Fetor hepaticus, also known as ‘breath of the dead’, is a condition in which the breath of the patient is sweetish, musty, and occasionally fecal in nature. It is associated with portal hypertension with portosystemic shunts.
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Portal hypertension is a condition in which there is an increase in the pressure present within the portal vein. This vein is large and formed by the union of the superior mesenteric vein with the splenic vein. The portal vein drains blood from the intestinal mucosa, spleen, and pancreas, into the liver. This blood is rich in absorbed lipids and other molecules formed by the digestion of food.
Inside the liver are sinusoids, which are blood channels lined by reticuloendothelial cells that contain blood received from the portal vein and the hepatic arteries. This blood drains into the hepatic veins and finally into the inferior vena cava before returning to the right atrium of the heart.
Common causes of portal hypertension include cirrhosis, which is most frequently due to alcohol abuse, schistosomiasis in developing countries, where the infestation is rife, as well as abnormalities of the hepatic vein.
As a consequence of portal hypertension, anastomoses between the portal system and the systemic veins become dilated and tortuous. These anastomoses, which are referred to as portosystemic shunts, are responsible for the development of dilated abdominal wall collaterals, radiating veins around the umbilicus (the ‘caput medusae’), esophageal varices, and dilated submucosal gastric and rectal plexus veins.
Results of portal hypertension
As a result of portosystemic shunting, certain volatile sulfur compounds (chiefly thiols) and some ketones pass directly into the systemic circulation, bypassing the liver. This means that these chemicals reach the lungs without first undergoing hepatic metabolism. As a result, these volatile chemicals are exhaled in the breath.
Substances that cause fetor hepaticus
Some of the substances that cause fetor hepaticus include dimethyl sulfide, acetone, 2-butanone, and 2-pentanone, all of which are found in higher concentrations in the blood of liver disease patients. Some research points to dimethyl sulfide being the primary odor-producing component in the breath of fetor hepaticus. Testing for dimethyl sulfide may therefore assist in determining the possibility of hepatocellular failure.
Trimethylamine is also increased in many patients with cirrhosis and may contribute to the odor of the breath. Another chemical that could potentially be involved in fetor hepaticus is ammonia.
Conditions associated with fetor hepaticus
Fetor hepaticus is a late sign of hepatocellular failure and indicates the onset of hepatic encephalopathy, a condition in which the consciousness is affected along with other motor parameters, by the elevated levels of toxic substances in the brain. Other conditions associated with fetor hepaticus include diabetic ketoacidosis, and isopropyl alcohol poisoning.