Blood Pressure Determination; Esophageal and Gastric Varices/etiology; Gastrointestinal Hemorrhage/etiology; Hypertension, Portal/diagnosis; Portal Pressure; Blood Pressure Determination/instrumentation; Blood Pressure Determination/methods; Calibration; Catheterization; Equipment Design; Esophageal and Gastric Varices/complications; Esophageal and Gastric Varices/mortality; Esophageal and Gastric Varices/physiopathology; Esophageal and Gastric Varices/therapy; Gastrointestinal Hemorrhage/mortality; Gastrointestinal Hemorrhage/physiopathology; Gastrointestinal Hemorrhage/therapy; Humans; Hypertension, Portal/complications; Hypertension, Portal/mortality; Hypertension, Portal/physiopathology; Hypertension, Portal/therapy; Manometry; Practice Guidelines as Topic; Predictive Value of Tests; Reproducibility of Results; Risk Assessment; Risk Factors; Survival Analysis