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actas urol esp. 2010;34(9):764–774
Revista Oficial de la AEU y de la CAU
ACTAS
ACTAS UROLÓGICAS ESPAÑOLAS
Actas Urológicas Españolas
Vol. 34. Núm. 2.
UROLÓGICAS
E S PA Ñ O L A S
EDITORIALES
129
¿Es realmente el cistocele un factor de obstrucción
infravesical?
¿Entran el axonema y las mitocondrias espermáticas
en el oocito durante el proceso de la fecundación?
132
ORIGINAL BREVE- CÁNCER DE TESTÍCULO
134
ORIGINAL BREVE- SUPRARRENAL
Infarto testicular segmentario: un pseudotumor infrecuente
REVISIÓN- CÁNCER RENAL
Tratamiento de los tumores renales localmente avanzados
Adrenalectomía laparoscópica por metástasis metácrona.
Experiencia en 12 casos
ORIGINALES- HISTORIA
Treinta años del Grupo de Trabajo de Urología Oncológica
de la Asociación Española de Urología (1978-2008)
Baltasar Llopis Mínguez (1934-1990). Pionero en
la investigación del cáncer vesical y en la introducción
de la informática en Urología
142
158
ORIGINAL- CÁNCER UROTELIO SUPERIOR
Abordaje del uréter distal en la nefroureterectomía
laparoscópica
165
ORIGINAL- ENDOUROLOGÍA
Fotovaporización prostática láser Greenlight HPS
en régimen de cirugía mayor ambulatoria
170
ORIGINAL- DISFUNCIÓN MICCIONAL
Distribución demográfica y prevalencia de la vejiga
hiperactiva en Venezuela
176
ORIGINAL- SUPRARRENAL
www.elsevier.es/actasuro
Febrero 2010
ORIGINAL BREVE- DISFUNCIÓN MICCIONAL
Comentario editorial al trabajo “Nefrectomía laparoscópica
asistida por la mano”
Suprarrenalectomía laparoscópica. Experiencia de 5 años
181
ORIGINAL BREVE- CÁNCER RENAL
Nefrectomía laparoscópica asistida por la mano
en casos difíciles
194
201
206
Tumor adenomatoide de túnica albugínea. Caso clínico
208
Seminoma testicular bilateral sincrónico en un paciente
adulto con criptorquidia bilateral: reporte de un caso
y revisión de la literatura
210
Blastomicosis prostática: presentación de un caso y revisión
de la literatura
212
Fractura de pene. A propósito de dos casos
213
Malformación arteriovenosa renal congénita: utilidad
de la resonancia magnética para el diagnóstico y abordaje
endovascular
215
IMÁGENES EN UROLOGÍA
Hernia paraestomal gigante en paciente con derivación
urinaria ileal
218
Carcinoma epidermoide balanoprepucial de nueva aparición
tras circuncisión
218
219
Perlas escrotales o escrotolitos
186
189
CARTAS CIENTÍFICO-CLÍNICAS
Tumor fibroso solitario vesical
Exéresis de masa residual retroperitoneal:
vena renal retro-aórtica
219
Edición electrónica: Free Full Text Español/Inglés
www.elsevier.es/actasuro
Special article
Intravenous urography is dead. Long live computerized
tomography!
Á. Franco*, M. Tomás, and A. Alonso-Burgos
Servicio de Radiología, Fundación Jiménez Díaz, Madrid, Spain
ARTICLE INFORMATION
A B S T R A C T
Article history:
Very important changes have happened in the field of the genitourinary image during
Received 20 April, 2010
the last half of the 20th century, so that for most of the historical intravenous urography
Accepted 27 April, 2010
indications, nowadays the computerized tomography (CT) is the technique of choice.
Keywords:
techniques in the adult-related most frequent urological pathology, including: urolithiasis,
Urogram
haematuria, infections, tumours, surgery follow-up and pyelectasis, specially focused in
Computered tomography
CT.
The aim of this report is to perform an update in the correct use of the imaging
Haematuria
Urolithiasis
Phielonefritis
A brief historical review of the urological imaging techniques is performed, emphasizing
the physical principles.
In the second part, the role played by plain X-ray, ultrasound, CT and MR in the different
urological pathologies are reviewed, discussing the sensitivity and specificity of each
technique.
A brief reflection is finally carried out on of the radiation doses.
© 2010 AEU. Published by Elsevier España, S.L. All rights reserved.
La urografía intravenosa ha muerto, ¡viva la tomografía computarizada!
