Update on infectious enterocolitides and the diseases that they mimic

Infectious Disease Pathology of the Gastrointestinal Tract: Diagnosing the Challenging Cases

Infectious diseases of the GI tract mimic a variety of other GI diseases, including chronic idiopathic inflammatory bowel disease and ischemia. It can be challenging to identify pathogens in tissue sections as well, as many trainees are not exposed to infectious disease pathology other than in the context of microbiology. Our ability to diagnose infections in formalin fixed, paraffin embedded material has grown exponentially with the advent of new histochemical and immunohistochemical stains, as well as more options for molecular testing. Correlating these diagnostic techniques with morphology has led to increasing understanding of the histologic patterns that are associated with specific pathogens.

Infectious Mimics of Inflammatory Bowel Disease

Distinguishing inflammatory bowel disease (IBD) from its mimics remains a diagnostic challenge for surgical pathologists. Several gastrointestinal infections produce inflammatory patterns that overlap with typical findings of IBD. Although stool culture, PCR, and other clinical assays may identify infectious enterocolitides, these tests may not be performed or the results may be unavailable at the time of histologic evaluation. Furthermore, some clinical tests, including stool PCR, may reflect past exposure rather than ongoing infection. It is important for surgical pathologists to be knowledgeable about infections that simulate IBD in order to generate an accurate differential diagnosis, perform appropriate ancillary studies, and prompt clinical follow-up. This review covers bacterial, fungal, and protozoal infections in the differential diagnosis of IBD.

Fatal gastritis and enterocolitis due to concurrent Helicobacter pylori and Campylobacter jejuni infection in a captive cheetah (Acinonyxjubatus)

A 3.5-year-old female cheetah (Acinonyx jubatus) died after a 10-day history of anorexia, regurgitation and diarrhoea despite symptomatic therapy. At gross post-mortem examination, the stomach was blood-filled with mucosal thickening and multifocal ulcerations. The intestinal mucosa was thickened and reddened, and the intestinal lumen was filled with dark red to black pasty content. Gastric histological lesions were compatible with gastritis due to Helicobacter infection, which was confirmed by polymerase chain reaction. Histology of the intestines revealed a severe necrotizing neutrophilic enterocolitis with abundant intralesional curved to spiral bacteria, corresponding to Campylobacter jejuni, which were subsequently isolated from both small and large intestinal contents. No other intestinal pathogens were detected despite thorough investigations. These findings suggest that C. jejuni may have played an aetiological role in the enterocolitis. Such an association has not been previously reported in non-domestic felids.

ECCO Topical Review on Clinicopathological Spectrum and Differential Diagnosis of Inflammatory Bowel Disease

INTRODUCTION

Many diseases can imitate inflammatory bowel disease [IBD] clinically and pathologically. This review outlines the differential diagnosis of IBD and discusses morphological pointers and ancillary techniques that assist with the distinction between IBD and its mimics.

METHODS

European Crohn's and Colitis Organisation [ECCO] Topical Reviews are the result of an expert consensus. For this review, ECCO announced an open call to its members and formed three working groups [WGs] to study clinical aspects, pathological considerations, and the value of ancillary techniques. All WGs performed a systematic literature search.

RESULTS

Each WG produced a draft text and drew up provisional Current Practice Position [CPP] statements that highlighted the most important conclusions. Discussions and a preliminary voting round took place, with subsequent revision of CPP statements and text and a further meeting to agree on final statements.

CONCLUSIONS

Clinicians and pathologists encounter a wide variety of mimics of IBD, including infection, drug-induced disease, vascular disorders, diverticular disease, diversion proctocolitis, radiation damage, and immune disorders. Reliable distinction requires a multidisciplinary approach.

