1. Inclusion and Exclusion Criteria Inclusion criteria: Inpatients who received laparotomy or laparoscopic splenectomy according to clinical, B-ultrasound scan, CT or MRI diagnosis of cirrhosis and portal hypertension.

Exclusion criteria:

1. ) Portal vein system thrombosis (PVST) found by preoperative color Doppler ultrasound or MRI examination;
2. ) Liver cirrhosis complicated with liver tumor;
3. ) Liver cirrhosis complicated with blood system diseases;
4. ) Patients who have not signed the informed consent form.

2. Research subgroup According to the order of the patients, the following groups are entered in turn, and the cycle is repeated.

1. ) Heparin group
2. ) Rivaroxaban group
3. ) Control group.

1. Inclusion and Exclusion Criteria Inclusion criteria: Inpatients who received laparotomy or laparoscopic splenectomy according to clinical, B-ultrasound scan, CT or MRI diagnosis of cirrhosis and portal hypertension.

Exclusion criteria:

1. ) Portal vein system thrombosis (PVST) found by preoperative color Doppler ultrasound or MRI examination;
2. ) Liver cirrhosis complicated with liver tumor;
3. ) Liver cirrhosis complicated with blood system diseases;
4. ) Patients who have not signed the informed consent form.

2. Research subgroup According to the order of the patients, the following groups are entered in turn, and the cycle is repeated.

1. ) Heparin group: Low molecular weight heparin 5000U ih Q12h was given 24 hours after operation, 5 days after operation. Warfarin 1.25-2.5 mg po qd, 30 days after operation. PT（prothrombin time）/INR（international normalized ratio） was kept at 1.25-1.5.
2. ) Rivaroxaban group: Rivaroxaban 10mg po qd from 24 hours after operation, 30 days after operation. PT/INR was kept at 1.25-1.5.
3. ) Control group: No preventive intervention measures. If platelets in the above groups are > 500× 109/L, aspirin 100 mg qd is added for 1 month. If platelets are > 1000× 109/L, platelet collection is performed.

3. Monitoring indicators Color Doppler ultrasound was reexamined 1, 2, 3 and 4 weeks after operation to find out whether PVST was present. Abdominal CT was performed when PVST was suspected. After the patient's condition is stable, the portal vein system ultrasound is reviewed monthly, and the follow-up time is 1 year.

Inclusion Criteria:

• Inpatients who received laparotomy or laparoscopic splenectomy according to clinical, B-ultrasound scan, CT or MRI diagnosis of cirrhosis and portal hypertension

Exclusion Criteria:

• Portal vein thrombosis found by preoperative color Doppler ultrasound or MRI examination;
• Liver cirrhosis complicated with liver tumor;
• Liver cirrhosis complicated with blood system diseases;
• Patients who have not signed the informed consent form.