Approximately 1% of all emergency department (ED) visits are for treatment of urinary
tract stone disease (renal colic, kidney stones, urolithiasis).1 Renal colic is a
common condition affecting approximately 7–13% of the population during their lifetime
and those who are afflicted are likely to have recurrent attacks throughout their
Noncontrast computed tomography (CT) of the abdomen and pelvis (CT KUB) is the gold
standard imaging modality for urolithiasis. CT, however, is costly and exposes patients
to potentially dangerous amounts of ionizing radiation, especially when performed
repeatedly over time. Ultrasound (US) has been studied extensively in urolithiasis,
specifically with regard to the finding of hydronephrosis as a secondary sign. Mentions
of sonographic bladder wall abnormalities in renal colic, however, are rare in the
literature and limited exclusively to a few brief descriptions of impacted uretovesicle
junction (UVJ) stones.4,5
Through the following case series, we present sonographic bladder wall findings in
patients with renal colic. These similar appearing abnormalities, which we propose
to uniformly name the “bladder bulge,” have not, to our knowledge, been previously
discussed in the emergency medicine literature. One variant, in fact, may represent
a novel sonographic description unto itself. The bladder bulge is easily obtained
and can best be seen on axial views as a unilateral, inward bulging and/or focal thickening
of the bladder wall on the symptomatic side, at the approximate level of the uretovesical
We attempted to identify previous descriptions of bladder wall abnormalities in urolithiasis
through a Medline search of English language journals using the following Medical
Subject Heading (MeSH) terms and text words: Ureteral calculi or renal calculi or
urolithiasis or renal colic or ureterolithiasis and combined with ultrasonography
and bladder. Two hundred thirtysix articles were found. We then searched using only
the keyword pseudoureterocele. Eight articles were found. We limited our search to
English language, humans and adults. Of the first search, 2 articles briefly mentioned
ureteral prolapse and edema as seen on US at the UVJ.4,5 The second search yielded
a single sonographic description of a pseudoureterocele in a patient with tuberculosis
of the bladder.6
The following 7 cases presented to 2 different ED’s between June 2011 and November
2011. These departments are part of general tertiary hospitals that include trainees
in emergency medicine. The sonographers included 2 emergency medicine physicians who
are fellowship-trained in emergency ultrasound and one emergency medicine trainee
with limited formal training in ultrasound.
The patients were identified retrospectively through a search of the emergency department
ultrasound (EDUS) logbook and image archive. All received both a bedside ultrasound
performed by an emergency physician that included views of the bladder and affected
kidney, and a CT KUB confirming the presence, location and size of the stone. We selected
the axial US images most representative of the bladder bulge, together with the corresponding
CT image, and presented them to a board certified radiologist for interpretation.
The radiologist was blinded to the purpose of the project and given specific instructions
to provide a highly detailed interpretation, describing as many aspects of the anatomy
as possible, including elements that may not normally be mentioned in a standard reading.
Only the portion of the reading relating to the bladder wall is included here. The
radiologist also determined the presence or absence of hydronephrosis on EDUS.
Patients’ bladders were thoroughly interrogated transabdominally in the axial plane
using a low frequency (1–4 MHz), curvilinear probe. There was no standardization of
The following 7 patients, aged 28 to 58, presented with symptoms consistent with renal
colic. The images show variations of the bladder bulge and are followed by our radiologist’s
interpretation. CT images are included where they were felt to represent the bladder
bulge. Table 1 contains additional clinical variables.
Case 1: A 33-year-old male with a left UVJ stone
Radiologist description: focal wall thickening and inward bulge along the left posterior
wall, centered around a subcentimeter echogenic structure with shadowing, consistent
with a distal ureteral calculus.
Emergency department ultrasound (EDUS). Direct stone visualization (S) with shadowing
(Sh) and protrusion of the left posterior bladder wall.
Case 2: A 33-year-old male with a right UVJ stone.
Radiologist description: focal thickening of the right posterior bladder wall, with
slight inward protrusion of this portion of the wall. There is also the suggestion
of a small cystic focus at the level of the right UVJ, which may represent dilation
of the intramural portion of the distal ureter.
Emergency department ultrasound (EDUS). A pseudoureterocele (P) showing characteristic
cystic appearance at the right posterior bladder wall.
Case 3: A 38-year-old male with a left UVJ stone
Radiologist description: Focal wall thickening around an echogenic calculus along
the left posterior wall, with protrusion of the thickened wall into the bladder lumen.
Emergency department ultrasound (EDUS). Direct stone visualization (S) with edema
(E) and possible ureteric prolapse (P) at the left posterior bladder wall.
Case 4: A 44-year-old female with a left ureteric stone (likely UVJ)
Radiologist description: inward protrusion of the left posterior bladder wall into
Emergency department ultrasound (EDUS). Inward protrusion from edema (E) without stone
visualization at the left posterior bladder wall.
Case 5: A 58-year-old man with a left distal ureteric stone (not near the UVJ).
Radiologist description: focal wall thickening and inward protrusion of the left posterior
Emergency department ultrasound (EDUS). Thickening (T) and inward protrusion (P) at
the left posterior bladder wall.
Radiologist description: minimal asymmetry along the posterior bladder wall, with
an inward bulge along the left side.
Computed tomography (CT) of the abdomen and pelvis (CT KUB). Inward protrusion (P)
of the left posterior bladder wall.
Case 6: A 28-year-old male with a left proximal ureteric stone.
