Histopathological evaluation of ulcerative colitis in colonoscopic biopsies

Email: rdhakhwa@gmail.com Background: Histopathologic evaluation of colonoscopic mucosal biopsy remains one of the earliest modalities of investigation in patients clinically suspected of ulcerative colitis. Pathologists should be aware of classical histomorphological features to avoid misdiagnosis. The aim of the present study was to evaluate histopathologic features as well as to determine possible atypical presentation.

of endoscopic biopsies remains a key step in the workup of affected patients and can be used for diagnosis and differential diagnosis, particularly in the differentiation of UC from Crohn's disease (CD) and other non-IBD related colitides. 2One of the earliest mode of histological 936 evaluation is colonoscopic mucosal biopsy.Biopsies also allow assessment of disease activity and identiication of pre-cancerous lesions and cancer. 1 Accurate diagnosis requires knowledge of classic morphological features; pathologists should however be aware of the atypical pathologic presentation as well to prevent misdiagnosis. 3ence the purpose of our study was to evaluate classic histopathologic features as well as to determine atypical presentations of Ulcerative colitis.

MATERIALS AND METHODS
Forty seven new cases suspected of ulcerative colitis clinically and/ or endoscopically undergoing colonoscopic biopsies at Pathology departments of Kathmandu Hospital Private limited and Kathmandu Medical College-Teaching Hospital from June 2013 to May 2015 were included in the study.Already diagnosed cases and patients who had taken speciic medications for colitis or coexisting disease were excluded from the study.Detailed endoscopic indings, extent of disease, clinical disease were recorded.Colonoscopic biopsies were taken from rectum as well as various areas of colon depending upon the clinical extent of involvement.Biopsy from terminal ileum was also taken where applicable.Biopsy tissue was immediately ixed in 10% Formalin, processed routinely and stained with Hematoxylin and Eosin stain.Histopathologic parameters assessed were pattern of inlammation, crypt architectural abnormalities, goblet cell depletion, types of inlammatory cells in the propria, basal plasmacytosis and activity (cryptitis and crypt abscesses).The slides were also analysed for presence of dysplasia or any unusual histopathologic features.Statistical analysis was performed using Epi-info wherever necessary.

RESULTS
Out of 47 cases suspected of ulcerative colitis, histopathologic features were consistent with Ulcerative colitis in active phase in 40 cases.Seven cases which showed non-speciic inlammatory changes were excluded from the study.Diffuse active colitis, crypt architectural abnormalities with loss of goblet cells and basal plasmacytosis were considered to be the typical histologic features associated with ulcerative colitis.
Most of the patients were between 21 -40 years of age, the youngest being 21 years and the eldest was 71 years of age.All patients presented with a history of bleeding PR.Most of them also had complains of diarrhoea with passage of stool mixed with mucus (25 cases, 62.5%).Some patients had constipation (7 cases, 17.5%) and abdominal pain (5 cases, 12.5%) while others had non-speciic symptoms (3 cases, 7.5%).These symptoms were present for few days to few years.All patients underwent colonoscopy with biopsy.Colonoscopy revealed left sided colitis with rectal involvement in 22 cases (55%).Eleven cases (27.5%) showed rectal involvement only.Rectal sparing was observed in 1 case (2.5%).Continuous left sided disease with right side involvement was noted in three cases (7.5%) while skip areas were observed on right side in two cases (5%).One case presented with pancolitis with backwash ileitis (2.5%).(Table 1; ig. 1) Among the forty cases, 26 (65%) had mild colitis, eight (20%) had moderate colitis and six (15%) had colitis of severe degree endoscopically.Pseudopolyps were noted in four (10%) of these cases.

