Bilateral loin pain and lower urinary tract symptoms.
Multiphasic kidney CT
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Both kidneys are mildly enlarged with patchy areas of hypoenhancing cortex at the corticomedullary phase and heterogeneous patchy contrast opacification at nephrographic phase with persistent patchy enhancement at the delayed excretory phase.
The swollen kidneys exert compression upon the pelvicalyceal system bilaterally with marked perinephric stranding as well as thickened Gerota's fascia.
Bilateral small foci of persistent hypoenhancement surrounded by perifocal edema suggestive of microabscesses.
There are alternating linear areas of contrast opacification of the renal parenchyma at the nephrographic and excretory phases giving the appearance of "striated nephrogram". Differential diagnosis includes acute pyelonephritis, renal vein occlusion, and acute ureteric obstruction. CT urography can provide good discrimination between the causes aided by the clinical status and laboratory studies. On the non-contrast study, there are no stones or evidence of acute ureteric obstruction. Renal vessels are well opacified. The marked stranding and the evolving microabscesses are consistent with the laboratory results of urinary tract infection.