R E S U M E N
Palabras clave:
Durante la última mitad del siglo xx se han producido cambios muy importantes en el
Urografía
campo de la imagen genitourinaria, de forma que para la mayor parte de las históricas
Tomografía computarizada
indicaciones de la urografía intravenosa la tomografía computarizada (TC) es ahora la
Hematuria
técnica de elección.
Litiasis
Pielonefritis
El objetivo de este trabajo es realizar una actualización del correcto uso de las pruebas de imagen, con especial enfoque en la TC, en la patología urológica del adulto
revisando las entidades más frecuentes: litiasis, hematuria, infecciones, tumores, controles de cirugía y pielectasia.
Hacemos un breve recorrido histórico por las pruebas de imagen utilizadas en urología a través de los años, haciendo hincapié en sus fundamentos físicos.
*Corresponding author.
E-mail: [email protected] (Á. Franco).
0210-4806/$ - see front matter © 2010 AEU. Published by Elsevier España, S.L. All rights reserved.
actas urol esp. 2010;34(9):764–774
765
En la segunda parte revisamos las diferentes patologías urológicas y el papel que
desempeñan la radiografía simple, la ecografía, la TC y la resonancia magnética, analizando su sensibilidad y su especificidad.
Por último, hacemos una breve reflexión acerca de las dosis de radiación de los diferentes métodos radiológicos.
© 2010 AEU. Publicado por Elsevier España, S.L. Todos los derechos reservados.
Introduction
Genitourinary imaging underwent very significant changes
during the last half of the 20th century which have resulted
in a limited use of intravenous urography (IVU) in the first
decade of the 21st century. IVU is a projection imaging
technique where superimposition of structures may hide
significant findings. As compared to it, multidetector
computed tomography (CT) technology allows for acquisition
of thin sections of the whole urinary tract in a single breathholding period. CT is currently the procedure of choice for
most traditional indications of IVU. There are in medical
literature many examples showing the decreased use of
IVU. Thus, at the Montefiore Center in New York, 323 IVUs
were performed in 1999 and only 17 in 2006. Similarly, no
urographies have been performed at the Brigham Hospital
since 2000.1
Despite acceptance of CT for many conditions, many
clinicians show a sometimes striking resistance to use the
new imaging procedures. We therefore decided to review in
this article the current status of imaging in urological adult
disease, paying special attention to the contributions and
advantages of CT examination of such conditions.
Urological imaging history and techniques
History of urological imaging started in the decade of 1920
with the advent of iodinated contrast, which allowed for
assessment of the excretory system. IVU was the “queen”
procedure in examination for urological disease, and was
performed in Spain by urologists or radiologists, depending
on the institution. It was indicated for arterial hypertension,
renal masses, renal colic, urinary tract infections, hematuria,
follow-up of surgery, congenital malformations, trauma, and
so on.
Toward the end of the 70s, ultrasound examination
(US) started to be widely used in clinical practice. It was
mainly helpful to differentiate solid from cystic masses, thus
avoiding the direct cyst puncture followed by cyst X-rays that
was done before widespread use of ultrasound.2
Ultrasound is a diagnostic procedure based on reflection,
or echo, of ultrasound in the organs. Ultrasound penetrance
depends on the emission source and biophysical characteristics
of the medium, i.e. its absorption and reflection. There are no
adverse events associated to use of ultrasound. The ability of
“insonated” structures to return echoes to its source is called
echogenicity. We therefore speak of hyperechoic, hypoechoic,
or anechoic structures.
CT scans started to be used in the 80s for the study and
staging of renal masses. Machines used at the time were
very slow. Some of them took 16 seconds to acquire a
single 10 or 15 mm-thick section. A cavogram was still done
before surgery. CT soon acquired a leading role not only for
diagnosis and staging of renal adenocarcinoma,3 but also for
diagnosis of angiomyolipoma, inflammatory renal disease,
and trauma.
From the technical viewpoint, CT equipment is an X-ray
tube that emits an X-ray beam collimated on an tomographic
plane of the object to be examined. Passage of X-rays through
tissue attenuates radiation, which is sensed by photoelectric
detectors and then analyzed by a computer that reconstructs
the different measurements obtained into two- and threedimensional images. CT initially collects images in shades of
gray representing the different tissue densities of the anatomy
examined (Hounsfield units [HU]) with a densitometric value
of zero for water and extreme values ranging from –1,000
(gas, hypodense images) and +1,000 (metal, hyperdense
images). Intravenous (IV) administration of iodinated
contrast media and their subsequent extracellular diffusion
allow for characterizing tissues of the different structures
based on their behavior over time or in the different study
phases. Thus, the following phases are distinguished in
urological examinations: a) Corticomedullary phase, occurring
25-30 seconds after contrast administration. This allows
for examination of vascular anatomy to detect bleeding
and for assessment of early vascular behavior of lesions; b)
parenchymal phase, in which kidney medulla is enhanced to
the same extent as renal cortex. This occurs within 50-180
seconds of the start of contrast injection. This phase is aimed
at tumor detection and should be included by default in most
renal examinations; c) excretory phase, starting 5-10 min after
contrast injection and allowing for urinary tract assessment;
and d) late excretory phase, occurring more than 30 min after
injection.
