The Digestive System - Lower Gastrointestinal Tract Flashcards
Diverticula
Sac like protrusion of the colonic mucosa through the muscular wall
Which part of the GIT does diverticula disease affect the most
Sigmoid colon
Diverticulosis
Presence of asymptomatic diverticula
Diverticular disease
Symptomatic diverticula (e.g. abdo pain) in the absence of infl (can be used as umbrella term)
Diverticulitis
Symptomatic a/c infl and infection of diverticula
Epidemiology of diverticulosis
Increases w/ age, affects up to 80% at 85
Lifetime risk of a/c diverticulitis 4-25%
Risk factors for diverticular disease
Diet - red meat, low fibre
obesity
Fhx
Smoking
Meds - NSAIDs, steroids
Pathophys of diverticular disease
Colonic mucosa protrudes through muscualris externa, only covered by serosa
Occurs in weak areas, related to increased intra-liminal pressure and abnormal colonic motility
Clinical features of diverticulitis
Abdo pain - LLQ/ LIF
Pyrexia
CIBH
Guarding/ peritonism
Tachycardia
Ix of diverticular disease
CT CAP - best for dx
Bloods
Classification of diverticulitis
Used to help guid need for surgical intervention
Ranges from confined pericolic infl to generalised faecal peritonitis
Out pt mx for a/c diverticulitis
For mild, uncomplicated disease
7-10 days of co-amoxiclav
Analgesia - avoid NSAIDs and opiates
Reassess after 2/7 and arrange colorectal clinic appt
What alternative abx can be used in diverticulitis
Cipro
Metronidazole
Why should NSAIDs and opiates be avoided in diverticular disease
Risk of perforation
In-pt mx of divertiuclitis
Admit pts who are elderly, co-morbid, unwell and peritonitis
If features of severe infection - sepsis 6
Commence IV abx and should be NBM
What should be advised for pts if diverticula disease
Start high-fibre diet
Complications of diverticula
Fistula
Colic stricture
Diverticular bleed
Imaging of SBO
Can see central stacked bowel loops >3.5cm but usually <6cm in diameter
Markings cross lumen diameter
Paucity of gas in large bowel
Pathologies causing SBO
Adhesions and bands
Hernia
Crohn’s disease
Infiltrating neoplasms
Intussecption
Intussusception
Piece of small bowel slides onto adjacent part of the Intestine
Typically, a paediatric dx, v concerning in adults (used by large polyps)
Imaging of large bowel obstruction
Peripheral air-filled loops >7cm in diameter
Haustra do not cross lumen diameter
Does dilated large bowel obstruction always cause SBO
Depends on competency of ileocoecal valve
Classification bowel obstruction
No fluid or gas is able to pass beyond the site of obstruction
Partial/ incomplete bowel obstruction
Some fluid or gas is able to pass beyond the site of obstruction
Mechanical bowel obstruction
Physical blockage to the flow of GI content
Non-mechanical bowel obstruction (ileus)
Obstruction to flow 2’ to neuromuscular dysfunction (e.g failure in peristaltic activity)
Closed loop bowel obstruction
The bowel is obstructed at two points, this prevents proximal or distal decompression os contents
High-risk of rapid necrosis and perforation
Causes of large bowel obstruction
Tumours
Volvulus
Diverticular strictures
Key positive finding in bowel obstruction
Raised lactate - indicator of ischaemia
Raised infl markers
3, 6, 9 rule in bowel obstruction
Dilatation of the small bowel >3cm, large bowel > 6cm or the caecum > 9cm is suggestive of abnormal dilatation
Supportive mx of bowel obstruction
Drip and suck - IV fluid and NGT insertion (aspiration)
Analgesia
Anti-emetic
Abx as needed
Correction of electrolytes
Surgery for bowel obstruction
Defunctioning stoma and resection - observe lesions
Adhesiolysis +/- bowel resections
