38 Inflammatory Bowel Disease and Microscopic Colitis
Marjolijn Duijvestein and Geert R. D’Haens
Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the gastrointestinal (GI) tract that comprise Crohn’s disease (CD) and ulcerative colitis (UC). Endoscopy not only plays an essential role in the diagnosis and characterization, enabling biopsy sampling of the affected digestive tract, but also contributes to the evaluation, monitoring, and management of the disease. Furthermore, endoscopy is used to detect dysplasia contributing to the surveillance of long-standig disease.
The direct visual appreciation of lesions, so much more accurate than radiologic studies, and the ability to collect biopsy samples have made endoscopic examinations the first-line procedures in the initial evaluation of patients with unexplained chronic diarrhea and suspected IBD. The need for an unpleasant bowel preparation, the high cost, and the discomfort sometimes caused by endoscopic procedures should nevertheless force the clinician to limit the indications as strictly and correctly as possible.
This chapter describes the endoscopic characteristics of CD and UC lesions, the role for endoscopy in the evaluation of disease severity using endoscopic indices, the use of endoscopic surveillance, indications for pre- and postoperative endoscopy in IBD, endoscopy in ileoanal pouches and pouchitis, and therapeutic endoscopic interventions. Furthermore, the clinical features and role of endoscopy in the diagnosis of microscopic colitis will be reviewed.
38.2 Endoscopic Characteristics of IBD
38.2.1 Lower Endoscopy
Endoscopically, CD is often characterized by areas of inflammation separated by normal-appearing mucosa, which are called skip lesions. Any part of the GI tract from mouth to anus can be affected, although most commonly the ileum is involved (▶Fig. 38.1). Early mild lesions include small (< 5 mm) aphthous ulcers (▶Fig. 38.2). In more severe disease deep irregular and longitudinal ulcerations (▶Fig. 38.3, ▶Fig. 38.4) can be seen as well as a cobblestone appearance of the mucosa (▶Fig. 38.5). As the inflammation is transmural, it can result in strictures and fistulae. Often rectal sparing is seen. Biopsy specimens to confirm the diagnosis should be taken from the edges of ulcers and aphthous erosions (▶Table 38.1). Specific guidelines on how many biopsies should ideally be taken are lacking.
Inflammation in UC tends to be continuous, confluent, and concentric. Characteristically, inflammation commences proximal to the anus. The demarcation between inflamed and normal areas is usually clear and in general there are no skip lesions. Initial lesions include loss of vasculature and hyperemia of the colonic mucosa (▶Fig. 38.6, ▶Fig. 38.7). In moderate disease, discrete ulcers surrounded by inflamed mucosa develop progressing to large, continuous ulcers with increasing severity of the disease (▶Fig. 38.8). “Backwash ileitis,” extension of macroscopic or histologic inflammation from the cecum into the most distal ileum, has been reported in up to 20% of patients with pancolitis 2 , 3 and is associated with a more refractory course of disease. 4
38.2.2 Upper Endoscopy
At least half of pediatric-onset CD patients have an upper GI localization, which is associated with a more severe disease course, therefore requiring more aggressive therapy. 5 In the pediatric and adolescent population, upper GI endoscopy is therefore routinely performed in the assessment of IBD. 6 In the adult population, the prevalence of upper GI involvement is suggested to be around 16%, of which only one-third of the patients are symptomatic. 7 It is to be debated if upper endoscopy should be in the diagnostic work-up of CD patients, but it should at least be performed in CD patients with dyspepsia, abdominal pain, and vomiting in order to rule out other causes for the symptoms and to correctly classify the distribution and extent of the disease.
In the esophagus, Crohn’s lesions can present as aphthous ulcerations, “punched-out” ulcers or larger perforating lesions. In the stomach inflammation is present as focal erythema with or without ulcerations and in the duodenum frank ulcerations are often seen, quite commonly complicated by stenosis at the level of the gastric outlet or in the midduodenum.
Upper endoscopy is not routinely performed in patients with UC. Occasionally, diffuse duodenitis can develop in patients with severe UC, even after proctocolectomy.
