Elevated plasma bilirubin levels are a frequent clinical finding. It can be secondary to alterations in any stage of its metabolism: (a) excess bilirubin production (i.e., pathologic hemolysis); (b) impaired liver uptake, with elevation of indirect bilirubin; (c) impaired conjugation, prompted by a defect in the UDP-glucuronosyltransferase; and (d) bile clearance defect, with elevation of direct bilirubin secondary to defects in clearance proteins, or inability of the bile to reach the small bowel through bile ducts. A liver lesion of any cause reduces hepatocyte cell number and may impair the uptake of indirect bilirubin from plasma and diminish direct bilirubin transport and clearance through the bile ducts. Various analytical methods are currently available for measuring bilirubin and its metabolites in serum, urine and feces. Serum bilirubin is determined by (1) diazo transfer reaction, currently, the gold-standard; (2) high-performance liquid chromatography (HPLC); (3) oxidative, enzymatic, and chemical methods; (4) direct spectrophotometry; and (5) transcutaneous methods. Although bilirubin is a well-established marker of liver function, it does not always identify a lesion in this organ. Therefore, for accurate diagnosis, alterations in bilirubin concentrations should be assessed in relation to patient anamnesis, the degree of the alteration, and the pattern of concurrent biochemical alterations.

Background The diagnosis of hepatitis B virus (HBV) infection requires HBV DNA testing and serologic testing for detection of the surface antigen (HBsAg) and the hepatitis B core antibody (anti-HBc). There is a population of patients with occult HBV infection (OBI), which is not detected by HBsAg or HBV DNA quantification in blood, despite the presence of active replication in the liver. Scope This document provides a definition of OBI and describes the diagnostic techniques currently used. It also addresses the detection of patients with risk factors and the need for screening for OBI in these patients. Summary Correct diagnosis of OBI prevents HBV reactivation and transmission. Diagnosis of OBI is based on the detection of HBV DNA in patients with undetectable HBsAg in blood. Perspectives A high number of patients with OBI may remain undiagnosed; therefore, screening for OBI in patients with factor risks is essential. For a correct diagnosis of OBI, it is necessary that new markers such as ultrasensitive HBsAg are incorporated, and a more comprehensive marker study is performed by including markers such as cccDNA.

Resumen Introducción En el contexto de la infección por SARS-CoV-2 no es infrecuente encontrar alteraciones hepáticas, tanto en pacientes con enfermedad hepática crónica previa como sin ella. Contenido En esta revisión, se examina el conocimiento actual sobre la relación entre la COVID-19 y el daño hepático, frecuentemente observado en el seno de esta enfermedad. Resumen Si bien no está completamente dilucidada la patogénesis del daño hepático, parece ser consecuencia de la combinación de varios factores, entre los que se encuentran el daño directo del virus, el derivado de la hiperactivación del sistema inmune, el isquémico y el farmacológico. El valor pronóstico de estas alteraciones también está bajo intensa investigación. La potencial repercusión de las mismas aboga por la necesidad de adecuar el manejo y el tratamiento de los pacientes, particularmente en el contexto de pacientes con enfermedad hepática crónica o trasplantados hepáticos. Perspectiva Se desconocen actualmente muchos aspectos relativos a la afectación hepática durante la COVID-19, particularmente en las formas graves de la enfermedad. El desarrollo de nuevos estudios referidos a las implicaciones clínicas de la COVID-19 en el hígado, tanto en estado sano como enfermo, podrían ayudar a ajustar las recomendaciones de tratamiento y vacunación según el perfil del paciente.