Chapter 28 — Anorectal Manifestations of Systemic and Inflammatory Bowel Disease

The anorectal region can be affected by disease that begins elsewhere in the body. This chapter covers the anorectal manifestations of inflammatory bowel disease, particularly Crohn's disease. Recognising these manifestations matters greatly, since their management differs fundamentally from the standard anorectal disease described earlier in this manual. This chapter covers presentation, examination, differential diagnosis, investigations, and management. This is the same pattern used for every disease chapter in this manual.

28.1 What Are Anorectal Manifestations of Systemic and Inflammatory Bowel Disease

Inflammatory bowel disease is a group of chronic conditions causing inflammation of the digestive tract. The two main types are Crohn's disease and ulcerative colitis.

Crohn's disease can affect any part of the digestive tract, from the mouth to the anus. Perianal disease is a common and distinctive feature.

Ulcerative colitis affects only the colon and rectum, in a continuous pattern starting from the rectum. This condition causes perianal disease far less often than Crohn's disease does.

This distinction matters greatly, and is described further in Sections 28.2 and 28.3.

28.2 Crohn's Disease — Anorectal Manifestations

Perianal fistulas are a hallmark feature of Crohn's disease. They are often complex, with multiple tracts, unlike the simpler cryptoglandular fistula described in Chapter 12. This complexity needs a different management approach, described in Section 28.9.

Perianal abscess, described in Chapter 13, can be more severe, and more likely to recur, in a patient with Crohn's disease.

An anal fissure in Crohn's disease often looks different from the typical fissure described in Chapter 11. It may sit off the midline, rather than in the usual posterior position. It may also be multiple, rather than single. This atypical appearance is an important diagnostic clue.

Skin tags in Crohn's disease are often large and swollen, sometimes described as oedematous or elephant-ear tags. They look different from the small, simple skin tags seen in other anorectal conditions.

Anal stenosis, described in Chapter 18, can develop from chronic inflammation and scarring.

A rectovaginal fistula, an abnormal connection between the rectum and vagina, can also occur in Crohn's disease, and needs specialist assessment.

28.3 Ulcerative Colitis — Anorectal Manifestations

Perianal disease is much less common in ulcerative colitis than in Crohn's disease. When a fissure does occur, it is usually less complex than a Crohn's-related fissure.

Pouchitis is a specific complication that can occur after surgery for ulcerative colitis, when the rectum has been removed and a pouch created from the small bowel. It causes inflammation of this pouch, with symptoms similar to a flare of the original disease.

28.4 Distinguishing Crohn's Perianal Disease from Ordinary Anorectal Disease

An atypical location is a key clue. A fissure off the midline, described in Section 28.2, should raise suspicion, rather than being treated as a standard fissure.

Multiple lesions, rather than a single lesion, should also raise suspicion.

A complex fistula, with more than one tract, is unusual for simple cryptoglandular disease, and should prompt consideration of Crohn's disease.

Coexisting gastrointestinal symptoms are an important clue. These include diarrhoea, abdominal pain, weight loss, and blood or mucus in the stool.

A known diagnosis of inflammatory bowel disease, or a family history of it, should immediately raise the possibility that a new anorectal finding is related.

28.5 Presentation

Follow the history-taking method described in Chapter 2.

Ask specifically about diarrhoea, abdominal pain, weight loss, and blood or mucus in the stool.

Ask about a known diagnosis of Crohn's disease or ulcerative colitis, and about any family history of either condition.

Ask about symptoms outside the digestive tract. These include joint pain, eye symptoms, and certain skin conditions, all of which can accompany inflammatory bowel disease.

A patient may present with a perianal symptom, such as pain or discharge, without yet having a diagnosis of inflammatory bowel disease. The anorectal finding may be the first clue to the underlying condition.

28.6 Examination

Follow the sequence described in Chapter 3.

Inspection, described in Chapter 4, should specifically look for the atypical features described in Section 28.2. These include an off-midline fissure, multiple lesions, large oedematous skin tags, and complex fistula openings.

Assess for anal stenosis, described in Chapter 18, which can develop from chronic Crohn's- related inflammation.

