Microscopic colitis is an umbrella term used to describe two distinct entities – collagenous
colitis and lymphocytic colitis [1]. The syndrome of microscopic colitis presents with chronic, nonbloody, watery, and
often severely debilitating diarrhea. Histological examination remains the reference
standard for microscopic colitis diagnosis. However, the term “microscopic” has been
hotly debated over the years, with an increasing number of publications confirming
that the initial proposal of “microscopic colitis” as a defining term comes from the
early days of the collagenous colitis/lymphocytic colitis syndrome diagnosis, when
neither advanced endoscopic imaging nor the combination of modalities during endoscopy
were readily or widely available [2]
[3].
Early reports, using standard white-light imaging and indigo carmine dye spraying
chromoendoscopy, had indicated the presence of abnormal vascular and surface patterns
[4]. Recently, nonspecific and subjective findings, to an extent dependent upon the
endoscopists’ experience [5]
[6], such as patchy mucosal erythema and/or mucosal edema, and abnormal vascular pattern,
can be seen with standard-definition endoscopy in up to 30 % of patients [5]. Nevertheless, the specificity of the aforementioned findings and others such as
cat scratch colon (i. e. bright red linear markings at the right side of the large-bowel
mucosa) is as low as 14 % [7]
[8]. That really only leaves acute mucosal lacerations or mucosal fractures (as described
by some) as almost pathognomic for collagenous colitis, and these findings have been
associated mainly with the use of proton pump inhibitors such as lansoprazole [3].
It therefore comes as no surprise that the other unresolved issue in collagenous colitis
is the correlation of the location (as well as the severity) of the endoscopic findings
with that of mucosal inflammation and more specifically the thickness of the collagenous
band. It has been suggested that the presence of a thick subepithelial collagen layer
(i. e. > 10 μm) makes the colon stiff and the mucosal layer easier to dehisce and
fragment [9].
Recently, we presented a detailed case series on collagenous colitis [2], and we proposed that the time has come to acknowledge the rise in the incidence
of endoscopic findings in “microscopic colitis” and, more specifically, in collagenous
colitis. We believe that increases in the reporting of endoscopic findings can be
attributed to an improvement of endoscopic equipment and an increased awareness of
the entities of collagenous colitis and lymphocytic colitis among colleagues, as well
as the application of advanced endoscopic imaging, such as chromoendoscopy (digital
or with application of dye), high definition endoscopy or confocal endomicroscopy
[4]
[8]
[10]
[11].
To this effect, the presentation of one more case series by Kobayashi et al. [12], in this issue of Endoscopy International Open, adds further ground to our claim. In this study, the authors re-endoscoped five
consecutive patients with biopsy-confirmed collagenous colitis. Four out of the five
cases were men and all were treated with lansoprazole to prevent aspirin-related gastroduodenal
ulceration. Interestingly, in all cases, complete resolution of clinical symptoms
of collagenous colitis was achieved within a month by stopping proton pump inhibitors.
Another 12 asymptomatic individuals who were also on lansoprazole for treatment of
reflux esophagitis or for prophylaxis against nonsteroidal anti-inflammatory drug-induced
ulceration, were evaluated as the control group in the study.
A magnifying video endoscope CF-HQ290ZI of the Lucera Elite spectrum (Olympus Corp.,
Tokyo, Japan) was used to perform the colonoscopies. Magnifying endoscopy was used
to observe white-light images, narrow-band images (NBI), and indigo carmine spraying
(0.5 %). To the best of our knowledge, this is the first time that all of the above
modalities have been applied in combination, albeit in a limited number of cases.
Biopsies were performed not only in abnormal-looking colon areas, but as a standard
one-sample per colonic segment as well.
In essence, in a clever manner the investigators applied the best possible diagnostic
techniques/modalities for each of the individual findings suggestive of collagenous
colitis: pathology of the subepithelial capillary network was examined by magnifying
NBI; presence or absence of mucosal edema was examined by indigo carmine dye spraying
and magnifying endoscopy. The latter revealed a whitish and clouded honeycomb-like
appearance at the orifice of the mucosal crypts, whereas the former showed an irregular-caliber
submucosal capillary network. In the long path of attempts to correlate endoscopic
findings with the presence of subepithelial collagen and essentially that of collagenous
colitis diagnosis, the study comes once again to support our long-held belief that
the so-called microscopic colitis does not lack macroscopic findings.
We should mention the limitations to this work. First of all, this was a single-center
study in a limited number of patients who had already been diagnosed with collagenous
colitis. Moreover, the application of magnification endoscopy is not something that
is applied in routine clinical practice, unlike the use of NBI. Finally, for a tool
to become widely used and available, it has to overcome the time constraints that
typically exist in busy, high-volume and fast-turnaround endoscopy units. Thus, a
“multimodal” approach such as the one proposed by Kobayashi et al. is time-consuming
and possibly still operator-dependent.
The quality of the images improves with the technology of the endoscope, allowing
for fast and clear recommendation following visualization of the surface and vascular
patterns of the colonic mucosa. It takes only a matter of time to confirm the type
and specificity of each of the endoscopic findings, thus allowing not only a more
accurate diagnosis based on histopathological examination of biopsy specimens, but
more immediate initiation of treatment when certain macroscopic findings are present.
The latter should be considered especially beneficial in high-volume centers, which
normally treat biopsies of endoscopic specimens from non-neoplastic conditions with
a lesser degree of urgency, thus disadvantaging patients with microscopic colitis
from more prompt initiation of therapy.
