Gastro Flashcards
Gastrin
G cells in antrum of the stomach
stimulus - * Stomach Distension
* extrinsic nerves Inhibited by:
* low antral pH * somatostatin
actions - ↑ HCL= ↑acidity, pepsinogen and IF secretion, ↑ gastric motility, ↑ gastric mucosa breakdown (trophic effect)
CCK
↑ secretion of enzyme-rich fluid from pancreas, contraction of gallbladder and relaxation of sphincter of Oddi, ↓ gastric emptying, trophic effect on pancreatic acinar cells, induces satiety
Secretin
↑ secretion of bicarbonate-rich fluid from pancreas and hepatic duct cells, ↓ gastric acid secretion, trophic effect on pancreatic acinar cells
VIP
Stimulates secretion by pancreas and intestines, inhibits acid and pepsinogen secretion
Somatostatin
↓ acid and pepsin secretion, ↓ gastrin secretion, ↓ pancreatic enzyme secretion, ↓ insulin and glucagon secretion
inhibits trophic effects of gastrin, stimulates gastric mucous production
Principle mediators of acid secretion
Gastrin
* V agal stimulation
* Histamine
Factors increasing acid secretion
Gastrinoma
* Small bowel resection (removal of inhibition)
* Systemic mastocytosis (elevated histamine levels)
* Basophilia
Factors decreasing acid secretion
Drugs: H2-antagonists, PPIs
* Hormones: secretin, VIP, GIP, CCK
Pharyngeal Pouch
posteromedial diverticulum or herniation through Killian’s dehiscence. Killian’s dehiscence is a triangular area in the wall of the pharynx between the thyropharyngeus and cricopharyngeus muscles. It is more common in older patients and is 5 times more common in men
Pharyngeal Pouch Features
- Dysphagia
- Regurgitation
- Aspiration
- Neck swelling which gurgles on palpation
- Halitosis (noticeably unpleasant odors exhaled in breathing)
Travellers’ diarrhea
may be defined as at least 3 loose to watery stools in 24 hours with or without one or more of abdominal cramps, fever, nausea, vomiting or blood in the stool. The most common cause is Escherichia coli
Escherichia coli
Common amongst travellers
Watery stools
Abdominal cramps and nausea
Giardiasis
Prolonged, non-bloody diarrhea
Cholera
Profuse, watery diarrhea
Severe dehydration resulting in weight loss Not common amongst travellers
Shigella
Bloody diarrhea
Vomiting and abdominal pain
Staphylococcus aureus
Severe vomiting
Short incubation period
Campylobacter
Most common cause in UK
A flu-like prodrome
followed by crampy abdominal pains
fever and diarrhoea which may be bloody Complications include Guillain-Barre syndrome
Bacillus cereus
Two types of illness are seen
vomiting within 6 hours
diarrhoeal illness occurring after 6 hours
Amoebiasis
Gradual onset bloody diarrhea abdominal pain and tenderness may last for several weeks
Incubation period
1-6 hrs: Staphylococcus aureus, Bacillus cereus
* 12-48 hrs: Salmonella, Escherichia coli
* 48-72 hrs: Shigella, Campylobacter
* > 7 days: Giardiasis, Amoebiasis
Clostridium difficile
Features:
Diarrhea
* Abdominal pain
* If severe, toxic dilatation
* Sometimes seen in nosocomial outbreaks
Clostridium difficile
pseudomembranous colitis.
clindamycin is historically associated with causing Clostridium difficile
Second and third generation cephalosporins (e.g ciprofloxacin) are now the leading cause.
Clostridium difficile
Diagnosis
Management:
is made by detecting Clostridium difficile TOXIN (CDT) in the stool
Management:
* ORAL metronidazole for 10-14 days
* If severe or not responding to metronidazole then ORAL vancomycin may be used.
* For life-threatening infections a combination of oral vancomycin and intravenous metronidazole
should be used
Bacterial overgrowth
gold standard investigation of bacterial overgrowth is small bowel
aspiration and culture.
