GI patho Flashcards
Define chronic and granulomatous
- Chronic inflammation - temporal sequence, non neutrophilic inflammatory response, eosinophils in GIT-subacute.
- Granulomatous inflammation - often vaguely referred to by many clinicians eg, post of granuloma, stitch granuloma, pyogenic granuloma - all misnomers
- Granulomatous inflammation - chronic, defined as collection of epitheliod histiocytes with typical slipper foot nuclei. Giant cells common of various/ variable types and may calcify over time-diagnostically useful.
Define an ulcer, sinus, fistula
- Ulcer - discontinuity in surface epithelium due to acute inflammatory reactioon- temporal sequence- constituted by neutrophils (polymorphs/polymorphouclear neutrphils).
- Sinus = ulcerated tracj +/- epithelial lining opneing to a surface or hollow viscus.
- Fistula - Ulcerated track +/- eputhelial lining connectin two hollow viscera or one hollow viscus to a different surface- diversion/bypss.
Ischaemia and infarction
- ischaemia - reduced to absent vascular supply to cells, tissue and organ
- Infarction - ischaemia resulting in tissue necrosis, when collateral vascular channels fail to develop or are inufficiently developed
- Important - infarction in bowel mzy be venous in nature due to reduced to absent venous drainage.
- Infarction - leads to gangrene - dry and then wet and supeadded putrefaction (bacterial)
Metaplasia
- metaplasia - conversion of a temrinallydifferentiated tissue to yet another terminally differentiated phenotype (trans-differentiation) reflective of an innate adaption to an abnormal and hotile environment
- Barretts oesophagus - GORD leading to cephalad prolongation of columnar mucosa replacing the native oesophageal squamous mucosa- reflecting a favourable (short term) phenotype
- Neo-metaplasia- retro-differentiation in tumour- reversal of ontogeny- e.g., yolk sac areas in adult granulosa cell tumour of ovary or YST like areas in colorectal carcinoma (enteroblastic)- foetal reprogramming- so not mature or terminally differentiated but immature
Dysplasia (abnormal development deifnition)
■Abnormal proliferation-maturation uncoupling in epithelium leading to a non- invasive cancer or a pre-cancerous state with intact basement membrane or incapacity to avail lymphovascular access
■Many exceptions- dysplastic naevus, dysplastic kidney, dysplastic hip, fibrous dysplasia, myelodysplasia, osseous dysplasia etc
Intraepithelial neoplasia development in to occult invasive carcinoma
What is acute appendicitis
■Luminal inflammation- pain around umbilicus- Dermatomal rule (referred pain).Mural and serosal inflammation (peritonitis) - shifts to RIF
■Peri appendicitis- only serosal inflammation without mural or luminal inflammation
■Usually related to the other D/D RIF pain- PID (pelvic inflammatory disease), typhlitis/caecitis and mesenteric lymphadenitis due to Yersenis often with appendicitis- serology and typical suppurative granulomas/follicles/germinal centres
The appendix = phylogenetically relatedto bursa fabricus (clacal end of avian species). Physiological diverticulum (cul de sac). Vesitgial organ, diverted from faecal stream - prominent lymphoid follicles
ACE appendix- appendicostomy for antegrafr continence enema - diversion to faecal stream- loss of fllicles.
Peritonitis
- Acute - inflammation of the outermost layer of serosa of any peritonealised intra-abdominal organ (hollow viscus) - visceral peritonitis. Or the outer layer of peritoneum related to the abdominal wall (parietl peritonitis)
- Rebound tenderness , guarding + rigidity
- Greater omentum acts as abdominal policeman to localise the inflammation - abdominal apron
- Common end result of disparate pathologic processes.
- Regional - visceral, localised to the organ involved,
- Diffuse - parietal
Diverticulum
- Herniation of the mucosal layer through a weak point of the muscle coat due to increased intra luminal pressure- colon (sigmoid)
- Rarely as anatomical variation or congenital anomaly- Meckels diverticulum
- urinayr bladder, small intestine, oeosphagus (abnormally tight upper sphincter - Zenkers diverticulum)
- Proximal colonic diverticulosis- strong genetic predispoition in individuals of asia pacific heritage
Pathology of sigmoid diverticular
- Western low fibre diet
- Relatively less genetic influence cf proximal diverticulosis of Asia- pacific
- Chronic constipation
- Diverticulitis, peridiverticulitis, diverticular abscess- pain abdomen
- Peritonitis - acute abdomen
- Serious complications - stricture leading to intestinal obstruction, colovesical and colovaginal fistula
- Misdiagnosis - crohns segmental colitis, due to granuloma and deep skin inflammation
Diverticular disease
■Sac like protrusion
■Diagnosed on endoscopy and CT scan
■Concertina like appearance on resection
■Port of perforating artery is a weak point of the wall
■Presentation- abdominal pain, per rectal bleeding, constipation, fever if complicated
■Acute presentation- intestinal obstruction, sepsis, pyrexia of unknown origin
■DO NOT BIOPSY AN INVERTED POLYP/DIVERTICULAR POLYP- WILL PERFORATE
Intestinal obstruction
■Intrinsic- lumen- tumour- polyp, intussusception, cancer and worms (tropical)
■Intrinsic- wall/mural- stricture
■Extrinsic- usually extra tubal compression by mass
■Proximal dilation- vomiting
■Distal collapse- inability to pass flatus and faeces
■Double barrel obstruction- volvulus- collapse of both afferent and efferent limbs
■Perforation and peritonitis- caecum, site of election, as most dependent and fixed
Vascular supply of the intestine
- Foregut- coeliac axis
- Midgut- SMA- Superior mesenteric artery
- Hindgut- IMA- Inferior
- Junctions are watershed zones and prone to ischaemia
- Atherosclerosis, thrombosis
- Venous occlusion, strangulated hernia
- Vasculitides- e,g IgA vasculitis (Henoch-Sconlein purpura)
- Drugs rare- 5’ Azacytidine
Ischaemic Bowel
- Acute emergency - acute abdomen, blood in stool
- Strangulated hernia
- Dusky cyanosis, irreversible, no change of colour on hot mop compress
- Must keep margins viable
- Needs histiologial confirmation
Factors in ischaemia
- Previous damage
- Susceptibility - metabolic demand for 02
- Presence of anastomosis
- Time of onset- suficient or not for collaterals to develop - will decide if acute bowel ischaemia or chronic ischaemic colitis (latter usually in atherosclerotic arteripathy)
Ischaemic colitis
- Vascular proliferation
- Crypt withering
- Mucin loss
- Focal active cryptitis
- Pseudomembrane