Measurement of Ureteric Stone Diameter in Different Planes on Multidetector Computed Tomography - Impact on the Clinical Decision Making

Abstract

To determine if the measurement of ureteric stone in coronal reconstruction plane is different from the measurement in axial plane and whether the difference can impact the management decision in patients with ureteric colic.
All patients who underwent unenhanced multidetector computed tomographic (MDCT) scan for the evaluation of reno-ureteral colic in outpatient clinics and emergency room were evaluated. The scans were evaluated on Picture Archiving Computer System with a 3-mm axial and reformatted 3-mm coronal sections. Maximal stone diameter was measured in 2 dimensions in the axial and reformatted coronal sections by 2 reviewers. Only scans with isolated, unilateral, solitary ureteric calculi were included in the final analysis. All patients were monitored up to 4 weeks after MDCT to determine the clinical outcome.
A total of 331 patients (272 male and 59 female; mean age ± standard deviation, 39.8 ± 13.8 years) were included. One hundred seventy-one (51.7%) stones passed spontaneously during the follow-up period. There was a 20% underestimation of maximal stone diameter in axial plane for all stones and a 17% for the stones that passed spontaneously or with medical expulsive therapy, as compared with measurement on coronal reconstruction.
Measuring the transverse stone diameter on axial images of MDCT scan underestimates size of ureteric stone size. This can have an impact on counseling of patients and their clinical outcome, coronal reformatted images be used for size estimation.

Full text

Endourology and Stones
Measurement of Ureteric Stone Diameter in
Different Planes on Multidetector Computed
Tomography eImpact on the Clinical
Decision Making
Syed M. Nazim, M. Hammad Ather, and Nadir Khan
OBJECTIVE To determine if the measurement of ureteric stone in coronal reconstruction plane is different
from the measurement in axial plane and whether the difference can impact the management
decision in patients with ureteric colic.
METHODS All patients who underwent unenhanced multidetector computed tomographic (MDCT) scan for
the evaluation of reno-ureteral colic in outpatient clinics and emergency room were evaluated.
The scans were evaluated on Picture Archiving Computer System with a 3-mm axial and
reformatted 3-mm coronal sections. Maximal stone diameter was measured in 2 dimensions in the
axial and reformatted coronal sections by 2 reviewers. Only scans with isolated, unilateral, solitary
ureteric calculi were included in the final analysis. All patients were monitored up to 4 weeks after
MDCT to determine the clinical outcome.
RESULTS A total of 331 patients (272 male and 59 female; mean age standard deviation, 39.8 13.8
years) were included. One hundred seventy-one (51.7%) stones passed spontaneously during the
follow-up period. There was a 20% underestimation of maximal stone diameter in axial plane for
all stones and a 17% for the stones that passed spontaneously or with medical expulsive therapy,
as compared with measurement on coronal reconstruction.
CONCLUSION Measuring the transversestone diameter on axial images of MDCT scan underestimates size of ureteric
stone. This can have an impact on counseling of patients and their clinical outcome, coronal
reformatted images be used for size estimation. UROLOGY -:-e-, 2013. 2013 Elsevier Inc.
Unenhanced helical computed tomographic (CT)
scan is the imaging of choice for the diagnosis of
urolithiasis in symptomatic patients with re-
ported sensitivity and specificity close to 100%.
1,2
The 2
most important factors that guide clinical management
are stone size and its location.
3
There is a reverse linear
relationship between stone size and spontaneous passage;
hence, determination of maximal stone size is crucial
while counseling the patient and selecting the appro-
priate treatment strategy. Determination of maximal
stone size is crucial indicator in clinical decision making
for intervention or use of medical expulsive treatment for
which various
a
blockers have been used with compara-
ble efficacy.
4
Lee et al
5
recently noted that longitudinal
stone diameter was a significant predictor of stone
expulsion with medical expulsive therapy (MET), and
coronal reconstruction might help to better choose a
patient who is suitable for MET.
With the improved resolution and multiplaner refor-
mations, multidetector computed tomography (MDCT)
has considerably improved imaging from cross sectional
(axial) imaging to true 3-D image.
6
The coronal recon-
struction of CT scan helps not only for better stone
detection but also reportedly for accurately assessing the
stone size oriented in vertical plane, especially the
ureteric stones.
7
Many modifications have been suggested
to improve the stone size estimation, including using an
algorithm.
8
However, the most commonly used method is
estimation on coronal and reconstructed images.
