Cirrhosis

How the Gut Community Changes as the Liver Scars

There's strong evidence here, and it's unusual in reaching all the way to randomised trials. Cirrhosis is advanced scarring of the liver, where healthy tissue has been replaced by fibrous tissue that can't do the same job. The gut matters because the liver receives about three quarters of its blood supply straight from the intestines. Whatever crosses the gut wall arrives at a liver already struggling to filter it.

Bacteria from the mouth colonising the gut

Researchers compared the bacterial genes present in people with cirrhosis against healthy people, and found 75,245 genes differing between them.

The striking part was where those bacteria came from. More than half of the species involved normally live in the mouth, not the intestine.

That points to something specific. Stomach acid and bile normally kill most swallowed oral bacteria before they get far. In cirrhosis, both defences weaken, so mouth bacteria survive the journey and take up residence lower down.

People with cirrhosis also have altered saliva and weakened defences in the mouth itself, so more of these bacteria are being swallowed in the first place.

Source: PROFIT, a PROspective, randomised placebo controlled feasibility trial of Faecal mIcrobiota Transplantation in cirrhosis

What crosses the wall, and what it does

A scarred liver raises the pressure in the vein carrying blood from the gut, which makes the gut wall leakier.

Bacteria and their fragments cross into the bloodstream, a process called translocation. Once through, they drive systemic inflammation and can seed infections in the abdominal fluid many people with cirrhosis accumulate.

The chemistry shifts too. Reviews pooling the measurements find faecal butyrate falling by 40% to 70%, with endotoxin in the blood rising two to fourfold. Butyrate is the compound gut bacteria make from fibre that the cells lining the gut use as fuel.

Secondary bile acids drop by roughly half. Those are the bile acids gut bacteria produce, and they act as signals telling the liver how much bile to make.

People in the lowest quarter for bacterial variety had around three times the risk of developing confusion from liver failure or an infection of the abdominal fluid.

Source: Combining amplicon sequencing and metabolomics in cirrhotic patients highlights distinctive microbiota features involved in bacterial translocation, systemic inflammation and hepatic encephalopathy

Replacing the community, and what happened

The obvious test is to put a healthier bacterial community in and see whether anything improves.

Hepatic encephalopathy is confusion and disorientation caused by a failing liver letting ammonia and other compounds reach the brain. Gut bacteria produce much of that ammonia, which is why the standard treatments are a laxative and a gut-targeted antibiotic.

A randomised trial gave people with cirrhosis and encephalopathy a faecal microbiota transplant, meaning stool from a healthy donor transferred to introduce their bacteria. Everyone stayed on their usual laxative and antibiotic. Some received it in 15 oral capsules, others by enema, against placebo, then were followed for six months.

Recurrence of the confusion fell in the transplant group. A separate analysis found the transplant also reduced antibiotic resistance genes in the recipients' gut bacteria.

This is specialist treatment under regulatory approval, not something to attempt outside a trial.

Source: Fecal Microbiota Transplant in Cirrhosis Reduces Gut Microbial Antibiotic Resistance Genes: Analysis of Two Trials

Why the food side still matters

Trials aside, the everyday picture points somewhere simpler.

The bacteria that decline in cirrhosis are largely the ones fermenting fibre and producing butyrate. Those compounds keep the gut wall sealed, which is exactly the defence that fails as the disease advances.

Malnutrition is also common in cirrhosis and worsens outcomes, so eating enough matters as much as eating well. Advice here needs to come from a dietitian who knows the case, because protein and salt requirements in advanced liver disease are specific and sometimes counterintuitive.

What this means for you

Cirrhosis needs specialist hepatology care, and treating the underlying cause, whether that's alcohol, viral hepatitis or fatty liver, is what changes its course. In addition, the trial above found replacing the gut community reduced recurrence of liver-related confusion on top of standard treatment, and people with more varied gut bacteria had markedly lower rates of serious complications. A varied, plant-rich diet supports the same gut bacteria this research ties to a sealed gut wall and less bacterial translocation. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.