Other possible investigations include:
* Hydrogen breath test
* 14c-xylose breath test
* 14c-glycocholate breath test: used increasingly less due to low specificity
Exotoxins
enerally released by Gram positive bacteria with the notable exceptions of Vibrio
cholerae and some strains of E. coli
Diphtheria toxin
diphtheric membrane’ on tonsils caused by necrotic mucosal cells.
Systemic distribution may produce necrosis of myocardial, neural and renal tissue.
Staph. aureus exotoxins
lead to acute gastroenteritis, toxic shock syndrome and Staphylococcal scalded
skin syndrome
Cholera toxin
causes activation of adenylate cyclase leading to ↑ in cAMP levels, which in turn leads to ↑ chloride secretion.
Acute treatment of variceal hemorrhage
ABC: patients should ideally be resuscitated prior to endoscopy
* Correct clotting: FFP, vitamin K
* Vasoactive agents: terlipressin is currently the only licensed vasoactive agent. It has been shown to be of benefit in initial hemostasis and preventing rebleeding. It acts by Constriction of the splanchnic vessels (contraindicated in
IHD, use Octreotide as alternative)
* Prophylactic antibiotics have been shown in multiple meta-analyses to ↓ mortality in patients
with liver cirrhosis
Prophylaxis of variceal hemorrhage
Propranolol: ↓ rebleeding and mortality compared to placebo
* Endoscopic variceal band ligation (EVL) is superior to endoscopic sclerotherapy. It should be
performed at two-weekly intervals until all varices have been eradicated. Proton pump inhibitor cover is given to prevent EVL-induced ulceration
Barrett’s Esophagus
efers to the metaplasia of the lower esophageal mucosa, with the usual squamous epithelium being replaced by columnar epithelium. There is ↑ risk of esophageal adenocarcinoma, estimated at 50-100 folds.
Barrett’s Esophagus
Histological features:
Histological features: the columnar epithelium may resemble that of either the cardiac region of the stomach or that of the small intestine (e.g. with goblet cells, brush border)
Barrett’s Esophagus Management
Management
* Endoscopic surveillance with biopsies
* Low grade dysplasia: high-dose proton pump inh
GERD investigation
24hr esophageal pH monitoring is gold standard investigation in GERD
Indications for upper GI endoscopy:
- Age > 55 years
- Symptoms > 4 weeks or persistent symptoms despite treatment
- Dysphagia
- Relapsing symptoms
- W eight loss
Pain on swallowing (odynophagia)
typical of esophageal candidiasis, a well documented
complication of inhaled steroid therapy
Esophageal cancer
Dysphagia
Dysphagia may be associated with weight loss, anorexia or vomiting during eating Past history may include Barrett’s esophagus, GERD, excessive smoking or alcohol use
Oesophagitis
candidiasis
here may be a history of HIV or other risk factors such as steroid inhaler use
Achalasia
Dysphagia of both liquids and solids from the start
Heartburn
Regurgitation of food - may lead to cough, aspiration pneumonia etc
Pharyngeal pouch
More common in older men
Represents a posteromedial herniation between thyropharyngeus and cricopharyngeus muscles
Usually not seen but if large then a midline lump in the neck that gurgles on palpation
Typical symptoms are dysphagia, regurgitation, aspiration and chronic cough. Halitosis may occasionally be seen
Systemic sclerosis
Other features of CREST syndrome may be present, namely Calcinosis, Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly, Telangiectasia
Myasthenia gravis
Other symptoms may include extraocular muscle weakness or ptosis Dysphagia with liquids as well as solids
Globus hystericus
May be history of anxiety Symptoms are often intermittent
Achalasia:
Clinical features
Dysphagia of BOTH liquids and solids
* Typically variation in severity of symptoms
* Heartburn
* Regurgitation of food - may lead to cough, aspiration pneumonia etc
* Malignant change in small number of patients
* 7% ↑ in risk of squamous cell carcinoma
The gold standard test for achalasia
osophageal manometry
Achalasia Manometery finding
Loss of peristalsis in distal esophagus, failure of LOS to relax during swallowing and (i.e ↑ residual relaxing pressure)
Loss of peristalsis in distal esophagus BUT ↓ resting LOS p
scleroderma Manometery finding
Loss of peristalsis in distal esophagus BUT ↓ resting LOS pressure
Achalasia: investigations
Manometry: excessive LOS tone which doesn’t relax on swallowing - considered most important diagnostic test
* Barium swallow shows grossly expanded esophagus, fluid level
* CXR: wide mediastinum, fluid level
Achalasia: Treatment
Treatment
* Intra-sphincteric injection of botulinum toxin
* Heller cardiomyotomy
* Balloon dilation
* Drug therapy has a role but is limited
by side-effects
Boerhaave’s syndrome -
Features:
Features:
* Complete transmural (full-thickness) laceration or perforation of the esophagus, distinct from Mallory-Weiss syndrome, a nontransmural esophageal tear also associated with vomiting.
