Diagnostic Ultrasound - Abdomen and Pelvis

Xanthogranulomatous Pyelonephritis
Diagnoses: Urinary Tract
TERMINOLOGY
• Chronic renal inflammation usually associated with
longstanding urinary calculus obstruction (75%)
• Renal parenchyma is gradually replaced by lipid-laden
macrophages
• Diffuse (> 80%) and focal (< 20%) forms
• 3 stages of XGP: Intrarenal → perirenal → perinephric ±
retroperitoneal involvement
IMAGING
• Staghorn calculus with renal enlargement and perirenal
fibrofatty proliferation on CT
• Multiple focal low-attenuating renal masses with rim
enhancement on CT
• Renal sinus fat obliterated with large central "staghorn"
calculus on any modality
• Perinephric extension ± adjacent organs or structures may
include sinus tracts or abscesses
KEY FACTS
• Diffusely enlarged kidney with hypoechoic round masses
replacing normal parenchyma on US
• Ultrasound ideal at initial investigation; CT good for
assessing excretory function and retroperitoneal
involvement
PATHOLOGY
• Lipid-laden "foamy" macrophages, diffuse infiltration of
plasma cells and histiocytes
CLINICAL ISSUES
• Flank pain, fever, palpable mass & weight loss
• Rare complications: Hepatic dysfunction, extrarenal
extension, fistulas
• Long-term chronic process with good prognosis if treated,
and rare mortality
• Antibiotic treatment is sometimes effective
• Severe disease or perinephric extension usually requires
nephrectomy
(Left) Graphic shows lower
pole XGP with a longstanding
ureteropelvic obstruction by a
large staghorn stone ,
causing replacement of
parenchyma by collections of
foamy macrophages .
(Right) Transverse color
Doppler US shows a dilated
collecting system with
internal debris and an
obstructing stone st at the
ureterovesical junction. The
parenchyma is replaced by
cystic spaces containing debris
ſt. Note the lack of
vascularity in the expected
region of renal parenchyma.
(Left) Two ultrasounds in
another patient show cystic
intraparenchymal spaces st
peripheral to calculi (calipers)
in central renal pelvis. Color
Doppler US shows twinkling
artifact with stones. (Right)
Axial CECT shows a large
central calculus , nearcomplete
replacement of
parenchyma by cystic
collections st, and formation
of an abscess and sinus tract
necessitating into adjacent
abdominal wall. Proliferation
of perinephric fat in this
otherwise cachectic patient is
a response to chronic
inflammation.
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