Radiologist description: irregularity of the bladder wall, with focal inward bulge
and apparent thickening of the left posterior wall.
Emergency department ultrasound (EDUS). Thickening (T) and inward protrusion (P) of
the left posterior bladder wall.
Case 7: A 44-year-old man with a left proximal ureteric stone
Radiologist description: minimal asymmetry along the posterior bladder wall, with
flattening of the left side.
Emergency department ultrasound (EDUS). Inward protrusion (P) of the left posterior
Radiologist description: slight inward protrusion of the left posterior bladder wall.
Computed tomography (CT) of the abdomen and pelvis (CT KUB). Flattening (F) of the
left posterior bladder wall.
All 7 patients in the case series had confirmed ureterolithiasis and an EDUS that
showed a unilateral inward bulge of their bladder on the symptomatic side. Stone size
and location varied (Table). In cases 5 and 7, there was the suggestion of a correlating
bulge seen on CT (Figures 5a, 7a), although this finding was subtler. The bladder
bulge sign is therefore felt to be primarily, if not exclusively, a sonographic finding.
Case 4 had the CT performed 12 days prior to the EDUS making it likely that her stone
had migrated to the UVJ by the time of her EDUS. Four of our patients had no hydronephrosis.
One patient had neither hydronephrosis nor hematuria.
Renal colic is a painful, but generally benign condition with a hospital admission
rate of 6–10%.1,7 Fortunately, less than 10% of renal colic patients require intervention
within 7 days and only 1–3% of patients undergoing CT KUB have an alternate diagnosis
requiring emergent intervention.1,7–9 Broder showed that of 262 patients who received
a CT KUB for suspected renal colic, 244 (93%) had neither a need for urologic intervention
nor an emergent cause for their symptoms.7
It is estimated that 1 CT abdomen/pelvis contains the equivalent radiation dose of
1000 single-view (posterior-anterior) chest x-rays, conferring an estimated lifetime
cancer risk of 6:1000 in a 20-year-old.10,11 Due to the nature of their disease, renal
colic patients are likely to have multiple presentations to the ED and multiple CTs,
as most emergency physicians, and even many radiologists, are not fully aware of the
degree of radiation exposure.12 To decrease their radiation risks, urolithiasis patients
need an imaging modality that is harmless and effective. Ultrasound is safe, and is
now recommended by the European Association of Urology as the first-line imaging modality
in suspected renal colic.13 Until American clinicians move away from CT and begin
ordering formal US studies for these patients, emergency physicians will likely continue
to perform most of the renal colic ultrasound studies.
Direct sonographic visualization of the ureters is extremely difficult. Hydronephrosis,
therefore, is used as a surrogate finding in patients with suspected renal colic.
The sensitivity and specificity of bedside ultrasound for the detection of hydronephrosis
have been shown to be 87% and 83% respectively.14 However, hydronephrosis is not always
present and mild hydronephrosis is a subtle finding. In addition, a recent study showed
that bedside sonography looking for hydronephrosis had only a limited impact on the
diagnostic impression of emergency physicians.15 Traditional EDUS renal colic studies
do not include a search for bladder wall abnormalities and the concepts of looking
for these findings and examining their diagnostic implications have not been previously
discussed in the literature.
A pseudoureterocele is an obscure term defined as “a lesion causing similar [to a
ureterocele] lucent-filling defect at the uretovesical junction on IVU (intravenous
urogram).”16 This case series introduces the bladder bulge as a unifying sonographic
description of bladder wall abnormalities seen in patients with ureterolithiasis that
includes pseudoureteroceles, focal wall thickening, edema, ureteric prolapse and inward
wall protrusion, all at the level of the UVJ. There may be some degree of overlap
among the findings. Our cases suggest that the mechanism by which the bladder bulge
occurs is not entirely explained by stone impaction at the UVJ. There may be additional
unilateral detrusor hyperactivity from inflammatory mediators released during ureteral
injury. Prostanoid and endothelin subtypes are known to directly contract human detrusor
muscle.17 This would explain the inward wall protrusion seen in cases 5, 6 and 7.
All of these patients first underwent EDUS then later had CTs confirming the presence
of stones considerably proximal to the UVJ. We believe that this particular finding
has not been previously described in the literature.
This report is a case series. All cases were identified retrospectively and some had
incompletely filled bladders. Potential stone migration during the interval between
US and CT makes exact stone location at the time of US difficult to assess. False
positives could theoretically occur with partially filled or inadequately interrogated
bladders, adjacent bowel or pelvic masses that may compress the bladder, ureteroceles,
bladder malignancy, enlarged prostate, altered anatomy from previous surgery, or normal
The bladder bulge is a novel sonographic term that describes focal bladder wall thickening
or inward wall protrusion at the level of the UVJ in patients with ureterolithiasis.
It may not be unique to impacted UVJ stones. We hypothesize that the bladder bulge
is commonly present in patients with renal colic, and sonographic visualization of
the bulge in patients with suspected renal colic will increase the likelihood of a
ureteral stone being present. If so, this finding has the potential to curtail unnecessary
CT, especially when used in the presence of hydronephrosis. Emergency physicians should
begin to look for the bladder bulge sign when renal colic is suspected. Further studies
need to be done to examine the sensitivity and specificity of the bladder bulge sign,
both alone and with hydronephrosis and hematuria; the duration it remains visible
after stone passage; the relationship of the sign to the stone location; and the ease
or difficulty with which the bladder bulge is obtained at the bedside.