* Perforation is almost always on Left side of Lower esophagus.
* Gastric contents enter the mediastinum and pleural cavity, if one were to perform a pleural fluid
aspirate; one is likely to aspirate gastric contents!
* ♂ > ♀ and typically between 50-70 years old
* Other clinical features that may suggest the diagnosis include odynophagia and surgical
emphysema in the neck
Boerhaave’s syndrome -
Causes:
Causes:
* Vomiting (against a closed glottis) in eating disorders such as bulimia
* Rarely: Extremely forceful coughing - Obstruction by food
Boerhaave’s syndrome Diagnosis:
Diagnosis:
* Radiographs show mediastinal gas, effusion, and later pneumothorax.
Esophagram is used to confirm leak, first with water-soluble contrast, then barium if no leak demonstrated.
Boerhaave’s syndrome Management:
Early operation after appropriate resuscitation offers the best chance of survival.
Dyspepsia: Causes
- NSAIDs
- Bisphosphonates * Steroids
The following drugs may cause reflux by reducing lower esophageal sphincter (LOS) pressure - Calcium channel blockers*
- Nitrates*
- Theophyllines
In 2004 NICE published guidelines for the management of dyspepsia in primary care.
Chronic gastrointestinal bleeding
* Progressive unintentional weight loss
* Progressive difficulty swallowing
* Persistent vomiting
* Iron deficiency anemia
* Epigastric mass
* Suspicious barium meal
Deciding whether urgent referral for endoscopy is needed
Recent in onset rather than recurrent and
* Unexplained (e.g. New symptoms which cannot be explained by precipitants such as NSAIDs)
and
* Persistent: continuing beyond a period that would normally be associated with self-limiting
problems (e.g. Up to four to six weeks, depending on the severity of signs and symptoms)
Helicobacter pylori
Gram negative bacteria associated with a variety of gastrointestinal problems, principally peptic ulcer disease
Helicobacter pylori eradication 7 day course of
H. pylori eradication 7 day course of:
* PPI + amoxicillin + clarithromycin, or
* PPI + metronidazole + clarithromycin
H pylori’s Associations
Peptic ulcer disease (95% of duodenal ulcers, 75% of gastric ulcers)
* Gastric cancer
* B cell lymphoma of MALT tissue (eradication of H pylori 80% causes regression)
* Atrophic gastritis
H Pylori tests
Urea breath test
Patients consume a drink containing carbon isotope 13 (13C) enriched urea
* Urea is broken down by H. pylori urease
* After 30 mins patient exhale into a glass tube
* Mass spectrometry analysis calculates the amount of 13C CO2
* Sensitivity 95-98%, specificity 97-98%
* Used to confirm eradication
H Pylori tests Rapid urease test
Rapid urease test (e.g. CLO test)
* Biopsy sample is mixed with urea and pH indicator
* Color change if H pylori urease activity
* Sensitivity 90-95%, specificity 95-98%
H Pylori tests Serum antibody
Serum antibody
* Remains positive after eradication
* Sensitivity 85%, specificity 80%
H Pylori tests Culture of gastric biopsy
Histological evaluation alone, no culture
* Sensitivity 95-99%, specificity 95-99%
Peutz-Jeghers syndrome
AD
autosomal dominant condition characterized by numerous hamartomatous polyps in the gastrointestinal tract. It is also associated with pigmented freckles on the lips, face, palms and soles.
