Challenges in the diagnosis of diversion colitis
Monika Tripathi, H-ECCO Member
Elective or emergency surgical interventions in the management of Inflammatory Bowel Disease (IBD) are mainly reserved for patients with medical refractory disease and life-threatening complications. Approximately 20%–30% of Ulcerative Colitis (UC) and 70%–80% of Crohn’s Disease (CD) patients will need surgery within the first to second decade following primary disease diagnosis .
Subtotal colectomy with ileostomy is the common treatment option for fulminant severe colitis and medically refractory disease. A proportion of IBD patients are left with a rectal stump post colectomy to avoid iatrogenic complications, including damage to pelvic structures . The final outcome in such cases depends on multifactorial parameters (medical co-morbidities, secondary surgical complications and extent of symptomatic complications, neoplasia risk, quality of life for the patient, etc.). Precise, validated recommendations for rectal stump surveillance and follow-up protocols still lack coherence.
The entity ‘diversion colitis’ was first mentioned by Basil Morson and Dawson in 1974 as a non-specific inflammation limited to the mucosa in the de-functioned segment of the colon. David Glotzer coined the term ‘diversion colitis’ in a case series of ten patients in 1981 . Although microscopic diversion changes are almost universal in patients with diverted faecal stream, only up to 33% of patients will present with clinical symptoms .
There is no significant association between diversion colitis and age, gender, type of stoma or mode of surgery. The rate of disease occurrence is 70%–74% in patients without pre-existing IBD and 91% in patients with pre-existing IBD. The time until manifestation ranges from 4 weeks to 3 years post index surgery. In most cases, complete regression of features occurs within 3 months of restoration of the faecal stream. The most widely accepted hypothesis regarding the aetiogenesis of this entity is lack of mucosal trophic factors of the faecal stream, including short chain fatty acids .
The role of pathologists in rectal stump surveillance is somewhat similar to that in the conventional IBD management, i.e. confirming the diagnosis of diversion colitis, defining the extent and severity of inflammation with or without additional components suggesting superimposed infection or an element of active IBD, and screening for premalignant and neoplastic conditions.
Occasionally pathologists may be presented with the task of evaluating the type of IBD in patients labelled as having indeterminate colitis at index surgery to aid in decision making regarding further ileal pouch–anal anastomosis when the distinction between UC and CD remains unclear after thorough clinical assessment. A change in diagnosis from UC or indeterminate colitis to CD should never be made on the basis of histological findings of the rectal stump alone; rather, there is also a need to review the findings in index biopsy, previous resection specimens and clinical parameters .
Microscopic assessment of the rectal stump biopsy or completion proctectomy specimen may be challenging for pathologists due to the lack of conclusive pathognomonic features . The most notable and consistent feature is the presence of lymphoid hyperplasia, which can be partial to transmural . In addition, almost all histological features seen in classical UC and CD can be identified in diverted rectum to a variable extent. Previous studies have also demonstrated that the extent and severity of microscopic changes are more likely to be related to the pre-existing condition of the background colon than to be time bound . Severe histological changes may reflect superimposed infection or an element of active IBD. Granulomas are more likely to be found in patients with CD than in those with UC .
Data on neoplastic complications in rectal stump are sparse, but the isolated risk appears to be low in the absence of a premalignant condition in the original colectomy specimen or a history of neoplasia.
To conclude, consistent follow-up protocols are needed for guidance on the surveillance of this entity, and a consolidated approach, including assessment of clinical, endoscopic and pathological parameters, is essential in order to evaluate diversion changes before defining the fate of rectal stump.
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