The present study is designed to determine if mea-
surement of ureteric stone in coronal reconstruction
plane is different from the measurement in axial plane
and whether the difference can predict the outcome for
urolithiasis in patients with renal colic.
MATERIALS AND METHODS
This prospective study was conducted over a duration of 12
months from April 1, 2011 to March 31, 2012. All the
consecutive unenhanced CT scan (CT kidneys, ureters, and
Financial Disclosure: The authors declare that they have no relevant financial interests.
From the Department of Surgery, Aga Khan University, Karachi, Pakistan; and the
Department of Radiology, Aga Khan University, Karachi, Pakistan
Reprint requests: M. Hammad Ather, M.B.B.S., F.C.P.S. (Urol), F.E.B.U.,
Department of Surgery, Aga Khan University, PO Box 3500, Stadium Road, Karachi
74800, Pakistan. E-mail: hammadather@gmail.com
Submitted: June 21, 2013, accepted (with revisions): September 16, 2013
ª2013 Elsevier Inc. 0090-4295/13/$36.00 1
All Rights Reserved http://dx.doi.org/10.1016/j.urology.2013.09.037

bladder [KUB]) done for the evaluation of reno-ureteral colic at
the outpatient clinics and emergency room were included.
The initial evaluation of all patients were done in the
emergency room and outpatient clinics with history, physical
examination, laboratory tests, and then with a subsequent
MDCT. All CT examinations were conducted on a 64-slice
MDCT machine (Aquilion, Toshiba Medical Systems, Shi-
moishigami, Otawara-Shi, Japan) without oral or intravenous
contrast. Three millimeters axial and reformatted 3-mm coronal
sections were evaluated on picture-archiving computer system
(View Pro-X version 4.0.6.2; Rogan-Delft, Veenendaal,
Holland). Our protocol for CT KUB scans the abdomen from
the xiphi-sternum to the lower border of symphysis pubis. It is
taken once the patient has an urge to void. All scans are ob-
tained with 120 kV and 250-300 mA exposure factors.
We analyzed only patients with a solitary, unilateral ureteric
stone in the line of ureter and excluded patients with multiple
and/or bilateral ureteric stone, stone in the kidney or bladder.
We also excluded patients who had stone in solitary renal unit,
pregnant female patients, those with fever and suspected active
urinary tract infection, and renal insufficiency requiring active
intervention. All patients were started on MET.
Stone Evaluation
The CT scan films were reviewed independently by a radiologist
(N.K.) and a urologist (S.M.N.) who had about 6þyears of
experience of reading CT KUB with an average of 20-25 films per
week. Patients’symptoms and side of pain were noted, and these
clinical findings were then correlated with the scan to support the
diagnosis of stone. Maximum diameter of the ureteral stone was
measured in axial and reformatted coronal sections on Picture
Archiving Computer System. The measurement of axial and
coronal plane for each stone was given to separate reviewers to
reduce bias. To facilitate the interpretation, the reviewers were
allowed to use the zoom function on the workstation. Each stone
was measured in 2 dimensions, along its maximum visualized
diameter and the other one perpendicular to it. This would also
give us an estimate of its area.
Stone area ¼maximum diameter perpendicular diameter
The stones were divided into 3 locations, upper, mid, and
lower. Calculi above the sacroiliac joint were deemed in upper
segment, those anterior to sacroiliac joint were midureteral, and
those below were deemed in lower segment. In addition, they
were also classified as at ureteropelvic junction and at ureter-
ovesical junction (UVJ). The patients were followed up pro-
spectively up to 4 weeks with x-ray KUB, urinalysis, ultrasound
KUB, and the clinical outcome (whether stone passed sponta-
neously/not passed or needed any surgical intervention).
Statistical Analysis
The statistical analyses were performed on SPSS version 19
software. The continuous variables were expressed as mean 
standard deviation, and ttest was used for comparison. For the
nominal variables, chi-square test, ANOVA, and post hoc tests
were used. A Pvalue of .05 was considered significant.
RESULTS
Over the duration of the study, total numbers of CT KUB
performed for evaluation of flank pain were 1587, out of
which 331 (21%) qualified the inclusion and exclusion
criteria and were included in the final analysis. The mean
age of patients was 39.8 13.8 years (range, 15-85).
There were predominantly male, that is, 272 (82.2%) and
59 (17.8%) female patients in the analysis. The distri-
bution of stone was same on the right (49%) and the left
sides (51%).
