Overview of Endoscopic Features of Gastrointestinal Pathology (Colon)

Abstract

Advances in endoscopic imaging technologies and techniques in recent decades have revolutionized the detection, diagnosis, and therapy of gastrointestinal pathology. New-generation endoscope systems produce high-definition images with over a million pixels that are three times higher in resolution than standard-definition images produced by older-generation endoscope systems. In addition, endoscopic image contrast can be enhanced with stains, and electronic imaging technologies such as narrow-band imaging (NBI, Olympus Corporation, Tokyo, Japan). These technologies are known collectively as “image-enhanced endoscopy,” which are known to improve the detection and facilitate real-time optical diagnosis or characterization of early gastrointestinal neoplasia. Optical diagnosis therefore improves tissue sampling for subsequent histologic evaluation and also enables real-time selection of appropriate endoscopic therapy for early gastrointestinal neoplasia while and avoiding unnecessary surgery. In this chapter, we present an overview of endoscopic features of colorectal pathology.

Endoscopic Anatomy

• Appreciation of endoscopic anatomical landmarks by the endoscopist is important for accurate localisation and documentation, especially for management of colorectal neoplasia.

• The colon is broadly divided into:

  • Proximal—proximal to the splenic flexure

  • Distal—distal to the splenic flexure

• In the absence of colonoscopic instrument looping, anatomical landmarks that can be identified during colonoscopy are (Fig. 13.1):

  Fig. 13.1

  

  (a) Rectum with view of the semilunar rectal folds , also known as “valves of Houston”. (b) Sigmoid colon at 25 cm from the anal verge characterised by a concentric circular luminal appearance. (c) Descending colon at 40 cm from the anal verge characterised by the presence of fluid level when the patient is in the left lateral decubitus position. (d) Blue splenic flexure discolouration through the lumen of the proximal descending colon. (e) Transverse colon at 55 cm from the anal verge characterised by a triangular-shaped lumen. The image also shows a transparent distal cap attachment on the instrument, which is used to assist in maintaining visualisation while inspecting proximal aspects of colonic folds. (f) Ascending colon, with the ileocaecal valve in the distance (top). (g) Distal ascending colon and hepatic flexure with the colonoscope tip in retroflexion, to assist visualisation of blind spots on the proximal surfaces of colonic folds and flexures. (h) Ileocaecal valve (left) appearing as a semilunar thickened fold. (i) Appendiceal orifice. (j) Terminal ileum. (k) Taenia coli (muscularis externa) can be seen extending longitudinally in the direction of the lumen (bottom)

  • Rectum

  • Sigmoid colon

  • Descending colon

  • Splenic flexure

  • Transverse colon

  • Hepatic Flexure

  • Ascending colon

  • Cecum

  • Appendiceal orifice

  • Ileocaecal valve

  • Terminal ileum

Colitides

Inflammatory Bowel Disease

Ulcerative Colitis

• Ulcerative colitis (UC) is endoscopically characterised by confluent colonic inflammation starting at the rectum and extending proximally (Fig. 13.3).

  Fig. 13.2

  

  (a–c) Moderately active ulcerative colitis with diffuse mucosal granularity, oedema, absent vascular markings, erythema, exudates, spontaneous bleeding, and luminal narrowing

  Fig. 13.3

  

  (a–c) Severe active Crohn’s colitis with deep linear ulcers, oedema, absent vascular markings, erythema, and luminal narrowing. A guide wire was passed through the stricture prior to balloon dilatation. The stricture was successfully traversed after dilatation

• Phenotypically, UC can be classified based on the anatomical extent of colonic inflammation (Table 13.1). The Montreal classification is used during colonoscopy to categorise UC into [1]:

  • E1, ulcerative proctitis—inflammation is limited to the rectum.

  • E2, left-sided ulcerative colitis (distal UC)—inflammation does not extend proximally beyond the splenic flexure.

  • E3, extensive ulcerative colitis (pancolitis)—inflammation extends proximally beyond the splenic flexure.

• Additionally, the severity of colonic inflammation is classified clinically as:

  • S0, clinical remission—asymptomatic

  • S1, mild UC—≤4 bloody or non-bloody stools daily, no systemic illness, and normal ESR

  • S2, moderate UC—>4 bloody stools daily with minimal sign of systemic illness or toxicity (Fig. 13.2)

  • S3, severe UC—≥6 bloody stools daily, tachycardia (≥90 bpm), temperature ≥37.5 °C, anaemia (Hb < 105 g/L), and ESR ≥30 mm/h

• Fulminant UC is characterised by >10 bloody stools daily, toxicity, abdominal distention and tenderness, severe anaemia requiring blood transfusion, and colonic dilatation on imaging.

