A focal infection of the kidney can cause a diagnostic dilemma by mimicking
a neoplasm. We describe a case of focal bacterial nephritis (acute lobar n
ephronia) caused by Escherichia coli in which the diagnosis was confirmed o
nly after surgical exploration. Although the patient had fever on admission
, urine and blood cultures were negative and fine needle aspiration of the
kidney could not rule out a well-differentiated carcinoma.