A Transjugular Intrahepatic Portosystemic Shunt (TIPS) is a procedure that creates a new path for blood flow in the liver to relieve high pressure in the portal vein system. While effective for complications like abdominal fluid or bleeding, the procedure has risks. A primary complication after a TIPS is an increase in the body’s ammonia levels, which can lead to neurological changes. This rise in ammonia is a known trade-off for the benefits the shunt provides.
The Link Between the TIPS Procedure and Ammonia
The liver’s primary role is to filter blood from the intestines, removing toxins like ammonia, which is produced by gut bacteria. In a healthy system, blood passes through the portal vein into the liver, where cells detoxify the ammonia before it enters general circulation. This process prevents ammonia from accumulating to harmful levels.
The TIPS procedure alters this natural pathway by placing a stent to create a channel, or shunt. This shunt connects the portal vein directly to a hepatic vein, which drains blood away from the liver. This new route allows blood to bypass the main functional tissue of the organ, lowering the pressure within the portal vein system.
This diversion of blood has a direct consequence on ammonia levels. By rerouting blood flow away from the liver’s filtering cells, the ammonia-rich blood from the gut is no longer effectively cleared. This is similar to a traffic detour that sends vehicles around a crucial inspection station. As a result, ammonia enters the systemic circulation in higher concentrations, leading to a condition known as hyperammonemia and creating the potential for neurological complications.
Recognizing the Signs of High Ammonia
The most direct consequence of elevated ammonia is a condition called hepatic encephalopathy (HE). HE is a spectrum of neurological and psychiatric changes that result from the liver’s inability to remove toxins from the blood. These signs can develop within weeks of the procedure and require prompt medical attention.
The symptoms of HE range from subtle to severe, reflecting ammonia’s effect on brain function. In its milder forms, called covert HE, an individual might experience difficulty concentrating, forgetfulness, mood swings, or changes in sleep patterns. These early signs can be easily missed or attributed to other causes.
As ammonia levels rise, symptoms become more obvious in a state known as overt HE. These can include:
- Significant confusion or disorientation
- Profound drowsiness that can progress to a coma
- Slurred speech
- A distinctive flapping tremor of the hands called asterixis
Diagnosis is based on observing these signs in a patient with a TIPS and is often confirmed with a blood test measuring ammonia concentration.
Medical Management and Treatment
Managing high ammonia after a TIPS procedure involves medication and dietary planning to reduce ammonia production and absorption from the gut. Two medications are central to this strategy: lactulose and rifaximin. Lactulose, a synthetic sugar, draws ammonia from the blood into the colon, where it is excreted through bowel movements. It also creates an acidic environment that traps ammonia, preventing its reabsorption.
Rifaximin is a gut-specific antibiotic that reduces the population of ammonia-producing bacteria in the intestines, lowering ammonia production at its source. Using lactulose and rifaximin in combination is an effective strategy, as it addresses both the production and removal of ammonia.
Dietary management requires a nuanced approach to protein. Historically, restrictive protein diets were used, but this can cause muscle wasting, which is problematic as muscle helps with ammonia detoxification. The modern strategy focuses on adequate nutrition to maintain muscle mass. This involves recommending protein from vegetable or dairy sources and advising that intake be spread evenly across several small meals to avoid a large ammonia load.
Long-Term Outlook and Monitoring
Managing high ammonia and hepatic encephalopathy after a TIPS is an ongoing process. It requires consistent, long-term follow-up with a liver specialist (hepatologist) to monitor symptoms and adjust treatments. Regular appointments and blood tests help ensure medications are working effectively, which is important for maintaining quality of life.
If medications and diet are not sufficient to control HE symptoms, a TIPS revision or reduction may be considered. In this procedure, an interventional radiologist narrows the shunt’s diameter. This adjustment directs more blood through the liver’s natural filtering pathways, lowering ammonia levels. However, this carries the risk of reversing the TIPS benefits, potentially causing a return of bleeding or fluid accumulation.
For individuals with severe, persistent HE that cannot be managed by other means, the condition may indicate that the underlying liver disease has progressed. This decline in liver function may prompt an evaluation for a liver transplant. A transplant remains the definitive treatment for end-stage liver disease and its complications.