Transcript for:
GI Tract Anatomy & Ultrasound

hi learners i'm from sound nerds and this video is going to be on unit 6 the gi track where we will learn about anatomy physiology and ultrasound appearance the digestive tract is also known as the alimentary tract and it is one big tube that starts at the mouth and ends at the anus it's about eight meters in length and the part that we consider to be specifically the gastrointestinal tract or the gi tract starts below the diaphragm the gi track anatomy that is relevant to ultrasound is going to include the esophagus the stomach small intestine and the large intestine imaging of the gi tract tends to be a little difficult due to its air content ultrasound energy is scattered and therefore unable to return meaningful echoes use of ultrasound to evaluate the gi tract is typically reserved for pediatric cases however if the conditions are good adult application is feasible now we're going to continue our study of the anatomy physiology and ultrasound appearance of the gi tract as portions of it do appear in most of our abdominal images and we need to familiarize ourselves with the anatomy prior to studying pathology that is diagnosable by ultrasound let's get started with section 6.1 gi tract anatomy we're going to focus on the four sections the esophagus stomach small intestine and large intestine looking at location key structures microanatomy if it's relevant and vasculature the esophagus extends from the pharynx travels inferiorly through the thoracic cavity pierces through the diaphragm into the abdominal cavity and then empties into the stomach the lower end acts as a sphincter and is the entrance to the stomach we call the connection of the esophagus to the stomach the gastroesophageal junction generally the sphincter is closed unless we're eating or vomiting but in people who have acid reflux the sphincter can relax allowing stomach acid to travel up the esophagus when we eat the esophagus moves food down in the stomach by something called peristalsis now peristalsis occurs all the way through the gi tract and it is contraction of the muscles that surround the gi tract anatomy so you'll see this kind of rhythmic contraction of the muscles that contraction is going to move the contents a little bit further down the big tube now paracelsus is actually very helpful for identifying bowel if you see a solid structure or just kind of something in your image and you're like i'm not real sure what that is if you wait a little bit and then you see it start gurgling around that's that peristalsis and that proves to you that you are looking at a piece of bowel it's especially helpful when we are trying to find normal anatomy uh ovaries quite often look a lot like bowel if you start seeing an error you think is an ovary and it starts moving probably not an ovary uh same idea of pathology if you see kind of something that looks like a solid structure in the abdomen if you wait a little bit and it starts moving again it's probably bowel but if it doesn't we might be a little bit more concerned that it truly is a solid structure that we need to investigate in these images here we can see a few gifts of paracelsus occurring in this top one here you can see how the muscles are squeezing the content down into the stomach so we do see the esophagus parasites the stomach peristalsis kind of turns all that stuff around we'll see bowel all the way through peristalsine it is the mechanism by which the gi tract moves the contents through the system in this example here we have fluoroscopy doing what we call a swallow study the patient will typically take a sip of some sort of fluid or apple sauce or something that has a radio opaque dye in it then they swallow it and we can watch how the food travels through their esophagus this is mostly done to see if maybe the patient aspirates where food goes into the lungs instead of down the tube that we expect it to this is an endoscope image of the esophagus you can see these kind of rings that go all the way down this is the smooth muscle that's going to help the food travel down the esophagus so after the esophagus stomach is going to next stop at the stomach it's a very large smooth muscular organ and it's responsible for secreting digestive juices and some other hormones that help break down the items that we ingest even though the stomach isn't very easily seen by ultrasound or evaluated well by ultrasound it actually serves as a landmark for a lot of connection points for other structures that we see in the abdomen in one of our earlier units we did talk about the lesser curvature and the greater curvature of the stomach the lesser curvature is on the liver side of the stomach it tends to be just kind of a smaller piece a smaller curve of the stomach and the greater curvature is the outer part of the stomach more towards the patient's left this is going to be the longer wider portion of the stomach the stomach is supported by four main ligaments within the abdomen on the lesser curvature side it is connected back to the liver with the gastro hepatic ligament which is also known as the lesser omentum and on the greater curvature we see the greater momentum which is also known as the gastrocolic ligament which connects the stomach to the transverse colon some other ligaments that we had mentioned earlier but have not taken a closer look