Peutz-Jeghers syndrome Genetics
Autosomal dominant
* Responsible gene encodes serine threonine
kinase LKB1 or STK11
Peutz-Jeghers syndrome Features
- Hamartomatous polyps in GI tract (mainly small bowel)
- Pigmented lesions on lips, oral mucosa, face, palms and soles
- classical histological appearance of smooth muscle “arborisation”
- Intestinal obstruction e.g. Intussusception
- Gastrointestinal bleeding
Esophageal Cancer
Until recent time esophageal cancer was most commonly due to a squamous cell carcinoma but the incidence of adenocarcinoma is rising rapidly. Adenocarcinoma is now (since 2010) the most common type of oesophageal cancer and is more likely to develop in patients with a history of gastro-esophageal reflux disease (GERD) or Barrett’s.
The majority of tumours are in the middle third of the esophagus.
Esophageal Cancer
Squamous Cell Carcinoma
Risk factors:
* Smoking
* Alcohol
* Achalasia
* Plummer-vinson syndrome
* Rare: coeliac disease, scleroderma
* Sensetive to radiotherapy
Risk factors:Adenocarcinoma
GERD
* Barrett’s esophagus
Gastric cancer
Epidemiology
* Overall incidence is decreasing, but incidence of tumors arising from the cardia is increasing
* Peak age = 70-80 years
* More common in Japan, China, Finland and Columbia than the west
* More common in ♂s, 2:1
Gastric cancer - Associations
- H. pylori infection (although it is protective against esophageal cancer)
- Blood group A: gAstric cAncer
- Gastric adenomatous polyps
- Pernicious anemia
- Smoking
- Diet: salty, spicy, nitrates
- May be negatively associated with duodenal ulcer
Gastric cancer Investigation
Diagnosis: endoscopy with biopsy
* Staging: CT or endoscopic ultrasound - endoscopic ultrasound has recently been shown to be
superior to CT
Colorectal cancer:
Screening:
Most cancers develop from adenomatous polyps therefore a screening program could theoretically ↓ mortality
* Main techniques being evaluated are faecal occult blood (FOB) testing, sigmoidoscopy and colonoscopy
* Fecal occult blood testing is the only method to have been proven to ↓ mortality (by about 20%) in trials. Sensitivity can be ↑ by DNA analysis for the APC gene
Causes for a positive fecal occult blood testing are:
2-10%: cancer (colorectal cancer, gastric cancer)
* 20-30% adenoma or polyps
* Bleeding peptic ulcer
* Angiodysplasia of the colon
Colorectal cancer: Staging and Grading:
The Dukes staging system is widely employed for classifying colorectal cancers and is a useful predictor of survival. Tumour grade and depth of penetration are also important:
* Duke A (Stage I) defines a tumour confined to the bowel wall (i.e. mucosa and submucosa).
* Duke B (Stage II) invades through the muscle wall.
* Duke C (Stage III) involves lymph nodes.
* After this the patient presents with metastatic disease at distant sites (Stage IV).
colorectal cancer Prognostic indicators post complete resection includes:
Poorly differentiated histological type.
* Tumour adherence to adjacent organs.
* Bowel perforation.
* Colonic obstruction at the time of diagnosis.
* Venous invasion by the tumour.
