Inflammatory Bowel Disease: Crohn’s disease and ulcerative colitis

Crohn’s disease and ulcerative colitis

Background: Inflammatory bowel diseases are common in Europe, with prevalences as high as 1 in 198 persons (ulcerative colitis) and 1 in 310 persons (Crohn’s disease).

Methods: This review is based on pertinent articles retrieved by a search in PubMed and in German and European guidelines and Cochrane reviews of controlled trials.

Results: Typically, the main clinical features of inflammatory bowel diseases are diarrhea, abdominal pain, and, in the case of ulcerative colitis, peranal bleeding. These diseases are due to a complex immunological disturbance with both genetic and environmental causes. A defective mucosal barrier against commensal bowel flora plays a major role in their pathogenesis. The diagnosis is based on laboratory testing, ultrasonography, imaging studies, and, above all, gastrointestinal endoscopy. Most patients with Crohn’s disease respond to budesonide or systemic steroids; aminosalicylates are less effective. Refractory exacerbations may be treated with antibodies against tumor necrosis factor (TNF) or, more recently, antibodies against integrin, a protein of the cell membrane. In ulcerative colitis, aminosalicylates are given first; if necessary, steroids or antibodies against TNF-α or integrin are added. Maintenance therapy to prevent further relapses often involves immunosuppression with thiopurines and/or antibodies. Once all conservative treatment options have been exhausted, surgery may be necessary.

Conclusion: The treatment of chronic inflammatory bowel diseases requires individually designed therapeutic strategies and the close interdisciplinary collaboration of internists and surgeons.

Crohn’s disease and ulcerative colitis, the two varieties of inflammatory bowel disease (IBD), both tend to arise in early adulthood, but can in fact arise at any age from early childhood onward. Their diagnosis is often delayed despite their prominent manifestations, including diarrhea, abdominal pain, and, in ulcerative colitis, peranal bleeding. Crohn’s disease can affect the entire gastrointestinal tract transmurally, from the mouth to the anus, while ulcerative colitis mainly affects the colonic mucosa. The clinical picture is rounded out by extra-intestinal manifestations in the joints, eyes, and skin, which can arise before the bowel disease does. An extensive monograph on IBD was published recently (1). For the special features of IBD in children, the reader is referred to another recent review in Deutsches Ärzteblatt International (2).

IBD are attracting increased attention at present for a number of reasons.

One reason is that that these diseases are far from rare, with prevalences of up to 1 in 198 persons for ulcerative colitis and 1 in 310 persons for Crohn’s disease (3). In most epidemiologic studies, an increasing incidence has been seen. A further reason is that their treatment has become more complex with the introduction of monoclonal antibodies against TNF and integrins.

Learning objectives

This article is intended to acquaint readers with:

• new pathophysiological concepts in IBD
• the fundamentals of diagnostic evaluation
• options for pharmacotherapy
• the fundamentals of surgical treatment.

Methods

This review is based on a literature search in PubMed employing the terms “Crohn’s disease” and “ulcerative colitis,” and on the current German (4, 5) and European (6–9) guidelines for these two conditions. The currently recommended diagnostic evaluation of IBD is mainly derived from case series; the treatment recommendations are generally based on the findings of clinical trials and meta-analyses of clinical trials, preferably Cochrane Reviews.