Magnetic resonance imaging (MRI) started to be used at the
end of the 80s. Magnetic resonance is a physical phenomenon
by which certain elements such as H+ may selectively absorb
radio frequency electromagnetic energy when placed under
a potent magnetic field. A volume (voxel) of body tissue has
a specific density (D) in H+ nuclei. Thus, water will have a
different D from blood, bone, and parenchyma of each muscle
or organ. When H+ nuclei in a given voxel are subjected to a
magnetic field and absorb radio frequency energy, they enter
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a resonant state. Each voxel will resonate differently from
the other voxels due to the differences in H+ density, and a
same voxel will resonate differently depending on the pulse
sequence (physical characteristics of the radio frequency
pulse) to which it is subjected. Excess energy of resonant
nuclei will be released as emission of radio frequency in a
so-called relaxation process (energy release from H nuclei
to return to their equilibrium position. An electric signal
is induced during relaxation and sensed by the receiving
antenna, which sends information to the computer to acquire
the tomographic image in MRI.
The decade of 1990 was first characterized by generalization
of the use of non-ionic contrast media, which dramatically
decreased allergic reactions to contrast, and second by a
spectacular progress of modern sectional techniques (US, CT,
and MRI) to the detriment of IVU.
Coinciding with the publication of several articles stating
the CT was a better procedure than IVU for detecting
urolithiasis,4 Amis published in 1999 an article entitled
“Epitaph for the urogram”.4 This author stated that continued
use of this procedure was due to ignorance of clinicians of
the possibilities for urinary tract visualization of the other
imaging techniques. Becker,6 in a letter in reply to this article,
stated that the death of IVU had been prematurely announced
because the most adequate examination in hematuria had
not been clearly defined yet.
At that time, IVU continued to be the procedure of
choice for monitoring pyeloplasties and for diagnosis and
follow-up of transitional cell carcinoma. In addition, IVU still
appeared to be the best examination for assessing congenital
abnormalities. Other more rare indications in moderate
hydronephrosis and tubular ectasis were then established.1
Today, eleven years after publication of the Amis article,
advances in CT and MRI allow for performing examinations
with a great spatial resolution and contrast resolution in very
short times. Both non-contrast CT (NCCT) scans and contrast
CT scans acquired in the excretory phase (uro-CT) should be
performed using multisection CT (MSCT) equipment, so that
scans with a very thin section thickness, allowing for a high
diagnostic yield, may be obtained.
Most hospitals currently have this technology available,
and the number of IVUs has markedly decreased as a
result. But what are the current indications of IVU? Nobody
questions MSCT as the procedure of choice for examination
and staging of renal adenocarcinoma or for renal trauma,
although some clinicians are still a bit reluctant to use new
imaging technologies in other conditions such as stone
disease or urothelial tumors (UTs).
1. Clinical conditions. Indications and feasibility
of imaging techniques
1.1. Renal colic
When a patient reports flank pain, the first diagnosis to
be considered as a ureteral stone, although many other
conditions may cause the same clinical signs, and even
some conditions may cause urinary tract obstruction
through extrinsic compression. A reliable and objective
diagnostic study is essential to assess the presence
or absence of ureteral obstruction and whether such
obstruction is caused or not by a stone. If ureteral
obstruction exists, an ideal diagnostic examination would
be required to show the cause and site of obstruction.
If no obstruction exists, the same test should ideally
determine the cause of pain.
If obstruction is caused by a stone, conservative treatment
is most often recommended because 80% of stones are
spontaneously voided.4
1.1.1. Plain abdominal X-rays
This is often used as first step in diagnosis of patients with
pain in the flank . Only 59% of stones are visible in abdominal
X-rays.7 An X-ray film is a reasonable initial diagnostic
method when the patient has a history of radiopaque stones
and recurrent clinical signs of renoureteral colic. If no such
history exists, the value of abdominal X-rays is highly
questionable.
1.1.2. Intravenous urography
This was the diagnostic procedure of choice in this type
of patient. IVU has a higher sensitivity for stone detection
than plain X-rays (97%).7 The advantage argued in favor of
this examination over CT was that it was able to provide
physiological information. However, new multidetector
technology allows for image acquisition in different phases
(corticomedullary, nephrographic, and excretory phases) and
provides additional information that may be greatly relevant
when taking decisions, as will be seen later.
