Bowel Obstruction - Causes and Pathophysiology

in this video we're going to look at bowel obstruction let's first begin with the signs and symptoms and how a person can present so the signs and symptoms of a bowel obstruction include nausea vomiting cramping abdominal pain ABS the patient an inability to basically do a poo diarrhea possibly there can be a distended abdomen fever as well as tachycardia so bowel obstruction as the name suggests is obstruction of the bowel it can be of the small intestine or it can be of the large intestine in this video we're going to mainly focus on the small intestine but it it applies for the large as well so let's first draw an obstructed bowel here I'm going to draw a sphincter like thing in red just to represent the obstruction and the obstruction can be can be caused by many things which we'll look at but essentially if you have an obstruction the food that we eat will pile up of course and this can cause some serious problems because you know normally in the intestine we actually find bacteria commensal organisms that live within our intestine and when the bacteria is exposed to all this nutrition it will begin to grow essentially but before looking at you know the pathophysiology structuring can be categorized and it can be categorized into a mechanical obstruction or a pseudo obstruction let us first focus on mechanical obstruction and there are five main types of mechanical obstruction the first type of mechanical obstruction the most common is what's known as an adhesion and it's essentially where two two parts of the bowel are basically are connected with each other by a sort of fibrous and so this is referred to as adhesion and this can cause an obstruction the other most common type of obstruction is where we have essentially a tumor a cancer growth within the bowel itself and this can lead to an obstruction another type of mechanical obstruction is known as a interception interception is essentially when up the part of the bowel invaginate itself so there's some terminal terminology we have to know about interception and the first one is the part of the bowel that goes into the other part of the bowel this is known as the into the septum and the part of the bowel that is on the outside surrounding it is now known as the into Sisyphean another cause of a mechanical obstruction a type of mechanical obstruction is a hernia and a hernia is essentially a protrusion of the part of the intestine through the abdominal wall because of because the up to the abdominal wall can be weak for example and this can sort of strangulate the part of the intestine causing obstruction finally the last type of mechanical obstruction is referred to as known as a volvulus and this is essentially where we get twisting of the bowel so now let us look at each of these five types and sort of describe it in a bit more detail the most common cause of mechanical obstruction is post-operative adhesion so this is essentially when you have a surgery of the of the abdominal cavity and opening the abdominal cavity it can cause fibrous and adhesions to cause between segments of the bowel so adhesions are fibrous bridges between bowel segments adhesions cause extrinsic compression of the bowel which thus can lead to a destruction now the cancer so colorectal cancer is a common and lethal disease and risk factors for cancer of the bowel include age family obesity inflammatory bowel disease and certain diets so this is self-explanatory a tumor can grow so large that it can cause an obstruction now interest is a interoception intussusception is rare in adults between about one to five percent of mechanical bowel obstruction is a result of intussusception common sight of intussusception is the ileocecal valve so this is essentially when the the valve the ileocecal valve just basically goes invaginate into the cecum resulting in an interception the next type of mechanical obstruction is hernia which is defined as a protrusion bulge or projection of an organ or a part of an organ through the body wall that normally contains it hernias can be internal or external so in the diagram above we have a example of a hernia that is bulging out the intestine that is bulging out of the abdominal cavity which is the wall that normally contains it the last type of mechanical obstruction we'll talk about is the volvulus which is twisting other segments of the intestine around a fixed point common sites of our volvulus include the cecum and sigmoid area of the colon I'm a small bowel adhesion adhesion the small bowel can lead to a volvulus so those are examples of mechanical obstruction adhesions cancer intussusception hernia and volvulus now let's look at pseudo obstruction suit obstruction as the name implies is pseudo false obstruction false obstruction but regardless it does result in an obstruction of the bow so the main examples we look at our myopathy problems with the muscle and neuropathy problems with the innervation of the bowel and then we'll look at a specific type of condition known as hirschsprung disease hirschsprung disease affects the distal part of the colon so am i Appa fee problem with the muscles result in no movement no peristaltic contraction and thus this can lead to an obstruction because the food just doesn't go through a neuropathy problems the nerve innervation of the bowel means that we can have no innervation of the smooth muscles which means we we have abnormal movement so we get an obstruction finally hirschsprung disease is a congenital condition so it's present in the baby and this is where we have nerves that are missing at the distal end of the colon which means that we have no - no or abnormal peristaltic contractions so movement and this can mean that we can have a obstruction our surgery can correct this so regardless of the cause you know pseudo obstruction or mechanical obstruction it results in obstruction and an obstruction means that the material the substance that we eat cannot pass through our bowels smoothly it accumulates in the area and this can result in a few things so let's just go back to the diagram here and look at what what it can cause so food that pileups here can be metabolized by the bacteria that are normally residing in the area to produce gas gas accumulates causing a bowel causing bowel distension bowel distension you know it can compress the vessels that supply the bowel so we can have venous compression when we have venous compression this means that we have decrease in oxygen supply to the area to the bowel and thus we have the increase in oxygenation decrease in oxygenation results in a few things firstly because we have no oxygen supply to the bow the cells of the intestine die second no oxygen supply decreases peristalsis further aggravating the bowel distension so essentially we have more distension decrease in oxygenation also promotes the bacteria in the area to enter circulation because they are anaerobic they can enter circulation so when the bacteria enter the circulation and when we have the intestinal cells dying all this essentially are toxic and they all these are these are toxins that can enter the circulation resulting in some form of sepsis septic reaction so that was one aspect of of it further when we breathe air goes down you know our intestine is normal but this realistically aggravates the bowel distension it promotes the distinction of the bowel so again we have you know bowel distension and it's compresses the vessels we get venous compression and when we have venous compression which we haven't looked at it can actually result in fluid being secreted because of all the fluid piling up in this area it just gets secreted out into the bowel when fluid is being secreted into the bowel we lose water and when we lose water we lose electrolytes and when we lose electrolytes and water this results in hypotension so we actually get shock so bowel distension simply results in hypotension also when we get a distinction of the bowel this sort of triggers some nerves in the bowel which sends signals up to the brain to trigger the vomiting response because the brain thinks that there's something wrong in this area and it wants to get rid of it so vomiting is triggered but vomiting doesn't really help this the killer scenario because when we vomit we lose water and we also lose electrolyte which result in hypertension again so we get shock hypovolemic shock so shock can result from hypotension or shock can result from sepsis which is when we get you know the bacteria entering the circulation so I hope that all made sense but the complications of bowel obstruction can be three main things one bowel ischemia which we just means that we have decreased supply of oxygen to the bowel to perforation if the bowel is distended first you know so much it can perforate three sepsis when the toxins of the bacteria enters circulation due to the necrosis of the area etc necrosis of tissue of the area so again when we have venous compression I mean this means that a healthy liver doesn't get a blood supply to it and though and thus it dies and when it dies this releases toxins to circulation it also allows the bacteria to move from the bowel into circulation number two the complication perforation so here we have the lumen of the bowel if it if the bowel grows distends due to the gas buildup and the air and whatnot it essentially perforates releasing gut content into the peritoneum this can cause peritonitis causing a massive problem next sepsis sepsis is due can be due to the perforation and due to the systemic dissemination due to the death the dying cells in the area so that was a sort of an overview of bowel obstruction the different types of bowel obstruction which is mechanical and pseudo obstruction as well as we looked at the pathophysiology and the complications associated with bowel obstruction I hope you enjoyed this video thank you for watching you