The mean largest coronal diameter measured for all
stones was 7.0 4.0 mm (range, 1.5-24), and the mean
largest axial diameter was 5.6 3.0 mm (range, 0.8-25;
P<.001). Similarly the mean largest coronal area was
41.6 50.4 mm
2
(range, 2.1-376.4) as compared with
mean largest axial area 29.2 35 (range, 0.64-347.4;
P<.001; Fig. 1).
Most stones were located in the distal ureter (n ¼150,
45%), followed by proximal ureter (n ¼131, 40%) and
Figure 1. Stone size measurement with implication in clin-
ical outcome in a 53-year-old man presented with left flank
pain. He required ureteroscopy after 4 weeks of failed con-
servative management. (A) Multidetector computed tomog-
raphy axial view shows distal ureteric stone measuring
4.9 mm in maximal diameter. (B) Coronal reformations
show a vertically oriented stone measuring 10.4 mm in
maximal diameter.
2UROLOGY -(-), 2013

midureter (n ¼50, 15%). All patients were considered
for MET unless they have significant pain requiring reg-
ular parenteral analgesia, significant obstruction with
hydronephrosis, and signs of sepsis. A total of 171 pa-
tients (51.7%) could manage to pass the stone sponta-
neously (with MET and analgesia), whereas 160 (48.3%)
did not pass stone or required intervention. The
maximum proportion of stones that passed spontaneously
was located at the UVJ (86%) followed by distal ureter
(61%), midureter (41%), and proximal ureter (37%).
The mean diameter of spontaneously passed stone on
the coronal reconstruction was 5 1.6 mm (range, 2-9),
whereas it was 4.1 1.5 mm (range, 1.0-9.8) in the axial
section (P<.001; Table 1).
The stones were grouped according to the clinical
threshold for spontaneous passage, and of 171 stones
reported 5 mm in largest diameter on axial image, 65%
were correctly classified in the same size category for
craniocaudal diameter on coronal reconstruction, whereas
29% were upgraded to 5-7 mm and 6% to 7-10 mm in
diameter. Similarly, 51% of stones were upgraded to 7-
10 mm diameter on craniocaudal measurement on coro-
nal reconstruction from 5-7 mm in axial image and 44%
of stones reported to be in 7-10 mm category on axial
image were upgraded to >10 mm on coronal recon-
struction (Table 2).
In the analysis of stones that passed spontaneously, 137
of 171 (80%) were 5 mm in largest diameter on axial
image, whereas only 101 of 171 (59%) were in this size
category on coronal images. Thirty percent of stones re-
ported to be 5 mm and 52% of stones reported to be 5-
7 mm on axial image were upgraded in size on coronal
reconstructions (Table 3).
The clinical outcome was also different for stone size
categories with 78.7%, 36.7%, and 6% of stones passed
spontaneously for stone diameters 5 mm, 5-7 mm,
and 7 mm on axial images vs 82%, 62% and 15% for
stones of respective sizes reviewed on coronal images.
There was statistically significant difference for stone
measurements in axial and coronal reconstructions for all
the locations. Two of the 6 parameters that were signifi-
cantly related to stone passage in the univariate analysis,
that is, coronal stone area and sagittal stone area were
derivative parameters and were not included in the
multivariate analysis because of multicollinearity prob-
lems. The remaining 4 parameters were entered into
Table 1. Impact of stone diameter on spontaneous passage at various locations in the ureter
Stone Location Outcome Coronal Diameter (Mean SD) Axial Diameter (Mean SD) PValue
UVJ Stone passed (n ¼43) 4.6 1.4 (2.0-8.0) 4.0 1.29 (1.3-6.6) .001
Stone not passed (n ¼07) 9.7 3.8 (3.7-13.0) 9.0 4.8 (2.3-14.4)
Distal ureter Stone passed (n ¼61) 4.7 1.6 (2.0-8.7) 3.7 1.4 (0.8-7.5) <.001
Stone not passed (n ¼39) 8.51 3.84 (1.5-18.0) 6.8 2.3 (2.0-12.8)
Midureter Stone passed (n ¼21) 5.5 1.9 (2.3-9.0) 4.6 2.0 (2.0-10.8) .019
Stone not passed (n ¼30) 9.1 4.3 (3.1-24.2) 7.3 3.8 (4.3-24.7)
Proximal ureter Stone passed (n ¼46) 5.4 1.5 (1.9-8.9) 4.4 1.4 (1.0-8.6) <.001
Stone not passed (n ¼78) 9.7 1.4 (3.5-20.9) 7.2 3.0 (2.4-16.1)
UPJ Stone passed (n ¼0) ee.94
Stone not passed (n ¼6) 12.4 5.0 (7.7-19.3) 12.3 6.6 (4.1-19.5)
SD, standard deviation; UPJ, ureteropelvic junction; UVJ, ureterovesical junction.
