Diagnostic ultrasound ( PDFDrive )

324 PART II Abdominal and Pelvic Sonography
At ultrasound, the majority of kidneys with acute pyelonephritis
appear normal. However, ultrasound indings of pyelonephritis
include (Fig. 9.19) renal enlargement, compression of
the renal sinus, decreased echogenicity (secondary to edema)
or increased echogenicity (potentially from hemorrhage), loss
of corticomedullary diferentiation, poorly marginated mass(es),
gas within the renal parenchyma, 26,27 and focal or difuse absence
of color Doppler perfusion corresponding to the swollen inlamed
areas.
If the pyelonephritis is focal, the poorly marginated masses
may be echogenic, hypoechoic, or of mixed echogenicity. Echogenic
masses may be the most common appearance of focal
pyelonephritis. 28
Sonography, including power Doppler, is less sensitive than
CT, magnetic resonance imaging (MRI), or technetium-99m
single-photon emission computed tomography ( 99m Tc-DMSA
SPECT) renal cortical scintigraphy for demonstrating changes
of acute pyelonephritis. However, ultrasound is more accessible
and less expensive and thus an excellent screening modality for
monitoring and follow-up of complications, 29 as well as in the
assessment of pregnant patients with acute pyelonephritis because
of its lack of ionizing radiation. 26,27
A unique renal infection known as alkaline-encrusted pyelitis
has been described in renal transplants and native kidneys of
Acute Pyelonephritis on Sonography
Renal enlargement
Compression of renal sinus
Abnormal echotexture (either increased or decreased)
Loss of corticomedullary differentiation
Poorly marginated mass(es)
Gas within renal parenchyma
Focal or diffuse absence of color Doppler perfusion
corresponding to the swollen inlamed areas
A
B
C
D
FIG. 9.19 Acute Pyelonephritis in Three Patients. (A) Subtle focal increased echogenic areas are seen in the anterior cortex of the right
kidney. (B) Power Doppler perfusion defect in lower pole of kidney of patient with documented E. coli pyelonephritis. Note normal corresponding
gray-scale image. (C) Sagittal and (D) transverse sonograms in a third patient show a swollen and edematous kidney with focal altered echogenicity
and loss of corticomedullary differentiation. The renal sinus fat is attenuated by swollen parenchyma.