A special case is represented by pregnant women, in
whom MRI or IVU with a single X-ray film at ten minutes of
injection may be performed.7
1.1.3. Ultrasound
Alone or combined with plain X-rays, ultrasound is less
sensitive than IVU and CT (sensitivity ranging from 24%77%). US is often used as the first imaging procedure to avoid
irradiation, especially in children and pregnant women. The
ability to detect stones will depend on size and location. US
shows a high sensitivity for detecting stones more than 5 mm
in size, while those located in the middle third of ureter are
very difficult to detect. Visualization of the ureteral jet rules
out the existence of complete obstruction (fig. 1).
1.1.4. Computed tomography
Computed tomography without contrast has a high
sensitivity (98%) and specificity (96%-98%) for detection of
ureteral stones,8 as well as the following advantages: a)
fast examination time, which allows for visualization of the
whole urinary tract within a single breath-holding period;
b) ability to visualize almost any type of stones; c) no risks
derived from a potential allergic reaction to contrast; and d)
diagnostic ability to establish other potential extraurinary
causes of flank pain.9
Differential imaging diagnosis of phleboliths and ureteral
stones may sometimes be difficult, and diagnosis may
initially be difficult in axial sections. Stones are usually
actas urol esp. 2010;34(9):764–774
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Figure 1 – Ultrasound scan showing a stone in the ureteropelvic junction (arrowhead). The Doppler color study shows a
bilateral ureteral jet, a finding that rules out complete obstruction of the excretory system.
Figure 2 – Image of non-contrast computed tomography
with multiplanar reconstruction in coronal projection
showing that the calcified image (arrow), corresponding to
a stone, is located in the ureteral tract.
surrounded by a hypodense ring, while fleboliths have
a characteristic “comet tail” image helpful for diagnosis.
Moreover, multiplanar reconstruction methods allow for
assessing whether calcification is inside the ureter or in the
vessel (fig. 2).
The multiplanar capacity of MSCT studies allows for
measuring all stone diameters, of which the cross-sectional
diameter is most important for potential spontaneous
voiding. Stones less than 3 mm in size are usually voided
spontaneously, while conservative therapy usually fails in
those greater than 6 mm7 (fig. 3)
CT also identifies the degree of urinary tract obstruction
through findings such as hydronephrosis, perinephric edema,
and periureteral edema. Perinephric edema, visualized as an
Figure 3 – Image of non-contrast computed tomography
with multiplanar reconstruction showing pyelic (arrows)
and ureteral (blank arrows) dilation secondary to the stone
visualized, 5.3 mm in cross-sectional diameter.
increased trabeculation of perirenal fat, is proportional to the
length of the process and the degree of obstruction. While its
prognostic implication has been questioned, many authors
think that perinephric edema indicates an increased pressure
within the excretory system and is associated to an increased
probability of spontaneous voiding.10
If evidence of obstruction and clinical signs exist, differential
diagnosis should usually be between an already voided stone,
pyelonephritis, or non-visualization of stone. Patients with HIV
treated with protease inhibitors are known to have radiolucent
stones.11 Thus, if consistent clinical signs and dilation of
excretory system are found in such patients, the presence of a
stone caused by indinavir crystal deposition could be assumed,
or IVU may be performed to document the stone.
New dual energy MSCT may characterize the type of stone,
which represents a great progress when selecting adequate
therapy.12
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An additional great advantage of CT is its ability to
diagnose other extraurinary conditions such as appendicitis,
pyelonephritis, and gynecological or vascular diseases.
1.1.5. Magnetic resonance imaging
MRI urography has a limited ability for detecting urinary tract
stones. Detection of parenchymal stones is very difficult,
while urinary tract stones become surrounded by static fluid
or gadolinium and therefore appear as signal defects with a
well-defined contour, a poorly specific finding that makes it
difficult to differentiate them from blood clots, surgical clips,
small urinary tract tumors, or flow artifacts.13
1.2. Hematuria
In the last decade, uro-CT has replaced IVU in diagnosis
of hematuria.14 Hematuria may be caused by multiple
conditions, some of them benign in nature such as renal colic
or recurrent infection. However, it may also be associated
to tumors such as renal or transitional cell carcinoma,
trauma, or renal parenchymal diseases. For study purposes,
hematuria is classified as gross or microscopic.
In the event of hematuria, tests for bacteriuria and pyuria
should be done first. If such tests are positive, a culture
should be performed to confirm the infectious etiology. If
no infection is found, the second step would be to try and
determine whether glomerular disease exists. Patients under
40 years of age should be referred to a nephrologist first
because of the low tumor incidence in this group.15 Once
glomerular disease is ruled out, patients with risk factors
should be subject to a complete urological examination to
rule out a tumor, including both renal and transitional cell
carcinoma.