Table 2. Difference in stone size based on clinical threshold for spontaneous passage; axial image vs coronal image
Craniocaudal Diameter on Coronal Reconstruction
5 mm 5-7 mm 7-10 mm >10 mm Total
Transverse diameter on axial image
5 mm 113 (65%) 51(29%) 10 (6%) e174
5-7 mm 7 (9%) 27 (34%) 40 (51%) 5 (6%) 79
7-10 mm 2 (4%) 4 (4%) 24 (44%) 24 (44%) 54
>10 mm 1 (4%) e1 (4%) 22 (92%) 24
Total 123 82 75 51 331
Table 3. Difference in stone size for spontaneously passed stones; axial image vs coronal image
Craniocaudal Diameter on Coronal Reconstruction
5 mm 5-7 mm 7-10 mm >10 mm Total
Transverse diameter on axial image
5 mm 96 (70%) 39 (28.5%) 2 (1.5%) e137
5-7 mm 4 (14%) 10 (34%) 15 (52%) e29
7-10 mm e2 (50%) 2 (50%) e4
>10 mm 1 eee1
Total 101 51 19 e171
UROLOGY -(-), 2013 3

backward stepwise binary logistic regression analyses that
demonstrated an independent relationship between stone
passage and largest coronal size (odds ratio 0.63, 95% CI
0.52-0.76; P<.001) and smallest axial size (odds ratio
0.57, 95% CI 0.42-0.79; P<.01).
On the post hoc analysis, when comparing the stone
area of passed stones on coronal reformation, the UVJ,
distal ureter, and midureteric stones were homogenous,
whereas proximal ureteric stone area was significantly
different (P¼.027; Tukey test). While comparing the
stone area of passed stones on axial reformations, the
UVJ, midureter, and proximal ureteric stones were ho-
mogenous, whereas distal ureteric stone area was signifi-
cantly different (P¼.029; Tukey test).
COMMENT
In view of its high accuracy and short acquisition time,
noncontrast CT scan has now become the gold standard
for the evaluation of patients presenting with acute flank
pain.
9,10
It not only provides information regarding
presence and localization of stones but also other details
that can help in management plan such as stone density,
degree of obstruction caused by stone, and obstructive
parameters such as hydronephrosis, hydroureter, and
perinephric stranding.
11
High quality multiplaner reformations with excellent
temporal and spatial resolution can be generated from
MDCT, by its ability to acquire thin slice volumetric
studies. It can display the urinary tract in its longitudinal
axis, thus improving the orientation of stones without
increasing the evaluation times.
12,13
Management of
ureteric stones depends on 2 most important parameters,
that is, stone location and size.
14
Various methods have
been described in the published data to measure the stone
size in radiographs, but there is no accepted standard
technique for stone measurement using CT scan.
15-18
Estimation of maximal transverse diameter from axial
image traditionally has been reported as the most
commonly used method. In a survey to determine the
radiological practices in the UK, Kampa et al
16
found lack
of uniformity among urologist in techniques for assessing
the stone size and they concluded that “Guestimation”
was the most prevalent method among radiologists for
assessing the maximal stone size.
13
The ureteric stones can be rounded or elongated. Most
of these are oriented vertically along the long axis of
ureter with maximal diameter in craniocaudal plane. It is
therefore imperative to have this dimension measured.
Accurate determination of these stone sizes is crucial in
helping the patient counseling and further management,
that is, conservative/expectant management vs inter-
vention, and even a difference of 1-2 mm can make a
significant difference in this regard.
Nadler et al
14
in their study showed that axial images
consistently underestimated the stone size compared with
coronal reconstructions. The indirect estimation of cra-
niocaudal diameter of ureteric stone from axial images
alone considering the slice collimation does not provide
precise measurement of stone size.
13,14
Coronal reformations from MDCT have several ad-
vantages. It provides important complimentary informa-
tion to axial images, and combining the 2 together
improves the diagnostic confidence and conspicuity of
stones by facilitating its differentiation from phlebolith,
calcified vascular plaques, or renal parenchymal calcifi-
cations.
