Labelling the diagnosis as Crohn’s disease when the features may be due to another aetiology
Prior to pouch formation a thorough pre-surgical assessment must be considered to rule out Crohn’s disease, to include small-bowel studies, histological samples reviewed for the presence of granuloma and the absence of a history of perianal disease. A preoperative diagnosis of Crohn’s disease of the pouch is a relative contraindication to pouch surgery18 because of the high rate of complications and pouch failure.19–21 Indeed, it has been estimated that pouch excision rates are 45–55% in patients who have a preoperative diagnosis of Crohn’s disease21,22 and that the pouch retention rate 5 and 10 years after formation is 58% and 50%, respectively.23 Despite this, some small studies have shown that in the absence of perianal or small-bowel disease, restorative proctocolectomy can be performed with similar outcomes to those who have a pouch for ulcerative colitis.24,25 Indeed, the European Crohn’s and Colitis Organisation (ECCO) suggest that restorative proctocolectomy can be offered to patients who have Crohn’s disease without perianal disease or small-bowel involvement,26 but we suggest that patients are very carefully counselled about the potential poor outcomes and such surgery is done highly selectively.
There are essentially two scenarios that lead to a diagnosis of ‘Crohn’s disease of the pouch’. The first arises when there has been a preoperative diagnosis of Crohn’s disease, and the second is the development of Crohn’s-like features after the formation of a pouch in a patient who has ulcerative colitis.
In one long-term study, 2–8% of patients who originally underwent restorative proctocolectomy for presumed ulcerative colitis had their original diagnosis changed to Crohn’s disease.21 We believe it is important to diagnose Crohn’s disease of the pouch accurately to help with prognostication and offer appropriate treatment. The criteria utilised to diagnose Crohn’s disease are varied. Some studies have defined Crohn’s disease of the pouch as including: inflammation of the pouch that is resistant to antibiotic treatment, stricturing of the afferent limb, stricturing of the small bowel, or fistulating disease.27–30 Furthermore, the presence of pre-pouch ileitis is controversial—some studies suggest this may be an endoscopic feature of Crohn’s disease,31,32 but this has been disputed by others.33
It is likely that Crohn’s disease of the pouch is an overused diagnosis, with one study highlighting that histological confirmation of Crohn's disease was found in only 20% of patients who underwent pouch excision for Crohn's disease of the pouch.33 It is also important to appreciate that strictures and fistulas that may mimic Crohn’s disease can be caused by other factors such as sepsis, anastomotic complications (e.g. leak and/or stricture) or ischaemia. We therefore suggest that Crohn’s disease of the pouch should only be diagnosed by conclusive histology (i.e. granulomas supporting Crohn’s disease) and/or the presence of characteristic skip lesions in the small bowel. The timing of when the Crohn’s-like problems of the pouch occur can often aid diagnosis—fistulas especially around the anastomosis that occur within a year of pouch formation are likely to be related to the surgery itself, whereas complications beyond this point could represent de novo Crohn’s disease, but this still requires thorough investigation.
We also believe that it can be unhelpful and confusing for patients to hear that their diagnosis has changed from ulcerative colitis to Crohn’s disease and suggest it is more useful to explain that they have active inflammatory bowel disease. It is more beneficial for the patient to be clear on the strategies of care for managing their problem, whether it be a fistula, stricture or inflammation, using the appropriate combination of surgical/endoscopic and medical therapies, than to become bogged down in semantics regarding terminology.
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