According to the O’Connor study, the incidence of malignancy
in patients with gross hematuria is 18.9%. This author detected
no urinary tract diseases in patients under 30 years of age
and no upper urinary tract tumors in those under 50 years of
age.16 Recent studies show a four-fold greater prevalence of
urinary tract tumors in current series as compared to prior
series.15,17 One of the reasons given to explain this change
has been an increased use of CT, which has a greater ability
to diagnose such tumors (bias from advances in diagnosis).
1.2.1. Plain abdominal X-rays
Plain abdominal X-rays have low sensitivity and specificity
for diagnosis of stones. They have no role in detection of
renal tumors or in diagnosis of hematuria when additional
imaging tests are planned.
1.2.2. Intravenous urography
Intravenous urography has a very low sensitivity for detection
of renal masses: 21%, 52%, and 85% for lesions less than 2 cm,
2-3 cm, and more than 3 cm in size respectively.17 In addition,
once a mass is detected, an additional imaging method would
be required to determine if the mass is solid or cystic.
1.2.3. Ultrasound
Ultrasound is a safe procedure to rule out stone disease.
Alone or combined with plain X-rays, particularly in
children, ultrasound has been used to assess internal
architecture of the lesion and the Bosniak grade of a
lesion with a cystic component. 18 The problem with US
when hematuria is assessed is its poor sensitivity for
detection of UTs in the upper urinary tract. Sensitivity for
detection of bladder tumors is very high, approximately
95%. 16,19
1.2.4. Computed tomography urography (uro-CT)
This is defined as a CT scan of the urinary tract before and
after IV administration of iodinated contrast, mandatorily
including an acquisition in the excretory phase. Indications
for uro-CT have rapidly increased and it has replaced IVU
at many centers. This examination would be what Englishspeakers call one stop shop, and saves diagnostic time,
patient visits to hospital, and costs.20
Uro-CT should therefore be considered as a first-line
test for patients with hematuria and risk of cancer, and its
benefits outweigh the theoretical risk of radiation.16
1.2.5. Magnetic resonance urography (uro-MRI)
Uro-MRI is a good alternative method, particularly in pregnant
women and young patients. Its main limitations include poor
visualization of calcium and air.7
1.3. Urothelial tumors
1.3.1. Intravenous urography
At IVU, 50%-75% of UTs appear as filling defects, while
uro-CT has a much greater sensitivity, up to 100%. Thus,
a neoplasm that does not protrude into the ureteropelvic
lumen, as occurs in carcinoma in situ, will not be seen in
the urographic sequence of uro-CT or in the IVU. Urography
has shown21 sensitivity and specificity rates of 62.5% and
100% respectively, a positive predictive value of 100%, and
a negative predictive value of 57% for UT diagnosis. These
values are substantially lower than those achieved with
uro-CT.
Five characteristic urographic findings are reported in UTs
located inside the pyelocalyceal system:
1. S
ingle or multiple filling defects. These are seen in 35%
of urothelial tumors of renal pelvis. Defects may have a
smooth or irregular surface.
2. Filling defect within a dilated calyx. This occurs in 26%
of cases. A tumor may partially obstruct a calyx, causing
hydrocalyx, or completely obstruct the calyx preventing its
opacification (“phantom calyx”). A distended, tumor-filled
calyx (“oncocalyx”) may appear as a focal defect in the
nephrogram.
3. Calyx amputation. This occurs in 19% of cases. If the
cut is smooth, an inflammatory condition (especially
tuberculosis) may be difficult to distinguish from a tumor.
4. Absent or decreased contrast excretion with no increased
kidney size. This occurs in 13% of cases. It is caused by
long-standing obstruction.
5. Hydronephrosis with an increased kidney size, caused by
ureteropelvic junction obstruction. This is seen in 6% of
cases.
actas urol esp. 2010;34(9):764–774
1.3.2. Ultrasound
Ultrasonographic findings in UTs are non-specific and have
no diagnostic value in the study of hematuria caused by a
urinary tract tumor. UTs show no specific ultrasonographic
signs suggesting a urothelial origin, except for their central
location. UTs appear in US as hypoechoic images as compared
to the normal excretory system, and may be associated to
dilation or amputation of a calyx, hydronephrosis, or a solid
intrarenal mass. The presence of focal thickening in the
adjacent renal cortex suggests cortical infiltration.
