Diagnostic approaches in patients suspected of Ischemic Colitis (IC)

Ischemic colitis (IC) is the most common form of gastrointestinal ischemia,
counting for half of all cases of gastrointestinal ischemia [1]. IC results
from inadequate blood flow to the colon which leads to colonic inflammation. IC
can present as non-gangrenous form, counting for 80-85% of cases and the
gangrenous form, concerning 15-20% of cases, the latter often requiring surgery
[2]. The histological findings in ischemic colon range from mucosal and
submucosal hemorrhage and edema with or without ulceration and strictures to
fulminant transmural gangrenous damage [1]. Non-occlusive disease is the most
common cause of IC. Development of IC is associated with postoperatively after
aortoiliac surgery, shock states, cardiac arrhythmia, renal failure,
vasculitides, coagulopathies and vasoconstrictive medication [1,2].The whole
colon can be involved, but the splenic flexure, descending colon and sigmoid
are the most common sites involved in an episode of IC [1]. Currently, there is
no golden standard diagnostic tool for diagnosing IC. Endoscopy and
histological confirmation is the first choice diagnostic approach in patients
clinically suspected of IC. However, endoscopic and histopathological findings
often show nonspecific abnormalities1-2, making it difficult to diagnose IC.
Visible light spectroscopy (VLS) has been introduced as a new technique which
directly measures the oxygen saturation of capillary hemoglobin during
endoscopy in a non-invasive manner, reflecting the adequacy of mucosal
perfusion. Friedland et al1 [3] investigated oxygen saturation levels in
mucosal colon of 40 normal controls. In addition, possible markers of hypoxia,
such as HIF-1 alpha, could help to improve the sensitivity of histological
findings in patients suspected of IC.

The aim of the study is to evaluate and develop new diagnostic tools for an
accurate diagnosis of IC:

Primary objective: to test whether mucosal oxygen saturation has added value to
endoscopy and histological examination.

Secondary objective: to test whether detection of hypoxia dependent molecular
changes in the mucosa can be used to improve sensitivity of histological
analyses.

A prospective cohort study conducted by the Department of Gastroenterlogy and
Hepatology, Erasmus MC University Medical Center Rotterdam.

1: Mucosal oxygen saturation measurement
During the diagnostic ileocolonoscopy mucosal oxygen saturation will be
measured at 7 defined points in colon (coecum, hepatic flexure, mid-transverse
colon, splenic flexure, descending colon, rectosigmoid and rectum). In the
presence of mucosal lesions, extra VLS measurements will be performed from the
lesions and the normal appearing mucosa adjacent to it. The mucosal oxygen
saturation measurement with VLS will add 5 minutes extra to the total time of
30 minutes of the ileocolonoscopy.

2: Detection of hypoxia dependent molecular changes
In each patient routine diagnostic biopsies will be taken from the
endoscopically visible lesions. In addition to these routine biopsies,
additional biopsies will be taken from the normal appearing mucosa adjacent to
the lesions and from the mucosa at the splenic flexure and rectosigmoid. The
latter biopsies will also be taken in the absence of visible lesions.
At every specified location 4 biopsies will be taken, 2 biopsies will be fixed
in formaline and embedded and 2 biopsies will be snap-frozen.
The 2 biopsies fixed in formaline will be used for protein detection of hypoxia
induced proteins such as HIF-1*, iFABP, or GLUT-1 using techniques such as
immunohistochemistry and FISH. The 2 biopsies which are snapped frozen will be
used for isolation of RNA and proteins. This will be used to detect differences
in expression levels between normal mucosa, normal appearing mucosa of
patients with IC and mucosal lesions of patients with IC or colitis due to
other etiologies.

Patients who will participate with the investigation are not at greater risk.
Colonoscopy is performed as a part of normal diagnostic approach. Due to the
mucosal oxygen measurements the (ileo-)colonoscopy will last about 5 minutes
longer. Mucosal biopsies will be taken for routine diagnosis from the lesions
and the normal appearing mucosa adjacent to the lesion. Extra biopsies will be
taken for RNA and protein isolation. This will be 4-8 additional biopsies which
adds only a minor risk of perforation and prolonges the colonoscopy with 2
minutes. The total time of elongation of the colonoscopy will be 7 minutes.