Role of appendix in diarrhoea
May serves as bacterial reservoir to repopulate enteric bacteria following illness
Unique colonic anatomy
Taeniae coli
Haustra
Epiploic appendages
Taeniae colic
There bands of smooth muscle that make up longitudinal muscle layer of muscularis, except at terminal end
Haustrae
Contraction of taemia coli bunch up
Causes of wrinkled appearance of colon
Epiploic appendages
Small, fat-filled sacs of visceral peritoneum
Attached to taenia colic
Recta valves
3 lateral bends in rectum
Separate faeces from gas to prevent simultaneous passage of faeces and gas
Differences in internal and external anal sphincter
Internal - made of smooth muscle, involuntary contractions
External - skeletal muscle, voluntary contractions
Anal sinuses
Depression between anal columns that’s secrete mucous to facilitate defectaion
Dentate line
Horizontal, jagged line that runs below anal sinuses
Represents junction between hindgut and external skin
Why is the area below the dentate line more sensitive than the area above
Due to innervation by somatic sensory fibres vs visceral, sensory fibres
Role of goblet cells in anal mucosa
Ease movement of faeces
Protects intensive from the effects of the acids and gases produced by enteric bacteria
How does immune system in healthy gut work
Peptidoglycan activates release of cytokines by mucosal epithelial cells, drafting immune cells e.g. dendritic cells
Dendritic cells becomes APCs and travel to lymphoid follicles to trigger an IgA-mediated response
How does fibre optimise activities of the colon
Softens stool
Increases power of colonic contractions
Mechanical digestion of large intestine
When chyme moves from ileum into caecum (ileocecal sphincter)
When caecum is distended w/ chyme, contraction of sphincter strengthen
When a hausturm is distended w/ chyme, its muscle contracts, pushing residue into next haustrum
How does chemical digestion occur in the large intestine
No digestive enzymes so done by bacteria
What is flatulence
Excessive flatus
Composition of faeces
Undigested food residue
Unabsorbed digested substance
Millions of bacteria
Old epithelial cells
Inorganic slats
Water to let it pass smoothly out of the body
What is defecation
Mass movement forces faeces from the colon into the rectum, scratching rectal wall and provoking defecation reflex
Defecation reflex
Parasympathetic reflex
Contracts sigmoid colon , rectum and eternal anal sphincter, relaxes internal
Faeces in anal canal triggers signal, allowing you to choose to open external anal sphincter
If you delay defecation, takes a few secs to relax
What happens if defection is delayed an extended time
Addn water is absorbed, making faeces firmer —> constipation
Dysentery
Severe diarrhoea w. blood or mucous
Blood test findings for IBD
Anaemia
Thrombocytosis
Rased ESR and CRP
Hypoalbuminaemia
Raised fecal calprotectin
Infective ddx for IBD
Gastroenteritis/ dysentrey
C diff
Amoebiasis
TB
CMV
Histoplasmosis
Non-infective ddx for IBD
Appendicitis
Diverticulitis
Carcinoma
Ischaemic colitis
Endometriosis
Indications of aminosalicylates
Indication of remission in active UC (not CD)
Maintenance of remission in uC (not CD)
Post-op prophylaxis in CD
Smoking
Mesalazine
Thiopurines
Metronidasole 3/12
(Biologics)
Episcleritis in IBD
Asymptomatic to itching and barring
Treat IBD and use steroid drops
Uveitis and IBD
Px w/ eye pain, blurred vision, photophobia
Doesn’t correlate w/ IBD activity
Treat w/ topical/ systemic steroids
Erythema noduosum and IBD
Seen in 15% of IBD pts
Mirrors IBD activity
Treat IBD and use steroids
Lower GI motility symptoms
Diarrhoea
Constipation
Definition of diarrhoea