at are the gastrophrenic ligament where the fundus of the stomach is connected back to the diaphragm and then we have the gastrosplenic ligament where the upper body slash fundus portion of the stomach is connected back to the spleen one of my favorite activities to do is to go to the science museum and i was actually there very recently and they had some interesting body parts on display so i took a picture of this one because i knew i was doing this lecture we have the esophagus coming in this is the esophageal junction and then it comes into the stomach we've got the greater curvature over here and the lesser curvature on this side the stomach then is going to empty into the duodenum so let's look at the parts of the stomach a little bit closer now you've already heard me mention a few of these terms but we have the fundus at the top of the stomach the body of the stomach makes up most of the mass and then the last part is the pylorus section of the stomach now the pylorus has a few other things in it we have the antrum which is the area right before the pyloric canal then we have the pyloric canal itself which acts as a sphincter to allow food to pass from the stomach into the duodenum if we take a closer look at the wall of the stomach we'll see that there is a very muscular layer to it and in that muscular layer there are three layers of muscles we have longitudinal muscles circular muscles and oblique muscles and it's these muscles that allow the stomach to pair cells which turn the food and help to start breaking it down kind of sloshing around through all the hydrochloric acid that is in the stomach but the muscle layer is actually only one layer of the stomach there are four layers that make up the stomach wall so moving from the inside to outside of the stomach we have the mucosa the submucosa the muscularis layer which has those three layers of muscles and then lastly the serosa in this image here we can see that the stomach wall has been cut away so we can see inside the stomach and you'll notice that it kind of has this like wrinkled folded look to it this is called rugged and all of this is the folded portions of the mucosa and submucosa as we eat the stomach will expand and these kind of wrinkles will start to smooth out to accommodate food in the stomach taking a little bit closer look at the stomach wall then we can see the serosa it's the very outer layer of the stomach wall moving in we get to the three layered muscularis so we have those longitudinal muscles circular muscles and then the oblique muscles moving towards the lumen of the stomach then we get to the submucosa the submucosa is going to have blimp channels traveling through it blood vessels and then we get into the mucosa and this is going to be the actual stomach lining along the stomach lining are all these tiny little cells that are going to be very specialized looking at those specialized cells then we will see that there are cells called goblet cells these are the cells responsible for making mucus it's that mucus that really protects the stomach from basically digesting itself so the goblet cells are the most plentiful and you'll see them along a good portion of the stomach wall we then also have parietal cells the parietal cells are responsible for making those gastric acids they are the ones that make hydrochloric acid we also have chief cells the chief cells are responsible for detecting proteins within the ingested food and they are going to make pepsinogen and when pepsinogen is present tells the pancreas to start making proteases because it knows that we're going to need to start breaking down some proteins another set of cells that we're going to see along the stomach lining are called g cells these cells are responsible for releasing gastrin you might remember we had g cells in the pancreas as well they are the same type of cell they both release gastrin but in the stomach they recognize that food has entered and they tell the stomach to increase its acid secretion so g cells tell the parietal cells they got to start making some hydrochloric acid the d cells then or delta cells again are also found in the pancreas and they both make somatostatin the d cells are responsible for kind of for monitoring how full the stomach is and when we get to the point where we don't need the hydrochloric acid anymore the d cells are going to activate telling the parietal cells to slow down the production of the acid remember the pancreas g cells were gamma cells they are in the stomach as well and d cells are delta cells as far as this microanatomy goes i mostly just wanted to point it out to you that the stomach and gastrointestinal tract still play a role in the exocrine and endocrine process of digestion and it just kind of points out how their roles kind of overlap in the production of those hormones and enzymes moving to a small intestine anatomy the small intestine is a long coiled tube and this one is about five meters long and only four centimeters in diameter the small intestine we learned in one of our earlier units is attached to the posterior abdominal wall by something called the mesentery and if you remember the mesentery were folds of peritoneum that kind of house the small intestine and anchor it back to the abdominal wall so this is another exhibit at the science museum and of course i had to grab a picture of this