• The severity of colonic inflammation is scored endoscopically using the Mayo endoscopic core as:

  • Normal or inactive disease

  • Mild (erythema, reduced mucosal vascular pattern)

  • Moderate (marked erythema, absent mucosal vascular pattern, mucosal friability, erosions)

  • Severe (spontaneous bleeding, ulceration)

Table 13.1 Mayo Endoscopic score for ulcerative colitis

Crohn’s Disease

• Crohn’s disease (CD) is endoscopically characterised by transmural inflammation (erythema, erosions, deep ulceration, strictures) of the terminal ileum with or without patchy inflammatory areas in the colon with intervening normal colonic mucosa (Figs. 13.4 and 13.5).

  Fig. 13.4

  

  (a–c) Severe neo-terminal ileal fibrotic anastomotic stricture in a Crohn’s patient following ileocolonic resection. A guide wire was passed through the stricture prior to balloon dilatation. The stricture was successfully traversed after dilatation

  Fig. 13.5

  

  Pseudomembranous colitis with typical yellow-white pseudomembranes

• Can affect the any part of the luminal gastrointestinal tract.

• Patients often present with abdominal pain and anaemia.

• The Vienna and Montreal classification is used during colonoscopy to categorise CD (Table 13.2) [1].

• The endoscopic recurrence severity score is used to assess the ileocolonic anastomosis and ileum (Table 13.3).

Table 13.2 Vienna and Montreal classification for categorising Crohn’s disease

Table 13.3 Endoscopic recurrence severity score for assessing ileocolonic anastomosis in Crohn’s disease

SCENIC and DALM

In 2015, an international expert multidisciplinary panel including gastrointestinal pathologists developed the International Consensus Statement on Surveillance and Management of Dysplasia in Inflammatory Bowel Disease (SCENIC) [2, 3]. Some of their key recommendations included:

• To abandon the use of less accurate endoscopic terminology including “dysplasia-associated lesion or mass (DALM)”, “adenoma-like”, or “non-adenoma-like” and use “endoscopically resectable” or “nonendoscopically resectable”.

• Using chromoendoscopy with targeted biopsy is superior to white-light colonoscopy with random biopsy.

• Confirmation of dysplasia by a specialised gastrointestinal pathologist.

Infectious Colitis

• Infectious colitis is diagnosed by the combination of:

  • Characteristic histologic inflammatory changes on colonic biopsies positive microbiological testing for the culprit organism (Table 13.4) [4].

  • Colonoscopic findings in early disease (within 4–5 days) usually show distal colitis with relative sparing of the rectum. Th e rectum can be severely affected later in the disease course, which causes endoscopic and histologic confusion for differentiating infectious colitis from ulcerative colitis.

• Colitis due to Clostridium difficile shows characteristic yellow-white pseudomembranes known as “pseudomembranous colitis” (Fig. 13.5).

Table 13.4 Common bacterial pathogens causing infectious colitis

Microscopic Colitis

• Colonoscopic examination is usually normal.

• Occasionally mild mucosal erythema, oedema, or reduced mucosal vascularity can be noted.

• Patients usually present with chronic diarrhoea.

Ischaemic Colitis

• Ischaemic colitis often referred to as mesenteric ischaemia can be acute or chronic.

• Endoscopic and histologic features vary according to the phase, severity, and duration of ischaemic injury.

• Anatomical involvement corresponds to the affected vascular territory but commonly affect the splenic flexure and rectosigmoid junction, also known as “watershed areas”.

• These features are usually segmental in distribution with an abrupt transition between injured and non-injured colonic mucosa. Endoscopic features can include:

  • Confluent necrosis of colonic wall

  • Colonic wall and colonic folds oedema

  • Mucosal friability, ulceration, and petechial haemorrhage

  • Intraluminal bleeding and clots

  • Segmental distribution with an abrupt transition between injured and non-injured

  • “Colon-stripe” sign (longitudinal ulcer along watershed area) or “double colon-stripe” sign, also known as a “tram-track” sign (Fig. 13.6).

  • Follow-up colonoscopy after resolution of ischaemic injury often shows complete resolution of colitis with healed mucosal scarring.

