Bad breath from bad liver

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  • Published: Oct 6, 2008
  • Author: Jon Evans
  • Channels: Laboratory Informatics
thumbnail image: Bad breath from bad liver

For most people, bad breath or halitosis is little more than an early morning annoyance that can be resolved by simply brushing their teeth. For some, however, it is a much more persistent condition and can have a major impact on their lives. And for others it can indicate the presence of a serious underlying illness.

Fetor hepaticus, also known as breath of the dead, is a form of bad breath associated with liver failure, in which the breath has a sweet, faecal smell. Doctors have thus been known to take advantage of feptor hepaticus by smelling the breath of patients in order to detect liver failure. But it's not a particularly accurate diagnostic technique, especially as the main odorous chemical causing fetor hepaticus - dimethyl sulphide - can also be present in normal bad breath.

But the idea of using fetor hepaticus to diagnose liver failure is a good one. It would be much safer and less intrusive than conducting a liver biopsy, which is currently the most accurate way of detecting damage to the liver. All that is needed for it to work is an analytical method that's more accurate and sensitive than the human nose.

This is what a team of Belgian medical researchers led by Marc Quirynen from the Catholic University of Leuven has now come up with. To develop this method, they first took samples of exhaled breath from 52 patients with liver cirrhosis, in which healthy liver tissue is gradually replaced by fibrous scar tissue as a result of chronic disease, and 50 healthy controls. They then identified the various volatile chemicals in these breath samples using gas chromatography-mass spectrometry and finally determined which of these chemicals were best at distinguishing between the two groups using the statistical technique known as discriminant analysis.

While the majority of bad breath arises from processes in the mouth, such as bacteria breaking down sulphur-containing amino acids, conditions like fetor hepaticus are caused by volatile compounds entering the lungs from the blood. In the case of fetor hepaticus, these volatile compounds are specifically produced as a result of liver damage.

So Quirynen and his team needed to make sure that they analysed breath coming from the lungs rather than the mouth. To do this, they only sampled the latter part of the exhaled breath, which should have come direct from the lungs.

Quirynen and his team detected a total of 12 volatile compounds in all the breath samples. Of these, four - dimethyl sulphide, acetone, 2-butanone and 2-pentanone - were present at significantly higher concentrations in the breath of the cirrhosis sufferers and two - indole and dimethyl selenide - were present at significantly lower concentrations. These findings all make sense in terms of what is known about the biochemical effects of liver cirrhosis.

Next, they applied discriminant analysis, which is a statistical technique for finding the combination of features that best separate two or more classes of objects, to the breath samples. This revealed that four of the detected chemicals best separated the breath of the cirrhosis sufferers from those of the healthy controls - dimethyl sulphide, 2-pentanone, dimethyl selenide and indole.

Building a model based on this finding, Quirynen and his team found that it could accurately classify 94 of the 102 breath samples. Interestingly, the three healthy controls that were incorrectly classified as cirrhosis sufferers were all smokers, which might be explained by the fact that 2-pentanone is a component of cigarette smoke.

Overall, Quirynen and his team conclude that this kind of breath analysis provides a powerful tool for detecting liver damage. As such, they are already using it on chronic halitosis sufferers to help determine those that could be suffering from cirrhosis. They are also attempting to extend the scope of the technique.

'We are planning to analyse the breath of patients in an earlier stage than cirrhosis in order to see whether the technique can also detect liver pathologies at the very beginning of the disease,' Quirynen told separationsNOW. 'We are also trying to find other (not specifically bad smelling) compounds which might be useful for a differential diagnosis.'

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Morning breath or liver disease?

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