as well we can see the liver here this is the stomach this is the greater momentum here connecting to the transverse colon but for this side why i included it in here is this is our mesentery these are little small bowel loops and they're all supported by this mesentery the folds of the peritoneum that kind of hang on to and house some important things for the small bowel now we can't see the mesentery on an average patient sometimes we aren't able to see it if there's a lot of fluid you'll see these kind of bands of tissue that connect back to the abdominal wall there are three segments to the small intestines the first segment is the duodenum that is the area that is going to get food from the stomach first after it passes through the duodenum it's going to enter into the jejunum and after the jejunum it goes into the ilium the ileum then is connected to the cecum and the cecum is the start of the large intestine for the sake of clarity i do pronounce this first part of the small intestine as duodenum but you may also hear it pronounced as duodenum both are correct and refer to this first section of the small intestine so speaking of the duodenum there are some special parts to it when food comes out of the pylorus it is going to be metered into the first part of the duodenum the duodenum has four sections to it we have the superior section it's going to curve around into the descending section as it travels more immediately again we're going through the transverse section and then we get a little curve up into the ascending section and from here it's going to go into the jejunum for ultrasound the duodenum actually holds quite a bit of significance it really surrounds a lot of anatomy that we see kind of in the midline here and it's home to the ampule of water where we see those bile and pancreatic enzymes entering into the duodenum recognizing where the duodenum lies in regards to a lot of our anatomy that we're interested in is important and that's because when air gets into the duodenum it can start to obscure these structures so it's helpful if we know what's being obscured and how to combat that so the first part of the duodenum after it comes out of the stomach is going to sit right above the common bile duct so if you have air in this area there's a good chance you're not going to see that common bile duct very well unless you can angle around it or roll the patient we then see that the second part of the duodenum curves around and the gallbladder sits like right here and sometimes again when air or food material is in the duodenum it can mimic gallstones so we want to make sure that we are separating duodenal echoes from true gallbladder echoes and determining are those echoes coming from the gallbladder or are they coming from the duodenum again another great spot to just kind of hang out and wait see if you see any paracelsus through this area to confirm bowel versus gallbladder we consider this first second and third section the c loop and you can kind of see why it looks like a c so this is the c loop of the duodenum and it kind of cradles the pancreas head within it so again if there is air within here there's a good chance we're not going to see the pancreas head very clearly lastly then as that transverse section comes across and the ascending portion goes up this is all in front of the aorta and ivc so if we again have a patient with air in their duodenum there's a chance we're not going to see that proximal and mid portion of the ivc or aorta very clearly so to get around this we want to make sure that we are either angling around the gas bubbles that are in there possibly giving the patient some water to kind of push water through here and push the air out or we can try rolling the patient or just kind of push a little bit harder trying to move that air manually out of the way very similar to the stomach the small intestine also has layers to its wall except we are adding in a fifth layer so starting from the outside we have the serosa again that's the outer layer of the wall coming into the muscularis layer then the sub mucosa layer and then the mucosa layer now where the fifth layer comes in is what we kind of consider the superficial mucosa layer or the lumen and when the bowel is flat against itself we will see kind of an interface of where the superficial mucosa layer kind of connects to one another and it's going to create a distinct line through the center of the intestine so we do consider that our fifth layer when we are talking about the five layer gut sign this little cutaway here shows that we have some rough patches to the inner lumen of the small intestine these are called villi and the villi end up increasing the surface area of the intestine so it improves how well we are able to absorb nutrients from the food that has been broken down and digested moving on to large intestine anatomy the large intestine is going to pick up from the small intestine at the junction of the ilium and the cecum the large intestine contains six sections they are the cecum which is home to the appendix we then have the ascending colon transverse colon descending colon sigmoid colon and the rectum which is home to the anus some other key features of the large intestinal anatomy we have the cecum and this is where the large vowel starts the ilium is going to kind of come in here and connect to the