1.3.3. Computed tomography
CT has been the procedure of choice for diagnosis and
staging of renal adenocarcinoma for two decades.22-24 CT
sensitivity and specificity for UT diagnosis has been debated
for years, but different studies have shown the superiority of
CT for diagnosis of UTs in both the upper urinary tract and
bladder.22-24 Uro-CT with virtual navigation techniques of
volumetric reconstruction (virtual cystoscopy) has even been
suggested in place of conventional cystoscopy because of its
high negative predictive value25 (fig. 4). Such sensitivity and
specificity are however highly limited when the patient has a
history of a bladder tumor subject to transurethral resection,
in which case cystoscopy continues to be mandatory.
Reference was previously made in the hematuria section
to the superiority of CT over IVU for UT detection.22,23 CT has
as an advantage that it allows for urinary tract examination
with no image superimposition problems. Wall thickening
in the whole excretory system may be assessed in the
nephrographic and excretory phases.
Local staging of the tumor may be done in the excretory
phase. If a thin contrast sheet exists between the tumor and
renal parenchyma, tumor is in a T1 or T2 stage (fig. 5). If, however,
decreased sinus fat or abnormal parenchymal enhancement
are seen, there is a T3 tumor. Images of stage T4 tumors show
invasion of perinephric fat. Advanced UTs invade parenchyma
and deform pyelocalyceal structure sparing the reniform
structure, unlike with adenocarcinoma26 (fig. 6).
IVU has been routinely used for monitoring these tumors
because of their trend to multicentricity. From 2% to 4% of
patients with bladder tumors develop during their lives an
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upper urinary tract tumor, and 40% of patients with such
tumors develop a bladder cancer. Since CT has a greater
sensitivity for detection of urinary tract lesions and most
of these occur in patients over 50 years of age, use of CT for
follow-up of these tumors is increasingly common.25
1.3.4. Magnetic resonance imaging
Although CT, particularly uro-CT, is superior to MRI for
assessment of upper urinary tract disease because of its
greater spatial resolution, MRI is equally helpful for diagnosis
of bladder disease and superior for assessing local staging.
In T1-weighted MRI images, UTs show the same or a slightly
lower signal intensity as renal parenchyma. Signal intensity
is slightly increased in T2-weighted images. Following
administration of paramagnetic contrast (gadolinium), UTs
show a similar lesion enhancement as seen in CT. Diffusionweighted sequences are a promising modality for diagnosis of
bladder tumors with high sensitivity and specificity.27
1.4. Urinary tract infection
No radiographic study is required for diagnosis of urinary
tract infection. The combination of clinical symptoms such
as fever, flank pain, and dysuria should lead to suspect acute
pyelonephritis (APN), which should be documented with
laboratory tests.
Imaging studies should be reserved for patients who do not
adequately respond to treatment in the first three days, have
severe symptoms, or in whom another condition (e.g. renal
infarction) is suspected to be the source of the symptoms.
Diabetic or immunocompromised patients may also benefit
from an imaging procedure. Early imaging studies should also
be performed when pyonephrosis is suspected.26
1.4.1. Acute pyelonephritis
1.4.1.1. Intravenous urography. Use of IVU during the acute
phase of infection has become obsolete. IVU depends on
renal function and only shows abnormalities in 25% of
cases. However, IVU clearly outlines the anatomy of the
pyelocalyceal system and is very helpful to study anatomical
abnormalities and potential sequelae.
Figure 4 – Patient with hematuria Computed tomography showing a tumor in the left lateral aspect of the bladder that
does not invade perivesical fat (arrows in A and B). Image of virtual cystoscopy of the same patient showing an intact right
ureteral meatus (arrow in C).
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actas urol esp. 2010;34(9):764–774
Figure 5 – Images of non-contrast computed tomography, with intravenous contrast in the excretory phase, and
reconstructions in the axial and coronal planes. Urothelial thickening is seen limited to the middle calyceal group and
left renal pelvis extending to the proximal ureter and intrarenal collecting system in relation to a small transitional cell
carcinoma (arrow in A) and a bigger tumor involving the pelvis, and extension to the upper third of ureter, which shows a
thickened wall (arrow and arrowhead in B respectively).
1.4.1.2. Ultrasound. US is often the first examination performed
in these patients because of its availability, rapidity, and
safety, and shows normal kidneys in most patients with APN.
In some patients, images may show an increased kidney
size (affected kidney greater than 15 cm or craniocaudal
diameter 1.5 cm longer as compared to the non-affected
side), dilation of pyelocalyceal system with no evidence of an
obstructive cause, ill-defined parenchymal areas (hypoechoic
[due to edema] or hyperechoic [due to bleeding]), or loss
of corticomedullary differentiation (fig. 7). A Doppler scan
increases sensitivity for detection of abnormalities, and most
lesion areas are hypovascular (tubular ischemia). Power
Doppler has a greater sensitivity than color Doppler for
detection and measurement of extension of this hypoperfused
area.
