Pathologic differentiation of IBD from chronic enteritis and isolated rectal ulcer

Preface

Inflammatory bowel disease (IBD), including ulcerative colitis (UC), Crohn's disease (CD), and indeterminate colitis IC, is characterized
by chronic, recurrent disease of unknown etiology.
IBD is a global disease with significant differences in incidence across regions and ethnicities
.

In recent years, the incidence of IBD has stabilized in Western countries with a previously high incidence, while it has gradually increased in Asian countries, and is in the first stage of disease evolution (disease emergence stage).

At this stage, the early diagnosis and treatment of IBD are particularly critical, and it also puts forward new requirements and challenges for clinicians and pathologists
.

Summary of learning knowledge points

First, standardize the pathological diagnosis of IBD, and clinical needs to be carried out first

1.
Overview:

IBD is a chronic, nonspecific inflammatory bowel disorder whose etiology is not well understood, including UC, CD, and Indeterminate Colitis (IC)
that cannot be clearly classified.
Pathological diagnosis plays an important role in diagnosis and treatment, running through all aspects
of diagnosis, efficacy evaluation and tumor monitoring.
However, histological manifestations lack specificity, and diagnosis is often difficult, so it is particularly
important to cooperate and effectively communicate with clinical, pathological, and radiologists.

2.
IBD endoscopic material requirements:

(1) Material selection criteria: IBD has continuous or segmental characteristics, and it is very important
to obtain materials for multi-site mucosal biopsy.
It is recommended to do at least five sites (including the rectum and terminal ileum), take no less than two grains of tissue in each site, avoid taking only the ulcer, and biopsy should also be taken if the mucosa that is not abnormal on endoscopy; Emphasis is placed on the diagnosis of IBD
from the primary endoscopic biopsy specimen.

(2) Indicate information: Different parts of biopsy tissue should be in different containers and indicate the patient's information and the site of material to avoid confusion
.

(3) Fix all mucosal biopsy tissues in time, and immediately soak in 10% neutral formalin for fixation
.

3.
IBD specimen production requirements:

(1) When embedding tissues, it is recommended to embed up to 2 pieces of tissue per wax block, and IBD specimens need to focus on observing the changes of surface villi or crypts, as well as the distribution of inflammation, and try to bury each piece of tissue immediately
.

(2) It is recommended to make multiple consecutive sections (6-10 pieces) of the largest surface of the specimen for each wax block, and the tissue orientation of each piece is consistent, which helps doctors determine whether it is a granuloma.

Second, mastering the normal intestinal mucosal tissue structure is the basis for learning IBD

1.
Normal small intestinal mucosa

(1) The ratio of villi to crypts is 3-5:1 (short ileal villi);

(2) Lymphocytes visible in the epithelium (<20/100);

(3) Pan cell nuclei goblet cells;

(4) The base of the crypt is adjacent to the mucosal muscle;

(5) Lymphocytes, plasma cells, eosinophils, histiocytes and mast cells in the mucosal lamina propria (the highest density at the duodenum);

(6) Brunner's gland is only found in the duodenum;

(7) Lymph nodes are most obvious
at the end of the gyrus.

2.
Normal large intestine mucosa

(1) The crypt base is adjacent to the mucosal muscle, the crypt structure is regular, there is no branching, no destruction, no shedding, and slight crypt structure changes can appear at the rectum and sigmoid colon biopsy;

(2) lymphocytes can be seen in the epithelium, the right colon is obvious, and the intrathelial lymphocytes on the surface of the lymphatic node are increased;

(3) Pan's cells only appear in the right colon and transverse colon, and children can have Pan's cells in the descending colon;

(4) There are more mononuclear inflammatory cells and eosinophils in the lamina propria of the right colon mucosa than on the left side;

(5) The distal end of goblet cells and mucophagocytes in the left colon gradually increases
.

Third, distinguish the histological features of acute enteritis from chronic enteritis

is key to diagnosing IBD

1.
Acute enteritis (Active Enteritis / Colitis)

(1) Mucosal erosion with ulcer formation;

(2) cryptitis and crypt abscess;

(3) Inflammatory cells are mainly neutrophils;

(4) interstitial edema;

(5) Vasodilation and hyperemia;

(6) epithelial degeneration, necrosis, regeneration;

(7) The crypt structure was not significantly deformed
.