Passage of loose/ watery stool, typically 3x/ day
Reduced consistency/ increased freq
Time period for diarrhoea - definitions
A/c - 14 days or less
Persistent - 15-30 days
C/c - 30+ days
What causes increased water content of stool in diarrhoea
Impaired water absorption and/or
Active water secretion by the bowel
What is a/c diarrhoea usually due to
Infections - viral, bacterial, protozoal
Drugs
Osmotic diarrhoea - pathophys
Water is drawn into or retained in the bowel due to presence of solutes within the lumen due to indigestion of poorly absorbed solutes or malabsorption
What type of diarrhoea can be reduced by fasting
Osmotic
Causes of secretory diarrhoea
Bacterial endotoxin
Stimulant laxatives
Hormones
Bile acid malabsorption
Mucosal infl
Rectal villous adenoma
Secretory diarrhoea
Disruption of epithelial electrolyte transport so water build up
Treatment of diarrhoea
Treat underlying disorder
Opiates
Anti-secretory drugs - octreotide (SST analogue)
Opiates for diarrhoea
Decreases urgency, bowel freq and stool volume
Codeine phosphate, loperamide
U&E’s changes w/ diarrhoea
Low potassium
Urea increases, before creatinine
Definition of constipation
Slow colonic transit, impaired rectal emptying or both
3x/day - 3x/ week
Treatment of constipation
General measure
Bulk forming laxatives
General measure for constipation
Identify anatomical abnormalities
Identify biochem causes
Stop constipating drugs
Exercise
Increase fluid intake
Increase dietary fibre - (SE: bloating, flatulence)
What are bulk forming laxative used for
Mild constipation
Improves bowel freq rather than consistency / straining
Examples of bulk forming laxatives
Ispaghula
Sterculia
When are stimulant laxatives used
C/c constipation
Increases motility, freq and improves consistency
Examples of stimulant laxatives
Biscadoyl
Senna
Sodium picosulphate
Examples of stool softeners
Sodium docusate
Liquid paraffin
Arachis oil enema
Examples of osmotic laxatives
Lactulose
Mg salts
Lactulose as an osmotic laxative
Decreases colic pH by generation of fatty acids and fermentation products
SE - bloating, flatulence
Novel therapies for constipation
Prucalopride
Lubiprostone
Linaclotide
Naloxegol
Epidemiology of colorectal cancer
2nd commonest cause of cancer death
Age - 85-89
Sex distribution same as colon cancer
Highest Unicode in Europe and North America
Prognosis of colorectal cancer
10 yrs survival 55%
>20% px w/ distant mets
Surgery in 80% but half have recurrence
Risk factors for colorectal cancer
Genetic syndromes
Diet - fat and cholesterol, red meath
Obesity
Alcohol
DM
Smokers
FAP
Familial Adenomatous Polyposis
Autosomal dominant
Characterised by hundreds of adenomatous polyps
FAP and colorectal cancer
Risk of cancer exceeds 90% by 70, if no surgery
Prophylactoc surgery 16025 yrs
Exctracolinc manifestations of FAP
DerMoid tumours/ duodenal adenomas
Congenital hypertrophy retinal pigment epithlioma (CHRPE)
HNPCC
Hereditary Non-polyposis Colorectal cancer
Autosomal dominant
HNPCC and CRC
Lifetime risk 85%
CRC < 45, R sided lesions
Colonoscopy screening every 2 yrs
Geneses related to CRC
ACP
CTNB1
AXIN1
Aetiology of CRC
Adenoma- carcinoma sequences
UBD
Acromegaly - related to serum growth hormones
Gastric surgery - changes to bile acid
Irradiation
Where do most cancer in large bowel px
Caecum
Sigmoid colon
Rectum
Diff routes of CRC px
Bowel screening
Symptomatic - 2 WW, emergency px
Bowel screening for CRC
Faecal occult blood & colonoscopy [FIT] - Every 2 yrs for those 60-75
Flexi sig
Clinical features of CRC
CIBH
Rectal bleeding
Anaemia
Abdo pain
Tenesmus
Wt loss
Emergency px of CRC
Seen in 25%
Obstruction
Peritonitis
Bleeidng
