[Acute pyelonephritis. Role of diagnostic imaging]

To asses the role of imaging in acute pyelonephritis by retrospectively evaluating a number of cases observed with special care to US and CT signs that may be useful for an early and correct diagnostic assessment.

From 1994 to the first quarter of 2000 we observed 95 patients clinically suspected of having acute pyelonephritis (81 females and 14 males, age range 2-80 years; 75% were under 40 years old). Sonography was performed as an emergency in 78 patients. CT scan with contrast media was performed in acute phase in 78 patients acquiring the images in the pre-contrastographic phase, 60 s after the administration of contrast media (portal phase), after 5 to 10 min (excretory phase), and after 3 to 6 hours (very late phase). In 47 patients, diagnosed as having acute pyelonephritis, a follow-up CT scan was performed at 30 days, 45 days, 3 months and 6 months from the acute episode.

In 78 of the patients clinically suspected of having acute pyelonephritis, the CT examination allowed to assess the presence or lack of the inflammatory focus. In 17 cases US discovered causes other than acute pyelonephritis on admission; in 25 out of 61 patients it allowed assessment of a pyelonephritic focus that was confirmed with CT. The CT examination with contrast media proved to be a reliable and fondaments method in the diagnosis of pyelonephritic focus especially as it revealed the lack of concentration of contrast media in the flogistic foci, in the very late fase. This method furthermore allows to discover alterations in peri and pararenal regions and to rule out abscesses and renal infarcts. US had a sensitivity of 50% and a specificity of 70% in the diagnosis of acute pyelonephritis, but those may be improved by power Doppler.

In suspected acute pyelonephritis US offers useful indications for a quick and correct diagnostic assessment, but CT examination with contrast media proved to be more reliable than US. In our experience US and above all CT examination rapidly identified patients affected by acute pyelonephritis, thereby allowing us institute a timely antibiotic therapy and obtain a brilliant therapeutic response.