Anatomy, Physiology, Disorders and Overview of

Diagnostic Tests of the Gastro-intestinal Tract

Tom WaterhouseTom Waterhouse

Learning Objectives Anatomy and physiology of the GI

Tract Gastro-Oesophageal Reflux Disease

(GORD) Tests for diagnosis

Motility disorders Diagnosis via oesophageal

manometry

Anatomy and Physiology

The GI TractThe GI Tract

Cross Section

Lumen

Overview of Digestive System

Physical Digestion

Teeth - chewingTeeth - chewing Tongue - shapes bolusTongue - shapes bolus Saliva - lubricates bolusSaliva - lubricates bolus Peristalsis + SegmentationPeristalsis + Segmentation Longitudinal muscles + circular musclesLongitudinal muscles + circular muscles

Stomach also has oblique musclesStomach also has oblique muscles

Peristalsis

Segmentation

Physical digestion - locations

Mouth - mastication Mouth - mastication Oesophagus - peristalsisOesophagus - peristalsis Stomach - mastication & some Stomach - mastication & some

peristalsisperistalsis Small intestine - segmentation & some Small intestine - segmentation & some

peristalsisperistalsis Large intestine - peristalsisLarge intestine - peristalsis

Physical digestion - control valves

(Epiglottus)(Epiglottus) Upper oesophageal sphincter (UOS)Upper oesophageal sphincter (UOS) Lower oesophageal sphincter (LOS)Lower oesophageal sphincter (LOS) Pyloric sphincterPyloric sphincter (sphincter of Oddi)(sphincter of Oddi) Ileocecal valveIleocecal valve Anal SphinctersAnal Sphincters

Chemical Digestion Carbohydrate digestionCarbohydrate digestion

Salivary amylaseSalivary amylase Pancreatic amylase, lactase, sucrase, maltase etcPancreatic amylase, lactase, sucrase, maltase etc

Protein digestionProtein digestion Stomach Stomach

Denaturation by HCl, pepsinDenaturation by HCl, pepsin Small IntestineSmall Intestine

Trypsin, proteases, peptidases (pancreatic)Trypsin, proteases, peptidases (pancreatic) Bile salts (Sodium Bicarbonate) neutralise stomach acidBile salts (Sodium Bicarbonate) neutralise stomach acid

Fat DigestionFat Digestion Lipase (pancreatic)Lipase (pancreatic)

Anatomy and Physiology

The oesophagus & stomachThe oesophagus & stomach

Oesophagus Muscular tube about 25cm long.Muscular tube about 25cm long. Upper third is skeletal type muscle.Upper third is skeletal type muscle. Middle third is a mixture between Middle third is a mixture between

skeletal and smooth muscle.skeletal and smooth muscle. Lower third is smooth muscle.Lower third is smooth muscle. When empty the oesophagus collapses When empty the oesophagus collapses

into itself in longitudinal folds. These into itself in longitudinal folds. These folds flatten out when food is in transit.folds flatten out when food is in transit.

Oesophagus - 2 The lower oesophageal sphincter The lower oesophageal sphincter

separates the oesophagus from the separates the oesophagus from the stomach. stomach.

Extremely important for (in)digestion.Extremely important for (in)digestion. Stops acid coming back up from the Stops acid coming back up from the

stomach into the oesophagus and stomach into the oesophagus and causing heartburn.causing heartburn.

Stomach

Acidic, why?Acidic, why? Denature (unfold) proteinsDenature (unfold) proteins Pepsinogen -> PepsinPepsinogen -> Pepsin

Quiz Time

What is the link between:What is the link between:

Søren Sørensen

Acidity

What is pH?What is pH? Sorensen definition Sorensen definition

p[H] = - logp[H] = - log1010[H[H++]] IUPACIUPAC

pH = - logpH = - log1010aaH+H+

How is pH measured? Circuit with two electrodesCircuit with two electrodes Forms a cell when immersedForms a cell when immersed Nernst equation (reduction potential) Nernst equation (reduction potential)

E = EE = Eindind - E - Erefref = E = Eoo + (RT/F x ln a + (RT/F x ln aH+H+)) E = measured voltage ( mV )E = measured voltage ( mV )

E E indind = voltage of indicator electrode (mV) = voltage of indicator electrode (mV)E E refref = voltage of reference electrode (mV) = voltage of reference electrode (mV)EEoo = standard electrode potential (mV) = standard electrode potential (mV)R = gas constant ( 8.3144 J/K )R = gas constant ( 8.3144 J/K )T = absolute temperature ( K )T = absolute temperature ( K )F = Faraday's constant ( 96485.31 Coulombs )F = Faraday's constant ( 96485.31 Coulombs )

