Transcript Role of radiologist in nephrolithiasis

RADIOLOGISTS’
ROLE IN
NEPHROLITHIASIS
May 2012
Dr W.J. Conradie
Department of Diagnostic Radiology
• Nephrolithiasis
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•
• Factors
influencing treatment
decision
• Imaging
•
•
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Adults
Children
Pregnancy
• Role
•
•
•
approach
in management
Antegrade pyelography
Percutaneous nephrostomy
Percutaneous nephrolithotomy
CONTENTS
•
Definition
Incidence
Classification
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Nephrolithiasis
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Presence of renal calculi.
Nephrocalcinosis

Form of nephrolithiasis, characterised by
diffusely scattered foci of calcification in the
renal parenchyma.


Stedman’s Concise Medical and Allied health dictionary. Third edition
“Kidney Stones” or “calculi”

Composed of a combination of crystals (organic and inorganic)
and proteins
NEHROLITHIASIS
DEFINITION
INCIDENCE

1.2 million Americans affected annually

Up to 14% of men and 6% of woman (M:V 3:1)

Any age: More than 1% < 18 years of age
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Recurrence rate
50 % in 5-10 years
 75% in 20 years
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Annual health care burden (USA)
$1.83 billion in 1993
 $5.3 billion in 2000
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CLASSIFICATION OF STONES
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Main role of Radiologist!!
Important: will impact patient treatment and
outcome!
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Stone size
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<5mm; 5-10mm; 10-20mm; >20mm
Stone location
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Upper-,middle- or lower calyx
Renal pelvis
Upper-, middle- or distal ureter
Bladder
X-ray characteristics
 Aetiology
 Stone composition
 Risk groups for stone formation
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X-RAY CHARACTERISTICS
AETIOLOGY OF STONE FORMATION
COMPOSITION
RISK GROUPS FOR STONE FORMATION
PERCUTANEOUS
NEPHROLITHOTOMY
±LASER
FACTORS INFLUENCING
TREATMENT DECISIONS
SIZE
AND
POSITIO
N
COMPOSITION,
AETIOLOGY
HU:
<450
-
Uric acid
600-900
-
Struvite
600-1100
-
Cystine
1200-1600
-
Hydroxyapetite (Calcium phosphate)
1700-2800
-
Clacium oxalate and Brushite (Calcium hydrogenphosphate)
Ultrasound
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Primary investigation?
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Varma G et al:
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Renal stones > 5mm - sensitivity 96%; specificity nearly 100%
All stone locations - reduces to 78% and 31%.
Sandu et al:
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“US has limited diagnostic value in the assessment of patients
with suspected renal stones…. particularly in the evaluation of
distal ureteral calculi “
Kidney-Ureter-Bladder radiograph (KUB)
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Sensitivity 44% to 77% and specificity 80% to 87%,
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KUB not be done if NCCT considered.
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Value:
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?Radiopaque/radiolucent
Follow up
IMAGING APPROACH
ADULTS
Intravenous urography (IVU)

Largely replaced by CT, MRI and US
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Contraindications:

General precautions to radiation and contrast agents (LOCM 370)
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Dosages
 Adult:
50-100ml
 Paediatric:
1ml per kg
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Technique
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KUB
15sec-1min film = Nephrogram phase
5 min film
= Excretion phase
10 min film
= Pelvi-ureteral phase
Release film
= Ureteral phase
Coned bladder view/ Post-void KUB
(Rapid injection of bolus)
(apply band)
(release band)
(empty bladder)
 Diagnosis
of calculi on IVP
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Nephrogram: Delayed or persistent due to ureteral obstruction
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Column of opacified urine proximal to stone
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Narrow ureter distal to calculus
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Oedema, inflammation
False impression of stricture
“Steinstrasse”
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Minimal dilated
Degree not related to stone size
German for “stone street” or “street of stones”
Several calculi are bunched up along ureter (common after
lithotripsy)
“Halo appearance”
(>2mm)
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(<2mm = Pseudoureterocele)
- oedema around distal ureter
IVU
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Non Contrast-enhanced CT (NCCT)
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Modality of choice
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sensitivity (95%–98%) and specificity (96%–100%)
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Superior to IVU in diagnosis of stones.
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Multidetector and Dual energy CT
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Multiplanar and 3D imaging – better
accuracy
All stones (except Indinavir and pure matrix stones)
Density, size, position, tissue differentiation
Stone-to-skin distance (ESWL)
Identify other causes for pain.
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Dalrymple et al - 55% of patients undergoing CT for acute flank pain did not have
stones; 15% other abnormalities that was detected.
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Drawback (NCCT)
Renal function?
 Anatomy of collecting
system?
 Radiation
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Reduce radiation by
low-dose CT
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100mAs; 120kv
BMI <30 or weight <90 kg
Dose similar to KUB study
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-Kluner et al
-Heneghan et al
Renal contrast study (CT or
IVU) recommended when
surgery is planned.
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CT preferred
Enables 3D
reconstruction
 Density/size
 Stone-to-skin
distance
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MULTIDETECTOR CT
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Signs of Nephrolithiasis
Stone within urethral lumen
 Dilated proximal- and normal
calibre distal lumen
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Technique
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No patient preparation
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Entire urinary tract
Dilatation may be absent!
Dalrymple et al:
Urethral stones more likely in
proximal (37%) and distal urethra
(33%) in
Diagnosis: NCCT
 Workup:
Contrast study
acute situation.
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Secondary signs:
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Thinner (1–3mm)
reconstructions recommended
- reduction in partial volume averaging
effect.
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Hydroureter
Hydronephrosis
Peri-nephric fat stranding
Peri-urethral oedema
Unilateral renal enlargement
Contrast filling defect (Indinavir
stones!)
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5-mm scans/3-mm coronal
reformatted images
- been found to improve stone detection
while allowing radiation dose benefits
Stone within urethral
lumen
Dilated proximal urethra
Secondary signs:
Hydronephrosis
Fat stranding
Renal enlargement
CALCULUS OR PHLEBOLITH?
CALCULUS
PHLEBOLITH
ANY SHAPE, HOMOGENOUS,
ALONG URETER
“SOFT-TISSUE RIM SIGN”
ROUND, CENTRAL LUCENCY,
IN TRUE PELVIS
“COMET TAIL SIGN”
STONE OR STENT?
FRAGILITY?
HOMOGENEOUS
VS HETEROGENEOUS
COMPOSITION?
DUAL-ENERGY CT SCANNER
STONE-TO-SKIN DISTANCE
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Magnetic Resonance urography (MRU)
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Relative insensitive for detection of calcification
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Relies on secondary signs of obstruction
Ureteral dilatation
 Perinephric fluid
 Persistant “filling defect”
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Technique dependant
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Excretory MR urography
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IV gadolinium
Sensitivities up to 90% reported
Static-fluid T2-weighted images
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T2 weighted technique
Sequences
• HASTE
• RARE
MRU
CHILDREN
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Ultrasound
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First line imaging
modality
Practical technique
No radiation or sedation
Information:
 Presence and size of
stones
 Location
 Degree of dilatation
and obstruction
 Cause
Nevertheless:
 Fail to identify stones
in 40 % of patients
 No information on
kidney function
CHILDREN