The pathophysiology of IBD

Explanatory concepts for IBD have changed in recent years. Twin studies (e1) have shown that a genetic predisposition (10), as opposed to environmental factors, plays a larger role in Crohn’s disease than in ulcerative colitis. More than 160 risk genes are associated with Crohn’s disease; most of them affect the interaction of microbes with the bowel (e2) and are dependent on phenotype (e3). Important environmental factors include antibiotic consumption during childhood and adolescence and, for Crohn’s disease, cigarette smoking (e4). The commensal microflora of the bowel are now thought to play a central role in the induction and maintenance of the chronic inflammatory process (11–13, e5, e6). The normally peaceful coexistence of about 10¹⁴ micro-organisms of at least 1000 bacterial species in the human gastrointestinal tract is an amazing phenomenon, particularly in the terminal ileum and colon, which is the site where the bacterial concentrations are highest and where the manifestations of Crohn’s disease and ulcerative colitis are most commonly found. There is a “dysbiosis” of the microflora (e7) of uncertain primary significance (e8); IBD patients, unlike normal individuals, have bacteria directly on and in their mucosal epithelium (12, e9, e10). The earlier interpretation of IBD as classic autoimmune diseases is obsolete (e11); instead, they are now thought of as complex barrier disorders. The mucosal barrier consists of the epithelial layer and the antibacterial mucus layer above it, which is made up of goblet cell mucins and epithelially secreted intrinsic peptide antibiotics (defensins) (Figure 1) (13, e12). In ulcerative colitis, a defective, thinned mucus layer is seen (e13). In Crohn’s disease of the small intestine, the Paneth cells at the base of the crypts and defective defensin formation seem to play a central role (13–15).Various defects of bacterial recognition (NOD2), autophagy, endoplasmic reticulum stress, and monocyte function (e14) impair antimicrobial defenses and alter the microbiome (14, 15). Invading bacteria induce an inflammatory response involving both the innate immune cells (granulocytes, macrophages, dendritic cells) and the adaptive immune cells (T cells) (16, e15).

Figure 1

The mucosal barrier in health

Diagnostic evaluation

The (initial) diagnosis of IBD is made on the basis of history and physical examination, along with the laboratory values and the findings of endoscopic, histological, and radiological studies. No single feature establishes the diagnosis (6). Chronic diarrhea is a characteristic manifestation, with bloody diarrhea typifying ulcerative colitis (e16); abdominal pain and weight loss are also typical. For differential diagnosis, the patient should be specifically asked about food intolerance, drugs taken (including nonsteroidal anti-inflammatory drugs [NSAID]), travel abroad, and cigarette smoking. IBD should be considered as a possible diagnosis in children with unexplained failure to thrive (2), nutritional deficiencies (particularly vitamin B₁₂ deficiency), certain skin changes (erythema nodosum, pyoderma gangrenosum), and seronegative rheumatic joint pain (a possible extra-intestinal manifestation of IBD) (4).

The initial laboratory tests comprise a complete blood count (anemia and thrombocytosis indicate chronic inflammation), inflammatory parameters, and renal and hepatic function tests. The measurement of calprotectin, a neutrophil protein, in the stool is now standard (17). The calprotectin level is nonspecifically elevated in gastrointestinal inflammation but is a useful parameter for noninvasive treatment monitoring. Gastrointestinal infections (including Clostridium difficile) must be excluded at the outset and sometimes also in new exacerbations, as they can take an atypical course in patients who are under treatment for IBD (18).

Endoscopy is the gold standard for the initial diagnosis of IBD (Figure 1) (19). If Crohn’s disease is suspected, the terminal ileum must be intubated, because most patients have mucosal changes there (e17). In severe exacerbations of ulcerative colitis, with maximum inflammation nearly always in the rectum, sigmoidoscopy often suffices for the acute evaluation. Histological examination yields important additional information; architectonic abnormalities confirm the diagnosis. In some cases, the two kinds of IBD can be distinguished from each other, and from other types of bowel disease (e.g., infection) only on further follow-up, but over 90% of patients have a definite diagnosis 5 years after presentation (e18). The upper gastrointestinal tract should be evaluated by esophagogastroduodenoscopy with biopsy at the time of initial diagnosis (4), because extensive involvement with Crohn’s disease confers a worse prognosis (e19). Ultrasonography and magnetic resonance enterography of the small intestine complete the initial diagnostic evaluation for the extent of disease (Figure 2). We also often use ultrasonography to monitor the course of disease (4), although MRI (or, in emergency cases, CT) is superior to ultrasonography for the demonstration of fistulae and abscesses (e20). MRI is also suitable for the evaluation of stenoses, showing not only their extent and prestenotic dilatation, but also wall thickening and perfusion (which can help distinguish fibrotic from inflammatory stenoses). This, in turn, is helpful in treatment planning, e.g., the decision whether to treat with anti-inflammatory drugs or to perform dilatation. Toxic megacolon can be a serious acute manifestation of ulcerative colitis; a plain abdominal x-ray demonstrating colonic dilatation over 6 cm without any distal stenosis is diagnostic.