15
It is also shown to improve better estimate the
maximal stone diameter, especially for stones that are
oriented in vertical plane.
19
Another advantage of coronal image is that it enables
visualization of kidney, ureter, and bladder simultaneously
in a plane that is almost parallel to the orientation of
these organs. This is more familiar and intuitive to urol-
ogist because it is analogous to projections of an
abdominal x-ray or excretory urogram.
13
Metser et al
7
compared axial vs coronal plane for renal
and ureteric stone size measurements and showed that for
all stones, the average underestimation of stone size was
approximately 13% in axial plane. Our study showed
significant underestimation of stone size on axial images
as compared with the craniocaudal measurement from
coronal plane. It also showed that for all stones, the
maximal diameter in the axial plane was 20% less than
the coronal plane, and for the stones that passed there
was 17% reduction on axial image. Similarly, a significant
proportion of stones were underestimated in size on axial
image measurements. Dundee et al
20
noted a 12% under-
estimation when comparing the CT scan in axial plane
with stone size on abdominal radiograph.
Lee et al
5
in their retrospective study evaluated the
difference between transverse and longitudinal stone di-
ameters on CT scan as a predictor of ureteral stone
expulsion after MET. They found the longitudinal
diameter to be significant predictor of stone expulsion for
ureteral stones and concluded that this measurement in
coronal reconstruction can help to better choose patients
who are suitable for MET.
The chances for spontaneous passage are more than
98% for ureteric stones smaller than 5 mm, whereas it is
almost 60% and 39% for stones between 5-7 mm and
>7 mm in diameter, respectively.
3
Smith et al
21
in a case
series of 312 patients showed that the average size of
stones that was passed spontaneously was 4.6 mm,
whereas the average size of stones requiring intervention
was 6.0 mm. Our study correlated with the findings of the
existing ones that the difference between the stones that
were passed spontaneously vs which could not were sig-
nificant. Moreover, this difference was significant be-
tween the sizes measured in coronal and axial sections.
The rate of spontaneous stone passage is the function
of stone location.
3,14
A linear relationship was observed
in our study for location of stones in ureter with most
stones located more distally could manage to pass.
However, Kishore et al
22
have shown a weak correlation
coefficient for comparing the actual size of passed stones
vs CT scan measurements (axial and craniocaudal) for
4UROLOGY -(-), 2013

distal ureteric stones with actual size of passed intact
stones significantly smaller than the one measured with
CT scan. Recently, Demehri et al
23
have proposed CT-
based determination of maximum ureteral stone area
(for complex ureteral stone) using a software program to
be superior to the stone diameter measurement. This is
the basis that long thin stones are more likely to pass than
a long thick one.
Our study has few limitations. First of all, the presence
of stone was assigned by a consensus between the 2 ob-
servers, and no standard of reference was followed for the
confirmation of stones. However, CT scan is the most
accurate way to diagnose the stones. Although we fol-
lowed up the patients to determine the clinical outcome,
we did not measure the actual size of passed stone and did
not compare it with radiological size. Similarly, not all the
passed stones were available for analysis.
To our knowledge, this is the first study comparing the
ureteral stone size estimation in axial vs coronal planes
along with the clinical outcome during follow-up. Further
prospective studies examining the clinical outcomes for
patients with ureteric stones measured on axial images
alone vs clinical outcome of ureteric stones measured on
axial þcoronal reconstructions should be performed
along with the determination of actual stone size to
correlate which measurement is more accurate.
CONCLUSION
Measuring the transverse stone diameter on axial images
of MDCT scan underestimates size of ureteric stone. This
can potentially impact management algorithm. To
counsel patients for need of intervention and clinical
outcome of MET, coronal reformatted images be used for
size estimation.
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EDITORIAL COMMENT
Urologists recognize that small distal ureteral stones are likely to
pass; however, predicting which patient with a ureteral stone
will fail medical expulsive therapy (MET) remains challenging,
as there is no threshold size for ureteral stone passage. In the
present study, this axiom is held true because, regardless of
location in the ureter, stones that passed were approximately 4-5
mm in coronal size and those that did not pass averaged 8-9 mm
in coronal length.
Noncontrast computed tomographic scanning (NCCT) is the
cornerstone of diagnosing urinary calculi, especially in an
emergency department setting.