US has however a number of limitations, including lack of
differentiation between calcium (“sharp shadow”) and gas
(“dirty shadow”) in some cases, inability to assess perinephric
extension of infection, and poor ability to assess small
microabscesses.
Figure 6 – Curved multiplanar reconstruction of the kidney
and left excretory system of a patient with advanced
urothelial tumor (asterisks). Note urothelial thickening
(arrows) and invasion of the upper calyceal group without
deforming renal morphology (blank arrows). Pelvic stone
(asterisk in detail).
1.4.1.3. Computed tomography. After IV contrast (IVC)
administration, a multiphasic CT scan is the procedure of
choice for assessing changes in renal parenchyma and in
adults. After adequate antibiotic therapy, even if symptoms
disappear and urine culture becomes negative, radiographic
changes may persist for months, which should be taken into
account to avoid confusing these residual changes with an
active infection.
In standard practice, a simple study, consisting of a phase
50-90 seconds after IVC and a late phase if obstructive disease
is seen, is commonly performed.
A baseline scan without IVC allows for assessing the presence
of gas, stones, calcifications, bleeding areas, inflammatory
masses, obstruction, and kidney enlargement.28
The most common finding following contrast administration
are ill-defined wedge-shaped lesions, less enhanced than
the rest of parenchyma, extending from the papilla (in the
medulla) to the cortical surface. Alternating hypodense
and hyperdense bands, parallel to the axis of tubules and
collecting ducts, may be seen (striated nephrogram). In diffuse
APN, poor contrast elimination from the involved kidney,
actas urol esp. 2010;34(9):764–774
771
Figure 7 – Ultrasonographic image of a 65-year old female patient with left flank pain and dysuria starting five days before.
Ultrasound shows a poorly outlined hypoechoic area in the upper pole of left kidney related to a focal pyelonephritis site
(curved arrow in A). A cystic image adjacent to this lesion (arrow in B) related to an infected cortical cyst is also seen. Note
in the CT scan performed the presence of a hypodense pyelonephritis site (curved arrow in E-F) and an overinfected cyst
(arrows in C-F) together with perirenal fat stranding as signs of inflammation (asterisks in C-D).
proportional to the severity of infection, may be evidenced.
Urothelial thickening, thickening of Gerota’s fascia, and
perinephric fat stranding may also be seen (fig. 7).
In
xanthogranulomatous
and
emphysematous
pyelonephritis, CT is also the examination of choice because
it allows for visualization of both gas and calcium.
1.4.1.4. Magnetic resonance imaging. MRI would be indicated
in pregnant women and patients with iodine allergy, and
has become widely used in renal disease in recent years.
In obstructive renal conditions, this procedure may provide
information about the degree of obstruction. MRI usually
allows for differentiating acute pyelonephritis from residual
lesions, and represents an alternative to scintiscans in children.
MRI examination for kidney disease requires a combination
of T1- and T2-weighted sequences associated to a dynamic
study following administration of paramagnetic contrast
(gadolinium). MRI findings in disease are superimposable to
those discussed for CT.
In chronic pyelonephritis, CT is also the examination
best visualizing scars and may differentiate them from
fetal lobulations. In renal abscess or tuberculosis, CT also
allows for visualizing not only renal involvement, but also its
potential extension to perirenal space (fig. 7).
Cystitis may usually be treated without the need for
imaging procedures. CT may provide information about
trabeculation of perivesical tissue and the presence of gas28
in emphysematous pyelonephritis.
1.5. Papillary necrosis
Clinical signs of papillary necrosis may be diverse and include
hematuria, bacteriuria, salt loss, inability to concentrate urine,
etc. The lesion has an ischemic origin and causes destruction
of the apex of renal pyramids. In many cases, diagnosis is not
clinically suspected and is made at autopsy.
1.5.1. Intravenous urography
Once established, papillary necrosis appears in IVU as a
contrast ring around a triangular filling defect that represents
the detached necrotic papilla. The remaining calyx has a
round, sac-like, or mallet shape (“ring sign”). The site of
detachment is initially irregular, but eventually acquires a
smooth appearance.
1.5.2. Ultrasound
US examination reveals a material within the collecting
system having the ultrasonographic characteristics of a stone
if the detached papilla is calcified, or echogenicity similar to
renal parenchyma if the papilla is not calcified. Calyces may
appear dilated where papilla was detached, or the whole
collecting system may be dilated when obstruction exists.
