Introduction:
Portal systemic encephalopathy is also called hepatic encephalopathy. It is a neuropsychiatric syndrome that can develop in patients with a portosystemic shunt. Any patient suffering from liver dysfunction and neuropsychiatric signs and symptoms. Depending on the cause, portal-systemic encephalopathy can be differentiated into types A, B, and C. The symptoms of portal encephalopathy are rigidity, tremors, or hyperreflexia.
What Is a Portosystemic Shunt?
A portosystemic shunt can either be congenital or acquired in nature. In a portosystemic shunt, the blood from the splanchnic venous circulation is shunted to collateral venous drainage rather than passing through hepatic sinusoids. Congenital portosystemic shunts are very rare and can be intrahepatic or extrahepatic. The acquired portosystemic shunt is caused due to cirrhosis which can lead to portal hypertension.
What Are the Causes of Portal Encephalopathy?
Depending on the cause behind portal encephalopathy, it is divided into three types:
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Type A: This type of portal encephalopathy is caused due to acute liver failure.
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Type B: This type is caused due to portosystemic shunt without any liver dysfunction.
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Type C: This type of portal encephalopathy occurs due to liver cirrhosis.
The leading cause of all three types of encephalopathy is the lack of metabolization of ammonia. The ammonia should be metabolized into a less toxic state through the urea cycle in the portal hepatocyte cells of the liver. The failure of ammonia metabolization occurs due to either liver dysfunction or the development of a portosystemic shunt. The low concentration of ammonia leads to crossing from the blood-brain barrier as the astrocyte cell membranes are highly permeable to ammonium ions. This deposition of ammonia in the brain can cause neuropsychiatric syndrome.
What Is the Pathophysiology of Portal Encephalopathy?
The most important causative factor of portal encephalopathy is higher ammonia levels in the blood. Some other neurotoxins leading to this condition are tyramine, octopamine, manganese, GABA, and short-chain fatty acids. The leading production site of ammonia is the gastrointestinal tract, and the three production mechanisms are hydrolysis of urea, bacterial deamination, and glutamine metabolism. In healthy individuals, this ammonia is excreted by the liver; however, in cases of portal encephalopathy, it accumulates, and its higher concentration passes the blood-brain barrier.
What Are the Symptoms of Portal Encephalopathy?
There is a wide range of symptoms seen in portal encephalopathy.
The initial symptoms are :
Babinski's Sign Is Positive: It occurs when there is an extension (upward movement) of the foot's big toe due to stimulation of the lateral plantar aspect of the foot.
Asterixis is a disorder in which motor control of some body parts is lost. The most common sign seen is a flapping hand tremor.
Hyperreflexia: It is characterized by over responsive reflexes or overactive reflexes. The signs include itching or spastic tendencies.
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Rigidity or stiffness of muscles.
Severe portal encephalopathy includes symptoms such as:
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Disorientation leads to confusion in time-space and persons.
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Agitation is a state of nervous excitement or anxiety.
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Frequent confusion leads to coma.
How to Diagnose Portal Encephalopathy?
The diagnosis of portal encephalopathy needs a thorough physical examination of the patients, followed by categorizing the signs and symptoms according to West Haven criteria.
West Haven Criteria: It is a method to categorize the symptoms of portal encephalopathy.
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Grade 1: It characterizes the initial symptoms of portal encephalopathy, such as changes in behavior and minimal changes in consciousness levels of a person.
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Grade 2: This stage includes gross orientation, inappropriate behavior, drowsiness, and asterixis.
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Grade 3: The patient suffers from incoherent speech, marked signs of confusion, and lots of sleep.
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Grade 4: Patient does not respond to pain, decorticate, or decerebrate posturing and, ultimately, is in a coma.
The diagnosis of portal-systemic encephalopathy is based on the following four main factors:
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Any peculiar clinical patterns are seen, such as drowsiness, disorientation, and confusion.
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Investigation of any liver dysfunction or portosystemic shunt. Increased levels of ammonia should also be evaluated.
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Ruling out any other similar disorder or disease. This can be done by performing an electroencephalogram (EEG), computed tomography (CT), and magnetic resonance imaging (MRI).
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Reaction and response of the body towards low ammonia therapy.
What Is the Treatment for Portal Encephalopathy?
The cases of portal encephalopathy are relevant for hospitalization. The management involves two prophylaxis- primary and secondary, dietary changes and liver transplants.
Primary Prophylaxis
Cases of upper gastrointestinal bleeding can potentially develop portal encephalopathy. Lavage of the gastrointestinal tract by mannitol or non-absorbable disaccharides will reduce the risk of developing portal encephalopathy. Some other measures in cases of cirrhosis include avoiding alcohol consumption, proper nutrition, and treatment of virus-related cirrhosis with antiviral drugs.
Secondary Prophylaxis
This maintenance procedure is for patients who have suffered a few episodes of hepatic encephalopathy and can witness further episodes. Administration of lactulose after an episode decreases the chances of another episode by almost 50 %. In cases of lactose intolerance, Rifaximin can be used. A combination of Rifaximin and lactulose further reduces the chance of episodes of portal encephalopathy. In cases of patients still suffering from episodes of portal encephalopathy, the portosystemic shunt should be located and obliterated.
Dietary Changes
In patients with portal encephalopathy, following dietary instructions should be followed:
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Decreased consumption of meat proteins.
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Add snacks in the middle of the meals and before bed at night. This reduces gluconeogenesis and catabolism of proteins.
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Meat protein should be replaced with milk protein.
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Probiotics should be added to the diet.
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Micronutrient supplements such as vitamins and minerals should be taken.
Liver Transplant
Cirrhosis can lead to chances of a liver transplant, but it is not a suitable option as the patient has a poor prognosis.
Conclusion
Portal encephalopathy is a hepatic disorder characterized by impaired metabolization of ammonia in the body leading to increased ammonia levels in the blood. The higher concentration of ammonia crosses the blood-brain barrier and leads to neuropsychiatric symptoms such as confusion and disorientation. The treatment includes prophylaxis followed by dietary changes. In case of a good prognosis, a liver transplant can be done.
