List of Abbreviations
Crohn’s Disease Activity Index
Ileal pouch-anal anastomosis
Magnetic resonance imaging
Nonsteroidal antiinflammatory drugs
Optical coherence tomography
Rectal vaginal fistula
Tumor necrosis factor
Video capsule endoscopy
Natural history of Crohn’s disease (CD) has dictated that most patients would eventually develop various complications, namely stricture, fistula, and abscess, and colitis-associated neoplasia. Most patients with CD would need at least one bowel resection surgery during the disease course. Stricture, fistula, and abscess can occur after surgery, which may be related to postoperative complications or recurrence of CD. The same complications often occur in patients with ulcerative colitis (UC) who underwent restorative proctocolectomy and ileal pouch-anal anastomosis (IPAA). Again stricture, fistula, or abscess in UC patients undergoing IPAA may result from the development of de novo CD-like condition of the pouch or the postoperative complications.
Clinical history, physical examination, and laboratory tests are important for the diagnosis and management of stricture, fistula, and abscess. Although abdominal and pelvic imaging modalities have extensively been used to assess those IBD- or IBD surgery–associated complications, those diagnosis-only modalities have limitations, including high costs, exposure to radiation, a limited use in patients with renal insufficiency, and inconsistent reliability in distinguishing fibrotic from inflammatory strictures.
Endoscopy provides direct visualization of mucosal pattern and structure of bowel lumen. It can also deliver therapy, if amenable lesions are detected. Endoscopy is the main tool to assess the mucosal inflammation and colitis-associated neoplastic lesions for the diagnosis, differential diagnosis, disease monitoring, and dysplasia surveillance. However, the role of endoscopic evaluation in the diagnosis of stricture, fistula, and abscess has continuously being explored.
Narrowed bowel lumen is common in patients with CD and in those with surgery. The causes of bowel lumen narrowing can be extrinsic and intrinsic. The extrinsic etiologies include adhesions and redundant bowel loop with angulation. The classic example is afferent limb syndrome in patients with IPAA, in which there is angulation between the afferent limb and pouch body. The intrinsic causes include strictures and intussusception. The stricture can further be divided into the primary, which is related to IBD disease or ischemia, and secondary, which is related to anastomosis or medicines (such as nonsteroidal antiinflammatory drugs [NSAIDs]). The diagnosis process for stricture should not only include the identification of its presence but also the assessment of number, location, degree, and associated conditions (such as fistula and abscess). Accurate diagnosis typically relies on a combined assessment of clinical, endoscopic, and radiographic (please see Chapter 7 ) features.
Patients with stricture may or may not present with obstruction (complete or partial) or with symptoms. Classic symptomatology of stricture-related partial bowel obstruction includes nausea, vomiting, bloating, abdominal pain, constipation or obstipation, dyschezia, or sense of incomplete evacuation. History and physical examination are an important part of clinical evaluation. Patients may have postprandial bloating and pain, poor appetite, weight loss, and malnutrition. The predominant symptom and its degree are dependent on the degree, number, and location of strictures. For example, patients with distal rectal or anal stricture may mainly present with dyschezia, incomplete evacuation, and post-obstruction diarrhea. Patients with stricture at the ileocolonic anastomosis may present with bloating, nausea, and abdominal cramps.
We have noticed that the severity of symptoms and degree of stricture are poorly correlated, although this correlation has not been systemically studied. Confounding factors include coexisting functional bowel disease, small intestinal bacterial overgrowth, and patient’s deconditioning due to long illness. The commonly used disease activity instruments, such as Crohn’s Disease Activity Index and the Harvey–Bradshaw Index, were not specially designed for stricturing CD.
Colonoscopy and esophagogastroduodenoscopy are the main tools for the evaluation of upper and lower gastrointestinal (GI) IBD. Other endoscopy modalities include push enteroscopy, balloon-assisted enteroscopy (see below), ileoscopy or colonoscopy via stoma, flexible sigmoidoscopy, and pouchoscopy. The main advantage of the conventional endoscopy is the direct visualization of diseased area and delivery of therapy if needed.
The degree of stricture can be empirically measured by the resistance at the passage of the scope and scored into mild, moderate, and severe, which is probably more accurate than radiographic measurement. Endoscopy can provide information on length and number of strictures, concurrent inflammation or ulcer in and around the strictures, and the presence of prestenotic bowel luminal dilatation. For severe stricture, which is not traversable to an endoscope, gentle antegrade balloon dilation or stricturotomy with needle knife may be needed. However, it is important for the endoscopist to distinguish the lumen of a tight stricture from a fistula opening. A preprocedure evaluation with abdominal and pelvic imaging is critical. In addition, the distinction can be made by spraying contrast through the orifice under fluoroscopy.