Plain films(KUB)
Identify stones
 Radio-opacity
 Facilitate follow up
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Intravenous urography (IVU)
Can be important tool
 Drawback: IV contrast
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Magnetic resonance urography (MRU)
“Filling defect” in T2 images
 Information:
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Anatomy of collecting system
Level of obstruction
Morphology of renal parenchyma
CHILDREN
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Helical CT
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Radiation risk
 Low-dose CT
 Reduced slices
5% of stones escape detection by non-enhanced helical CT
Sedation or anaesthesia - rarely needed with modern
high-speed CT apparatus.
Nuclear medicine
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99mTc-dimercaptosuccinyl acid scanning
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information about cortical abnormalities (such as scarring)
not for primary diagnosis of nephrolithiasis
Diuretic renogram
 Radiotracer (MAG3 or DPTA) and furosemide used to demonstrate:
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renal function
identify obstruction
indicate the anatomical level of the obstruction
PREGNANCY
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Remains diagnostic and
therapeutic challenge
Approach
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Ultrasound
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Limited Excretory Urogram (IVU)
for symptomatic patients
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Abdominal
Transvaginal
Endoluminal
Preliminary KUB;
15min;
60min after contrast
MRU!!
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Static T2 images
Antegrade pyelography
Needle through renal parenchyma into
minor calyx (posterior lower pole preferred)
 Inject contrast to demonstrate obstruction.
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Percutaneous nephrostomy
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Introduction of drainage catheter into
collecting system of kidney.
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obstruction due to stone
prior to percutaneous nephrolithotomy.
Percutaneous nephrolithotomy
Removal of larger renal calculi through a
nephrostomy line.
 After series of dilatations; nephroscope
inserted
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Direct removal of stones <1cm
Stone disintegration with US or
electrohydraulic disintegrator.
ROLE IN MANAGEMENT

http://www.uroweb.org/guidelines/online-guidelines/Guidelines on Urolithiasis.
European Association of Urology 2011. C. Türk (chairman), T. Knoll (vice-chairman),
A. Petrik, K. Sarica, M. Straub, C. Seitz
2.
Kambadakone A, Eisner B, Catalano O, Sahani D. New and evolving concepts in
the imaging and management of urolithiasis: Urologists’ Persapective.
Radiographics 2010. 30: 603-623
3.
Varma G, Nair N, Salim A, Marickar YM. Investigations for recognizing urinary
stone. Urol Res. 2009 Dec;37(6):349-52.
4.
Sandhu C, Anson KM, Patel U. Urinary tract stones I. Role of radiological
imaging in diagnosis and treatment planning. Clin Radiol 2003;58(6): 415–421.
5.
Dalrymple NC, Verga M, Anderson KR, et al. The value of unenhanced helical
computerized tomography in the management of acute flank pain. J Urol
1998;159(3):735–740.
6.
Kluner C, Hein PA, Gralla O, Hein E, Hamm B, Romano V, Rogalla P. Does ultralow-dose CT with a radiation dose equivalent to that of KUB suffice to detect
renal and ureteral calculi? J Comput Assist tomog. 2006 Jan-Feb; 30(1):44-50
7.
Heneghan P, McGuire KA, Leder RA, DeLong DM, Yoshizumi T, Nelson RC. Helical
CT for Nephrolithiasis and Ureterolithiasis: Comparison of Conventional and
Reduced Radiation-Dose Techniques. Radiology. 2003: 229:575–580
8.
Silverman SD, Leyendecker JR, Amis ES. What is the current role of CT
urography and MR urography in the evaluation of the renal tract? Radiology
2009; 250: 309-323
9.
Garcia-Valtuille R, Garcia-Valtuille L, Abascal F, Cerezal L, Arguello MC. Magnetic
resonance urography: a pictorial overview. BJR 79 (2006), 614-626.
10.
A guide to radiological procedures. Fifth edition. Frances Aitchison. Saunders
puplishers.
11.
Stedman’s concise medical and allied health dictionary. Third edition. Williams
and Wilkins publisher.
REFERENCES
1.