Fetor hepaticus, also called ‘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.
Portal hypertension is a condition in which the pressure in the portal vein is increased. This vein is a large one formed by the union of the superior mesenteric vein with the splenic vein. It drains blood from the intestinal mucosa, the spleen, and the pancreas, into the liver. This blood is rich in absorbed lipids and other molecules formed by the digestion of food.
Inside the liver, there are sinusoids – these 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, most frequently due to alcohol abuse, as well as schistosomiasis in developing countries where the infestation is rife, and 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 are called portosystemic shunts. They 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 sulphur compounds (chiefly thiols) and certain ketones pass directly into the systemic circulation, bypassing the liver. This means that they reach the lungs without undergoing hepatic metabolism. As a result, being volatile, they are exhaled in the breath.
Substances Which Cause Fetor Hepaticus
Such substances 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. It is thought that testing for dimethyl sulphide may help to evaluate and predict the possibility of hepatocellular failure.
Trimethylamine is also increased in many patients with cirrhosis, and may contribute to the odor of the breath. Another component may be 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 are diabetic ketoacidosis, and isopropyl alcohol poisoning.
Reviewed by Afsaneh Khetrapal BSc (Hons)