side at the ileocecal junction the cecum is going to give rise to the ascending colon and when it turns literally into the transverse colon this is called the hepatic flexure this is where the ascending colon twists and comes across the abdomen so that paddock flexure is named so because it's right by the liver transverse colon goes across the top of the abdomen just below the stomach and is going to turn again at the splenic flexor so the left side has the splenic flexure again because it's right next to the spleen turning inferior then we have the descending colon there's going to be a slight turn into the sigmoid colon and that is going to turn again into the rectum and the rectum then is controlled by the anus and a sphincter there to control the release of feces the walls of the large intestine still have five layers but they're going to lack the villi portion of the mucosa they're not involved as much in absorption of nutrients they're going to be more involved in the absorption of water they have a little bit of a segmented saccular appearance and the sags are called the house draw if we're just referring to one sec it'd be a house drum as far as ultrasound is concerned one of the more significant parts of the large intestine is going to be the appendix and the appendix is found right by the ileocecal junction it's in the right lower quadrant of the abdomen and it represents a remnant of the apex of the cecum so here you can see the ilium joining to the cecum and just inferior to this joining is where we expect to see the appendix sometimes it's referred to as the vermiform appendix vermiform basically means worm-like and so it explains the visual appearance of the appendix the general location of the appendix is about two-thirds of the way to the right anterior spine of the iliac crest and that is if we were to draw a line from the umbilicus or the belly button to the iliac crest so from the belly button or umbilicus we would draw a line out to the hip bone we're looking at the anterior spine of the hip bone and about two thirds of the way out we are going to get to a point called mcburney's point and this is the standard location for where the ilium and the cecum join up therefore representing most likely where the appendix is originating from so again we have our ilium joining up with the cecum and we expect the appendix to be just inferior to this area this is where it originates however after that it has kind of a mind of its own most appendices are going to travel inferior and a little bit more medial into that pelvic or about the five o'clock position as this diagram demonstrates though there are actually quite a few different positions which the appendix can take it can go sub sequel which means that it goes below and more off to the side of the cecum we can have retrocycle where it travels back underneath the cecum post ileal it takes a turn underneath the ilium or we can have pre-ileal where it lies over the top of the ilium again most commonly though we will see it in this pelvic five o'clock position kind of lying over the psoas muscle towards the iliac artery and vein now in adults appendix is actually really difficult to see but with the safety of ultrasound we can always attempt a look our biggest limiting factors to being able to see the appendix by ultrasound is going to be patient body happiness so on thinner patients we have a better chance of seeing the appendix how much gas is in the area which can vary from person to person and exactly where that appendix is traveled to again a retrosequel or post ileal position is going to be harder to see than that pelvic position so in adults the appendix is typically pretty difficult to see but we can always try sometimes we'll even see it incidentally if we're doing a transvaginal ultrasound that tip of the appendix can travel near the right ovary and we might catch a little glimpse of it over there however it is very very common to take a look for an appendix for pediatric examinations typically they're much smaller bodies we can see to the appendicile area very well and we save them from a little bit of radiation from a ct to round out the anatomy we're going to talk briefly about the gi tract vasculature in section 6.2 there are a ton of blood vessels that are responsible for bringing blood into the gi tract now not all of these are going to be significant by ultrasound but as a person who works with anatomy it is important that we understand what blood vessels bring blood in and how these organs drain their blood looking at the esophagus which is slightly cut off in this image here we do have some esophageal branches of the left gastric artery we also have some up higher ones that come from like the subclavian and other parts of the aorta specifically concerning about the esophagus is when we have issues with the liver accepting blood sometimes that blood can kind of back up through the system and then what we'll see are esophageal varices these vertices are basically dilated blood vessels that surround the esophagus and should they rupture a patient would start to bleed into their esophagus they'd start vomiting blood and it can actually be very life threatening very quickly so esophageal varices can be seen arising from the liver traveling towards that esophageal junction that we can see by ultrasound the stomach then has some major