7.1 IBD Flashcards
what is IBD?
inflammatory bowel diseases are a group of gut conditions characterised by idiopathic inflammation of the gut
on an age graph, how are IBDs represented?
bimodal age graph as the populations that are usually diagnosed are young adults and elderly.
what epithelium is in the large intestine?
columnar epithelium
what is the main functions of the large intestine?
removes water from the indigestible gut contents, turning chyme into semi solid waste
production of vitamins
environment of the microbiome
temporary storage
where does the colonic mucosa get the majority of its nutrients from?
short chain fatty acids derived from the fermentation of dietary fibre
in relation to the peritoneum, where does the large intestine lie?
ascending and descending colon are retroperitoneal
transverse colon and sigmoid colon are intraperitoneal and have their own mesentery
describe the relation of the rectum to the peritoneum?
the upper 1/3 is intraperitoneal
the middle 1/3 is the retroperitoneal
the lower 1/3 has no peritoneum
describe the blood supply to the large intestine?
midgut component ( caecum to the proximal 2/3rds of the transverse colon) = superior mesenteric artery. SMA gives the branches ileo-colic (caecum), right colic ( ascending colon), middle colic (transverse colon) hindgut component of the large intestine is supplied by branches of the inferior mesenteric artery, the left colic supplies the proximal part of the descending colon, the sigmoid artery supplies the distal part of the descending colon and the superior rectal artery supplies the upper intraperitoneal 1/3rd of the rectum
describe the venous drainage of the large intestine
midgut drains into the superior mesenteric vein
hindgut drains into the inferior mesenteric vein
upper 1/3rd of the rectum drains into the superior rectal vein
middle and lower 1/3rds of the rectum drain into the systemic venous system
describe the structure of the large intestine
has crypts in the epithelium, not villi
has three bands of the external longitudinal muscle (teniae coli)
haustra
epiploic appendices
what are epiploic appendices?
small pouches of the peritoneum filled with fat and situated along the colon, but are absent in the rectum.
how does water absorption in the colon occur?
facilitated by ENaC channels which are induced by aldosterone
most absorption occurs in the proximal colon
much tighter tight junctions allow a bigger gradient to form and reduces paracellular diffusion
what are the 2 common types of inflammatory bowel disease?
crohns disease
ulcerative colitis
describe the key features of crohns disease
affects anywhere in the GI tract - usually involves the terminal ileum transmural inflammation - thickening of the bowel wall and narrowing of the lumen skip lesions mouth ulcers strictures or fistulas non-bloody frequent loose stools weight loss joint pain tender mass in RLQ with pain perianal inflammation and ulceration low grade fever mildly anaemic cobblestone appearance due to mucosal oedema and discrete superficial ulcers
describe the key features of ulcerative colitis?
begins in the rectum can extend to involve the rest of the colon continuous pattern mucosal inflammation mildly tender abdomen weight loss mild lower abdominal pain and cramping painful red eye bloody stool
what are some of the extra-intestinal problems involved with IDB?
MSK pain (arthritis)
skin (erythema nodosum / pyoderma gangrensum/ psoriasis)
liver / biliary tree ( primary sclerosing cholangitis )
eye problems
what are some of the risk factors involved with IBD?
family history / genetics
gut organisms causing altered interaction
immune response - exposure to a trigger such as antibiotics, infection, smoking or change in diet
how does crohns disease appear on microscopy?
granuloma formation (organised collection of epithelioid macrophages)
what investigations are used in crohns disease?
bloods - anaemia
CT/MRI - bowel wall thickening, obstruction, extramural problems
barium enema/follow through - shows strictures and fistulaes
colonoscopy - can see gross pathological changes
what are the microscopic pathological changes in ulcerative collitis?
chronic inflammatory infiltrate of lamina propria
crypt abscesses
crypt distortion (irregular shaped glands with dysplasia and darker crowded nuclei)
reduced number of goblet cells
what can be used to investigate ulcerative colitis?
bloods - serum markers stool cultures colonoscopy - continuous inflammation, pseudopolyps, crypt abscesses and loss of haustra plain abdominal radiographs barium enema in mild cases CT/MRI (not very useful in UC)
what is indeterminate colitis?
IBD that can neither be classified as UC or crohns disease
what is backwash ileitis?
Backwash ileitis is seen in patients with ulcerative colitis (UC), where the entire colon is involved. In such cases the terminal ileum is inflamed and inflammation travels through the ileo-caecal valve
what is a aphthous ulcer?
a mouth ulcer
why is endoscopy not advised for ulcerative colitis?
as the mucosa is very friable and if it is touched and irritated it is likely to bleed
on a barium follow through, what can be seen in a patient with crohn’s disease?
string sign of kantour
- strictures in the small intestine and dilations following them
what is a double contrast enema?
a contrast of medium and air that goes through the anus. contrast is put in first and then the air. air forces the contrast out into the epithelium and edge of bowel
what radiological features are seen in UC in a double contrast enema?
lacking haustral markings
lead pipe colon
continuous lesions without skipping
mucosal inflammation causes a granular appearance as contrast forced into the pseudopolyps and ulcerations
what is pancolitis?
Pancolitis is a form of ulcerative colitis (UC) which affects the entire large intestine
what are the medical treatment options for IBD?
- aminosalicylates (sulfasalazine) for flares and remission
- corticosteroids - prednisolone used for flares
- immunomodulators - azathioprine (fistulas / maintenance of remission)
what are the surgical treatment options for crohns disease ?
surgical treatment for crohns disease is not curative
removes part of the inflammed bowel if there are strictures or fistulas, removes as little bowel as possible. removing too much bowel restricts the amount of absorption in the bowel.
what are the surgical treatment options for ulcerative colitis?
surgery in ulcerative colitis can be curative. a colectomy is the removal of the whole colon
surgery is considered if the inflammation is not settling, is precancerous changes are seen, or in toxic megacolon
