A case of histopathologically confirmed infective endocarditis with no vegetations observed during preoperative diagnosis.

An 81-year-old woman on maintenance hemodialysis (HD) was admitted to the hospital with fever and repeated positive blood cultures for coagulase-negative staphylococci. The patient had a history of aortic valve replacement for aortic valve stenosis (AS). Although one major criterion and two minor criteria from the Duke criteria were met and therefore infective endocarditis (IE) was suspected for this case, no definitive diagnosis was made. Vegetations were not observed on the transesophageal echocardiography, but AS was prominent. The patient was refractory to antibiotic therapy using vancomycin, and blood cultures did not convert to negative. To treat the suspected IE and AS, aortic valve replacement was performed. Although vegetations were not observed in the resected valve, gram-positive cocci were found in clusters, and a histopathological diagnosis of IE was made. The postoperative blood culture converted from positive to negative, and the patient was subsequently discharged from the hospital. While relative risk of IE is high in HD patients, a definitive diagnosis of IE may be difficult due to calcification of the valve and valve replacement. In HD patients with bacteremia, suspicion of IE should be aggressively pursued if other sources of infections are negative, and if the patient is refractory to medical treatment, surgical treatment may be necessary.