Evaluation of CRC pts
Hx and exam
Rectal exam
Sigmoidoscopy
Colonoscopy
Staging - CT/ US/ MRI
Bloods - CEA
When is colonic stenting used
Pt w/ metastatic disease, who have large bowel obstruction
Occasionally in benign strictures
Possible surgeries for CRC
R or L hemicolectomy
Resection w/ colostomy
Pan proctocolectomy and ileostomy
Sub-tital colectomy
Defunctiong stoma
Complication from surgery for CRC
Anastomotic leak
Wound infections
DVT/ PE
Bleeding
Nerve injury
Stoma complications
When to consider anastomotic leak following CRC surgery
Any deteriotatation in condn within 10 days
Elderly - cardiac/ reps sx
Raised CRP, metabolic acidosis
How doe we excl anastomotic leak following CRC surgery
CT w/ contrast
Methods of spread of CRC
Nodal
Vascular
Direct
Transcoelemic
Histopathology of anal cancer
90% SCC
Risk factors for anal cancer
HPV - type 16/18
Smoking/ lowered immunity - hIV
Hx cervical cancer/ large no. sexual partners
Faecal incontinence
Inability to control bowel movements causing faeces to leak unexpectedly from rectum
How can we classify causes of faecal incontnences
Trauma
Neuro
Colorectal causes
Traumatic causes of faecal incontinence
Iatrogenic
Obstetric
Neuro causes of faecal incontinence
Cauda equina
MS
Neuropathy
Colorectal causes of faecal incontinence
Hx
Neuro problems
Rectal exam
QoL - Wexner score
Obstructive defecation syndrome
Difficulty in evacuation which may or may not be associated w/ constipation
Causes of ODS
Pain
Rectocele
Rectal invagination/ intussecpition
Internal anal sphincter
Anal stenosis
Faecal impaction
Rectal/ anal cancer
Clinical features of ODS
Incomplete or unsuccessful of emptying
Rectal pain
Prolonged episodes of evacuation
Prolapse
Diagnostic approach for ODS
Clinical assessment
Colonoscopy/ CTC - excl tumours
Colonic transit studies
Defecation proctogram
Mx of ODS
Conservative
Stool consistency - fibre
Laxative/ loperamide/ codeine
Rectal enema
Biofeedback
Surgery
Surgical mx of faecal incontinence
Sphincter repair
Artificial sphincter
Anal plugs
Sacral nerve stimulation
Stoma
Sacral nerve stimulation for faecal incontinence
Low voltage of sacral nerves, S3
Significant improvement (50%)
70-80% success rate
Surgical mx of ODS
Anterior rectocele repairs
Rectopexy
How can rectal prolapse be classified
Complete - full thickness
Partial - only mucosa (circumferential, only portion of mucosa)
Clinical features of rectal prolapse
Prolapse during straining, coughing, lifting weights
Constipation (60%)
Faecal incontinence
Mucous discharge
Bleeding
Pain
Ix for rectal prolapse
Assess general health of pt
Flex sig/ colonoscopy
Proctogram, if prolapse not obvious
Mx of rectal prolapse
Reduce oedema - ice wrapped in cloth or sugar
Usually surgical - abdo vs perineal approach
Delormes procedure (perineal)
Rectopexy (abdo)
Referral for CRC
40+ w/ unexplained wt loss and abdo pain
50+ w/ unexplained rectal bleed
60+ w/ IDA and CIBH
Occult blood in faeces
Sx of diverticular disease
Abdo pian in LLQ
Constipation, diarrhoea or rectal bleed
Tenderness in LLQ
Which pts are most likely to have recurrence in diverticular
Higher in young pts
Pts w/ abscess formation
Px of IBS
Abdo pain - relived by defecation
Altered bowel habit
Abdo distension
Rectal mucous
No nocturnal sx
Classification of IBS
Constipation predominant - IBS-C
Diarrhoea predominant - IBS-D
Mixed bowel habits - IBS-M
Neither predominant - IBS-U
Mx of IBS-D
Avoid legumes and dietary fibre
Anti-diarrhoea drugs: loperamide, codeine, cholestyramine
If sx persist, amitriptyline in night
Mx of IBS-C
High fibre diet
Laxatives: lactulose, ispaghula
Epidemiology of iBS
10-20% of general pop.
