Transcript acute pyelonephritis: going throughout all imaging aspects?

INFECTIONS URINAIRES DU HAUT
APPAREIL URINAIRE : ASPECTS EN
IMAGERIE TOMODENSITOMETRIQUES
SUR UNE REVUE ICONOGRAPHIQUE DE
88 CAS
R.BENMOUSSA, M.SABIRI, N.TOUIL, O.KACIMI, N.CHIKHAOUI
Service de Radiologie des Urgences
CHU Ibn Rochd - Casablanca - Maroc
INTRODUCTION
• Acute pyelonephritis (APN) is known as an inflammation
of the kidney and upper urinary tract, most commonly
resulting from bacterial infection of the bladder.
• 10% to 30% of patients with APN require hospitalisation
and may even present with life-threatening complications
including shock, septicemia and multi-organ dysfunction
syndromes, what shows the importance of assessing
diagnosis.
• Bacterial nephritis or renal infection can be regarded as a
spectrum of clinical entities, progressing from mild APN to
renal abscesses or emphysematous pyelonephritis.
PURPOSES
To provide through an iconographic review, a
support showing different aspects of this
disease.
Grading radiological facts as in Picolli’s
classification according to severity of lesions.
To demonstrate impact of imaging, especially
CT on APN and renal infection radiological
analysis.
To recognize on imaging the most common
complications of APN and main differentials.
PATIENTS AND METHODS
• We studied patients showing with suspected diagnosis of
APN, during a period of two years (from May 2011 to May
2013).
• Inclusion criterias:
 Clinical criterias: presence of classical symptoms of APN
 Fever
 Presence of loin or flank pain with or without lower urinary
tract symptoms
 Positive urine dipstick for leukocytes and/or nitrites
 Biological criterias:
 Cytobacteriological urine
necesserally positive
examination
realized
but
not
• All patients underwent first an ultrasound
examination then Computed Tomography scanning.
CT SCAN TECHNIQUE
PARAMETERS
Scan duration (s)
Pitch
Section thickness (mm)
PELVIS
32 – 40
1–2
3
Table speed (mm/s)
3–6
Reconstruction interval (mm)
2–3
Kilovolt peak
120
Milliampere seconds
280
Use of intravenous contrast
Reconstruction algorithm
+
Standard soft tissue
RESULTS
•88 patients were included in the study.
•The diagnosis of APN was established half of cases (44
cases)
• Age: 33,2±8,6 years
• Gender:
-Women: 78%
-Men: 22%
22%
78%
Women
Men
RESULTS
• Ultrasonography:
-diagnosis of APN
established: 65,9%
-dismissed diagnosis: 34,1%
Ultrasonographic signs
n
%
Increase of kidney size with
hypoechoic areas
47
53,6
Blurred margins
21
24,4
Reduction of Doppler
vascularity
32
36,6
• The abdominal CT showed in 34,1% of dismissed
ultrasonographic diagnosis of APN,
4 cases of
perinephitic abscess and many perfusion troubles in the
other cases.
RESULTS
• Microbiological exams:
-Escherichia coli: 85,3%
-Others: 6,1%
-None: 8,6%
Germs
E.Coli
None
Others
85.30%
8.50%
6.10%
DEFINING APN ?
APN can be defined clinically, pathologically or radiologically:
• The British Medical Research Concil Bacteriuria Committee
defined APN as a clinical syndrome of flank pain, costovertebral
tenderness and fever accompanied by laboratory evidences of
renal infection including leukocytosis, pyuria, haematuria,
bacteriruria, positive urine culture and sometimes bacteraemia.
• Hill defined APN pathologically as a suppurative inflammation
of the renal parenchyma and pyelocaliceal system typically
distributed along one or more medullary rays supporting as
ascending route of infection.
• Radiologically, APN manifests on contrasted computed
tomography (CT) scans as hypoenhancing regions with or
without renal swelling, and may be focal or diffused.
ROLE OF CT
• CT imaging is often the modality of choice for the
evaluation of APN and renal abcesses.
• It is superior to intravenous urogram or renal
ultrasonography
in
detecting
renal
parenchymal
abnormalities like perinephric stranding, inflammatory
masses, decreased or delayed cortical enhancement, kidney
enlargement or gas formation, all of which may indicate
more severe APN.
• Non-contrast CT imaging will be able to rule out an
obstructed
collecting
system
requiring
urgent
decompression and drainage but it is not ideal for
diagnosing renal abcesses or APN.