2.
Chronic enteritis (Chronic Enteritis / Colitis)

(1) Crypt structure destruction, atrophy, branching, deformation;

(2) chorionic transformation of the colonic mucosa;

(3) atrophy of small intestinal villi;

(4) crypt basal plasma cell increase;

(5) Pan's cell metaplasia and pyloric gland metaplasia;

(6) diffuse mixed inflammatory cell infiltration;

(7) Interstitial fibrosis or collagenomy
.

4.
Standardized systematic method was used to evaluate the mucosa of intestinal biopsy,

It helps to improve the pathological diagnosis of IBD

According to the above systematic diagnostic steps, that is, changes in tissue structure, changes in epithelium, and changes in the lamina propria of the mucosa, some useful information can be avoided, and preliminary judgments
can be made according to the morphological characteristics of IBD.

5.
According to the type of inflammation and whether the mucosal structure changes,

Master the pathological diagnosis ideas of intestinal mucosal biopsy

1.
IBD has different manifestations at different times, which can be manifested as active inflammation, chronic active or inactive enteritis, and the diagnosis needs to be closely combined with the comprehensive judgment of medical history, endoscopic performance and imaging performance
.

2.
The microscopic manifestations of drug-induced enteritis are non-specific and can be manifested in various patterns, so the diagnosis needs to be questioned in detail about the drug history and the relationship
between symptoms and drugs.

3.
In addition to observing inflammation and mucosal structural changes, it is necessary to pay attention to changes in the interstitium proprium, whether there is fibrosis, glassy deposition, and whether there is microbial infection or granuloma.

4.
Intestinal mucosal lesions dominated by neutrophil infiltration need to be comprehensively judged
in combination with the presence or absence of ischemia or bleeding.

5
.
Eosinophil infiltration is difficult to diagnose as the main lesion.
First, a detailed history (allergy or drug history) should be taken, the interstitial search for pathogenic microbial infection, vascular changes to be observed, and eosinophil infiltration may also be present in neoplastic disease
.
Eosinophilic gastroenteritis is an exclusive diagnosis and needs to be judged
in combination with clinical manifestations and laboratory tests.

Misdiagnosed disease analysis:

Solitary rectal ulcer syndrome

Mucosal prolapse is a group of diseases that include:

(1) Solitary rectal ulcer syndrome;

(2) inflammatory cloacal polyps;

(3) rectal prolapse;

(4) inflammatory cap polyps;

(5) inflammatory myogland hyperplastic polyps;

(6) Deep cystic enteritis
.

Features of solitary rectal ulcer syndrome:

1.
Age: It can occur at all ages, young adults are more likely to occur, constipation, blood
in the stool.

2.
Causes: puborectal muscle function defects, stretching during defecation, rectal mucosal prolapse, submucosal vascular traction, ischemia
.

3.
Location: anterior rectal wall, 4-10cm
above the margin.

4.
General: single or multifocal, may present as ulcers or polyps (0.
5-4 cm in diameter).

5.
Morphological characteristics:

(1) Early focal ischemia pattern, epithelial injury with ulcer formation;

(2) propria propria and muscle fiber;

(3) vasodilation, congestion and bleeding;

(4) mucosal myodysplasia disorder and interspersed into the mucosa;

(5) The crypt is elongated and expanded and jagged;

(6) Epithelial reactive hyperplasia, mucus loss
.

6.
Differential diagnosis: villous adenoma or tubular adenoma; Serrated lesions; P-J polyps; adenocarcinoma

Summary

In everyone's mind, pathological diagnosis is often considered to be the "gold standard" for disease diagnosis, but in the diagnosis of IBD, pathological diagnosis is not easy
.
Because there are no set criteria for diagnosing IBD, the disease often lacks specificity
.
Pathological biopsy can directly obtain tissue, reflect the nature of the disease, and has a very important role; However, the microscopic morphology of IBD has different manifestations and changes in different disease periods, and many infectious enteritis, drug-induced enteritis, etc.
have morphological characteristics
very similar to IBD.

Therefore, pathologists must fully understand the patient's history, clinical manifestations, endoscopic findings, and imaging characteristics before they can make a relatively reliable diagnosis
.
At the same time, IBD is mainly young patients, and we need our care and accurate early diagnosis as much as possible, so that patients can receive accurate treatment
.

It is for these reasons that the training of IBD pathologists is particularly urgent and important, as a pathologist, doing a good job in the pathological diagnosis of IBD is not only a responsibility, but also a ability, but also a lifelong thing
.