S7: IBD & distal tract pathology

Question 1

Describe the arterial supply of the large intestine

Answer 1

Midgut component – superior mesenteric artery
Ileocolic – caecum
Right colic – ascending colon
Middle colic – transverse colon
Hindgut component – inferior mesenteric artery
Left colic – descending colon
Sigmoid – descending colon
Superior rectal artery – upper 1/3 rectum

Question 2

Describe the venous drainage of the large intestine

Answer 2

Midgut drains into the superior mesenteric vein
Hindgut drains into inferior mesenteric vein
Rectum:
Upper 1/3 drains into superior rectal vein
Middle and lower 1/3s drain into systemic venous system – site of portosystemic anastomosis

Question 3

Describe the longitudinal muscle of the large intestine

Answer 3

External longitudinal muscle is incomplete:

• three distinct bands (teniae)
• haustra are sacculations cause by contraction of teniae coli

Question 4

Describe water absorption in the colon

Answer 4

Facilitated by ENaC 
Similar to principle cells of the late distal convoluted tubule 
Most absorption in proximal colon
Much tighter tight junctions:
-allows bigger gradient to form
-less back diffusion of ions

Question 5

Define inflammatory bowel disease

Answer 5

Group of conditions characterised by idiopathic inflammation of the GI tract
Affect function of the gut

Question 6

Describe Crohn’s disease

Answer 6

Affects anywhere in GI tract, but ileum involved in most cases
Transmural – affects whole gut wall
Skip lesions

Question 7

Describe ulcerative colitis

Answer 7

Begins in rectum & can extend to involve entire colon
Continuous pattern
Mucosal inflammation

Question 8

Describe other symptoms which are common with inflammatory bowel disease

Answer 8

MSK pain – arthritis
Skin – erythema nodosum, pyoderma gangrenosum, psoriasis
Liver/biliary tree – primary sclerosing cholangitis
Eye problems

Question 9

Describe macroscopic and microscopic features of Crohn’s disease

Answer 9

Macroscopic – skip lesions, hyperaemia, mucosal oedema, discrete superficial ulcers, deeper ulcers, transmural inflammation, fistulae & cobblestone appearance
Microscopic – granuloma formation (if this is found – definite diagnosis is Crohn’s)

Question 10

Describe investigations for Crohn’s

Answer 10

Bloods – anaemia
CT/MRI – bowel wall thickening, obstruction & extramural problems
Barium enema/follow through – used less now
Colonoscopy – gross pathological changes can be seen

Question 11

Describe pathological changes which occur in UC

Answer 11

Chronic inflammatory infiltrate of lamina propria
Crypt abscesses (neutrophilic exudate in crypts)
Crypt distortion – irregular shaped glands with dysplasia, darker crowded nuclei
Reduced number of goblet cells
Pseudopolyps can develop after repeated episodes
Loss of haustra

Question 12

Describe investigations for UC

Answer 12

Bloods – anaemia & serum markers 
Stool cultures 
Colonoscopy 
Plain abdominal radiographs 
Barium enema 
CT/MRI – less useful for diagnosing uncomplicated UC

Question 13

What is indeterminate colitis?

Answer 13

Even after diagnostic evaluation, 10% have disorders that cannot be classified

Question 14

Describe radiological features of Crohn’s

Answer 14

Barium follow through – sometimes see long strictures

String sign of kantour

Question 15

Describe radiological features of UC

Answer 15

Featureless descending and sigmoid colon – lacking haustral markings & lead pipe colon
Continuous lesions without skipping
Whole colon
Mucosal inflammation – causes granular appearance

Question 16

Describe surgical treatment for inflammatory bowel disease

Answer 16

Crohn’s – not curative, strictures/fistulas, as little bowel removed as possible
UC – curable (colectomy) -> inflammation not settling, precancerous changes & toxic megacolon

Question 17

Describe the presentation of Crohn’s

Answer 17

Multiple non-bloody loose stools/day
Weight loss 
Right lower quadrant pain 
15-30 year old  
Smoking makes it worse

Question 18

Describe the presentation of UC

Answer 18

Multiple bloody stools/day
Middle abdominal pain
20-30 year old
Smoking can help

Question 19

Define diarrhoea

Answer 19

Symptom and occurs in many conditions
Loose/watery stools
More than 3 times a day
Acute diarrhoea (less than 2 weeks)

Question 20

Describe the pathophysiology of diarrhoea

Answer 20

Unwanted substance in gut stimulates secretion and motility to get rid of it
Primarily down to epithelial function (secretion) rather than increased gut motility
Colon is overwhelmed and cannot absorb the quantity of water is receives in the ileum

Question 21

Describe diarrhoea due to osmotic causes

Answer 21

Gut lumen contains too much osmotic material (malabsorption)
Ingested material that is poorly absorbed
Inability to absorb nutrients
Will settle if you stop consuming offending substance
Other: too little absorption of sodium

Question 22

Describe diarrhoea due to secretory causes

Answer 22

Electrolyte transport is messed up
Too much secretion of ions
Cause of diarrhoea will affect the messenger systems that control ion transport -> infectious toxins
Diarrhoea continues in response to fasting

Question 23

Describe constipation

Answer 23

Suggestive if hard stools, difficulty passing stools or inability to pass stools
Straining, lumpy/hard stools, feeling of incomplete evacuation, feeling of obstruction or blockage & having fewer than three unassisted bowel movements a week
Risk factors: female, certain medications, low level of physical activity & increasing age