1
Simply measuring the coronal
length of a ureteral stone is an additional data point that all
radiologists and urologists can easily ascertain and thereby better
discriminate who is likely to fail MET. In addition, using
magnified bone windows on the NCCT, as described by Eisner
et al,
2
might offer the most accurate size estimate of ureteral
stones. Biomarkers such as C-reactive protein might help
UROLOGY -(-), 2013 5

discriminate which patients with stones of a “passable size”will
fail MET and require surgical intervention.
3,4
Using these data to create a nomogram would help patient
counseling; however, the means of assessing stone passage in this
study and in the stone literature in general remain far from
standardized.
5
Since not all patients in this study presented with
their passed stone for analysis or had a repeat NCCT to prove
they were stone free, the rate of passage might be less than re-
ported by the authors, and thus bias a nomogram constructed
from these data.
Until a biomarker is widely available, stone size remains one
of the best indicators of passage for ureteral calculi. The prac-
ticing urologist should use measurements of ureteral stones in
the axial and coronal planes to better counsel patients with a
ureteral calculus.
Peter L. Steinberg, M.D., Division of Urology, Department of
Surgery, Beth Israel Deaconess Medical Center, Boston, MA
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2. Eisner BH, Kambadakone A, Monga M, et al. Computerized to-
mography magnified bone windows are superior to standard soft tissue
windows for accurate measurement of stone size: an in vitro and
clinical study. J Urol. 2009;181:1710-1715.
3. Aldaqadossi HA. Stone expulsion rate of small distal ureteric calculi
could be predicted with plasma C-reactive protein. Urolithiasis. 2013;
41:235-239.
4. Angulo JC, Gaspar MJ, Rodriguez N, et al. The value of C-reactive
protein determination in patients with renal colic to decide urgent
urinary diversion. Urology. 2010;76:301-306.
5. Deters LA, Jumper CM, Steinberg PL, et al. Evaluating the definition
of “stone free status”in contemporary urologic literature. Clin
Nephrol. 2011;76:354-357.
http://dx.doi.org/10.1016/j.urology.2013.09.040
UROLOGY -:5e6, 2013. 2013 Elsevier Inc.
REPLY
The indication for intervention in the treatment of uncompli-
cated ureteral stones in both the major international urologic
association guidelines (ie American Urological Association and
European Association of Urology)
1
is based on stone size.
However, methods for determining stone size are not stan-
dardized. Even in contemporary published data there are only
sparse reports regarding the preferred method for stone mea-
surement using the noncontrast computed tomography. The
most commonly used method is by estimation of maximal
transverse dimension from axial images.
Medical expulsive therapy has become the standard of care for
most symptomatic small- to medium-sized uncomplicated
stones. However, success of medical expulsive therapy (MET) is
difficult to predict. Currently, the most studied parameter is
stone size and site. Therefore, it is important that the stone size
estimation should be as accurate as possible. Some recent work,
2
including the present one is an attempt to see if size estimation
on reconstructed film is a better predictor of successful MET
compared with conventional axial films. The transverse calculus
measurement on axial slices often underestimates stone size and
provides incorrect clinical parameter for management decision.
Use of bone windows in particular when low-dose protocol is
used. Recently, Sohn et al
3
noted no significant difference in the
measurement of stone size, Hounsfield units, or skin to stone
distance between the low-dose and conventional-dose
computed tomographic scans. However, the low-dose computed
tomographic scan have an inherent advantage of marked
reduction in the radiation dose to the patient.
Stone clearance spontaneously or with pharmacologic support
is dependent on many diverse factors; therefore, it also makes
sense that multiparametric models should be developed for ac-
curate assessment of successful MET. Studies with robust design
looking at various clinical, demographic, anatomic, and
biochemical parameters besides stone size and location are
needed to answer these questions.
M. Hammad Ather, M.D., F.C.P.S. (Urol), F.E.B.U.,
Aga Khan University, Karachi, Pakistan
References
1. Preminger GM, Tiselius HG, Assimos DG, et al. 2007 guideline for
the management of ureteral calculi. J Urol. 2007;178:2418-2434.
2. Berkovitz N, Simanovsky N, Katz R, et al. Coronal reconstruction of
unenhanced abdominal CT for correct ureteral stone size classifica-
tion. Eur Radiol. 2010;20:1047-1051.
3. Sohn W, Clayman RV, Lee JY, et al. Low-dose and standard
computed tomography scans yield equivalent stone measurements.
Urology. 2013;81:231-234.
http://dx.doi.org/10.1016/j.urology.2013.09.041
UROLOGY -: 6, 2013. 2013 Elsevier Inc.
6UROLOGY -(-), 2013