A general examination should check for weight loss and for pallor, which can indicate anaemia from chronic disease.

28.7 Differential Diagnosis

Ordinary cryptoglandular fistula, described in Chapter 12, versus a complex Crohn's-related fistula. The distinction changes the management approach significantly.

A typical, posterior midline fissure, described in Chapter 11, versus an atypical, off-midline, or multiple fissure suggesting Crohn's disease.

A simple skin tag versus the large, oedematous tag characteristic of Crohn's disease.

Anorectal malignancy, described in Chapter 26, can occasionally arise within a long-standing Crohn's fistula tract, and should be considered in a chronic, non-healing case.

28.8 Investigations

MRI, described in Chapter 8, is the key investigation for assessing a complex Crohn's-related fistula, showing the full extent of the tracts clearly.

Colonoscopy, with biopsy, confirms the diagnosis of inflammatory bowel disease if this is not already known, and assesses disease activity elsewhere in the bowel.

Examination under anaesthesia is often needed for a full, accurate assessment of complex perianal Crohn's disease, and is frequently combined with MRI for the most complete picture.

Blood tests assess inflammatory markers and check for anaemia, both of which help gauge overall disease activity.

28.9 Principles of Management

Management of Crohn's-related anorectal disease differs fundamentally from the management of ordinary anorectal disease, and this distinction is the single most important message in this chapter.

Medical treatment of the underlying inflammatory bowel disease is often the first priority. This may include immunosuppressive medication or biologic therapy, coordinated closely with a gastroenterologist.

Surgical treatment is deliberately more conservative in Crohn's disease. A standard fistulotomy or sphincterotomy, described in Chapters 12 and 10, carries a higher risk of poor healing in active Crohn's disease, and can result in a non-healing wound.

A loose seton, providing gentle drainage without dividing the sphincter, is often preferred over definitive fistula surgery in active Crohn's disease.

A multidisciplinary approach, combining gastroenterology and colorectal surgery, gives the best outcome. Optimising medical control of the underlying disease before any elective surgery, wherever possible, improves the chances of successful healing.

28.10 Special Situations

A rectovaginal fistula in Crohn's disease, described in Section 28.2, is complex, and needs specialist multidisciplinary assessment.

Anal stenosis in Crohn's disease is best approached conservatively where possible, given the same healing concerns that apply to fistula surgery in this condition.

Pouchitis, described in Section 28.3, needs assessment and treatment coordinated with the gastroenterology team that manages the patient's underlying ulcerative colitis.

28.11 Complications

A non-healing wound is a characteristic and troublesome problem in Crohn's disease, reflecting the impaired healing associated with active inflammation.

Recurrent or multiple fistula tracts, despite treatment.

Anal stenosis, described in Chapter 18, from chronic scarring.

Malignant change, rarely, within a long-standing, chronic fistula tract.

28.12 Common Mistakes to Avoid

Treating a Crohn's-related fistula or fissure with a standard technique, such as fistulotomy or sphincterotomy, without recognising the underlying disease, risking a non-healing wound.

Missing a diagnosis of inflammatory bowel disease in a patient with an atypical, multiple, or off- midline anorectal lesion.

Proceeding to surgery without first coordinating with a gastroenterologist to optimise disease control.

Being unnecessarily aggressive surgically, when a more conservative approach, such as a loose seton, would serve the patient better.

28.13 Recording and Follow-Up

Record the anorectal findings, the suspected or known diagnosis, and the management plan. For example: "Complex perianal fistula, multiple tracts, known Crohn's disease. Plan: MRI, gastroenterology referral for medical optimisation, loose seton insertion." Arrange follow-up jointly with the gastroenterology team managing the underlying disease, rather than in isolation.

28.14 Why This Chapter Matters

Anorectal disease in a patient with inflammatory bowel disease needs a different mindset from standard anorectal practice. Recognising the atypical features described in this chapter, and treating conservatively while the underlying disease is optimised, protects the patient from a non-healing wound and a difficult recovery. This chapter completes Part II of this manual. The next chapter turns to the author's own techniques, beginning with OPB-MOLIS.