branches it has one major ranch off the scaliac trunk called the left gastric artery another major branch is the right gastric artery and that's going to arise from the hepatic artery and we'll also have some major branches that arise from the splenic artery the small intestine is mostly going to receive its blood via the superior mesenteric artery so that is a direct branch off the aorta once it branches it's going to have kind of this webbing pattern to it as it goes to feed both the small and large intestine and then we'll also see the inferior mesenteric artery giving rise to kind of that branching webbing pattern again to head off to the colon as you can see from this image there are a ton of blood vessels and this is just part of them and not even all of these are seen or appreciated by ultrasound we have major branches that come off the aorta those major branches are going to give rise to secondary branches and kind of after those secondary branches it's kind of the end of where ultrasound can see anything we can't see the left gastric guard or we can't see the right gastric artery but we can see the hepatic artery we can see the splenic artery and when we understand how the blood is traveling through this area and where it's going we can perform doppler studies on some of these more major branches and then be able to analyze those doppler waveforms that we get to understand what's going on further to understand if there's some sort of problem in the bowel is there an aneurysm or a blockage somewhere along the splenic artery it can tell us quite a bit so very outside of the purview of this lecture but that is why we want to know where this blood is headed as it leaves those major and secondary branches as far as blood coming back from the intestines most of this is all going to be drained by the inferior and superior mesenteric vein recall that the inferior and superior mesenteric vein are going to join up with the splenic vein to form the portal vein from there the portal vein heads off to the liver so all those nutrients and toxins everything that the intestines absorb is going to be brought back into the bloodstream and dumped into the portal vein to bring back to the liver and then the liver is responsible for filtering that blood metabolizing what it can storing what it needs to and transforming other toxins for excretion we've already talked extensively about the physiology of digestion when we discuss the gallbladder and the pancreas however the gi tract actually has a pretty big role in it too not so surprisingly but the role that the gi tract has in the physiology of digestion and how it works is a little less important to ultrasound than the pancreas and the gallbladder are however we're going to still discuss it just to kind of round out our discussion about it so we left off in the pancreas lecture talking about the fact that we have gotten down to enzymes breaking down the macronutrients in the duodenum but before we pick that up we're going to talk a little bit more again about how the food gets into the stomach so remember we eat our food and in the mouth we chew it up and add saliva to it and that saliva has some amylase and then the amylase gonna start breaking down those carbohydrates we swallow and the food is going to move down the esophagus and into the stomach now remember the stomach has those specialized cells that are lining it we have the gastrin cells that are going to recognize there's food there and tell the parietal cells to start making hydrochloric acid we've got the parietal cells making that hydrochloric acid to kind of help start breaking down the big chunks of food that we just ate the chief cells are recognizing what's in there getting some hormones sent out to the pancreas to start making some proteases and then we've got the goblet cells that are making mucus to help protect the stomach while all of this acidic breakdown is starting to happen the muscles of the stomach are going to start contracting and mashing and pushing on all that food mixing it up with the hydrochloric acid and that's going to make a substance called chyme chyme then is going to move towards the pylorus remember that's the muscle at the end of the stomach the pylorus is going to open let a little bit of chyme through and that's going to shut and wait a little bit open again a little a little bit of chyme through and it's going to keep doing that to slowly empty the stomach of the kind once the stomach is relatively empty those d cells will activate recognize that the stomach is relatively empty and again tell those parietal cells hey we can stop making hydrochloric acid we're on to the next section so the acidic chyme now is in the duodenum bile is coming in from the gallbladder we've got enzymes coming in from the pancreas and those are going to really start to break down those still relatively big nutrients that are in the chimes or proteases to break down our proteins amylase to break down the carbohydrates and lipases to break down the emulsified fats from the bile in the small intestines then is where chemical digestion occurs it's going to just keep further breaking it down breaking it down breaking it down as those nutrients pass by the villi they are now small enough to be absorbed through the villi and into the bloodstream remember those vessels are going to carry all those nutrients anything