DISCUSSION
The histologic diagnosis of IBD is based on analysis of a full series of colonoscopic biopsies.A study by Dejaco et  al. showed that the accuracy of diagnosing colitis increases from 66% to 92% when segmental biopsies are taken rather than two biopsies throughout the colon. 4Rectal biopsies are necessary to either conirm or reject rectal involvement and may be additionally helpful in differentiating IBD from other inlammatory lesions. 2 All tissue samples should be ixed immediately by immersion  in buffered formalin or an equivalent solution prior to transport.6][7] The diagnostic yield increases with the number of sections examined.However the ideal number of sections to be examined in routine practice has not been established with numbers varying between 2 and 6 in different studies. 6,8cerative colitis classically shows a diffuse and continuous chronic inlammation without skip areas which involves the and spreads proximally with gradually decreasing severity of inlammation.Unusual inlammation patterns are rectal sparing, caecal patch and backwash ileitis. 2 Our study also demonstrated one case (2.5%) of rectal sparing, one (2.5%) with backwash ileitis and two (5%) with skip lesions.Although rectal sparing and patchy disease suggest diagnosis of Crohn's disease, the cases included in our study showed diffuse active colitis on histology favoring ulcerative colitis.0][11][12][13] We however included only those patients who did not receive any form of medical therapy prior to initial endoscopic procedure.Hence, it should be emphasized that awareness of unusual macroscopic distribution patterns, such as skip lesions, rectal sparing and backwash ileitis is important to avoid wrong subtyping of the inlammatory bowel disease.
Untreated UC in an active phase represents the prototypic diffuse active colitis.Biopsy specimens usually demonstrate a diffuse abnormality, meaning that the changes are of approximately the same intensity in all areas of the tissue. 14e observed diffuse active colitis in almost all cases (39, 97.5%) although the degree of architectural distortion and degree of inlammation varied in different cases.One of the cases however showed focal active colitis.Clinical presentation, endoscopic indings and other histopathologic features favored ulcerative colitis over Crohn's Disease in this case.Diffuse active colitis though diagnostic of UC can also be seen in some examples of Crohn's colitis and in some cases of documented infectious colitis, although the latter could represent an infectious exacerbation of underlying latent primary inlammatory bowel disease.The diffuse active colitis pattern can also be seen in a form of colitis associated with diverticular disease; this entity is distinguished from classic UC by its rectal sparing and its presence exclusively in areas of diverticula. 14cal active colitis refers to the patchy distribution of combined architectural change and inlammation in a mucosal biopsy specimen.The focal active colitis pattern consists of limited areas of increased inlammatory cells associated with focal architectural distortion; characteristically, some areas of the biopsy specimen maintain an essentially normal appearance.The focal active colitis pattern is usually not seen with UC, and, when it is present, suggests Crohn's colitis or infectious colitis and/or acute self-limited colitis.[16] Microscopic diagnosis of UC is based on widespread crypt architectural distortion, a diffuse transmucosal inlammatory iniltrate with basal plasmacytosis, eventually associated with an active component, causing cryptitis and crypt abscesses.Goblet cell depletion is less speciic, but a helpful diagnostic feature. 2 We observed variable degree of crypt architectural distortion in the form of crypt branching and budding and crypt atrophy.8][19][20] However in long standing cases restoration of architecture may result in a normal mucosa. 14e noticed normal crypt architecture in ten cases (25%).The inlammatory iniltrate was composed of lymphocytes, plasma cells, neutrophils and eosinophils.Plasma cells are predominantly observed in between the crypts and the muscularis mucosae (basal plasmacytosis) which is the earliest diagnostic feature with the highest predictive value for the diagnosis of UC. 14 In our study also, basal plasmacytosis was a constant feature (present in 34 cases).Basal plasmacytosis is helpful in the differentiation between a irst attack of UC and infectious colitis, but not CD.Cryptitis as deined by presence of neutrophils within crypt epithelium and crypt abscesses deined by the presence of neutrophils within crypt lumina are features suggestive of active inlammation. 14,17,19sinophil iniltrate was prominent in 27 cases.There has been increasing evidence about the involvement of eosinophils in the pathogenesis of inlammatory bowel disease.Eosinophils play an important role as proinlammatory and pro-motility agents thus producing diarrhoea, tissue destruction and ibrosis. 21lammation may cause mucin depletion of the epithelium, a less feature as it can also be found in infectious colitis and CD.We observed goblet cell depletion in 20 cases.Ajioka et al have reported that in the remission phase of ulcerative colitis inlammation is reduced and goblet cell mucus is reduced however evidence of past inlammation such as irregular crypts, paneth cell metaplasia and muscularis mucosa hypertrophy can still be appreciated. 14,22eserved crypt architecture and the absence of a transmucosal inlammatory cell iniltrate do not rule out ulcerative colitis at an early stage.Le Berre et al. have shown that distorted crypt architecture with crypt atrophy, mucin depletion and cryptitis are features highly predictive of UC.Nevertheless features may change depending upon disease duration, patient's age and treatment.Hence it is recommended that rather than individual histomorphological features, combination of these changes need to be considered before giving the diagnosis of UC. 2,23 Atypical presentation in UC is not uncommon.We noted one case with rectal sparing.Review of current literature reveals that in long standing disease the extent of gut involvement decreases with time ultimately leading to complete restoration of the rectal mucosa (rectal sparing) in 34 to 44% of patients. 13,24Our patient gave history of per rectal bleeding for 2 years before the irst colonoscopy attempted, hence rectal sparing can probably be attributed to long history of ulcerative colitis.
One of the cases had pancolitis with involvement of ileum (backwash It has been known that ulcerative colitis can spread to other portions of the gastrointestinal tract.Review of literature shows that ileum is involved in approximately one third of cases.This involvement is always in continuity with the colonic disease; it rarely spreads more than 10 cm away from Ileocaecal valve. 25 our study we observed only one case (2.5%) showing low grade dysplasia.No invasive carcinoma was detected.Studies have shown colorectal cancer risk is associated with disease duration and disease extent and raises at the rate of approx.7][28] The incidence of dysplasia or malignancy   may appear lower in present study as we included only newly diagnosed cases.An elaborative study with regular follow up biopsies is required to understand the true risk for dysplasia or malignancy associated with ulcerative colitis.Pathologists should also be aware of possible atypical presentation.
Accurate diagnosis of UC requires elaborate knowledge of histological features.The histological indings should be correlated with clinical and endoscopic indings.