Figure 2

Typical endoscopic and tomographic findings in chronic inflammatory bowel disease

Over the course of follow-up, a good clinical response to treatment is often associated with the normalization of previously pathological laboratory values. If there is a discrepancy, endoscopy can yield further information to be considered in the decision whether to intensify or modify the treatment. The high co-prevalence of irritable bowel syndrome in as many as one-third of all patients with IBD (5, e21, e22) must be considered when symptoms persist despite mucosal healing. If the clinical picture remains unclear, the entities to be ruled out include stenosis (particularly in Crohn’s disease), carcinoma (particularly in ulcerative colitis, but in Crohn’s disease as well), and infection (particularly in immune-suppressed patients; e.g., cytomegalovirus, Clostridium difficile). Starting 8–10 years after the initial manifestation of either type of IBD, colonoscopy should be used to monitor for dysplasia. Chromoendoscopic surveillance with methylene blue or indigo carmine is better than white-light endoscopy for this purpose (e23). There is not yet enough evidence to determine whether it is best to monitor endoscopically for dysplasia every 1–5 years in risk-group-adapted fashion, as recommended in the European guidelines (19), or to do so every 1–2 years in all patients, as recommended by the German Society for Digestive and Metabolic Diseases (DGVS) (5). Circumscribed neoplastic lesions can be endoscopically resected regardless of their classification as sporadic or colitis-associated, as long as a complete resection, absence of tumor elsewhere in the bowel, and good further surveillance can be ensured (19).

The natural course of IBD is highly variable: a patient may experience a mild course after a severe initial episode, a slowly or episodically progressive condition, or chronically intermittent or persistent symptoms (e24–e26). After an initial acute episode, there is a 40% chance of a remitting course with prolonged phases of disease inactivity between episodes (e19). About 20% of all patients develop steroid-refractory disease; the remainder are steroid-dependent, i.e., they rapidly develop recurrent disease when any attempt is made to lower the steroid dose. In population-based studies of ulcerative colitis, about half of all patients were oligosymptomatic or asymptomatic five years after the initial diagnosis (e27); in Crohn’s disease, complications were more frequent, with a more severe effect on the quality of life (e17). It is debated whether IBD increase mortality (e28–e31), although it is clear that mortality is higher in patients who have both IBD and primary sclerosing cholangitis (e32).

The treatment of IBD

The pharmacotherapy of IBD as recommended in current guidelines is wholly based on the findings of controlled trials and meta-analyses. An overview of the evidence levels of the more important recommendations is given in Table 1. The treatment should always be adapted to the site, extent, and course of disease in the individual patient, with further adaptations guided by the clinical response; there is inadequate evidence to support basing treatment escalations on endoscopic findings alone. A strategy of immediate, maximal immunosuppression, including antibody administration, at the time of diagnosis has not been incorporated into the guidelines, as this would constitute overtreatment for many patients, with frequent adverse effects. Thus, the standard therapeutic strategy is clinically guided, stepwise treatment, beginning with relatively well-tolerated drugs and proceeding incrementally toward aggressive immunosuppression (eFigures 1 and 2). As the individual course of disease is unpredictable, clinical follow-up should be frequent, and the treatment should be escalated whenever there has been an unsatisfactory response. This strategy enables the early detection of disease complications, while avoiding the costly and unnecessary provision of antibody therapy to uncomplicated patients.

Table 1

Evidence levels of treatment recommendations for chronic inflammatory bowel disease*

Crohn’s disease

A therapeutic algorithm for the induction and maintenance of remission in Crohn’s disease is shown in eFigure 1.

eFigure 1

Treatment algorithm for Crohn’s disease, developed by K.H. and E.F.S.

Induction of remission in relapsing disease

If the ileocecal region is involved, budesonide, a drug that works best topically, is the treatment of choice. A recent trial, however, showed that mesalazine (4.5 g/day) is equally effective against mild to moderate ileocecal involvement in Crohn’s disease (20). Sulfasalazine is now only rarely used because of its adverse effects but can still be given to treat Crohn’s colitis, particularly if the patient also has joint pain. Isolated involvement of the rectum or sigmoid colon can be treated locally with enemas, rectal foam, or suppositories containing steroids or aminosalicylates. If these options fail, the standard treatment of acute relapses is systemic steroid administration. The optimally effective dose is 1 mg per kg of body weight (BW); once the symptoms have responded, the dose should be slowly reduced.

