AJR 2004; 183:1708-1710
© American Roentgen Ray Society
Necrotizing Fasciitis Caused by Xanthogranulomatous and Emphysematous Pyelonephritis: Importance of the Inferior Lumbar Triangle Pathway
Kousei Ishigami1,
Jody A. Bolton-Smith1,
Barry R. DeYoung2 and
Thomas J. Barloon1
1 Department of Radiology, University of Iowa Carver College of Medicine, 200
Hawkins Dr., 3885 JPP, Iowa City, IA 52242-1077.
2 Department of Pathology, University of Iowa Carver College of Medicine, Iowa
City, IA 52242-1077.
Received January 5, 2004;
accepted after revision March 9, 2004.
Address correspondence to K. Ishigami
(Kousei-ishigami{at}uiowa.edu).
Introduction
The superior and inferior lumbar triangles are areas of relative weakness
in the abdominal wall caused by the absence of external muscle layers. These
pathways provide an anatomic explanation for the classic sign of subcutaneous
discoloration in the costovertebral angle (Grey Turner sign) associated with
acute pancreatitis and unusual traumatic lumbar hernias
[1,
2]. We present a case of
xanthogranulomatous and emphysematous pyelonephritis complicated with
necrotizing fasciitis of the left flank, in which the inferior lumbar triangle
pathway played an important role in development. CT clearly showed not only
characteristic findings of three uncommon entities but also the inflammatory
spread through the unique anatomic location. In this case, awareness of this
pathway was important to elucidate the development of necrotizing fasciitis
from the retroperitoneal infection.
Case Report
A 42-year-old woman had a 2-week history of vague left lower abdominal
pain. She was immunosuppressed as a result of prednisone and azathioprine
therapy for a 15-year history of neurosarcoidosis. Her vital signs were
normal, and the WBC was 9,100/µL3 (normal range,
3,700–10,400/µL3) with a normal differential. Her serum
glucose level was 190 mg/dL (normal range, 65–110 mg/dL). No skin
discoloration was found in her left abdominal wall.
We performed IV contrast-enhanced CT to clarify the cause of her left lower
abdominal pain. CT showed the left kidney replaced by multiple hypodense
masses with a staghorn calculus (Fig.
1A). Gas bubbles were present in the renal parenchyma (Figs.
1B and
1D) and the perinephric space.
A fluid collection contained gas below the left kidney, which extended toward
the subcutaneous tissue of the left flank through the inferior lumbar triangle
(Figs. 1C and
1D). From these findings, we
made the diagnosis of xanthogranulomatous pyelonephritis with emphysematous
pyelonephritis. The presence of gas in the left abdominal wall suggested
necrotizing fasciitis and an extension of the inflammatory process that spread
from the retroperitoneal gas-forming abscess.
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Fig. 1A. —42-year-old woman with xanthogranulomatous and emphysematous
pyelonephritis complicated with necrotizing fasciitis. Contrast-enhanced CT
scan shows that left kidney is replaced by multiple hypodense masses
(asterisks) with enhancing walls. Staghorn calculus (arrow)
is noted in renal pelvis. These findings are consistent with
xanthogranulomatous pyelonephritis. Small air bubbles (arrowheads)
are also seen in perinephric space.
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Fig. 1B. —42-year-old woman with xanthogranulomatous and emphysematous
pyelonephritis complicated with necrotizing fasciitis. CT scan shows
emphysematous pyelonephritis by presence of gas in left kidney parenchyma.
Arrow indicates gas in renal parenchyma; arrowhead indicates staghorn stone
material in renal pelvis.
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Fig. 1D. —42-year-old woman with xanthogranulomatous and emphysematous
pyelonephritis complicated with necrotizing fasciitis. Oblique coronal
reformatted image shows gas-forming abscess extending from left kidney
(white arrows). Black arrows indicate that inflammatory process
extends to abdominal wall through inferior lumbar triangle. Gas, staghorn
calculus, and hypodensity masses are noted in left kidney.
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Fig. 1C. —42-year-old woman with xanthogranulomatous and emphysematous
pyelonephritis complicated with necrotizing fasciitis. CT scan shows
gas-forming abscess in posterior pararenal space at level of left iliac crest.
Inflammatory process extends to subcutaneous tissue in left flank and back
through inferior lumbar triangle (arrow). Note multiple gas bubbles
(arrowhead) in subcutaneous tissue, consistent with necrotizing
fasciitis.
