Lec 1 GIT Dr.Hassan aljumaily
Introduction :
oesophagus muscular 25 cm from the cricoid cartilage to the cardiac orifice of the stomach.
It has an upper and a lower sphincter. A peristaltic swallowing wave propels the food bolus
into the stomach.
* stomach acts retaining and grinding food, and then actively propelling it into the upper
small bowel.
Gastrin, histamine and acetylcholine are the key stimulants of acid secretion from gastric
parietal cells into the lumen of the stomach by a hydrogen–potassium adenosine
triphosphatase (ATPase) (‘proton pump’.
Protective factors
Bicarbonate ions, stimulated by prostaglandins, mucins and trefoil factor family (TFF)
peptides, together protect the gastroduodenal mucosa from the ulcerative properties of acid
and pepsin.
Small intestine
The small bowel extends from the ligament of Treitz to the ileocaecal valve .
Functions of the small intestine are:
• digestion of fat,pr and carb (mechanical, enzymatic and peristaltic)
• absorption – the products of digestion, water, electrolytes and vitamins
• protection against ingested toxins
• immune regulation.
Water and electrolytes:
In healthy individuals, fluid balance is tightly controlled, such that only 100 mL of the 8 litres
of fluid entering the gastrointestinal tract daily is excreted in stools.
Vitamins and trace elements.
Water-soluble vitamins are absorbed throughout the intestine.
Physical defence mechanisms
1- the gut lumen contains host bacteria ,mucins and secreted antibacterial products,
including defensins and immunoglobulins that help combat pathogenic infections
2- epithelial cells have relatively impermeable brush border membranes and passage
between cells is prevented by tight and adherens junctions.
Immunological defence mechanisms
Gastrointestinal mucosa-associated lymphoid tissue (MALT) constitutes 25% of the total
lymphatic tissue of the body and its the heart of adaptive immunity.
Colon
absorbs water and electrolytes. acts as a storage organ and has contractile activity.
Two types of contraction occur.
1-ring contraction which leads to mixing but not propulsion; this promotes absorption of
water and electrolytes.
2- Propulsive (peristaltic contraction) waves occur several times a day and propel faeces to
the rectum.
Intestinal microbiota ‘
refers to the microorganisms that live in a particular niche,many environmental factors that
can impact, including diet, drugs, physical activity, smoking, stress and natural ageing.
or imbalance between the different components of the intestinal microbiota has
A dysbiosis
been associated with diseases of the gastrointestinal tract, such as inflammatory bowel
disease and colorectal cancer; liver disease, including hepatocellular carcinoma; and
pathologies outside the gastrointestinal tract, such as diabetes, obesity, cardiovascular
disorders, cerebrovascular disorders, asthma
invex:
1-Plain X-rays
intestinal obstruction or paralytic ileus, where dilated loops of bowel and (in the erect
position) fluid levels
.Calcified lymph nodes, gallstones and renal stones can also be detected.
Chest X-ray erect :for suspected perforation,as it shows air under diaphragm
2-Barium study:
barium swallow and meal Motility disorders (achalasia and gastroparesis)
Perforation or fistula (non-ionic contrast)
- Barium follow-through: indicated for
♠Diarrhoea and abdominal pain of small bowel origin
♠ Possible obstruction by strictures
♠ Suspected malabsorption
♠Assessment of Crohn’s
-Barium enema
♠ Altered bowel habit
♠ Evaluation of strictures or diverticular disease
♠Megacolon
♠ Chronic constipation
3-Ultrasound Abdominal
masses
Organomegaly
Ascites
Biliary tract dilatation
Gallstones
Guided biopsy of lesions
4-Computed tomography (CT)
Assessment of pancreatic disease
Hepatic tumour deposits
Tumour staging
Assessment of lesion vascularity
Abscesses and collections
5- (MRI)
Hepatic tumour staging
MRCP
Pelvic/perianal disease
Crohn’s fistulae
Small bowel visualisation
6-CT–positron emission tomography (CT-PET)
Detection of metastases not seen on US or CT.
OGD:
•Dyspepsia in patients > 55 years of age or with alarm symptoms
• Atypical chest pain
• Dysphagia
• Vomiting
• Weight loss
• Acute or chronic gastrointestinal bleeding
• Screening for oesophageal varices in chronic liver disease
• Abnormal CT scan or barium meal
• Duodenal biopsies in the investigation of malabsorption and
confirmation of a diagnosis of coeliac disease
• Therapy, including treatment of bleeding lesions, banding/injection of
varices, dilatation of strictures, insertion of stents, placement of percutaneous
gastrostomies, ablation of Barrett’s oesophagus and
resection of high-grade dysplastic lesions and early neoplasia in the
upper gastrointestinal tract
COLONOSCOPY:
• Suspected inflammatory bowel disease
• Chronic diarrhoea
• Altered bowel habit
• Rectal bleeding or iron deficiency anaemia
• Assessment of abnormal CT colonogram or barium enema
• Colorectal cancer screening
• Colorectal adenoma and carcinoma follow-up
• Therapeutic procedures, including endoscopic resection, dilatation of strictures, laser,
stent
Endoscopic ultrasound (EUS) :
-visualisation through the wall of the gastrointestinal tract and into surrounding tissues, e.g.
the pancreas or lymph nodes.
-used to perform fine needle aspiration or biopsy of mass lesions. ----EUS is helpful in the
diagnosis of pancreatic tumours, chronic pancreatitis, pancreatic cysts, cholangiocarcinoma,
common bile duct stones, ampullary lesions and submucosal tumours.
-It also plays an important role in the staging of certain cancers, e.g. those of oesophagus
and pancreas.
- EUS can also be therapeutic, as in drainage of pancreatic fluid collections and coeliac plexus
block for pain management.
Capsule endoscopy .
it transmits images to a battery powered recorder worn on a belt round the patient’s waist.
After 8 hours, the capsule is excreted. Images from the capsule are analysed as a video
sequence and it is usually possible to localise the segment of small bowel in which lesions
are seen.
(MRCP) :
largely replaced (ERCP) in the evaluation of obstructive jaundice since it produces
comparable images of the biliary tree and pancreas, providing information that
complements that obtained from CT and
endoscopic ultrasound examination (EUS).
ERCP:
ERCP is used mainly in the treatment of a range of biliary and pancreatic diseases that have
been identified by other imaging
techniques such as MRCP, EUS and CT
Tests of infection
1-Bacterial Stool cultures
essential in the investigation of diarrhoea, especially when it is acute or bloody, in order to
identify pathogenic organisms
2-Serology
Detection of antibodies plays a limited role in the diagnosis of gastrointestinal infection
caused by organisms such as Helicobacter pylori, Salmonella species and Entamoeba
histolytica.
3-Breath tests
Non-invasive breath tests for H. pylori infection
otility
Oesophageal m
A barium swallow can give useful information about oesophageal motility.
Oesophageal manometry, often in conjunction with 24-hour pH measurements, is of value in
diagnosing cases of refractory gastro-oesophageal reflux, achalasia and non-cardiac chest
pain.