Induction of remission in case of steroid resistance

If the patient does not respond adequately to systemic steroid treatment, the anti-TNFα antibodies infliximab (21) and adalimumab (22) and the anti-integrin antibody vedolizumab (23) can be used. Infliximab is given intravenously, adalimumab subcutaneously; they are of equivalent efficacy and bring about remission in roughly half of all patients treated. The decision which of these two drugs to use is made according to the patient’s preference, taking the mode of administration into account.

The anti-integrin antibody vedolizumab is the first drug in this substance class to be approved for the treatment of refractory Crohn’s disease. It has few side effects; after six weeks of treatment, the remission rate is 14.5%, compared to 6.8% with placebo (p = 0.02). The main advantage of this drug is long-term maintenance of remission (23).

Maintenance of remission

Treatment to maintain remission is not indicated for all patients, but only for those who have had a complicated course. Despite their frequent use for this purpose (e33), aminosalicylates are not effective for the maintenance of remission in Crohn’s disease (although they are effective in ulcerative colitis) (24). Patients who become steroid-dependent or who have frequent relapses should be given permanent immunosuppressive therapy; the first line of treatment is one of the two thiopurine drugs, azathioprine or 6-mercaptopurine (25). If these are poorly tolerated, methotrexate is an alternative (e34). If a relapse has been successfully treated with anti-TNFα antibodies, this treatment can be continued to maintain remission (e35, e36). The treatment can be successfully switched to azathioprine in about half of all cases (e37); sometimes, combined long-term immunosuppression is necessary (a thiopurine plus anti-TNFα antibodies). In combined treatment, the thiopurine drug lessens the immunogenicity of the anti-TNFα antibodies and may therefore prevent the loss of their effect. The risks and benefits of such treatment must be carefully weighed, however, as opportunistic infections and lymphoma are markedly more frequent under combined immunosuppression (e38). Thus, immunosuppression with a single drug is desirable if the clinical situation permits. Continuation of the treatment with a thiopurine drug alone (after, e.g., six months of combined immunosuppression) has the further advantage that anti-TNFα antibodies can still be used to induce remission after the next relapse. Steroids generally should not be given to maintain remission. If the treatment fails, vedolizumab can be given, as mentioned above. In the postoperative setting, e.g., after ileocecal resection, metronidazole (e39), mesalazine (e40), or, in complicated cases, a thiopurine drug (26, e40) or anti-TNFα antibodies (e41) can be given.

Ulcerative colitis

For patients with ulcerative colitis (as with Crohn’s disease), the treatment should be individually tailored to the site, extent, and severity of illness, and adapted to the treatment response (5). A treatment algorithm incorporating these features is shown in eFigure 2.

eFigure 2

Treatment algorithm for ulcerative colitis, developed by K.H. and E.F.S.

Induction of remission in relapsing disease

Mildly to moderately active proctitis is treated initially either with mesalazine suppositories (at least 500 mg/day) or, alternatively, with mesalazine enemas or foam (5, 27, e42). If this does not bring an adequate response, topical steroids can be given in addition. If these, too, are ineffective, tacrolimus suppositiories are a potential alternative, although only case series of their use are available to date (e43).

Mildly to moderately active left colitis and pancolitis should be treated initially with mesalazine foam and/or enemas combined with oral mesalazine (at least 3 g/day) (28).

If remission is not achieved, corticosteroids should be given systemically (0.5–1.0 mg prednisone equivalent) (5). A severe relapse generally necessitates hospitalization for intravenous steroid treatment.

Induction of remission in case of steroid resistance

If steroid therapy does not induce remission within 3–4 days, the remaining choice is between the use of calcineurin inhibitors, such as cyclosporine (5 mg/kgBW/day) and tacrolimus (0.15 mg/kgBW/day) (29), and anti-TNFα antibodies (infliximab, adalimumab, or golimumab) (5, e44). These two substance classes are about equally effective (30) Calcineurin inhibitors have the advantage of a much shorter half-life and, therefore, the option of switching to antibodies in case of a lack of response. Combining the two substance classes is contraindicated.