that we ingested through the bloodstream into the portal system and that's going to return back to the liver for metabolism storage and excretion whatever the small intestines can't break down is going to continue then through the large intestine in the large intestine there is going to be salt reabsorbed and water reabsorbed and by the end we are left with a relatively solid piece of feces so waste is removed from the body then via the anus in the form of poop now there aren't really any laboratory tests that are going to be helpful to the sonographer regarding gi tract function however there are some stool presentations that we can use to kind of clue us in to some of the issues now we normally expect feces to be brown and the brown color is going to come from the bile that is left within the fecal matter when we have dark kind of black tarry stools that is indicative of an upper gi bleed it ends up being black because if it's an upper gi bleed we're bleeding up like towards the esophagus and the stomach up towards that area that blood is going to travel all the way through the system and by the time it gets to the large intestine to be expelled it has kind of clotted off it's lost all of its hemoglobin it's kind of just this black old yucky blood and that is why we see upper gi bleeds present with dark tarry stools opposite of that then if we have bright red blood in the stool then we know that there's going to be some sort of lower gi bleed blood hasn't been hanging around long enough to coagulate or lose any of its structure and so it still is very much in its original form very common to see it with like hemorrhoids diverticulitis can also cause it as well another very common thing that you'll see in notes is that the patient mentions pale stool so they might call it white or clay colored and that is typically going to be gallbladder disease remember we normally expect it to be brown in the setting of gallbladder disease if bile can't get into the duodenum then that color is no longer there and so we'll see a much paler form of fecal matter and while not very specific to the gi tract doctors can run what we call a complete blood count that's where they're going to look how many red blood cells how many white blood cells and how many platelets are circulating in the body we will see that if we have a low amount of red blood cells that could mean some sort of internal bleeding so that could lead to our upper gi bleed or lower gi bleed or we might see that the patient has an increased amount of white blood cells and if that is accompanied by pain in the abdomen or fever then we might start to suspect some sort of infection along the gi tract let's go ahead and take a look at how these structures look by ultrasound in section 6.4 ultrasound appearance now the esophagus can be seen in the neck and it's typically seen posterior to the thyroid so we've got an example of the thyroid gland here that's all this kind of hyperechoic area and the esophagus is this target-shaped area just posterior to it this is the trachea off to the side here so the trachea runs very medial in the neck esophagus is slightly displaced to the left we've got the carotid artery here and then some muscles in the neck as well so target area in the neck that's the esophagus running posterior to the thyroid the esophagus then is going to travel down through the thoracic cavity we're not good at seeing that because of the lung tissue there it's going to pierce through the diaphragm and right below the diaphragm we should be able to see the esophageal junction so here is our diaphragm this is the aorta and the left lobe of the liver you again will see a slight target shaped area it's usually kind of hypochoic with a hyperechoic central portion this is the esophageal junction right before it empties into the stomach it is not uncommon for inexperienced sonographers when looking for the pylorus remember that's the muscle at the end of the stomach it might mistake the esophageal junction as the pylorus but next time you're scanning the aorta take a look see if you can see that esophageal junction kind of sandwiched between the left lobe of the liver and the aorta the stomach takes on a lot of appearances based on what the patient has eaten or has not eaten or if there's a tumor in there or if they've drank something so there's just really no normal stomach appearance per se but we can talk about some of these appearances so in this example here this is a relatively collapsed stomach we can almost see that fifth gut layer sign because we're seeing the collapse the mucous membranes being all the way connecting to each other but then we have the mucosal layer the submucosa layer the muscle layer and then right on the outside here we have the serosa so this is relatively collapsed down on itself kind of making that star pattern we can see the rugged within the collapsed stomach in this example here this looks like maybe some sort of kind of mass within the stomach but there's also some fluid in it as well the reason we know it's the stomach it's in that left upper quadrant this is the left lobe of the liver and transverse so we'll see it just to the side of it in this example we are seeing some through transmission because of the fluid in the stomach in this example here the stomach is very distended it's got a lot of fluid in it it's got a lot