A 73-year-old man presented
to the emergency department after noting dysuria and fecal matter in his urine
for 1 day. The patient had a medical history consisting of prostate cancer
treated with brachytherapy, Crohn disease, colonic stricture, diabetes, and no
prior surgeries. Other than episodic lower abdominal pain that had been
occurring for months, the patient did not have any additional symptoms, denying
any fever, chills, vomiting, diarrhea, constipation, rectal pain, chest pain,
or dyspnea.
On initial examination, the
patient was in no acute distress, afebrile, and hemodynamically stable. His
abdomen was soft with mild tenderness of the lower abdomen without palpable
masses, guarding, rigidity, or rebound. There was no scrotal or inguinal swelling
or tenderness. Initial laboratory results were notable only for a white blood
cell count of 14,100 cells/μL with 88% neutrophils and a venous lactate level
of 0.83 mmol/L. Fecal matter was noted on gross examination of the urine, and
urinalysis results were negative for nitrite, positive for leukocyte esterase,
and showed more than 182 white blood cells per high-power field and many
bacteria.
Point-of-care sonography was
performed by the emergency physician using a curvilinear transducer (Figure 1, A and B, and Video 1) and revealed a
collection of mixed echogenicity throughout the bladder, representing stool,
along with multiple hyperechoic foci with a reverberation artifact and
shadowing, consistent with pneumaturia. A hyperechoic band leading from the
bowel into the bladder was noted, consistent with a fistula. A computed
tomographic (CT) scan of the abdomen and pelvis (Figure 1C) was obtained to assess for
associated intra-abdominal disease and to provide further anatomic detail given
the patient’s complicated history. Computed tomography revealed a heterogeneous
collection of soft tissue and fecal matter within the pelvis bordering the
posterosuperior wall of the bladder and air within the bladder, supporting the
diagnosis of an enterovesical fistula. Subsequent surgical exploration and
cystoscopy confirmed a colovesical fistula from the distal sigmoid to the left
bladder near the left ureteral orifice and copious stool within the bladder.
Enterovesical fistulas are
classified as colovesical, which is the most common form, rectovesical,
ileovesical, and appendicovesical. Most commonly a complication of
diverticulitis, malignancy, or Crohn disease,1 fistulas may also occur after trauma, pelvic
surgery, or pelvic radiation therapy, including brachytherapy.2 The fistula is often difficult to identify on
imaging studies; hence the lack of a reference standard imaging modality.3 The most sensitive and commonly recommended
initial study is CT,1,3 although the fistula itself is not
consistently identified.3–7 Findings used to confirm the presence of a
fistula include gas in the bladder in patients without recent urinary
instrumentation, local colonic thickening immediately adjacent to an area of
locally thickened bladder, and oral contrast medium in the bladder on
nonintravenous contrast-enhanced CT.1,4,8 Alternatively, intravenous contrast medium
noted within the bowel when an oral contrast medium is not used also implies
the presence of a fistula.6
Like CT, sonography can
visualize soft tissue in multiple planes and has been used in the diagnosis of
colovesical fistulas.9–11 Suggestive findings include pneumaturia,
which is represented by multiple reverberation artifacts within the bladder,
and stool within the bladder, which is hyperechoic.9,10 The fistula itself appears hypoechoic,12 but if gas is present in the tract, the
fistula may instead be visualized as a hyperechoic “beak” connecting the
peristaltic bowel lumen and the bladder. Air bubbles or hyperechoic material
may be noted flowing from the beak into the bladder with direct compression
either manually or using the ultrasound transducer.9,11 This finding must be distinguished from
ureteral jets emanating from the ureterovesical junction due to normal
peristalsis of the ureter.9,11
Figure 1.
Enterovesical fistula in a 73-year-old man. A and B, Longitudinal (A) and transverse (B) views of the suprapubic window illustrating the bladder (B) with a
hyperechoic artifact consistent with air (A) and heterogeneous material
consistent with stool (S). There is a hyperechoic band connecting the bowel to
the inside of the bladder, consistent with a fistula (F). C, Transverse CT scan of the pelvis illustrating air within the bladder.
In contrast to CT, sonography
is used infrequently in the initial evaluation of suspected enterovesical
fistulas. In addition to identifying the presence of a fistula, CT may reveal
associated intra-abdominal processes and provides anatomic details for any
surgical planning. There are also limited data regarding the sensitivity of
sonography for diagnosing these fistulas. Sonography did not identify any
fistulas in 27 patients from 3 retrospective studies with confirmed
enterovesical fistulas.3,4,13 In another retrospective study of patients
with colovesical fistulas secondary to diverticulitis, sonography identified a
fistula in 1 of 23 patients.14 None of these studies, though, describe the
experience of the sonographers or specific imaging protocols. In a prospective
study by Maconi et al,15 sonography enabled the diagnosis of all 4
enterovesical fistulas in patients with Crohn disease who underwent surgical
intervention.
The diagnosis of an
enterovesical fistula is strongly suggested by the presence of fecaluria,
pneumaturia, or recurrent urinary tract infections, but it may present more subtly.
Fewer than half of affected patients have fecaluria, and although pneumaturia
is found in approximately 60% of patients, other causes such as recent bladder
instrumentation and emphysematous cystitis must be considered.1 Although this patient presented with classic
signs of an enterovesical fistula, this case shows that point-of-care
sonography can be used to make the diagnosis. As it is performed at the
bedside, it may be used early in the course of evaluation, especially when the
patient’s presentation is less clear and CT not immediately indicated. Findings
suggestive of a fistula, including air or stool in the bladder, or
visualization of the fistula itself, can lead to timely diagnosis of this
disease process. Furthermore, especially if pain, fever, and unstable vital
signs are present, point-of-care sonography allows for concomitant evaluation
for other possible causes of these symptoms and guiding of further interventions.
