ascites.
None of the techniques that I've talked about are particularly useful for detecting very small amounts of peritoneal fluid. So when it's important to detect small amounts of ascites, diagnostic imaging, most often with ultrasonography, will be needed. >> Thanks very much, Dr. Williams, for this helpful snapshot of recognizing ascites. Additional information about this topic is available in Chapter 6 of the Rational Clinical Examination. This has been Joan Stephenson of JAMA talking with Dr. John Williams about ascites for JAMAevidence.