Pattern-based Histologic Approach in Very Early Onset IBD: Main Features and Differential Diagnosis

Very early onset inflammatory bowel disease (VEO-IBD) is a clinical umbrella classification composed of IBD-like diseases encompassing both classic IBD (Crohn's disease and ulcerative colitis) and monogenic disorder, both arising before 6 years of age. VEO-IBD patients present significant clinical differences from IBD occurring in older children and in adults, including more severe disease, often unresponsive to conventional IBD therapy and a greater proportion of cases featuring an underlying genetic alteration. Histologic findings of gastrointestinal biopsies can show an IBD-like pattern (both Crohn's disease-like and ulcerative colitis-like pattern), an apoptotic-like and enterocolitis-like pattern. Findings of specific morphologic alterations, such as villous blunting, apoptosis, dense eosinophilic infiltrates, lack of plasma cells and severe glandular atrophy, can suggest a monogenic disorder. Moreover, individuals with monogenic disorders may develop significant problems such as primary immunodeficiency, impacting treatment options. Finally, IBD histology in childhood can differ from that in older patients and adults. This complexity makes a differential diagnosis between IBD and other pediatric diseases involving the gastrointestinal tract difficult, especially considering that histologic features can be similar between different diseases. Without an appropriate diagnosis, the clinical course of VEO-IBD has greater potential for escalated treatment regimens involving extensive surgery and more intensive medical therapies rather than specific therapy directed toward the underlying defect. For these reasons, a pattern-based histologic approach correlated with clinical and laboratory findings with a multidisciplinary approach is fundamental to reach a correct diagnosis in an adequate clinical context.

Histopathology of Non-IBD Colitis. A practical approach from the Italian Group for the study of the gastrointestinal tract (GIPAD)

Non-IBD colitides (NIBDC) are intestinal diseases clinically and endoscopically overlapping with Inflammatory Bowel Diseases (IBD), sometimes with a similar histological picture. NIBDC include entities such as infectious colitis, ischemic colitis, pseudomembranous colitis, eosinophilic colitis, autoimmune enterocolitis, segmental colitis associated with diverticulosis, drug-induced colitis, radiation-induced colitis, diversion colitis, and microscopic colitis, this last including two entities: collagenous and lymphocytic colitis. The knowledge of the most useful histological features and the main clinical data for each entity is mandatory in daily clinical practice, for correct pathological diagnosis and clinical management.

Navigating the jungles of tropical infectious gastrointestinal pathology: a pattern-based approach to the endoscopic biopsy

International travels and global human migration have had the unforeseen consequence of increasing the exposure of histopathologists in developed countries to the pathology of tropical infectious disease. The gastrointestinal tract (GIT) is often the primary site of infection due to the faecal-oral route of transmission and the high risk of exposure to contaminated water, food or soil when travelling to these regions. Whilst current microbiologic techniques are far more sensitive than histology in detecting infectious pathogens, the histopathologist nonetheless retains a pivotal role in diagnosing tropical GIT disease. This role entails evaluating endoscopic biopsies for any characteristic inflammatory pattern, identifying pathogens which may be present and excluding other look-alike pathologies. Recent advances in commercially available diagnostic modalities, including molecular techniques, have further broadened the scope of the histopathologist's armamentarium. This review outlines a practical pattern-based approach to diagnosing tropical GIT infections in endoscopic material, so as to assist pathologists less familiar with this spectrum of pathology.

Diagnostic dilemmas in chronic inflammatory bowel disease

Histopathological assessment of biopsy and resection specimens of chronic inflammatory bowel disease (CIBD), or possible CIBD, forms a significant component of the routine workload in most tissue pathology laboratories. In this review, we have chosen selected areas of particular diagnostic difficulty in CIBD pathology, providing key advice for pathology reporting. Those mimics of CIBD which have the greatest potential for misdiagnosis are discussed, particularly the wide range of infectious colitides which represent possible diagnostic pitfalls. The most important distinguishing features between the two main forms of CIBD, ulcerative colitis and Crohn's disease, are addressed, first in relation to resection specimens, and then with emphasis on features which may also be diagnostically useful in endoscopic biopsy material. The importance of assessment of the index endoscopic specimen is stressed, before treatment has been instigated, along with careful correlation with clinical and endoscopic features. Problems in the assessment of post-surgical CIBD specimens are described and then the role of upper gastrointestinal pathology specimens in diagnosing both Crohn's disease and ulcerative colitis, with increased recognition of upper gastrointestinal tract involvement in the latter condition. Finally, with recent developments in endoscopic surveillance techniques and local excision options, modern approaches to reporting and managing neoplasia complicating CIBD are reviewed.