Recent decades have witnessed rapid advances in imaging technology, and one example is video capsule endoscopy (VCE). VCE may be among the most sensitive modalities for the detection of small bowel lesions. Various formats of VCE have been developed, ranging from the conventional small bowel VCE and colon VCE to wide-angle, panoramic VCE, to pan-enteric VCE or small bowel and colon VCE. Even the endoscopy activity scores, such as the Capsule Endoscopy Crohn’s Disease Activity Index, have been developed based on VCE. Leighton et al. recently screened a total of 114 patients with a known diagnosis of CD and were able to enroll 66 patients for both small bowel and colon video capsule endoscopy (SBC-VCE) and ileocolonoscopy. The authors found that the per-subject diagnostic yield rate for active CD lesions was 83% for SBC-VCE and 70% for ileocolonoscopy. Despite its high sensitivity, not all small bowel lesions detected on VCE are from CD, even after the exclusion of the use of NSAIDs. It was reported that 14% of healthy individuals may have small bowel lesions on VCE. Although various modalities are used to the diagnosis of CD, histopathology plays the key role. Pathology is not everything, but without pathology, we could not make a diagnosis of IBD. The main disadvantage of VCE is its lack of ability to get tissue samples. Some authors suggest that there are certain features on conventional endoscopy or VCE, such as the depth, size, number, and shape of ulcers, which are specific for CD. This notion, however, is highly debatable.
Stricturing disease in IBD is considered as a contraindication for the use of VCE, due to the concern of capsule retention. Since fistulizing CD often occurs concurrently with stricture, VCE is usually not used in this situation.
Push enteroscopy can reach proximal or mid jejunum. Antegrade or retrograde balloon-assisted enteroscopy can reach whole small bowel in experienced hands. The advantages of deep enteroscopy over VCE are their abilities to take tissue sample and to deliver therapy, such as balloon dilation of strictures, without concern of capsule retention. Isolated jejunum and proximal ileum involvement by CD occasionally can occur, especially in pediatric patients with CD. If those patients have stricturing CD, deep enteroscopy would be particularly useful. In a retrospective study of 170 pediatric patients who underwent ileal intubation, the terminal ileum was macroscopically normal or showed nonspecific inflammation in 73 (43%). Thirty-six of the 73 (49%) with normal or nonspecific findings at ileocolonoscopy had active disease with a median length of small bowel involvement of 20 cm (range, 1 to >100 cm) on abdominal imaging study; and nine patients with disease in the upper GI, jejunum, or proximal ileum, skipping terminal ileum. Deep enteroscopy, along with conventional upper endoscopy and colonoscopy, is able to estimate the number (limited number), degree, and length of strictures and assess the prestenotic luminal dilation. It may also help distinguish inflammatory stricture from fibrotic stricture.
Small-caliber endoscopes, such as cholangioscope and ultrathin endoscope, have been used for the passage of strictured area and for the assessment of gut mucosa proximal to the stricture ( Fig. 6.1 ). The assessment of disease status of the bowel segment proximal to the stricture may lead to continuation or adjustment of medical therapy for CD. This author has used antegrade, wire-exchange endoscopic balloon dilation to pass the stricture and get the access to the bowel segment proximal to a tight bowel stricture that was not traversable to regular upper endoscope or pediatric colonoscope.
Endoscopic Ultrasonography and Optical Coherent Tomography
Transabdominal ultrasound with or without contrasts (such as microbubbles) has been studied for the evaluation of CD strictures, particularly for the differentiation between inflammatory and fibrostenotic strictures. Various ultrasonographic modalities have been studied for the same purpose, including sonoelastography, and patency capsule–assisted ultrasonography.
The role of endoscopic ultrasonography (EUS) in the assessment of stricturing CD is limited mainly due to the difficulty in passage of the large-caliber endoscope. However, probe-based EUS and optical coherence tomography (OCT) have been used for the diagnosis and differential diagnosis of IBD. This author’s group has conducted ex vivo and in vivo studies of probe-based OCT in the differential diagnosis of CD versus UC. The disruption of the layered structure, suggestive of transmural inflammation and/or fibrosis on OCT is a reliable sign for the distinction between CD and UC. However, the limitation of depth of penetration of OCT limits its application in strictured disease in CD.
A combined assessment of clinical, endoscopic, and imaging features is important to identify and characterize fistula.
Symptomatology of patients with fistulizing CD is largely dependent on the number and location of fistula, and the presence or absence of associated stricture or abscess. For example, patient with enteroenteric fistula (EEF) from the distal ileum to sigmoid colon may complete asymptomatic, whereas patients with EEF from the duodenum or jejunum to colon may present with malnutrition. Enterocutaneous fistula (ECF) or perianal fistula may be presented with fistula drainage or abscess. Physical examination may reveal tender and abscess. Perianal fistula can usually be palpated with careful examination.
Endoscopy has traditionally not been the main modality to evaluate and diagnosis of fistula. However, this role is recently explored by the author. It is recommended that abdominal imaging with computed tomography (CT) or magnetic resonance imaging (MRI) along with careful physical examination be obtained before the endoscopy. The abdominal imaging, such as CT, MRI, or contrasted fistulogram ( Fig. 6.2 ), can provide the roadmap for endoscopic examination. Fluoroscopy guidance during endoscopy may also be helpful.