AJR 2000; 174:667-669
© American Roentgen Ray Society
Renal Carcinoma Presenting with Flank Pain
A Potential Drawback of Unenhanced CT
W. K. Chong1,2,
M. Wysoki1,
L. G. Heller1 and
H. G. Zegel1
1
Department of Radiologic Sciences, Medical College of
Pennsylvania—Hahnemann University Hospitals, 3300 Henry Ave.,
Philadelphia, PA 19129.
2
Present address: Department of Radiology, Medical College of Virginia, P.O.
Box 980615, Richmond, VA 23298-0615
Received December 1, 1998;
accepted after revision August 30, 1999.
Address correspondence to W. K. Chong.
Introduction
Unenhanced CT has become widely used in recent years for examination of
patients with renal colic. Many studies recognize the advantages of CT: it is
safe, quick, more sensitive, and more specific than excretory urography for
detection of ureteric calculi and avoids the use of IV contrast material
[1,
2]. Direct visualization of a
ureteric stone is diagnostic, but secondary signs of ureteric obstruction are
helpful in confirming the diagnosis. These secondary CT signs include
perinephric stranding, hydroureter, hydronephrosis, and unilateral renal
enlargement [3]. The
disadvantages of unenhanced CT have not been as widely reported. Unenhanced CT
is routinely used for examining patients with suspected renal colic in our
institution. In the past 12 months, we encountered two patients who presented
with acute flank pain and hematuria but had unsuspected renal tumors that were
not diagnosed on initial unenhanced CT.
Case Report
A 29-year-old man presented to the emergency department with right flank
pain and gross hematuria. Ureteric obstruction caused by calculus was
suspected and CT was performed. Unenhanced CT of the abdomen was performed
with 5-mm collimation using a non-helical scanner (GE-9800; General Electric
Medical Systems, Milkwaukee, WI). The right kidney was uniformly enlarged with
hydroureter and mild hydronephrosis. A small amount of perinephric stranding
(Figs.
1A,1B,1C)
without calculus was seen. The appearance was interpreted as consistent with
ureteric obstruction and recent passage of a stone.
The patient presented 3 months later with signs of a deep venous
thrombosis. CT showed a large tumor centered on the right renal sinus
(Fig. 1D). This mass was
causing hydronephrosis. The inferior vena cava was occluded by the tumor, and
thrombus was seen extending inferiorly the length of the inferior vena cava
into the right iliac and femoral veins. Biopsy showed poorly differentiated
adenocarcinoma. The tumor was considered unresectable at laparotomy.
View larger version (92K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D. —29-year-old man with renal colic and hematuria. Enhanced CT scan
obtained 3 months after A and B shows infiltrating mass centered
on right renal sinus. Dilated calices are seen in obstructed kidney. Tumor
invades through renal capsule. Inferior vena cava is compressed and displaced
anteriorly.
|
|
In the second case, a 48-year-old woman presented with right renal colic
and hematuria. Helical unenhanced CT of the abdomen and pelvis was performed
with a Somatom 4 scanner (Siemens, Erlangen, Germany) with 5-mm collimation
and a pitch of 1. The right kidney was uniformly enlarged without evidence of
a focal mass (Fig. 2A).
Hydronephrosis, hydroureter, and perinephric and periureteral stranding were
present but no calculus was seen (Fig.
2B). A contrast-enhanced CT performed the next day showed a solid
renal mass (Figs.
2C,2D).
View larger version (136K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B. —48-year-old woman with renal colic and hematuria. Unenhanced CT scan
obtained more inferiorly than A shows perinephric stranding and right
hydroureter (arrowhead). No calculus was seen.
|
|
Discussion
Unenhanced CT is becoming more popular as an alternative to excretory
urography in the evaluation of renal colic
[1,
2]. The definitive criterion
for diagnosis of ureteric colic is visualization of the ureteric calculus.
However, a ureteral stone may not be visible because of its recent passage or
because of volume averaging, and pelvic phleboliths may be difficult to
distinguish from calculi. Katz et al.