NORMAL NEPHROGRAPHIC
DEVELOPMENT ON CT
NON ENHANCED
Before CMI
VASCULAR PHASE
10-15 seconds after
CMI
CORTICAL
NEPHROGRAPHIC
PARENCHYMAL
PHASE
NEPHROGRAPHIC
20-45 seconds after CMI
PHASE
45 seconds to 2 minutes after CMI
EXCRETORY PHASE
2-3 minutes after CMI
UNENHANCED CT SCAN
THROUGH THE KIDNEYS
CT SCAN OBTAINED 20-45 SECONDS AFTER
BEGINNING CONTRAST MATERIEL
ADMINISTRATION : CORTICAL NEPHROGRAM
WITH A CLEAR CORTICOMEDULLARY
INTERFACE
CT SCAN OBTAINED AT
45 SECONDS TO 2 MINUTES:
GENERALIZED NEPHROGRAM
CT SCAN OBTAINED AT 2-3
MINUTES: CONTRAST MATERIAL
IN THE COLLECTING SYSTEM
ACUTE PYELONEPHRITIS (APN)
Clinical and biological presentation
• Clinical signs:





Lumbar pain is unilateral more often than bilateral.
High temperature (fever of 39°C).
Pyuria.
Functional urinary signs (pollakiuria, dysuria).
Positive urine dipstick (screening): positive for leukocytes and
nitrites.
• Biological Signs:
o Cytobacteriological urine examination: bacteriuria ≥ 105/mL,
leukocyturia ≥ 104/mL and antibiogram.
o Inflammatory signs (polynucleosis, raised CRP and
procalcitonin).
ACUTE PYELONEPHRITIS (APN)
When do I use CT Scan for diagnosis?
 Patients whose clinical diagnosis is unclear.
 Patients who fail to respond to conventional médical treatment.
 Diabetic patients.
 Immunocompromised patients
Objective
« The primary value of CT scan is in delineating the extent of
the disease process and identifying significant complications
such as renal emphysema and abscesses with or without
perirenal extension or the presence of urinary obstruction »
ACUTE PYELONEPHRITIS (APN)
CT findings
• Typical: « a striated nephrogram on a conventionel CT scan
obtained during the excretory phase »
CT phase
aspect
Cortical and parenchymal nephrographic
phases
Wedge-shaped areas of hypoattenuating cortex and poor
corticomedullary differentiation
Excretory phase
Smaller wedge-shaped areas of diminished enhancement and
linear band of alternating hyper and hypoattenuation parallel
to the axes of tubules and collecting ducts
• Other signs:
•
•
•
•
•
Soft-tissue stranding and thickening of the Gerota’s fascia
Obliteration of the renal sinus
Caliceal effacement due to adjacent affected renal parenchyma
Thickening of the walls of the pelvis and calices
Mild dilatation of the renal pelvis and ureter
Acute Pyelonephritis in a 42 year-old-woman
Enhanced abdominal CT Scan during the cortical nephrographic
phase showing wedge-shaped areas of hypoattenuating cortex in the
left kidney which volume is increased
Acute pyelonephritis in a 29 year-old-woman
Enhanced helical CT Scan during excretory phase: sriated nephrogram
Acute pyelonephritis in a 34 year-old-woman
Enhanced CT Scan in excretory phase: smaller wedge-shaped areas of
diminished enhancement and linear band of alternating hyper and
hypoattenuation parallel to the axes of tubules and collecting ducts
Main differential
of APN:
RENAL
INFARCTION
« Cortical rim
sign » is a fine layer
of
cortical
enhancement and
is highly suggestive
of renal infarction
Right kidney infarction
Contrast-enhanced CT Scan in axial plane: Wedge-shaped
enhancement defect of the postérior lip of the right kidney
with cortical contrast uptake showing the « cortical rim
sign » confirming thet ischaemia is the mechanism of the
lesion
Ifergan J, Pommier R, Imaging in upper urinary tract infections.
Diagnostic and Interventional Imaging. 2012;93:509-519
ACUTE PYELONEPHRITIS (APN)
Keypoints of analysis
1. Identify the typical lesion
2. Chatecterize CT finding: Society of Uroradiology
 Unilateral or bilateral?
 Focal or diffuse?
 Focal swelling or no focal swelling?
 Renal enlargement or no renal enlargement?
3. Looking for complications:




Renal emphysema?
Renal abscess?
Perirenal extension?
Presence of renal obstruction?
COMPLICATIONS
RENAL ABSCESS
• Mechanism: liquefactive necrosis and abscess formation
resulting from severe vasospasm and inflammation.
• CT Scan findings:
 Well-defined mass of low attenuation with a thick, irregular
wall or pseudocapsule, which is better imaged with contrast
enhancement.
 Gas within a low attenuation or cystic mass.
 Renal parenchyma around the abscess cavity poorly enhanced
on early views, hyperattenuating on delayed views.
 Fascial and septal thickening and perinephric fat obliteration.