Management:
- Surgical excision of a colonic carcinoma is the main treatment
- Adjuvant chemotherapy (5-fluorouracil and folinic acid) is warranted in high-risk stage II
Causes for a positive fecal occult blood testing are:
* 2-10%: cancer (colorectal cancer, gastric cancer)
* 20-30% adenoma or polyps
* Bleeding peptic ulcer
* Angiodysplasia of the colon
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colonic carcinomas and all stage III colonic carcinomas.
* The addition of oxaliplatin has been shown to improve survival in these patients in a large
multicentre trial (MOSAIC study), but the additional drug can cause a severe peripheral
neuropathy.
* Adjuvant radiotherapy is used in rectal carcinomas. This is combined with chemotherapy in
stage II and III rectal carcinomas to reduce the risk of local as well as metastatic relapse.
sporadic colon cancer
eries of genetic mutations. For example, more than half of colon cancers show allelic loss of the adenomatous polyposis coli (APC) gene. It is believed a further series of gene abnormalities e.g. activation of the K-ras oncogene, deletion of p53 and DCC tumour suppressor genes lead to invasive carcinoma
HNPCC,
utosomal dominant condition, is the most common form of inherited colon cancer.
Proximal colon cancer
Amsterdam criteria for HNPCC
At least 3 family members with colon cancer
* The cases span at least two generations
* At least one case diagnosed before the age of 50 years
HNPCC screening for ↑ risk group:
- Colonoscopy every 2 years from 20 to 40 years age then annually
- Check mutation in DNA or mismatched repair gene.
Familial Adenomatous Polyposis (FAP)
rare autosomal dominant condition which leads to the formation of hundreds of polyps by the age of 30-40 years
mutation in a tumour suppressor gene called adenomatous polyposis coli gene (APC), located on chromosome 5.
=total colectomy with ileo-anal pouch formation in their twenties.
Gardner’s syndrome
A variant of FAP called Gardner’s syndrome can also feature osteomas of the skull and
mandible,
jaw osteomas which give a “cotton-wool” appearance to the jaws,
as well as multiple odontomas, Congenital Hypertrophy of the Retinal Pigment Epithelium
(CHRPE)
NICE recommend the following patients are referred urgently (i.e. within 2 weeks) to colorectal services for investigation:
Patients > 40 years old, reporting rectal bleeding with a change of bowel habit towards looser stools and/or ↑ stool frequency persisting for 6 weeks or more
* Patients > 60 years old, with rectal bleeding persisting for 6 weeks or more without a change in bowel habit and without anal symptoms
* Patients > 60 years old, with a change in bowel habit to looser stools and/or more frequent stools persisting for 6 weeks or more without rectal bleeding
* Any patient presenting with a right lower abdominal mass consistent with involvement of the large bowel
* Any patient with a palpable rectal mass
* Unexplained iron deficiency anemia in men or non-menstruating women (Hb < 11 g/dl in
men, < 10 g/dl in women)
Zollinger-Ellison Syndrome
s condition characterized by excessive levels of gastrin, usually from a gastrin secreting tumour usually of the duodenum or pancreas.
30% MEN 1
Zollinger-Ellison Syndrome clinical presentation
typically presents with multiple gastroduodenal ulcers causing abdominal pain, diarrhea and malabsorption. High-dose proton pump inhibitors are needed to control the symptoms.
Zollinger-Ellison Syndrome
Diagnosis
Fasting gastrin levels, the single best screen test: done in 3 different days as the gastrin secretion is pulsatile
* Secretin stimulation test: considered +ve if there is ↑ in gastrin >200 pg/mL after secretin injection (Normally Secretin supresses gastrin, but in ZE, it simply shows that the source of gastrin is not the stomach and it is somewhere else like pancresae)
Zollinger-Ellison Syndrome Management:
- If not mets, surgical resection is the cure
- Octreotide can be used to alleviate symptoms with interferon and chemotherapy to attempt cure
non respectable tumor - PPI is used to control symptoms in actute stages
Gastric MALT Lymphoma
Associated with H. pylori infection in 95% of cases
* Good prognosis
* If low grade then 80% respond to H. pylori eradication
* Paraproteinemia may be present