More common in young women
Stress associated w/ episodes of IBS
Ix for IBS
Bloods - FBC, U&Es, CRP, TSH, tTG/ IgA
Faecal calprotectin
-ve findings on endoscopy, X-ray, blood tests
Dx criteria for IBS
Recurrent bro pain for at least 1/7 in the last 3/12
Related to defecation
Associated w/ change in form/ freq of stool
Px of ascariasis infection
Depends on parasite burden, can be asymptomatic
Malabsorption
Rare, obstruction
Biliary sepsis/ obstruction
Ix for ascariasis
Stol microscopy
Ultrasound
ERCP
Mx of ascaris
Antiparasitic agents - albendazole, ivermectin, melbendazole
MOA of bendmidiazoles
Degeneration of parasites cytoplasmic microtubules
Blocking of glucose uptake –> depleted energy stores –> reduced ATP formation
MOA of ivermectin
Similar to macrolide button antibacterial effect
Increased cell membrane permeability to Cl- –> cellular hyper polarisation –> paralysis and death
Where do adult hookworms live
Lumen of small intestine, where they attach to intestinal wall
Px of hookworms
Transient pneumonitis
Epigastric pain, diarrhoea, anorexia, eosinophilia (small bowel)
C/c abdo pain
IDA
Malnutrition in children
Ix for hookworms
Stool microscopy
Expelled adult worms
PCR
Mx for hookworms
Iron replacement
Anti-helminthic therapy - albendazole, mebendazole, pyrantel pamoate
Prevention strategies for hookworms
Annual deworming - targeting children and pregnant women
Vaccine development
Immune reaction to eggs and larvae seen in schistosomiasis
Skin rash (cellular infiltration of skin) - ‘swimmers itch’
Katyama syndrome (circulating immune complexes)
Granuloma formation in tissues
Hepatomegaly
Ix for schistosomiasis
Microscopy
Serology
Mx for schistosomiasis
Praziquantel - adults worms only, may work w/ artemisinin
Oxamniquine
Prevention of schistosomiasis
No swimming in fresh water
Vaccine in development
Non-spp px of tapeworms
Reduced nutrient absorption
Altered gut motility
What blood finding may be seen in c/c tapeworm infection
Megaloblastic anaemia
Ix for tapeworms
Microscopy:
Stool - eggs
Tissue bx
Mx of tapeworms
Praziquantel
Niclosamide
Prevention of tapeworm infection
Met inspection
Good animal husbandry
Adequate cooking
Relevant protozoa in GIT
Entamoeba histiolytica
Giardia intestinalis
Cryptospporidium hominis
Features of intestinal protozoa - amoebiasis
Entamoeba histolytic can attach to intestinal walls with the aim to perforate and enter blood vessels (liver, lungs, brain 15-20cm)
Px of amoebiasis
Abdo pain, NO fever
Later at abscess disease (2-3/12) - fever, v raised ESR
Dx of amoebiasis
Surgery
CT
Mx of amoebiasis
Metronidozale
Paromomycin
Px of Giardia
Asymptomatic
A/c self limiting diarrhoea w/ abdo cramps, bloating and flatulence
C/c diarrhoea, malasbsorption and wt loss
Ix for giardia
Microscopy
Antigen detection (EIA)
Treatment for giardiasis infections
Metronidazole
CEA
Carcinoembryonic antigen
Detected in blood and elevated in CRC
Prevention of giardiasis
Water quality
Features of crytosporidium infection
Seen in <5s and immunocompromised
Source is contaminated water
Diarrhoea - a/c and self-limiting
No effective drug mx
Px of enteriobiasis
Asymptomatic
Pruritus ani
Vaginal discharge
Dysuria and enuresis
Non-spp: anorexia, irritability, abdo pain