[3] found that secondary
criteria were present in most patients with ureteric calculi and were helpful
in confirming obstruction. These secondary criteria were unilateral renal
enlargement, hydronephrosis, hydroureter, and perinephric stranding. Smith et
al. [4] found that in eight of
109 patients with ureteric stones, the stone was not visible on CT. They
suggested that this could be caused by recent passage of a stone or by volume
averaging and proposed that a diagnosis of ureteric calculus can be made when
secondary signs alone are present.
Unenhanced CT has been advocated for examining patients with acute flank
pain. Unilateral hydronephrosis and stranding of perinephric fat have a
predictive value of 97% for stone disease
[5]. If unilateral
hydronephrosis or hydroureter and stranding of perinephric fat are seen but a
stone is not visualized in patients with acute flank pain, then the diagnosis
is likely to be a small ureteric calculus that is present but not visualized
[5].
In our patients, secondary signs of obstruction were present, but the cause
was not a calculus but a renal tumor. Most renal neoplasms form discrete
masses, but some develop by diffusely infiltrating the kidney
[6]. Such tumors may be
difficult to see on unenhanced images because of a lack of renal contour
deformity. A blood clot obstructing the ureter may have been responsible for
the colicky pain that our patients experienced. So-called clot colic is more
commonly associated with transitional cell carcinoma
[7], but our first patient had
an unusual centrally located adenocarcinoma that ultimately invaded the
collecting system. The erroneous CT diagnosis of recent passage of a stone in
this patient led to a 3-month delay in identifying the tumor. After 3 months,
the tumor was clearly not resectable.
Renal carcinoma can present with the same symptoms as ureteric stones
(i.e., hematuria and flank pain). In our patients, unenhanced CT showed
unilateral nephromegaly, perinephric stranding, and hydronephrosis mimicking
the secondary CT signs of ureteric obstruction caused by stone disease.
Contrast-enhanced studies would probably have facilitated detection of the
tumors. To avoid missing renal malignancy, contrast material should be
administered if secondary signs are present but a ureteric calculus is not
seen on the unenhanced study. However, identifying ureteric calculi can
sometimes be complicated because pelvic phleboliths can mimic calculi
[8].
Unenhanced CT is an important new technique for examining patients with
renal colic. However, our experience suggests tumors that do not produce a
focal bulge in the renal contour can go undetected on unenhanced CT. The
diagnosis of the recent passage of a calculus on unenhanced CT should be made
with caution when only secondary signs such as unilateral nephromegaly,
perinephric stranding, and hydronephrosis are present. If a ureteric calculus
is not visible, a more sinister cause for the CT appearance of these symptoms
may be present.
References
-
Smith RC, Rosenfield AT, Choe KA, et al. Acute flank pain:
comparison of unenhanced-enhanced CT and intravenous urography.
Radiology
1995;194:789-794[Abstract/Free Full Text]
-
Smith RC, Verga M, McCarthy S, Rosenfield AT. Diagnosis of acute
flank pain: value of unenhanced helical CT. AJR
1996;166:97-101[Abstract/Free Full Text]
-
Katz DS, Lane MJ, Sommer FG. Unenhanced helical CT of ureteral
stones: incidence of associated urinary tract findings. AJR
1996;166:1319-1322[Abstract/Free Full Text]
-
Smith RC, Verga M, Dalrymple N, McCarthy S, Rosenfield AT. Acute
ureteric obstruction: value of secondary signs of helical unenhanced CT.
AJR
1996;167:1109-1113[Abstract/Free Full Text]
-
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;159:735-740[Medline]
-
Ambos MA, Bosniak MA, Madayag MA, Lefleur RS. Infiltrating
neoplasms of the kidney. AJR
1977;129:859-864[Abstract]
-
Holland JM. Cancer of the kidney: natural history and staging.
Cancer
1973;32:1030-1042[Medline]
-
Heneghan JP, Dalrymple NC, Verga M, Rosenfeld AT, Smith RC. Soft
tissue "rim" sign in the diagnosis of ureteral calculi with use of
unenhanced CT. Radiology
1997;202:709-711[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Case Report
