Diagnostic Ultrasound - Abdomen and Pelvis

Emphysematous Pyelonephritis
Diagnoses: Urinary Tract
TERMINOLOGY
• Gas-forming upper UTI involving renal parenchyma &/or
perinephric space
IMAGING
• Highly echogenic areas within renal sinus and parenchyma
with "dirty" shadowing
• Ring-down artifacts: Air bubbles trapped in fluid
• Perinephric fluid collections may be seen
• Type I (33%): Parenchymal replacement by gas,± crescent
of subcapsular or perinephric gas
• Type II (66%): Renal or perirenal fluid abscesses with bubbly
gas pattern ± gas within renal pelvis
• CT is ideal to determine location and extent of renal and
perirenal gas
• Evaluation for psoas abscess and spinal osteomyelitis is
essential
KEY FACTS
TOP DIFFERENTIAL DIAGNOSES
• Emphysematous pyelitis
○ Gas is limited to renal collecting system and pelvis, not
parenchyma
○ Less clinically serious than emphysematous
pyelonephritis, unless obstructed
PATHOLOGY
• Single or mixed organism(s) infection
• Escherichia coli (68%), Klebsiella pneumoniae (9%)
• Proteus mirabilis, Pseudomonas, Enterobacter, Candida,
Ilostridia species
CLINICAL ISSUES
• Extremely ill at presentation: Fever, flank pain,
hyperglycemia, acidosis, dehydration and electrolyte
imbalance
(Left) Ill-defined hyperechoic
material in the posterior renal
cortex causes posterior
acoustic shadowing .
However, the shadowing is
much less dense, or obscuring,
than would be expected for
something like a calcification
of this size. (Right) As on the
transverse image, gas in the
central left kidney is highly
echogenic with posterior
"dirty" shadowing . The
renal sinus is obscured and it is
hard to differentiate
emphysematous
pyelonephritis from
emphysematous pyelitis on
this image.
(Left) NECT in the same
patient shows gas in the renal
parenchyma and pelvis st.
The adjacent posterior renal
fascia is thickened by edema
and inflammation, but there is
no perinephric collection .
(Right) Sagittal reconstruction
CT shows a lobulated area of
intraparenchymal gas with
sparing of the renal sinus fat
.
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