of little particles within it too if we were scanning this live it's not uncommon to kind of see all the stuff kind of swirling and sparkling around in this area and here we have an example of a slightly distended stomach again we can kind of see those layers to the wall a little bit of fluid within it at the end of the stomach then is the pylorus so this is the stomach over here we're moving into the antrum of the stomach so remember the antrum is part of that pyloric section and then we get into the pyloric muscle and sphincter here so this darker part is the muscle we can see the pyloric canal going through here and this muscle is going to open a little bit and we'll see food content going through and into the duodenum so this muscle is going to be the controller of how the chyme exits the stomach and enters the duodenum on pediatric patients it's very common that we are looking at the pyloric muscle to see if it's thickened to the point where it won't let the canal open and then it causes a big backup in the stomach and then those patients end up kind of projectile vomiting everywhere the normal pylorus is going to be three centimeters in length so the canal should be less than three centimeters and the muscle should be less than 1.4 centimeters or 14 millimeters this image is from a newborn this is how you're going to see the pylorus well is definitely not well seen on patients that are adults or even early adolescents to older children but we can see it very well on infants the pyloric sun empties into the duodenum remember the duodenum kind of wraps over the common bile duct medially to the gallbladder down and around the pancreas head and then connects to the jejunum we've got a little video here and if we look just medial to the gallbladder we're going to see this kind of shadowed area right along here this is gas in the duodenum this is all duodenum through here so you can see why it's really important that we isolate the duodenum from the gallbladder so we don't mistake any air and shadowing from the duodenum as gallstones within the gallbladder lumen if there's a lot of gas in this area remember to kind of push down through that area see if you can kind of get it to move along or just really wait and see if the peristalsis will bring it out of the area looking a little closer at the layers of the intestinal tract by ultrasound we can see them if conditions are good we can see them actually fairly well looking at the top one here we have some fluid within the intestinal tract so what we are seeing is that kind of superficial portion of the mucosal layer so that looks a little bit more echogenic and then we have the deeper part of the mucosa layer and that is going to be hypochoic then we go to the submucosal area that again is hyperechoic the muscularis is hypoechoic and then the serosa is hyperechoic again so it's kind of neat that we go bright dark bright dark bright and if you look at our labels here we have smsms so if you can remember that the muscularis and the mucosal layers are dark that'll help you to identify those two and then you're just looking for the bright lines around it to identify the other three this is a cross section of the intestinal tract again we have the lumen with a little bit of fluid in it so we are seeing the superficial mucosal layer the mucosa layer submucosal muscularis and then lastly the serosa that surrounds it now both of these examples do have a little bit of fluid within the lumen of the intestine so it's easier to see all five layers it's more common to see that these are collapsed on one another and then for oftentimes the submucosal echogenic layer is going to kind of blend in with the chyme or the feces whatsoever in the intestines at that moment we talked about peristalsine is an event that occurs all the way through the gi tract it's the mechanism by which it moves content through and the peristalsia is very very helpful for identifying bowel so in this little clip here we can see kind of the swirling gurgling area there's actually another little bit down here this is peristalsis so had we just stopped here when this wasn't moving we might think well that might be a mass right there but if you wait long enough you'll most likely see it move along because of that peristalsis so it's very helpful in identifying solid structures for what they are or confirming that it is indeed bowel that you're looking at here's another example of some peristalsis now this is not normal appearance i want to point that out but i like this picture because we can really see the contents moving and we can see the ville within the small intestine so this patient actually happens to have a small bowel obstruction which is causing all the content to kind of back up dilate the intestines and fill it with fluid so we can see that internal part of the small intestine very well but again this is not normal to be able to see the villi this well sometimes we'll see this again with small bowel obstruction sometimes people have some sort of like norovirus and so with diarrhea they just have a lot of extra fluid in their intestinal system so it's not necessarily an uncommon appearance but it's definitely not a healthy normal appearance either here we're taking a look at the transverse colon this shows nicely the haustra so the house jaw are kind of these little lumps that make the colon