Cytomegalovirus infection after liver transplantation: Epidemiology, risk factors, and management

Cytomegalovirus (CMV) is the most common viral infection that causes clinical disease after liver transplantation. CMV infection in liver transplant recipients can either be asymptomatic or can manifest clinically as fever with myelosuppression (termed CMV syndrome) or as tissue invasive CMV diseases that could involved the gastrointestinal tract, lungs, and the liver allograft. The most common risk factor for CMV disease after liver transplantation is the lack of CMV-specific immunity. In particular, CMV-seronegative recipients of liver allograft from CMV-seropositive donors (D+/R- mismatch) are considered at highest risk. Severe impairment in cell-mediated immunity from the use of lymphocyte-depleting drugs further augments the risk. In addition to its direct effects, CMV can increase the risk of other clinically relevant indirect effects such rejection, opportunistic infections, and mortality. Prevention of CMV infection and disease is of utmost importance after liver transplantation. In this regard, prevention of CMV disease can be achieved either with preemptive therapy (antiviral therapy is administered only in the presence of a positive CMV PCR or pp65 antigenemia) or antiviral prophylaxis (antiviral drug is administered to all patients at risk of CMV disease). Both approaches are similarly effective in preventing CMV disease, although antiviral prophylaxis is preferred for the highest risk liver transplant recipients. Treatment of CMV disease consists of intravenous ganciclovir (for severe disease) or oral valganciclovir (for mild to moderate CMV disease), and the duration of treatment should be guided by clinical and virologic monitoring. CMV resistance is an emerging concern after solid organ transplantation, although it remains rare after liver transplantation.