How is pH measured(2)? E = EE = Eoo + (RT/F x ln a + (RT/F x ln aH+H+)) E = EE = Eoo + (2.303 x RT/F x log + (2.303 x RT/F x log1010 a aH+H+)) But pH = -logBut pH = -log1010 a aH+H+

pH = (EpH = (Eoo-E)/(2.303*RT/F)-E)/(2.303*RT/F) EEo o is constant, RT/F is constant at constant temperature is constant, RT/F is constant at constant temperature

(25.693 mV at 25(25.693 mV at 25ooC)C) Because activity is hard to quantify, pH is defined in Because activity is hard to quantify, pH is defined in ISO 31-ISO 31-

8:1992, superceded by ISO/IEC 80000-9:2009 with 8:1992, superceded by ISO/IEC 80000-9:2009 with reference to standard solutionsreference to standard solutions

How is pH measured(3)? - Glass electrode

1.1. Glass sensing bulbGlass sensing bulb2.2. AgCl precipitate AgCl precipitate 3.3. 0.1 0.1 mol/Lmol/L HCl for pH electrodes HCl for pH electrodes 4.4. internal AgCl/Calomel electrodeinternal AgCl/Calomel electrode5.5. non-conductive body non-conductive body 6.6. reference electrode, usually same as reference electrode, usually same as

447.7. Porous (eg ceramic) junction with Porous (eg ceramic) junction with

studied solutionstudied solution

How is pH measured(4)? - Equivalent circuit

pH Electrodes Glass

Broad accurate response (gold standard) Fragile

Antimony Robust Smaller Low cost Linear between pH~1 and 10

pH Electrodes - Antimony vs Glass

Summary

Anatomy, Physiology of GI tractAnatomy, Physiology of GI tract What is acidityWhat is acidity How we measure itHow we measure it

Gastro-oesophageal Reflux Disease and 24hr Ph Studies.

Gastro-oesophageal Reflux Disease - GORD

Stomach contents ==> oesophagus via Stomach contents ==> oesophagus via LOS.LOS.

pH (Stomach contents) normally < 4 pH (Stomach contents) normally < 4 Typically pH~2.Typically pH~2.

Digestion of oesophagus!Digestion of oesophagus! 24 hour pH studies are performed to 24 hour pH studies are performed to

determine the levels of acid reflux.determine the levels of acid reflux.

GORD- Paediatric Complications/referral Criteria VomitingVomiting ApnoeaApnoea De-saturationDe-saturation Chronic coughChronic cough Recurrent chest infectionsRecurrent chest infections Failure to thrive/ gain weightFailure to thrive/ gain weight Colour changesColour changes

GORD- Adult Complications/referral Criteria VomitingVomiting RegurgitationRegurgitation HeartburnHeartburn Epigastric/ chest painEpigastric/ chest pain Barrett’s epitheliumBarrett’s epithelium

Oesophageal Ph Study - 1 This can be performed on both adults and

paediatrics. Normally lasts 24 hours. All medication that affects stomach acid is stopped

prior to the investigation. This can be up to 7 days in some instances.

Reports on the % time the ph measured drops below pH4.

Currently this tests involves the use of a naso-gastric catheter which is positioned in the oesophagus above the LOS.

Oesophageal Ph Study - 2 Catheter placement is different for adults and Catheter placement is different for adults and

paediatrics.paediatrics. Adults- catheter is placed 5cm above the Adults- catheter is placed 5cm above the

LOS.LOS. Results from manometry.Results from manometry. HPZ FormulaHPZ Formula

Paediatrics- catheter is placed 2.5cm Paediatrics- catheter is placed 2.5cm above the LOS.above the LOS.

Modified Strobel regression formula.Modified Strobel regression formula. Occasionally checked using CXR.Occasionally checked using CXR.

Oesophageal Ph Study - 3 Strobel Regression Fit (Paediatrics)

5 + 0.252 x Child’s Height(cm)=___x 0.87 HPZ formula for use in adults (Not commonly

used): Mx x 0.4 + 33

(bone at top of rib cage to Xiphi-sternum) Cx x 0.4 + 30

(chin to Xiphi-sternum) Add the above and divide by 2.

Oesophageal pH study - 4 Calibration of the probe is performed Calibration of the probe is performed

using buffer solutions at pH values of 1 using buffer solutions at pH values of 1 or 4 and 7.or 4 and 7.

Pre and post calibration is performed to Pre and post calibration is performed to check for any drift during the 24 hour check for any drift during the 24 hour period of the test.period of the test.

