The purpose is to investigate the effect of faecal microbiota transplantation (FMT) on complications, progression, and mortality of patients with liver cirrhosis. Further, the investigators want to examine the impact of FMT on the gut microbiota, gut barrier function, systemic inflammation, and immune function.

Patients with liver disease have a disturbed gut microbiota. This is often associated with disease progression and development of complications, so-called episodes of decompensation. In this trial, we will change the microbiota of these patients by transferring a healthy microbiota through faeces from a healthy donor, a procedure known as faecal microbiota transplantation (FMT). We will examine the effect of FMT on the prognosis and disease progression of the patients. Further, we will examine the mechanistic effects of FMT. We will at random divide 220 patients admitted with decompensation of liver cirrhosis evenly into two groups. One group will receive FMT and the other group will receive placebo. After the treatment, we will follow the patients for one year and examine disease progression as well as changes in their gut microbiota, gut barrier, and immune function.

Inclusion Criteria:

• Age 18-75 years
• Liver cirrhosis with Child-Pugh ≤ 12
• Acute decompensation requiring intervention (ascites, gastrointestinal bleeding, infections leading to progressive liver failure, overthepatic encephalopathy, alcoholic hepatitis)

Exclusion Criteria:

• More than one organ failure defined by CLIF-SOFA score
• Untreated malignancy apart from non-melanoma skin cancer
• Untreated viral hepatitis
• HIV
• Inflammatory bowel disease
• Celiac disease
• Clostridioides Difficile infection
• Pregnancy
• Unable to participate based on medical judgement