Ix for enterobiasis
Sellotape slide - adult worm
Stool microscopy - eggs
Mx for enterobiasis
Albendazole
Mebendazole
Ivermectin
Piperazine
Monitor household contacts and take good hygiene measures
Bacterial perinanal infections
Perianal abscesses
Perianal fistulae
Pilonidal abscesses
LGV
Lymphogranuloma venereum
STD caused by chlamydia
Seen in MSM
Px of LGV
Ulcerative proctitis
1st stage - single skin lesion
2nd stage - painful, enlarged inguinal lymphadenopathy
Px of rectal gonorrhoea
Usually asymptomatic, but some pts have a/c proctitis
Sx are anal pruritus, tenesmus, purulent discharge or rectal bleeding
Viral perianal infections
HSV
HZV
Warts - HPV
Features of SIRS
HR 90+
RR 20+
Temp <36 OR >38
WCC >12,000 OR <4,000
Sepsis = 2 of above w/ suspected source of infection
Sepsis 3qSOFA
RR 22+
Change in mental state
SBP <100mmHg
Score of 2 or above w/ suspected infection
NEWS and sepsis
Score of 5 or more in the presence of known infection, signs and sx of infection
Acute abdomen
Abdo pain of less than 7/7 duration needing hosp admission
Where is pain experienced in appendicitis
Visceral peritoneum around umbilicus then RIF, parietal peritoneum
Why might pts w/ cholecystitis have pain in R shoulder
Phrenic nerve
Features of peritoneal infl
Diffuse tenderness (widespread) or localised
Rebound tenderness
Guarding - spasms of muscles
Ix for a/c abdo
Bloods
Urine
XR - erect CXR, AXR
ECG (inferior MI?)
Cultures
CT/ US
Bloods for a/c abdomen
FBC
U&Es
Amylase
CRP
LFT
Clotting
Blood gases
Urine ic for a/c abdomen
Disptick
Pregnancy tests
Sepsis 6
Blood cultures
Urine Output
Iv fluids
Abx
Lactate
Oxygen
Condns giving rise to intra-ab sepsis
Biliary
A/c appendicitis
A/c diverticulitis
Perforations - DU, diverticula, appendix
Post-op leak
Ischaemic bowel
When is early operation indicated in a/c abdomen
A/c appendicitis
Perforations
Ischaemic bowel
Theatre after limited resus/ ix
Which factors are considered in decision making process for a/c abdomen
Haemodynamic status
Rigid/ non-rigid - abdomen
Poorly/ well localised
Pt comorbidities / fitness for operation
General measures for pts admitted w/ a/c abdomen
Analgesia
IV fluids
Oxygen
Abx
Catheter insertion
VTE prophylaxis
FluId balance
NG pan
Decide if NBM
Imaging for appendicitis
US scan pelvis - first line in children and pregnant women
Contrast enhanced CT
What is the peritoneal cavity lined with
Serous membrane that serves as conduit for fluids
Peritoneal cavity in M vs F
Cavity closed in males and open in females
Intra peritoneal organs
Organs completely or almost completely enclosed by peritoneum
Examples of intraperitoneal organs
Stomach
Liver
GB
Transverse colon
Jejunum
Ileum
Caecum/ sigmoid colon
Duodenum (1st part)
Examples of retro-peritoneal organs
Duodenum (2nd, 3rd, 4th)
Ascending colon
Descending
Pancreas
Kidneys
Retro-peritoneal organs
Organs that are located mostly or completely behind the posterior parietal peritoneum
Role of normal flora in abdomen
Competition for nutrients and mucosal binding sites
Gut motility
Local pH
Bile flow
Production of antimicrobial substances
When should rectal prolapse be referred for surgery
Irreducible or recurrent
Substantial incontinence
Obstructed defectaion