38.2.3 Small Bowel Imaging
CD can affect segments of the small bowel out of reach of the colonoscope. Small bowel video capsule endoscopy should be considered in patients with suspected CD and negative ileocolonoscopy. 8 The Lewis score (LS) 9 has been developed to assess mucosal inflammatory disease in the small bowel. This scoring index is based on three capsule endoscopic variables: villous appearance, ulceration, and stenosis. In addition, each variable is assessed by other parameters including size and extent of the change. Using these parameters, a score range of 8 to 4,800 points was established: LS less than 135 reflects normal mucosal appearances, LS 135 to 790 mild mucosal inflammatory change, and an LS value greater than or equal to 790 moderate-to-severe mucosal inflammatory changes.
In patients with obstructive features or known stenosis, a cross-sectional imaging modality such as magnetic resonance enterography (MRE) or computed tomography enterography (CTE) should be the method of choice. 10 Furthermore, MRE can objectify the transmural nature of the disease, its anatomical distribution as well as the presence of extraluminal disease.
38.2.4 Endoscopic Ultrasonography
The cumulative incidence of perianal fistulas in CD range from 23 to 38%. 4 , 11 Perianal fistula are often diagnosed and classified by using a combination of both clinical and imaging findings. Endoscopic ultrasound (EUS), magnetic resonance imaging (MRI), and examination under anesthesia (EUA) are accurate tests for determining fistula anatomy in patients with perianal CD. 12 Combining two of the three modalities gives an accuracy of 100%. Examination under anesthesia in the hands of an experienced surgeon has been considered the gold standard in the assessment of perianal CD, with the advantage that surgical drainage of any abscesses and placement of noncutting setons can be performed as required. 13 Currently, it is advised to first perform a noninvasive procedure such as MRI to visualize perianal fistula unless there is a need for immediate drainage of sepsis. 14 For endoscopic ultrasonography endoanal probes are used transrectally. Fistulas are visible as hyperechoic tracks or beads within a larger hypoechoic tract consistent with surrounding inflammation. 15 Data from three small clinical trials suggest that fistula imaging by EUS can guide in medical decision making with better clinical outcomes. 16 , 17 , 18
38.2.5 Endoscopic Retrograde Cholangiopancreatography
Primary sclerosing cholangitis (PSC) is a chronic, cholestatic liver disease characterized by chronic inflammation and fibrosis of the biliary tract affecting both intrahepatic and extrahepatic bile ducts leading to the formation of bile duct strictures. The vast majority of patients with PSC have accompanying IBD. The presence of PSC increases the risk of colorectal cancer (CRC) development almost by a 10-fold, 19 furthermore PSC patients are at increased risk of developing cholangiocarcinoma with a 20% lifetime risk. 20 Endoscopic retrograde cholangiopancreatography (ERCP) is the gold standard for diagnosing PSC. ERCP is used for diagnostic (brush cytology) and therapeutic purposes, that is, balloon dilation or stent placement.
38.3 Endoscopy in Established IBD
38.3.1 Acute Colitis
In patients with chronic bloody diarrhea, endoscopy with mucosal biopsies is an important tool to evaluate the severity of disease 21 and to exclude other (infectious) causes of acute colitis, 22 such as cytomegalovirus (CMV) colitis, rectal mucosal prolapse, malignancy, and hemorrhoidal bleeding. 23 In most cases unprepped sigmoidoscopy with minimal inflation is sufficient. Biopsies are particularly useful to exclude CMV colitis in patients with prolonged exposure to steroids and/or azathioprine. 24 Furthermore, the endoscopic appearance predicts the course of the disease and may guide treatment intensification. For example, in UC it is known that the presence of extensive and deep ulcerations at endoscopy is associated with an increased risk of colectomy. 25 , 26
38.3.2 Routine Endoscopy
Routine endoscopy in IBD patients in clinical remission, besides surveillance for dysplasia and after surgery, has been considered to be unnecessary. In these cases, noninvasive tests and surrogate markers of disease activity, 27 such as fecal levels of calprotectin 28 or lactoferrin, 29 , 30 can be used to assess disease activity. Whether treatment intensification to attain “mucosal healing” despite the absence of symptoms is to be recommended remains to be studied. In the cases of a suspected relapse, refractory disease, new/unexplained symptoms, change of medical therapy, or when surgery is considered, endoscopy should be seriously performed.