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Left nephrectomy and débridement and necrotomy of the left flank
were performed. Intraoperative findings showed an abundant amount of purulent
material extending from the retroperitoneal space to the subcutaneous tissue
above the level of the left iliac crest. On examination of the gross specimen,
we found that nearly the entire left kidney was necrotic, with two laminated
stones with large dilated calices and areas of yellow rubbery tissue. The
calices also contained a green purulent exudate. Microscopically, many areas
of the kidney architecture were completely destroyed by inflammatory
infiltrates. Abscesses contained necrotic debris, neutrophils, and
microorganisms, which were surrounded by large amounts of foamy histiocytes
and lymphohistioplasmacytic infiltrates. Examination of the gross specimen
from the left flank revealed that much of the fat and soft tissue was purulent
and necrotic. However, the skin appeared uninvolved. Microscopically,
fibroadipose tissue and skeletal muscle contained an abundance of lymphocytes,
histiocytes, some plasma cells, and a few neutrophils. In some areas of
necrosis, hemorrhage and granulation tissue were present. The inflammation did
not involve the dermis or epidermis. Therefore, histologic diagnosis of
xanthogranulomatous pyelonephritis and necrotizing fasciitis was made.
A culture from the abdominal wall abscess grew many mixed anaerobic
organisms including Bacteroides fragilis. Urine culture grew
Escherichia coli and Proteus mirabilis. The results of blood
culture were negative.
The patient was discharged 1 month after surgery, and she is being followed
up at the outpatient clinic.
Discussion
Xanthogranulomatous pyelonephritis and emphysematous pyelonephritis are two
uncommon variants of pyelonephritis. The combined occurrence is rare, with
only six cases reported
[3–6].
Necrotizing fasciitis is a life-threatening and widespread infection in the
underlying fascial plane. Although there has been no case report regarding
concurrence of these three entities, diabetes mellitus is the most common
predisposing factor for emphysematous pyelonephritis and necrotizing fasciitis
[5,
7]. Necrotizing fasciitis can
develop secondary to deep infection or malignancy
[7]. Wysoki et al.
[7] reported that the CT
criteria of asymmetric fascial thickening and gas are valuable in assessing
suspected necrotizing fasciitis. Therefore, necrotizing fasciitis should be
suspected in a patient with diabetes or an immunosuppressed patient with both
deep and superficial gas-forming infections.
Two sites of anatomic weakness in the abdominal wall of the flank are
caused by the superior and inferior lumbar triangles. The grynfeltt-lesshaft
superior lumbar triangle is an inverted triangle bordered by the 12th rib
superiorly, the internal oblique muscle anteriorly, and the quadratus lumborum
muscle posteriorly [2]. Petit's
inferior lumbar triangle is upright and bordered by the iliac crest
inferiorly, the external oblique muscle anteriorly, and the latissimus dorsi
muscle posteriorly [2]
(Fig. 2). Because these
triangles are void of muscular layers, they are areas of relative weakness in
the abdominal wall, and unusual traumatic lumbar hernias are known to develop
through them [2]. These
pathways also provide an anatomic explanation for the classic sign of
subcutaneous discoloration in the costovertebral angle (Grey Turner sign)
associated with acute pancreatitis because the extravasated pancreatic enzymes
or blood-stained fluid tracks along these structural defects to the
subcutaneous tissue of the flanks
[1]. Awareness of this pathway
is crucial to elucidate an unusual presentation of retroperitoneal infection
and development of necrotizing fasciitis.
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Fig. 2. —Volume-rendered image of different patient shows lack of
muscular layers. Petit's inferior lumbar triangle is just cephalad to crest
(asterisk), which is bordered by external oblique muscle
anterolaterally, latissimus dorsi muscle posteriorly, and quadratus lumborum
muscle medially.
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CT findings of our case were sufficient to diagnose xanthogranulomatous
pyelonephritis and emphysematous pyelonephritis. However, extrarenal extension
and fistula formation are common in xanthogranulomatous pyelonephritis,
including extension to the perirenal space, anterior and posterior pararenal
spaces, ipsilateral psoas muscle, diaphragm, posterior abdominal wall, skin,
and bowel wall [8]. Thus, care
must be taken to search for a renocolic fistula, which can also cause abnormal
gas in the renal parenchyma. In addition, in our case, the anatomic weakness
of this pathway was thought to be more accentuated by the debilitated
condition of the patient because of atrophic muscles and susceptibility to
infection.
In summary, we presented a case of xanthogranulomatous and emphysematous
pyelonephritis complicated with necrotizing fasciitis through the inferior
lumbar triangle pathway. CT showed typical findings of two uncommon types of
pyelonephritis and a gas-forming abscess extending to the abdominal wall
through the inferior lumbar triangle pathway. This case not only represented a
concurrence of three uncommon entities but also alerted us to the importance
of anatomic considerations in the imaging interpretation of disease
extension.
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Introduction
Case Report