Oesophageal Ph Study - 5 Paediatric results based on published criteria Paediatric results based on published criteria

from the RHSC (Glasgow).from the RHSC (Glasgow). Normal – below 5%.Normal – below 5%. Borderline – between 5 and 10%.Borderline – between 5 and 10%. Abnormal – over 10%.Abnormal – over 10%.

Adult resultsAdult results In the West of Scotland and elsewhere, In the West of Scotland and elsewhere,

Demeester and Johnson scores above Demeester and Johnson scores above 14.7214.72

Demonstrate Catheter

Wireless pH monitoring systems

Medtronic developed Medtronic developed an FDA approved an FDA approved wireless pH wireless pH monitoring device, the monitoring device, the Bravo pH Bravo pH Measurement SystemMeasurement System (now sold by (now sold by Given Given Imaging, Ltd., Israel)Imaging, Ltd., Israel)

Wireless pH monitoring systems

Deployment is achieved Deployment is achieved with suction that pulls with suction that pulls esophagealesophageal mucosa into mucosa into a small well on the side a small well on the side of the probe, after whichof the probe, after which

the metallic retaining bar the metallic retaining bar is triggered to pierce the is triggered to pierce the suctionedsuctioned tissue and the tissue and the placement catheter is placement catheter is withdrawn. withdrawn.

Acid Suppression Therapies Gaviscon (infant & adult).Gaviscon (infant & adult). Ranitidine (H2 receptor antagonist) (Zantac).Ranitidine (H2 receptor antagonist) (Zantac). Proton pump inhibitors.Proton pump inhibitors.

Esomeprazole (Nexium).Esomeprazole (Nexium). Omeprazole (Losec).Omeprazole (Losec). Lansopazole (Zoton).Lansopazole (Zoton). Pantoprazole (Protium).Pantoprazole (Protium).

Surgery - Nissen Fundoplication – tightening of Surgery - Nissen Fundoplication – tightening of the lower oesophageal sphincter.the lower oesophageal sphincter.

Acid Suppression Therapies cont.

Oesophageal Motility Disorders

Examples of Oesophageal Motility Disorders

DysphagiaDysphagia Oesophageal spasmOesophageal spasm AchalasiaAchalasia Hypercontractile distal oesophagusHypercontractile distal oesophagus

(nutcracker oesophagus)(nutcracker oesophagus) StrictureStricture CarcinomaCarcinoma

Dysphagia Defined asDefined as

the inability to swallow or the inability to swallow or the sensation of the obstruction of food the sensation of the obstruction of food

between mouth and stomach.between mouth and stomach. It can also be used to describe difficulty in It can also be used to describe difficulty in

swallowing and occurs from paralysis or a swallowing and occurs from paralysis or a weakness of the muscles in the soft palate. weakness of the muscles in the soft palate.

This can occur after stroke or in certain This can occur after stroke or in certain neurological disorders.neurological disorders.

Oesophageal Spasm Oesophageal spasm is characterised by Oesophageal spasm is characterised by

repetitive non-peristaltic contractions of repetitive non-peristaltic contractions of the oesophageal smooth musclesthe oesophageal smooth muscles

Contractions can either be spontaneous Contractions can either be spontaneous or triggered by swallowingor triggered by swallowing

Unknown causeUnknown cause

Achalasia the absence of oesophageal peristalsis the absence of oesophageal peristalsis

and a failure of the LOS to relax and a failure of the LOS to relax unknown cause unknown cause

may be associated with damage to may be associated with damage to the nerve fibers of the myenteric the nerve fibers of the myenteric plexus supplying the oesophagus plexus supplying the oesophagus

Hypercontractile Distal Oesophagus

Commonly referred to as nutcracker Commonly referred to as nutcracker oesophagus.oesophagus.

High distal pressures measured in the High distal pressures measured in the oesophagus above 180mmHg.oesophagus above 180mmHg.

Can mimic cardiac chest pain.Can mimic cardiac chest pain. Buscopan or glycerol trinitrate have Buscopan or glycerol trinitrate have

been used as potential treatments.been used as potential treatments.

Stricture - 1 A stricture is a stenosis (narrowing) of A stricture is a stenosis (narrowing) of

the oesophageal lumen caused by the the oesophageal lumen caused by the formation of fibrous scar tissue. formation of fibrous scar tissue.

This can result from the inflammation This can result from the inflammation caused by acid reflux from the stomach. caused by acid reflux from the stomach. About 50% of oesophageal strictures About 50% of oesophageal strictures are associated with Barrett’s epithelium. are associated with Barrett’s epithelium.

