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Pathophysioliogy of Intestinal obstruction Chirantan Mandal 3rd MB Proffessional part IIDept of Surgery, Medical College Kolkata

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Intestinal obstruction• Dynamic - peristalsis is working against a mechanical Obstruction• Adynamic - absent peristalsis (Paralytic ileus) non-propulsive peristalsis form

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Changes proximal to Bowel obstruction Intestinal Obstruction & Increased Peristalsis Obstruction not relieved Peristalsis ceases Fluid collection Proximal to obstruction (Bacterial multiplication and Toxaemia) Flacid, paralysed, dialated Bowel Inflammation (bowel Wall) Cytokine releasing Macrophages Accumulates Increased release of NO with ROS production

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Changes at site of Bowel obstruction Venous Return Inpairedincreased intraluminal pressure exceeding bowel wall venous pressure Congestion & edema of Bowel Further Dialatation & Ischaemic Injury Involvement of Arterial Supply Blockage of arterial perfusion Loss of Peristalsis Bowel wall necrosis Gangrene Bacterial Toxin release & mucosal damage Translocation to submucosa Toxaemia

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STRANGULATION

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Closed-loop obstructionLoop of Bowel obstructed at entryand Exit point of a closed loopi.e at proximal and distal loop ofbowel

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Closed-loop obstructionGangrenous Bowel

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External Hernia

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Internal hernia portion of the small intestine becomes entrapped in the retroperitoneal fossae other Sites of Internal Hernia :-• the foramen of Winslow• a hole in the mesentery• hole in the transverse mesocolon• diaphragmatic hernia

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transverse colon volvulus Volvulus Twist in axis of bowel loop type CV Each arrow on the diagram of the normal colon represents a possible torsion mechanism bascule type ceacal volvulus(Constricting Band Around Ascending Colon) bascule = Sea Saw

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loop type CVCaecum distended andfound in centre of Abdomen

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Compound Volvulus& Ileosigmoidal Knotting

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Intussusceptionportion of the gut becomes invaginatedwithin an immediately adjacent segmentpart that advances = apexMass = IntussusceptionNeck =junction of the entering layer with the massstrangulating obstruction as the blood supply of the inner layerdegree of greatest at ileocaecal valveIn children intussusception is ileocolic(50cm terminaL Ileum)In Adult colocolic intussusception is common

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Obstruction by adhesions and bands

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CausesObstruction by adhesions • Ischaemic areas • Reperitonealisation of raw areas • trauma, vascular occlusion • Foreign material Talc, • Infection Peritonitis, tuberculosis • Crohn’s disease types – • ‘avscular’ flimsy • ‘poorly vascular’ dense

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Obstruction by BandsStrangulation of Bowel loops by Knotting Diverticulum Dense Fibrous String attaching one portion of abdo to other; entraping intestine into Strangulation Causes:- • following previous bacterial peritonitis • a portion of greater omentum adherent to the parietes.

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Bolus obstruction

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Gallstones Ileuspassage of a GBstone from the biliary tract into the intestinal tract (by fistulousconnection between the GB & duodenum) usual location is at or 60 cm proximal to the ileocaecal valve obstruction is frequently incomplete or relapsing as a result of a ball-valve effect.

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AscariasisObstruction of the small intestine due to Ascaris lumbricoides

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Trychobezoars & phytobezoars firm masses of undigested hair balls & fruit/vegetable fibre associated with an underlying psychiatric abnormality Phytobezoars Predisposition to phytobezoars • high fibre intake •inadequate chewing •previous gastric surgery • hypochlorhydriaTrychobezoars

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Food Bolus obstruction • may occur after partial or total gastrectomy • when unchewed articles can pass directly into the small bowel. • Fruit and vegetables are particularly liable to cause obstruction

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Stercolith associated withFaecal Impaction Diverticulosis and ileal stricture

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Meconeum IleusMeconium becomes thickened and causes mechanical obstruction in ileum(associated with cystic fibrosis )Hypertrophy dialatation of Proximal BowelDistal ileum contains Pellets and gets narrowed

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Congenital Intestinal Obstruction

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DuodenalAtresia Duodenal Stenosis Fibrous cord AtresiaComplete Atresia With Separation

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Most common site of Intestinal atresia Defective fusion of foregut and Midgut With failure of recanalisationAssociated with1. Annular Pancreas2. Down syndrome3. Maternal polyHydroamnios

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Fibrous Atresia Mucosal Atresia Complete Single Atresia Complete jejunal Atresia (Vshaped Mesentry) with Coiled Ileum (christmas tree deformity)Gresifield Classification Jejunoileal Atresia Multiple Atresia

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Most common at prox. Ileum Proximal bowel:- dialated & hypertrophy normal sized VilliDistal bowel:- collapsed hypertrophied Villi

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Malrotation

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Small bowel in right sidecolon on left sideCaecum suspended midline

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Incomplete RotationMost common typeCaecym subhepatic RthypochondriumLADDs band connects to postr wallLADDs compresses 2nd part ofDuodenumMidgut hangs along SMA

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Reverse Rotation180deg clockwise rotationColon posterior to duodenum & SMA

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Paralytic ileus (Adynamic ) Intestine Fails to transmit any peristalsis due to failure of nueromuscular mechanism Auerbachs and Meissners Plexus

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Thank You

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Normal Rotation of Midgut

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Strangulated Bowel due to Omental Adhesion