Question 24

Describe the pathophysiology of constipation

Answer 24

Normal transit constipation (often related to other psychological stressors)
Slow colonic transport
Defaecation – cannot coordinate the muscles of defaecation/disorders of the pelvic floor or anorectum

Question 25

Describe treatments for constipation

Answer 25

``` Psychological support Increased fluid intake Increased activity Increased dietary fibre Fibre medication Laxatives ```

Question 26

Describe the anatomy of the appendix

Answer 26

Diverticulum off the caecum Separate blood supply to caecum - ileocolic branch of SMA Can be different locations of the appendix – retro-caecal, pelvic, sub-caecal & para-ileal

Question 27

Describe the pathophysiology of appendicitis

Answer 27

Blockage of appendiceal lumen creates a higher pressure in the appendix Causes venous pressure to rise (causing oedema in walls of appendix) – makes it harder for arterial blood to supply appendix -> ischemia in walls of appendix & bacterial invasion follows Alternative explanation: viral/bacterial infection causes mucosal changes that allow bacterial invasion of appendiceal walls

Question 28

Describe the symptoms of appendicitis

Answer 28

``` Poorly localised peri-umbilical pain Anorexia Nausea/vomiting Low grade fever After 12-24 hours, pain is felt more intensely in right iliac fossa (if appendix is retro-caecal or pelvic may not get this pain – might get supra-pubic pain, right sided rectal/vaginal pain instead) ```

Question 29

Describe the signs of appendicitis

Answer 29

Appear slightly ill Slight fever/tachycardia Generally lie quite still as peritoneum is inflamed Localised right quadrant tenderness Rebound tenderness in right iliac fossa (relatively specific)

Question 30

Describe diagnosis and treatment of appendicitis

Answer 30

Blood tests History/physical examination – if classic, this may be enough In non-classical presentations – CT scan will show distended appendix that doesn’t fill with contrast Treatment – open appendicectomy or laparoscopic appendicectomy

Question 31

Describe diverticulosis

Answer 31

Asymptomatic Occurs in colon Outpouchings of mucosa and submucosa herniate through the muscularis layers Occurs along where nutrient vessels penetrate the bowel wall Thought to be caused by increased intra-luminal pressure

Question 32

Describe acute diverticulitis

Answer 32

Diverticula become inflamed or perforate +/- bleeding and abscess formation Pathophysiology is similar to that involved in appendicitis Uncomplicated – inflammation and small abscesses confined to colonic wall Complicated – larger abscesses, fistula & perforation

Question 33

What is diverticular disease?

Answer 33

The patient experiences pain but there is not inflammation or infection

Question 34

Describe the symptoms and signs of acute diverticulitis

Answer 34

Symptoms: abdominal pain at the site of inflammation, fever, bloating, constipation & haematochezia Signs: localised abdominal tenderness, distension, reduced bowel sounds & signs of peritonitis

Question 35

Describe the diagnosis and treatment for acute diverticulitis

Answer 35

Diagnosis – blood tests, USS, CT scan | Treatment – antibiotics, fluid resus, analgesia & surgery if perforation or large abscesses need to be drained

Question 36

Describe the anatomy of the rectum

Answer 36

Continuous band of outer longitudinal muscles Curved shape anterior to sacrum Parts of it are covered in peritoneum Temporary storage of faeces prior to defaecation

Question 37

Describe the blood supply to the rectum

Answer 37

Arterial supply – several arteries that form a plexus -> superior, middle & inferior rectal arteries Venous drainage – portal drainage through superior rectal vein & systemic drainage through internal iliac vein

Question 38

Describe the anatomy of the anal canal

Answer 38

Narrowed portion of the GI tract that continues from the rectum Starts at the proximal border of the anal sphincter complex Puborectalis sling changes the direction of anatomy -> anal canal points posteriorly Contains the dentate line -above: visceral pain receptors, columnar epithelium -below: somatic pain receptors, stratified squamous epithelium

Question 39

Describe the anal sphincter complex

Answer 39

Internal involuntary sphincter – thick circular smooth muscle, under autonomic control External anal sphincter – striated muscle -nerve supply from pudendal nerve

Question 40

What are the anal cushions?

Answer 40

Anus contains a complex venous plexus, which is divided into 3+ areas of tissues = anal cushions Play a role in anal continence

Question 41

What are haemorrhoids?

Answer 41

Symptomatic anal cushions Internal haemorrhoids – caused by loss of connective tissue support, above dentate line (relatively painless, bleed bright red/pruritis) External haemorrhoids – swelling of the anal cushions which may then thrombose, below dentate line (very painful)

Question 42

Describe the treatment for haemorrhoids

Answer 42

Increased hydration/high fibre diet Avoid straining Rubber band ligation Surgery

Question 43

Describe anal fissures

Answer 43

Linear tear in the anoderm – passing of hard stool, pain on defecation & haematochezia (blood in stool) Underlying causation – high internal anal sphincter tone & reduced blood flow to anal mucosa Treatment – hydration, dietary fibre, analgesia, warm baths & medication trying to relax the internal anal sphincter

Question 44

List common causes of haematochezia

Answer 44

``` Diverticulitis Angiodysplasia Colitis Colorectal cancer Anorectal disease Upper GI bleeding ```

Question 45

Describe melaena

Answer 45

Black tarry stools – offensive smelling Due to haemoglobin being altered by digestive enzymes and gut bacteria Common causes – upper GI bleeding -> peptic ulcer disease, variceal bleeds, upper GI malignancy Uncommon causes – gastritis & Meckel’s diverticulum