Stricture –2 Barrett’s Epithelium

This occurs in reflux oesophagitis and is This occurs in reflux oesophagitis and is a columnar epithelium, which replaces a columnar epithelium, which replaces the normal squamous epithelium in the the normal squamous epithelium in the mucosa of the lower third of the mucosa of the lower third of the oesophagus.oesophagus.

Barrett’s epithelium carries a significant Barrett’s epithelium carries a significant risk of malignant transformation into risk of malignant transformation into adenocarinoma.adenocarinoma.

Barrett’s Epithelium

Carcinoma A carcinoma is a malignant tumour A carcinoma is a malignant tumour

consisting of epithelial cells. consisting of epithelial cells. 70% of oesophageal cancers are 70% of oesophageal cancers are

squamous cell carcinoma. squamous cell carcinoma. Nearly all the rest are adenocarinomas Nearly all the rest are adenocarinomas

using occurring from Barrett’s using occurring from Barrett’s epithelium.epithelium.

GORD Summary Motility disordersMotility disorders

DysphagiaDysphagia Oesophageal spasmOesophageal spasm AchalasiaAchalasia Hypercontractile distal oesophagusHypercontractile distal oesophagus

Tissue changesTissue changes StrictureStricture

Barrett’s OesophagusBarrett’s Oesophagus CarcinomaCarcinoma

Oesophageal Manometry

Oesophageal Manometry -1 This investigation uses a catheter which has a This investigation uses a catheter which has a

minimum of 4 pressure transducersminimum of 4 pressure transducers The investigation is used to determine:The investigation is used to determine:

The length of the LOS (by drawing catheter through The length of the LOS (by drawing catheter through LOS)LOS)

The pressure it exerts when asked to do nothingThe pressure it exerts when asked to do nothing Where the LOS is in relation to the nares of the Where the LOS is in relation to the nares of the

nose. This is used in the placement of the pH nose. This is used in the placement of the pH cathetercatheter

The function of the oesophagus during swallowing The function of the oesophagus during swallowing sequencessequences

Oesophageal Manometry -2

Can be used in the diagnosis of a Can be used in the diagnosis of a number of motility disorders.number of motility disorders.

Investigation performed on patients who Investigation performed on patients who are being considered for surgical are being considered for surgical interventions which can involve the interventions which can involve the manipulation of the LOS.manipulation of the LOS.

Water Perfused System Typically 4 to 8 thin Typically 4 to 8 thin

plastic tubes with plastic tubes with outward facing holes.outward facing holes.

Spaced along the length Spaced along the length of catheter.of catheter.

Perfused with water as Perfused with water as the non-compressible the non-compressible medium.medium.

Volume in the tube is Volume in the tube is monitored by a water monitored by a water displacement transducer.displacement transducer.

Advantages & Disadvantages of Water Perfused System

AdvantagesAdvantages Greater flexibility in configuration of cathetersGreater flexibility in configuration of catheters Lower ownership costsLower ownership costs Disposable catheters and transducersDisposable catheters and transducers

DisadvantagesDisadvantages Stationary studies onlyStationary studies only Slow response rate – less suitable for upper Slow response rate – less suitable for upper

oesophageal sphincter measurementsoesophageal sphincter measurements Water perfusion system requiredWater perfusion system required

Intra-luminal Micro-transducers

Linear and non-linear arrangement of Linear and non-linear arrangement of between 4 and 8 solid state strain between 4 and 8 solid state strain gauge transducers spaced radially gauge transducers spaced radially along the catheter.along the catheter.

Direct measurement of intra-luminal Direct measurement of intra-luminal pressure.pressure.

Advantages and Disadvantages of Solid State Catheters

Advantages. Fast response rates – upper oesophageal

sphincter measurements possible. Suitable for ambulatory recordings. Easy to use and calibrate.

Disadvantages. Fragile. Overall ownership costs higher.

Catheter Calibration Water Perfused manometry systems

Apply a relative hydrostatic pressure equivalent to 50cm of water relative to a pre-determined zero point.

Solid state catheters Insert catheter into a small tube with an air seal at

one end and a manometry gauge at the other. Apply a positive pressure of between 50 and 100mmHg equivalent depending on software configuration.

High resolution Manometry

Sensor at least every cmSensor at least every cm micro-manometric water-perfused micro-manometric water-perfused

assemblies with 21–32 channels assemblies with 21–32 channels solid-state - up to 36 pressure sensors solid-state - up to 36 pressure sensors

Manometry overview

UsesUses Types of system availableTypes of system available CalibrationCalibration