Vedolizumab has recently been found effective against ulcerative colitis as well (3), but it should be reserved for not very severe cases, in view of its relatively long latency of effect. At present, all patients with steroid-resistant ulcerative colitis should be seen in consultation by a surgeon, so that the option of colectomy and pouch creation can be considered.

Maintenance of remission

In general, aminosalicylates (preferably mesalazine) should be given to maintain remission in ulcerative colitis for at least two years, and even for life if indicated (32). The mode of administration depends on the site of disease; patients tend to dislike topical maintenance therapy with enemas or foam, and thus mesalazine is more commonly given by mouth (at least 1.5 g/day).

Mesalazine intolerance is rare (up to 15% of patients) (e45); in such cases, treatment with E. coli Nissle is of equivalent efficacy (e46). As in Crohn’s disease, steroids are not suitable drugs for the maintenance of remission. They are contraindicated for long-term therapy because of their adverse effects.

Immune suppressants should be given in addition to aminosalicylates in case of frequent relapses, a single severe relapse, a relapse despite the use of reserve medication, or steroid dependence (5). Usually, after steroids are given, either azathioprine (2.0–2.5 mg/kgBW/day) or 6-mercaptopurine (1.0–1.5 mg/kgBW/day) is given next; if this treatment is poorly tolerated, methotrexate can be used (despite a poor evidence base). The same holds for steroid dependence: after three months of immunosuppressive treatment, an attempt should be made to reduce the steroid dose slowly to zero.

In general, calcineurin inhibitors should also be switched to thiopurines, as long as the remission did not occur under immunosuppressive treatment, while anti-TNFα antibodies can continue to be given to maintain remission (e44). However, just as in Crohn’s disease, the combination of anti-TNFα antibodies with a thiopurine is more effective than either substance alone (e47). Once again, vedolizumab (31) is an alternative for refractory disease.

Surgery

The surgical treatment of IBD is based largely on case series from major treatment centers. Controlled trials are the exception and have often been terminated prematurely because of slow recruitment (33).

Laparoscopic techniques have been found safe for the treatment of patients with IBD and confer the advantages of minimally invasive surgery (rapid recovery, little postoperative pain). They are therefore now used routinely (34).

The surgical treatment of Crohn’s disease

40% of patients with Crohn’s disease undergo surgical treatment within 5 years of receiving the diagnosis, and 70% within 10 years. The surgical success rates 10 years after resection depend on the site of involvement: 90% for resection of a segment of ileum, 40% for ileocecal resection, and 85% for colonic resection (Table 2). The disease recurs at the anastomosis or in the segments neighboring the resected, diseased bowel segment in 10% to 60% of cases. 20% of patients who undergo surgical treatment need surgery again within 5 years (35).

Table 2

Symptomatic recurrence rates and reoperation rates depending on the site of primary surgery in Crohn’s disease

The indications for surgical treatment in Crohn’s disease, aside from the classic disease manifestation (terminal ileitis), include complex inflammatory changes along the entire small and large bowel, with the formation of abscesses, fistulae to the skin, to the bladder, and to other segments of the gastrointestinal tract, including the duodenum, stomach, and colon. The overarching principle of any surgical intervention is the removal of inflammatory foci, including drainage of abscesses and excision of fistulae, with maximal preservation of the normal bowel (36). Small-bowel ileus due to inflammatory blockage of the bowel lumen necessitates surgery in 5% to 10% of patients. In patients with chronic small-bowel obstruction with fixed stenoses, it can be difficult to determine preoperatively whether the cause is inflammatory or neoplastic. Crohn’s disease increases the risk of small-bowel cancer—a very rare disease—by a factor of 10 to 12 compared to the general population (37), yet 70% of small cancers arising in patients with Crohn’s disease are still not diagnosed until after surgery. Acute gastrointestinal bleeding rarely occurs in patients with Crohn’s disease; its diagnosis and treatment are the same as in non-Crohn's disease patients.

