Ulcerative colitis involves inflammation of only the large intestine, starting in the rectum and extending proximally, with clear demarcation of normal and abnormal mucosa. At endoscopy, the mucosa is edematous, granular and has a change in vascular pattern [43]. In more severe disease easy friability and bleeding, ulceration, and pseudopolyps can occur [43]. Despite the fact that it has been more than 50 years since the first report on endoscopic lesions and mucosal healing by Truelove and Witts [44], it is not until recently that attempts have been made to validate any of the many subsequent systems (Table 24.2). As there are many scoring systems available, this chapter focuses specifically on the most common endoscopic scoring system used in clinical trials, the Mayo Clinic endoscopy sub-score, and the newer scoring systems currently undergoing validation, the ulcerative colitis endoscopic index of severity (UCEIS) and the ulcerative colitis colonoscopic index of severity (UCCIS) .

Currently the most widely used endoscopic scoring system to quantify mucosal disease activity in UC in clinical trials is the Mayo Clinic endoscopy sub-score (Fig. 24.1) [54]. This score assesses vascular pattern, erythema, friability, bleeding, erosions, and ulceration. It is a four-point scale ranging from 0 to 3, with 0 being inactive disease and 3 being severe disease. It is a simple score that is easy to calculate. In most trials, mucosal healing is defined as a Mayo score of either 0 or 1 [11]. Evidence for the appropriateness of this definition was found in a post hoc analysis of the Active Ulcerative Colitis Trials (ACT)-1 that demonstrated that patients with an 8-week post-treatment Mayo score of 0 or 1 had a lower risk of undergoing colectomy and had better clinical outcomes at 1 year compared to those with higher scores [3]. Of note, however, is that patients achieving a Mayo score of 0 also had higher rates of symptomatic remission, corticosteroid-free remission and subsequent mucosal healing at weeks 30 and 54 compared to those with a score of 1 but did not have lower rates of colectomy [3]. Despite its ease of use and frequent uptake in clinical trials, the Mayo endoscopic sub-score is hampered by a lack of validation and a high inter-observer discrepancy, particularly in regard to the inclusion of friability in the score of 1, which has been found to be so subjective as to lead to inconsistent results [58]. To overcome this, some studies have adapted the index and made the presence of friability an automatic Mayo sub-score of 2 [59–61].

Until recently, no endoscopic score to assess disease activity in UC was prospectively or completely validated. To overcome these limitations the ulcerative colitis endoscopic index of severity (UCEIS) [57, 62] and the ulcerative colitis colonoscopic index of severity (UCCIS) [55, 56] have recently been developed as the first prospectively validated scoring systems for UC. The UCEIS was a collaborative effort between 40 IBD specialists from 13 counties and evaluates three variables that were determined to be the most discriminating; vascular pattern, bleeding and erosions and ulcers (Table 24.3) [62]. The worst segment of the colon is given a score of 0–2 or 0–3 for each variable to give a total score of 0–8 and the scoring system has demonstrated excellent intra and inter-observer agreement [57, 58]. Limiting its use currently is the fact that cutoff scores to define disease severity or mucosal healing have not yet been determined and the sensitivity of the scoring system to change in disease activity and mucosal improvement remains unknown. However, validation of thresholds for defining mucosal healing and response are anticipated in the near future. With this in mind, this scoring system is likely to be increasingly adopted in clinical trials and applied to clinical practice.

Unlike the previously mentioned scores , which assess only the recto-sigmoid area of the colon, the UCCIS grades mucosal changes throughout the entire colon, which may provide further important prognostic data. The score examines vascular pattern, granularity, ulceration, bleeding/friability, and severity of damage in each colon segment and overall using a four-point scale and a 10-cm visual analogue scale [55]. As with the UCEIS, the UCCIS has excellent inter-observer agreement apart from the included variable of friability and has been found to have moderate correlation with laboratory markers of disease activity including CRP and albumin and patient-defined remission [55, 56]. However, as with the UCEIS, there is no validation or definition of response or remission and its future use may be limited due to the need for full colonoscopy limiting its practical application [59].

Crohn’s disease can affect any part of the gastrointestinal tract from the mouth through to the anorectum and inflammation occurs in a patchy pattern. On endoscopy, findings in CD typically consist of segmental erythema, strictures and apthoid ulceration that can progress to stellate, longitudinal, tortuous, or serpiginous ulcers and a cobblestone appearance [43]. The terminal ileum can be involved and anal or perianal disease is suggestive of CD over UC. There are two validated endoscopic indices for evaluating CD disease activity and a further index that is routinely used to assess postoperative recurrence in CD (Table 24.4).

The Crohn’s disease endoscopic index of severity (CDEIS ) [12] and the simple endoscopic score for Crohn’s disease (SES-CD) [63] have been prospectively validated and been shown to be reproducible, have good inter-observer agreement, have good correlation with the Crohn’s disease activity index (CDAI) and are sensitive to changes in endoscopic mucosal appearance and healing [26, 64–66]. The CDEIS was the first endoscopic scoring system developed for CD (Table 24.5) and is the most commonly used endoscopic tool to assess disease activity in clinical trials. The score ranges from 0–44 and examines superficial ulcers, deep ulcers, ulcerated stenosis, and non-ulcerated stenosis in addition to the percentage of ulcerated and affected colonic surface in all five bowel segments (terminal ileum, right colon, transverse colon and rectum). Despite the CDEIS score being reliable and reproducible, its use is limited due to the fact that it is a complex scoring system that is time-consuming and not practical for routine clinical use [58]. To overcome these shortcomings, a simplified index, the simple endoscopic score for CD (SES-CD) was developed and consists of measuring ulcer size, ulcerated and affected surfaces and stenosis in each of the five intestinal segments to give a total score range of 0–56 (Table 24.6). The SES-CD correlates highly with the CDEIS and is a faster and more practical tool [63].