look like it has little sections or segments to it and they kind of take on a little bit more of a sacular appearance the houser kind of gives the colon a little bit more of a cloud like appearance here we have a normal appendix the normal appendix can be a little bit difficult to find but again we want to take a good look through the right lower quadrant and we're going to typically see it near the psoas muscle and the right iliac vein and artery we want to prove that the appendix has a blind end that blind end proves that it is not just a loop of small intestine that we are indeed seeing the appendix and then we also want to follow it back all the way to the cecum and show where the cecum is and the ilium connecting appendix exams definitely get much easier the more that you do them it's just a matter of seeing enough numbers to be comfortable identifying the structures in the right lower quadrant once you identify the appendix if it is normal it will measure less than six millimeters if you push on it it should collapse so we call that compressible there should not be any pain in the area and we aren't going to see any fluid or echogenic fat surrounding the appendix so again this is a very normal appendix we can actually see the five layer gut sign on this appendix as well we have the we have the superficial mucosal layer mucosal submucosal muscularis and then the serosa so we have that kind of target appearance and the alternating layers it's also not uncommon for us to be scanning through the pelvis and notice kind of a large area posterior to the bladder or posterior to the uterus in our female patients this is typically representing the rectum with feces in it so you'll see kind of a large circular area it has a very bright echogenic rim and then kind of some shadowing behind it so this is usually the rectum if it looks incredibly abnormal to you absolutely take pictures of it i think some newer stenographers tend to see this and think it's a solid mass within the pelvis versus thinking about where it's connecting and what it's connecting to and that it means most likely the rectum with stool in it to finish up this lecture then we're going to briefly touch on protocol in section 6.5 now protocol for the gi tract is going to be very targeted for example in pediatrics they can order an abdomen ultrasound to look for just appendicitis which is inflammation of the appendix or they'll order an ultrasound just to look for pyloric stenosis that's the thickening of the pyloric muscle or they can order an ultrasound just to look for intussusception and intussusception is when the bowel kind of telescopes onto itself all pediatric pathologies in adults we might look for hernias uh we can look for the appendix we might be able to look for a diverticulitis but in adults the ct scan is going to be more often the choice for bowel related differentials but because it is so targeted to a diagnosis the protocols for the bowel are very specific and we'll cover them more when we talk about those pathologies but in general if you are looking through the bowel you want to be very slow with your movements you want to use very calculated movements as you can see in the top picture here they are kind of demonstrating go down across up across down across up across you want to be very methodical in the way that you evaluate the bowel you want to look in different planes because the bowel is very twisty and loopy you want to make sure that you're evaluating it in all planes you're definitely going to want to start with an age-appropriate and patient-size appropriate transducer in our pediatric patients we quite often start with a high frequency linear transducer might drop down to a little bit lower frequency linear transducer for older thicker patients and then for adults if we can't see with either the linear higher frequency transducers you can switch to a low curve linear transducer but you're not going to get nearly as much detail and it might start to degrade the quality of the image that we are getting so always use the highest frequency possible and typically start with a linear transducer when we are not performing bowel specific protocols you'll notice that the bowel is in most of your abdominal pictures and most likely causing some artifact which is going to obscure other organs you want to make sure that you are trying to roll your patient try different breathing techniques see if you can kind of angle around those bowel bubbles possibly try again when the patient has been npo or try something called graded compression now graded compression is helpful anytime you're looking through the bowel we most commonly use it when we are looking at the appendix but basically what you're doing is slowly pushing more and more pressure onto the area and that's going to squeeze the bowel out of the way kind of push any air out of the way as well and it gets you closer to the area that you want to see and that brings us to the end of our unit 6 lecture ultrasound definitely has a place in evaluating the gi tract however it is not always the easiest exam for ultrasound to be used for make sure you are going through your activities in your workbook there are some labeling activities in there and then you have your nerd check questions that are great for making flashcards with so you can evaluate your recall of the information presented