Fig. 13.6

A resolved tram-track sign in a patient with healed ischaemic colitis

Radiation Colitis

• Diffuse mucosal changes caused by radiotherapy.

• Radiation proctitis can be frequently seen in men following radiation therapy for prostate cancer.

• They appear as an acquired angioectasias and can frequently cause bleeding (Fig. 13.7).

• Treatment with argon plasma coagulation is effective.

Fig. 13.7

(a–c) Chronic radiation proctitis characterised by neovascularisation with telangiectatic mucosal capillaries, loss of normal vascular background, patchy erythema, and mucosal oedema

Colorectal Neoplasia

The latest-generation, high-definition endoscope systems all have built-in electronic image-enhancement technologies that can be used for optical diagnosis of colorectal polyps [5,6,7]. The most widely used technology is narrow-band imaging (NBI) for differentiating serrated from adenomatous colorectal polyps. Endoscopic imaging has revolutionised real-time management of colorectal polyps during colonoscopy. Historically, large polyps were biopsied initially to exclude the presence of carcinoma before being removed endoscopically. Modern therapeutic approaches advocate avoiding tissue biopsy, which can induce submucosal fibrosis and may compromise the technical success of complete and safe endoscopic removal of colorectal polyps.

The NBI International Colorectal Endoscopic (NICE) classification is a simple and validated classification that can be used in real time to optically diagnose colorectal polyps into serrated, adenomatous, or carcinoma with deep submucosal invasion (Table 13.5) [8,9,10]. Increasingly, expert colonoscopists can detect focal areas within polyps that may contain invasive cancer. This allows the selection of an appropriate en bloc endoscopic therapy, such as endoscopic submucosal dissection, or piecemeal endoscopic mucosal resection with targeted sampling of potentially invasive regions and submission for separate histologic assessment.

Table 13.5 NBI International Colorectal Endoscopic (NICE) classification

Colorectal Cancer

• Colorectal cancers range in endoscopic morphology from large, fungating, and firm luminal masses to subtle, flat or depressed lesions (Fig. 13.8). The endoscopic surface and vascular pattern correlates with the depth of submucosal invasive cancer. Deep (1000μm or greater) submucosally invasive cancers are characterised by a NICE type 3 appearance with disruption or absence of mucosal surface and vascular pattern (Fig. 13.9).

• When large and circumferential, cancers can cause luminal obstruction with inability of the colonoscope to traverse the lesion.

Fig. 13.8

Colorectal cancer

Fig. 13.9

A small malignant polyp (with deep submucosal invasion) showing NICE type 3 under NBI

Colorectal Polyps

• The endoscopic morphology of colorectal polyps should be described using the Paris classification (Table 13.6) [11].

• Optical diagnosis using the Kudo pit pattern classification (Table 13.7) requires topical dye spray together with magnifying endoscopy to accurately and reliably differentiate between normal, nonneoplastic, neoplastic, and cancerous lesions [12]. Electronic imaging using the NICE classification offers a quicker and more convenient approach to optical diagnosis.

• colorectal polyps have characteristic endoscopic features that are highly predictive of the pathological diagnosis (Fig. 13.10) [8, 13].

Table 13.6 Paris classification

Table 13.7 Kudo pit pattern classification

Fig. 13.10

(a) Characteristic endoscopic appearance of a sessile serrated adenoma/polyp in the ascending colon. Endoscopic features including flat morphology, indistinct margins, and yellow mucus cap. (b) Characteristic endoscopic appearance of a sessile serrated adenoma/polyp with NICE type 1 and open crypts that correlate histologically with dilated mucin filled crypts. (c) Hyperplastic polyp under NBI. (d) Tubular adenoma under NBI. (e) Panels 1–3: A pedunculated polyp in the proximal sigmoid colon removed by snare polypectomy with electrocautery. Resection yields a clear margin of normal tissue; a haemostatic clip was applied to prevent delayed haemorrhage. (f) Panels 1–3: A large rectal tubulovillous adenoma removed using endoscopic mucosal resection (EMR). Panel 4: The EMR scar on endoscopic surveillance at 4 months showing no endoscopic evidence of residual adenoma

Diverticular Disease

• Diverticular disease appears endoscopically as outpouchings of the colonic wall that vary in size and number (Fig. 13.11).

• Occurs most commonly in the sigmoid colon but can be seen throughout the colon.