Renal abscess of the left kidney in a diabetic 43 year-old-man
Enhanced helical CT Scan within excretory phase showing a welldefined mass of low attenuation with a thick wall evident with
contrast enhancement
Renal abscess of the right kidney in a 35 year-old-woman
Enhanced helical CT Scan within parenchymal phase showing a
well-defined mass of low attenuation deforming outline of the
right kidney
Main differential
of renal abscess:
SURINFECTED
RENAL CYST
Thickening
and
enhancement of the
cyst
wall
and
inflammatory
changes surronding
the affected cyst are
highly suggestive of
surinfected renal cyst.
Surinfected right kidney cyst
Contrast-enhanced CT Scan in axial plane during the
parenchymal nephrographic phase: Thickening and
contrast uptake in the wall of a right kidney cyst with
oedema of the perilesional parenchyma
Ifergan J, Pommier R, Imaging in upper urinary tract infections.
Diagnostic and Interventional Imaging. 2012;93:509-519
PICOLLI’S CLASSIFICATION
ACCORDING TO SEVERITY
Picolli GB, Colla L, Development of kidney scars after acute uncomplicated pyelonephritis:
relationship with clinical, laboratory and imaging data at diagnosis. World J Urol 2006;24:66-73
COMPLICATIONS
PERINEPHRIC ABSCESS
• Mechanism:
 Rupture of a renal abscess into the perirenal space.
 Developing directly from APN
• Context: Diabetic patients and patients with septic emboli
• CT Scan findings:
 Areas of soft-tissue or fluid attenuation within the perirenal
space.
 May involve the psoas muscle and extend to the pelvis.
 Gas occasionally present.
 Rarely, a postinflammatory cystic fluid collection < 3cm in
diameter without appreciable thickening or enhancement of the
wall.
Perirenal abscess of the left kidney in a 35 year-old-woman, already having
renal abscess 6 days before
Enhanced helical CT Scan within cotical nephographic phase showing a mass
of low attenuation deforming outline of the left kidney and extending the
perirenal space
COMPLICATIONS
EMPHYSEMATOUS PYELONEPHRITIS
• Mechanism: fulminant gas-forming infection with
commonly E.Coli, Klebsiella pneumoniae and Proteus mirabilis.
• Context: symptoms of severe APN in uncontrolled
diabetes mellitus patients
• CT Scan findings: GAS
 Renal or perirenal fluid collections with bubbly or loculated gaz
in the parenchyma or collecting system.
 Localiszed in the renal parenchyma, the subcapsular,
perinephric or pararenal space, the collecting system or
occasionally the vascular system.
• Differential:
CLASSICAL
EMPHYSEMATOUS
PYELONEPHRITIS
which
is
characterized
by
parenchymal destruction, streaky or motted gas, and little or
no fluid.
Emphysematous pyelonephritis in a diabetic 59 year-old-woman
presenting with clinical signs of APN
Renal ultrasonography showing the presence of gas in the sinus of the
right kidney
Emphysematous pyelonephritis in a diabetes mellitus patient
Enhanced CT Scan during parenchymal phase showing the presence of gaz
among the right renal parenchyma
COMPLICATIONS
PYONEPHROSIS
• Mechanism: concomitant suppuration of
the
parenchyma and the collecting system, usually
secondary to a calculus and more rarely to other causes
of obstruction.
• Ultrasonography:
 Dilation of the pelvicalyceal system.
 Fine mobile or sloping echoes in the calyces.
• CT Scan findings:
 Dilation of the pelvicalyceal system.
 Thickening of the walls of the renal pelvis.
Pyonephrosis in a 52 year-old-man
Contrast-enhanced CT Scan during excretory phase showing a
dilated left renal pelvis, with poor excretion and increased density
within the renal pelvis.
SUMMARY
• APN is a severe stat responsible for a considerable
mortality if not assessed in time.
• The ultrasonography is often insufficient to define
APN, but when realized eartly possesses value for
looking for obstruction and indicating Ct Scan and
ponctions.
• Nowadays, abdominal CT Scan is the best exam for
assessing upper urinary tract infections and their
complications.
• Therefore, respecting the recommandations for good
CT scan technique is essential for good assessment.
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•
Lim SK, Ng FC, Acute pyelonephritis and renal abscesses in adults: correlating clinical parameters
with radiological (computed tomography) severity. Ann Acad Med Singapore 2011; 40:407-13
•
Picolli GB, Colla L, Development of kidney scars after acute uncomplicated pyelonephritis:
relationship with clinical, laboratory and imaging data at diagnosis. World J Urol 2006;24:66-73
•
Kawashima A, Sandler CM, CT of renal inflammatory disease. Radiographics 1997;17:851-866
•
Wan YL, Lee TY, Acute gas-producing bacterial renal infection: correlation between imaging findings
and clinical outcome. Radiology 1996; 198:433-438
•
Ifergan J, Pommier R, Imaging in upper urinary tract infections. Diagnostic and Interventional
Imaging. 2012;93:509-519
•
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