Acute Pyelonephritis

  • Etiology: ascending urinary tract infection or hematogenous infection
  • US: focal spherical swelling, hypoechoic, hypoperfused on color / power doppler US
  • CT: low density on contrast enhanced CT, striated nephrogram
  • DDX: renal tumor which will not resolve on antibiotics
  • Complications: focus of infection can progress to abscess
  • Clinical: when the diagnosis of a “mass” (lobar nephronia) is made get a followup US in 1 month to ensure the “mass” has resolved

Cases of Acute Pyelonephritis

CT of acute pyelonephritis
Immediate (above) and delayed (below) axial CT with contrast of the abdomen shows multiple low density wedge-shaped lesions in the left kidney and a striated nephrogram on the delayed images.
US of duplicated kidney with ectopic ureterocele and hydroureteropyonephrosis
Sagittal US of the right kidney (upper left) shows a duplicated renal collecting system with the upper pole replaced by a round structure filled with echogenic material. Sagittal US of the right upper pole ureter (upper right) shows a tortuous ureter filled with echogenic material. Transverse US of the bladder (lower left) shows a round structure in the right side of the bladder that has echogenic material in its inferior portion and anechoic material in its superior portion. Sagittal US of the right ureter and bladder (lower right) shows the tortuous right ureter filled with echogenic material on the left side of the image and the rounded structure with the fluid-fluid level in the right side of the bladder.
US of acute pyelonephritis / acute lobar nephronia
Sagittal US of the right kidney (above) shows an ill-defined hypoechoic mass in the right upper pole that is obscuring the normal outline of the echogenic fat in the renal hilum. The mass was hypoperfused on color and power doppler US. AP image from a voiding cystourethrogram (below) shows bilateral vesicoureteral reflux, grade II on the left and grade III on the right