The surgical treatments of choice for isolated small-bowel involvement are small-bowel segmental resection, stricturoplasty, ileocecal resection, and, in rare cases, gastroenterostomy (if the duodenum is involved) (e48, e49). In Crohn’s colitis, the extent of surgery required depends on the pattern of involvement; either subtotal or total colectomy is usually performed, with proctocolectomy and terminal ileostomy being much less common (38). Interruption of intestinal continuity with a stoma (discontinuous resection) should remain a rare exception. Even complete bowel occlusion only rarely necessitates emergency surgery, and a conservative approach is valid, at least initially, in most cases. Endoscopic dilatation is preferable to repeated surgery for the treatment of accessible, short stenoses, mainly at the sites of anastomosis.

Perianal fistulae are among the more common complications of the disease. The main goal of treatment, along with preservation of sphincter function, is drainage of the fistula with the aid of a reinforcing loop or thread (seton), accompanied by pharmacotherapy with antibiotics and/or anti-TNFα antibodies, finally leading to closure of the fistula. Even today, such treatments are associated with recurrence rates of up to 70%. In fistulae that have been active for many years, fistular carcinoma is a rare, but therefore all the more serious complication (38).

The surgical treatment of ulcerative colitis

Patients with ulcerative colitis are less likely than those with Crohn’s disease to need surgical treatment for their disease at some point, with an overall likelihood of about 35%. The fulminant form of ulcerative colitis (15% of cases) is characterized by 27%–57% mortality if primary treatment fails; on the other hand, surgery is hardly ever needed for purely left-sided colitis or proctitis (39).

Aside from absolute surgical indications, such as bowel perforation, severe bleeding, toxic megacolon with or without perforation, and colon carcinoma, the most common reasons for surgical treatment are an intractable disease course, the development of dysplasia, and morbidity due to extra-intestinal manifestations. The method of choice to treat active colitis is subtotal colectomy without any intestinal anastomosis, with a transient ileostoma, followed by proctectomy and pouch creation at a later time (a triple-staged procedure). On the other hand, during the inflammation-free period, the standard surgical treatment for ulcerative colitis is restorative proctocolectomy with ileo-pouchanal anastomosis (IPAA) and protective ileostoma (a double-staged procedure) (e50). This is the only curative surgical method available, although pouchitis arises again in about half of all cases.

Conflict of interest statement

Prof. Wehkamp has served as a paid consultant for MSD, Takeda, Novartis, Shire, Abbvie, and Ardeypharm. He has received reimbursement of meeting participation fees and of travel and accommodation expenses from Takeda. He has received payment for lecturing at continuing medical education events from the Falk Foundation, Abbvie, Takeda, MSD, Roche, Ferring, and Shire. He has received third-party research funding for carrying out clinical trials on behalf of Amgen, Novartis, Falk Pharma, and Abbvie. He is a member of the board of Defensin Therapeutics.

Prof. Götz has served as a paid consultant for MSD, Takeda, and Pentax. He has received reimbursement of meeting participation fees and of travel and accommodation expenses from Takeda, MSD, and Abbvie. He has received lecture honoraria from Takeda, MSD, Abbvie, and the Falk Foundation. He has received funding from Pentax for a research project that he initiated.

Prof. Herrlinger has served as a paid consultant for MSD and Takeda. He has received payment from Falk Pharma, Medac, and Abbvie for preparing continuing medical education events.

Prof. Stange has served as a paid consultant for Merck, Takeda, and Janssen. He has received reimbursement of travel and accommodation expenses, as well as lecture honoraria, from Abbvie, Falk, Ferring, and Takeda. He has received third-party research funding for carrying out clinical trials on behalf of Abbvie, Falk, Takeda, Celgene, Gilead, Amgen, Boehringer, Salix, and Pfizer.

Prof. Steurer states that no conflict of interest exists.

Manuscript submitted on 28 June 2015, revised version accepted on 14 December 2015.

Translated from the original German by Ethan Taub, M.D.

Corresponding author
Prof. Dr. med. Eduard F. Stange
Zentrum Innere Medizin I
Gastroenterologie, Hepatologie und Endokrinologie
Robert-Bosch-Krankenhaus
Auerbachstr. 110,D- 70376 Stuttgart, Germany

@Supplementary material
For eReferences please refer to:
www.aerzteblatt-international.de/ref0516

eFigures:
www.aerzteblatt-international.de/16m0072

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