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General Surgery: Lower GI Session 1 - Anatomy & small bowel Chiara Dell'OroLearningObjectives • Describe the anatomy of the abdominal areas, including: • Abdominal cavity • Calot's triangle • Peritoneum & mesenteries • Inguinal Canal • Hesselbach's Triangle • Anterolateral abdominal wall • Posterior abdominal wall • Describe and identify the anatomy and key features of the lower GI tract and key landmarks: • Small intestine • Appendix • Caecum • Colon (ascending, transverse, descending, sigmoid) • Rectum • Anal canal • Understand and describe the arterial supply and venous drainage of the lower GI tract.LearningObjectives • Small Bowel Conditions • Inguinal hernia, Femoral hernia, Hiatus hernia, GastroenteritisIntroductiontotheAbdominalCavity • Definition:The space between the diaphragm and pelvic brim, containing abdominal organs IntroductiontotheAbdominalCavity • Boundaries: • Superior – diaphragm • Inferior – pelvic inlet • Anterior & lateral – abdominal wall • Posterior – vertebralcolumn & muscles IntroductiontotheAbdominalCavity 9regionsofthe abdomen IntroductiontotheAbdominalCavity 4Quadrants ofthe abdomenAnterolateral abdominal wall • The anterolateral abdominalwall consists ofmultiplelayersofmuscles,fasciae, and peritoneum that as respiration,posture, andincreasingintra-abdominalpressure (e.g.,duringcoughing,vomiting,or childbirth). • Layersofthe abdominalwall:Anterolateral abdominal wall • The anterolateral abdominalwall consists ofmultiplelayersofmuscles,fasciae, and peritoneum that provideprotection, movement, andsupport to the abdominalviscera.It iscrucialinfunctionssuch as respiration,posture, andincreasingintra-abdominalpressure (e.g.,duringcoughing,vomiting,or childbirth). • Layersofthe abdominalwall:lateral SubcutaneousFat Anterolateral abdominal wall Anterior abdominalwall: Anterolateral abdominal wall Anterior abdominalwall:Posterior abdominal wall Theposterior abdominalwall is a strong, musculoskeletalregionthat supports the abdominalvisceraand serves as a conduitformajorneurovascularstructures. It is clinicallyimportant due to its roleinlumbar stability,posture, andhousing keyorganssuchas the kidneys,aorta, andinferiorvenacava.Peritoneum Membranethat lines the abdominalcavity andcoversmost abdominalorgans: • Layers of the Peritoneum • ParietalPeritoneum:Linestheabdominaland pelvicwalls • VisceralPeritoneum:Coverstheabdominalorgans • PeritonealCavity • Potential space betweenthe two layers,containingserous fluid for lubricationPeritoneum • Greater Omentum vs. Lesser OmentumPeritoneum • Mnemonic for retroperitoneal structures: SAD PUCKER (Suprarenalglands,Aorta/IVC, Duodenum (2nd/3rd),Pancreas (except tail), Ureters, Colon(asc/desc),Kidneys,Esophagus,Rectum)Question! Which of the following correctly describes Camper’s fascia? a) A membranous layer deep to Scarpa’s fascia b) A fatty layer more prominent in the lower abdomen c) A fibrous sheath enclosing the rectus abdominis d) A smooth muscle layer contributing to intra-abdominal pressureQuestion! Which of the following correctly describes Camper’s fascia? a) A membranous layer deep to Scarpa’s fascia b) A fatty layer more prominent in the lower abdomen d) A smooth musclelayer contributing to intra-abdominal pressure Inguinal Canal The inguinalcanalis an obliquepassagein the lower abdominalwall thatservesas a pathwayfor structures passing betweentheabdomen and the externalgenitalia. It is clinically important because it is a commonsite foringuinalhernias. Boundariesof the Inguinal Canal(Mnemonic:MALT) Wall Structure M (Roof) Muscles: Internal oblique & transversus abdominis A(Anterior) Aponeurosis of the external oblique (reinforced by internal oblique) L (Floor) Ligament: Inguinal ligament (folded lower part of external oblique aponeurosis) T (Posterior) Transversalis fascia (reinforced medially by conjoint tendon)Inguinal CanalInguinal Canal Contents of the Inguinal Canal (Mnemonic: "I Love CreamyIce") •Ilioinguinalnerve(sensory to medial thigh,scrotum/labia) •Lymphatics •Cremastericmuscle (inmales, derivedfrominternaloblique) •In males: Spermatic cord (containsvas deferens,testicular artery, pampiniform plexus) •In females: Round ligamentof the uterusCalot’sTriangle(CystohepaticTriangle) Superiorborder: Inferiorborderof liver Medial border Lateral borderQuestion! Which of the following structures passes through the inguinal canal in both males and females? a) Spermatic cord b) Round ligament of the uterus c) Ilioinguinalnerve d) Inferior epigastric arteryQuestion! Which of the following structures passes through the inguinal canal in both males and females? a) Spermatic cord b) Round ligament of the uterus c) Ilioinguinal nerve d) Inferior epigastric arteryInguinal Canal Contents of the Inguinal Canal (Mnemonic: "I Love CreamyIce") •Ilioinguinalnerve(sensory to medial thigh,scrotum/labia) •Lymphatics •Cremastericmuscle (inmales, derivedfrominternaloblique) •In males: Spermatic cord (containsvas deferens,testicular artery, pampiniform plexus) •In females: Round ligamentof the uterusOrgansintheAbdomenSmallBowel SmallBowel • Wallthickness • Decreasesfromduodenum → ileum • Duodenum has thick walls for lots of glands that secreteenzymes that helpfinishdigesting food SmallBowel • Plicae circulares Folds in the bowelwall that help increasesurface area for absorption • Mostly in the jejunum • Some in the duodenum • Sparse in theileum,almost noneby the terminalileum SmallBowel • Blood vessels Jejunumhas fewerarcades, but long, straightvasa recta Ileum has many arcades but short vasa recta(good forabsorbing smaller moleculesand water) Appendix • Narrowworm-likeextensioninthe caecum • McBurney’sPointLargeBowel LargeBowel • Taenia coli arethree longitudinalbands of muscle • Start at base of appendix, end at the rectosigmoid junction LargeBowel LowerAbdomenandBowel| Radiology Key • Haustra • Sacculations formed the taenia contraction • Epiploicappendages • Fat filledpouches that are attached to the outer surface of the colonRectumandAnalCanalQuestion! Which clinical landmark is commonly associated with tenderness in acute appendicitis? a) Murphy’s point b) McBurney’s point c) Lanz point d) Hesselbach’s triangleQuestion! Which clinical landmark is commonly associated with tenderness in acute appendicitis? a) Murphy’s point b) McBurney’s point c) Lanz point d) Hesselbach’s triangleArterialSupplyoftheLowerGITract Coeliactrunk --> stomach, spleen,pancreas, gallbladder, oesophagus,duodenum SuperiorMesenteric Artery (SMA) Suppliesmidgutstructures: - Distal duodenumto proximal 2/3transverse colon InferiorMesenteric Artery (IMA) Supplieshindgutstructures: - Distal 1/3 oftransversecolonto upperanal canalArterialSupplyoftheLowerGITractVenousDrainageoftheLowerGITractInguinalHernia Inguinal hernia – protrusion ofabdominal contents through a weaknessin the inguinal canal Indirect: protrudes throughthe deep inguinalring Direct:protrudesdirectlythroughthe posteriorwall ofthe inguinalcanal InguinalHernia Key Differencesat a Glance Feature IndirectHernia Direct Hernia Cause Congenital(failureofprocessus Acquired (abdominalwall weakness) vaginalisto close) Location Lateral to inferiorepigastric vessels Medial to inferiorepigastric vessels Pathway Passes throughdeep inguinalring Protrudes directlythrough andinguinalcanal Hesselbach’s triangle Scrotal Involvement Can extend intothe scrotum Rarelyextends intothe scrotum Common in Youngmales, infants OldermenInguinalHernia • Investigations • Clinicaldiagnosisbasedonhistoryandexamination • Makepatientstand up, reducethe hernia and askthem to cough to see ifyou canelicitthe hernia poppingout • Ultrasoundifthe diagnosisis uncertain • Management • First-line: o Watchfulwaitingin asymptomaticcases • Second-line: o Surgicalrepair(open meshrepairorlaparoscopicsurgery)ifsymptomatic orcomplicationsarise • Herniacomplications:Obstruction(bowelblocksina hernia), Strangulation(lossof blood supply) • Signs+ Symptoms: - Pain - Redness - Nausea+ Vomiting - Systemicallyunwell (tachycardia,hypotension,fever)InguinalHernia Obstruction HerniationQuestion! A direct inguinal hernia typically occurs: a) Lateral to the inferior epigastric vessels b) Medial to the inferior epigastric vessels c) Withinthe deep inguinal ring d) Through the femoral canalQuestion! A direct inguinal hernia typically occurs: a) Lateral to the inferior epigastric vessels b) Medial to the inferior epigastric vessels c) Withinthe deep inguinal ring d) Through the femoral canalFemoralHernia Femoral hernia – whenpart of the intestine or fatty tissue pushes through a weak spot in the femoral canal Appearsas a lump / bulge in the upper thigh / groin area Takenfromosmosis.comFemoralHernia • Investigations • Clinicalexamination • Ultrasoundor CT scanforconfirmationif necessary • Management • First-line: o Electivesurgicalrepair,even if asymptomatic(due tohigh riskof complications) • Second-line: o Emergencysurgery if strangulationor bowel obstructionoccurs HiatusHernia A hiatusherniaoccurswhenpart ofthe stomach pushesup intothe chest cavity throughan openinginthe diaphragm. Differenttypes of hiatushernia–rollingandsliding Slidinghiatushernia(90%) Rollinghiatushernia(10%)HiatusHernia • Signs and Symptoms • Management • Signs: • First-line: o Often asymptomatic o Lifestylemodifications(e.g., weight loss, dietarychanges,elevatinghead of bed) • Symptoms: o Heartburn • Second-line: o Acidreflux o Proton pumpinhibitors(PPIs) or H2 o Chest discomfort receptor antagonistsfor acid suppression • Investigations • Third-line: • Endoscopy • Bariumswallow radiograph o Surgical intervention(e.g., fundoplication)for severeor refractory casesGastroenteritis • Gastroenteritis is inflammationofthe stomach andthe intestines, usuallydue to infection • The mostcommoncausesofgastroenteritis: • Viral: - Norovirus - Rotavirus • Bacterial: - Campylobacter - Salmonella - E.Coli • Parasites: - GiardiaGastroenteritisGastroenteritis • Management • First-line: o Oral rehydration therapy (ORT) for mild to moderate dehydration o Encourage fluid intake and regular diet • Second-line: o Intravenous (IV) fluids for severe dehydration or persistent vomiting • Third-line: o Antibiotics only if bacterial cause is suspected (e.g., severe cases of bacterial gastroenteritis)