• Diverticular disease spectrum includes:

  • Asymptomatic diverticular disease

  • Symptomatic uncomplicated diverticular disease

  • Complicated diverticular disease which can manifest as:

    • Diverticulitis (acute or chronic)—Microscopic perforation results in localised inflammatory response caused by bacterial overgrowth.

    • Diverticular disease-associated colitis—Rare and usually associated with diverticulitis.

    • Diverticular bleeding (Fig. 13.12).

    • Diverticular perforation (Table 13.8).

Fig. 13.11

(a–d) Diverticular disease

Fig. 13.12

Diverticular bleeding

Table 13.8 Complications of diverticular perforation

The majority of diverticular disease is simple without complications. Complicated diverticular disease can develop peritonitis, sepsis, abscesses, fistula, and bowel obstruction (Table 13.8).

Anorectal

Anorectal Junction

Retroflexion in the rectum conveniently shows the dentate line demarcating transition from colonic mucosa to anal squamous mucosa (Fig. 13.13).

Fig. 13.13

(a, b) Rectal retroflexion under white light and NBI showing anorectal junction

Anal Intraepithelial Neoplasia (Condyloma Accuminata)

• Raised verrucous-like lesions within the dentate line (Figs. 13.14 and 13.15)

  Fig. 13.14

  

  (a, b) AIN under white-light and narrow-band imaging

  Fig. 13.15

  

  Patient on immunosuppression with clusters of AIN

Anal Squamous Cell Carcinoma (SCC)

• Endoscopic features vary by stage:

  • Early SCC can be small and appear similar to condyloma acumulatuma

  • Advanced lesions can be large, ulcerated, or fungating.

  • They can be differentiated endoscopically from distal rectal carcinoma by their verrucous appearance, and that they arise from the anal squamous mucosa at or beyond the dentate line (Fig. 13.16).

    Fig. 13.16

    

    (a, b) Ulcerated squamous cell carcinoma in a 79-year-old lady presenting with rectal bleeding seen on rectal retroflexion. The lesion was arising from the anorectal junction and invading the rectal mucosa

Haemorrhoids

They appear as protruded or polypoid vessels in the distal rectum (Fig. 13.17).

Fig. 13.17

non-bleeding internal and external haemorrhoids seen on retroflexion view

Miscellaneous

Melanosis Coli

• Reversible mucosal brown pigmentation of the colon (Fig. 13.18).

  Fig. 13.18

  

  (a, b) Melanosis coli

• Caused by use of anthraquinone laxatives (Table 13.9).

• Adenomas do not take up the lipofuscin pigment and can be easier to detect in melanosis coli during colonoscopy (Fig. 13.19).

  Fig. 13.19

  

  (a, b) Adenomas can be easier to detect when melanosis coli is present

Table 13.9 Anthraquinone laxatives

Mucosal Prolapse (Solitary Rectal Ulcer Syndrome)

• Erythematous and/or ulcerated mucosa of the most distal rectum

• Can present with rectal bleeding

Angiodysplasia

• Flat red vascular lesions.

• Under NBI they appear brown or darker in colour than surrounding normal mucosa (Fig. 13.20).

  Fig. 13.20

  

  (a–d) Non-bleeding angiodysplastic lesions of the colon (under white light and NBI)

• Often a feeding vessel can be seen.

• Mostly found in the ascending colon and cecum.

• Can be an incidental finding during colonoscopy, or patients may present with history of painless intermittent rectal bleeding, haematochezia, or anaemia

• If symptomatic, they can be treated with argon plasma coagulation (APC).

Lipoma

• Smooth sessile lesions

• Normal underlying mucosa with a tinge of yellow discolouration (Fig. 13.21)

  Fig. 13.21

  

  Lipoma of the ascending colon with smooth surface and yellow discolouration

• Soft when palpated using endoscopic accessory device, also known as “pillow sign” (Fig. 13.22)

  Fig. 13.22

  

  Lipoma “cushion” or “pillow” sign

Bowel Preparation-Related Mucosal Changes

• Non-specific

  • Normal

  • Mild patch erythema

  • Mild oedema

  • Small haemorrhages

• Commonly seen in the distal rectum but can be seen throughout the colon

Summary

Effective communication between gastroenterologists and pathologists is important for high-quality patient care. Advances in endoscopic imaging have improved the endoscopic detection, characterisation, and therapy of gastrointestinal pathology.