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History:
77 year old female underwent conventional screening colonoscopy. The
gastroenterologist could not pass the colonoscope beyond the
descending colon. The patient was referred to Main Street Radiology
for a virtual colonoscopy (CT colonography).
Findings:
A 2 cm pedunculated polyp was identified within the ascending colon on
virtual colonoscopy (figures 1 and 2). On the routine axial
image (figure 3), the polyp (red arrow) is of similar density as the
mesenteric fat (white arrows), compatible with a lipoma.
Discussion:
Colonic lipoma is the second most
common benign colonic tumor (next to adenoma), and the most common
intramural tumor. The colon is the most common site of
gastrointestinal lipomas. Colonic lipomas may be sessile or
pedunculated, usually submucosal in location, and covered by normal
mucosa.
Colonic lipomas usually do not cause
symptoms. Rarely, patients may present with abdominal pain secondary
to intussusception. Ulceration of a lipoma may occasionally cause
bleeding.
Traditionally, definitive diagnosis was
made with resectional biopsy. Higher incidence of bowel perforation
has been reported with biopsy of colonic lipomas, due to their
intramural location. Definitive diagnosis can be made on CT
colonography, negating the need for biopsy.
Main Street Radiology has been
performing CT colonography for the past three years. Major advantage
of CT colonography is that it is non-invasive. It has been especially
beneficial after a failed or incomplete conventional (optical)
colonoscopy.
On a published study (N Engl J Med
2003; 349: 2191-2200), new techniques were discussed, showing accuracy
comparable to conventional colonoscopy. The sensitivity of virtual
colonoscopy for polyps greater than 10 mm was 93.8 %, compared to
87.5% with conventional colonoscopy. Newer techniques utilized
included, thin (1.25-2.5 mm) slices with a multidector (4 or 8 slice)
spiral CT, and 3D "fly-through" software
With our 16-detector CT, at MSR, we are
now performing virtual colonoscopy with 0.75 mm slices, with
resolution higher than obtained by the NEJM authors. We also utilize
3D "fly-through" software. With these new techniques,
virtual colonoscopy may become a viable alternative to conventional
colonoscopy, at lower cost and morbidity.