772
actas urol esp. 2010;34(9):764–774
Figure 8 – Papillary necrosis. Cross-sectional plane of uro-CT in the excretory phase showing a hypovascular area
protruding into the distal medullary pyramid of the middle calyceal group (curved arrow in A) and several oval-shaped
hypovascular lesions in the distal portion of renal medulla (asterisks in B). These findings are characteristic of early
ischemic changes in medullary and papillary necrosis in a patient abusing analgesics who initially showed microscopic
hematuria.
1.5.3. Computed tomography
Diagnosis of papillary necrosis has been one of the main
arguments of those who advocate IVU29 based on the
widespread belief that CT does not have sufficient spatial
resolution to identify these changes.
However, a study by Lang et al30 showed that CT may
detect medullary necrosis at an early stage, when adequate
treatment may prevent papillary detachment (fig. 8).
The typical image is a hypoechoic area less than 1 cm in
size, often not well defined, adjacent to the pyramid apex
with an attenuation coefficient that ranges from +24 and
+30 HU at baseline examination and slightly increases to +44
HU after contrast administration. Lesions are often multiple.
Such changes are more evident in the nephrographic phase.
In the excretory phase, they may be seen as cracks adjacent
to pyramids. This study concluded that CT achieves an earlier
diagnosis, and performance of multiphase CT whenever this
condition is suspected was therefore recommended.30
1.6. Hydronephrosis, lithotripsy follow-up, and surgery
IVU was traditionally considered to be required before
lithotripsy. Currently available reports show that IVU is not
required before lithotripsy.31 Similar results were achieved
in groups undergoing IVU and in those undergoing US or CT
without contrast.
IVU may still play a role in diagnosis in young patients
who have ureteropelvic dilation, recurrent urinary infections,
or after pyeloplasty because uro-CT involves a much greater
dose of radiation, although an ultrasound examination often
provides adequate information in such patients.
multiple ways to decrease radiation. If NCCT is performed
with an 80 mA load, providing for an adequate diagnostic
quality in patients with a body mass index within the normal
range, the radiation dose is approximately 3.8 mS. Use of
protocols especially designed to address specific clinical
problems allows for optimizing this type of examination. In
addition, the increased radiation as compared to conventional
urography should be considered in the context of the amount
of information required for diagnosis. Thus, a CT scan for
locating stones may be done using low-dose acquisition
protocols (80 mA) in a single phase, involving a radiation dose
of approximately 3.8 mS, as previously noted. Administration
of IVC and multiple acquisitions should be avoided in young
patients with renal colic.
Radiation from uro-CT is markedly higher as compared
to IVU because two or three phases are usually performed.
Radiation doses with both examinations reported in medical
literature are 2.5 mSv for IVU and more than 10 mSv for CT,
but CT has a very high diagnostic yield and avoids the need
for additional tests.7 The dose of radiation with uro-CT is
unquestionably higher as compared to IVU, but the most
harmful diagnostic test is that which subjects patients to
radiation and gives little or no information, thus requiring
subsequent use of additional examinations involving an
increased patient exposure to radiation.
Summary
IVU was the most important examination in urinary disease
in adults until the end of the 20th century, but is barely
used today. There are very few conditions where IVU is still
indicated:
2. Dose of radiation
Dose of radiation has always been a controversial subject.
Radiation dose of IVU is approximately 2.5 mSv, but the
number of X-ray films is sometimes increased because of
the need for obtaining films in the late phase. The dose
from a standard abdominal CT scan is approximately 10
mS. However, if CT is the examination chosen, there are
iH
IV-infected patients treated with protease inhibitors
showing clinical signs of renal colic and dilation of the
excretory system.
i Postoperative revisions, hydronephrosis, or recurrent
urinary infections in young patients in whom information
obtained with US and abdominal X-rays is not considered
to be clinically sufficient.
actas urol esp. 2010;34(9):764–774
CT is the successor to IVU. There are two types of
examination: NCCT, which is helpful in the study of stone
disease, and uro-CT, which has a relevant role in diagnosis
of hematuria and many other conditions in which IVU was
previously performed, such as papillary necrosis.
Radiology departments should make efforts to decrease
the radiation dose from uro-CT by adjusting parameters such
as kilovolts, milliamperes, and pitch, and trying to avoid
unnecessary phases. On the other hand, industry is constantly
working on the possibilities of minimizing radiation doses by
using filters and algorithms which allow for dose reduction
without impairing diagnostic capacity.
When this is possible and uro-CT involves a radiation dose
less than 10 mS, urologists and radiologists will undoubtedly
be able to sing together: “IVU is dead, long live CT!”.
Conflict of interest
The authors declare no conflicts of interest.
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