Intestinal Failure

Welcome to First Incision, the podcast about preparing for the General Surgery Fellowship exam. I'm your host, Amanda Nikolic. Let's get started with our team timeout. Our patient today is the small bowel and the sepsis and critical care modules from the general surgical curriculum. And today, the operational topic we're going to be covering is intestinal failure. Questions about intestinal failure and nutrition are absolutely fair game for the exam and do come up pretty often.

In terms of intestinal failure the definition is a reduction of gut function below the minimum necessary for the absorption of macronutrients and or water and electrolytes so that intravenous supplementation is required to maintain health or growth. It can be an extremely debilitating condition that affects the quality of life of patients and does require multidisciplinary teams to manage these patients.

In some states, there may be intestinal failure units or in other states, it may just be up to the team to deal with these problems. There are a number of different classifications.

when talking about intestinal failure. There's ones that are more of a functional classification. So this includes talking about type 1, type 2 and type 3 intestinal failure. Type 1 is an acute short-term condition that's usually self-limiting. And some examples are things like a post-operative ileus or patients with critical illnesses like a head injury or pancreatitis. Type 2 intestinal failure is a prolonged acute condition.

often in metabolically unstable patients that requires complex multidisciplinary care and intravenous supplementation of nutrition over a period of weeks to months. So this is short to medium-term intestinal failure. This is most often seen in the setting of an interabdominal catastrophe, such as mesenteric ischemia, small bowel volvulus, or abdominal trauma.

And it can also be a complication following intestinal surgery, such as patients who develop an anastomotic leak or an unrecognized intestinal injury. The natural history is that about 40% of them will resolve. 10% will require some sort of enteral nutrition, including distal feeding, and about 50% will progress to type 3 intestinal failure.

So type 3 intestinal failure is a chronic condition in patients who are now metabolically stable and require IV supplementation over months to years. And it can be either reversible or irreversible. And some potential causes include progressive gastrointestinal or systemic diseases that require multiple bowel resections such as Crohn's disease, radiation enteritis.

FAP, or chronic intestinal pseudo-obstructions. And the natural history is that 20% to 50% of patients who have a benign cause may be able to wean from TPN over one to two years. but the rest of patients will have irreversible nutritional requirements and might need lifelong TPN or even a small bowel transplant. So that's one classification, which is more of a functional classification.

The next classification I've come across is a pathophysiological classification, so based on the cause of the intestinal failure. And the ESPN classification is the main one of these. This splits intestinal failure up into five main pathophysiological conditions, and this includes short bowel, intestinal fistula, intestinal dysmotility, mechanical obstruction, or extensive small bowel mucosal disease.

And then the last classification is a clinical classification, which is quite a complex table I've come across where they look at the amount of... calories of supplementation that is required and also the amount of intravenous volume. in terms of meals that are required and they split that up into four categories for each and then depending on where you cross over with those you get one out of 16 different subtypes.

I'm not going to remember that one for the exam, I think. So let's talk a little bit more about the ESPN classification and these five main pathophysiological conditions. And I think... In general, we'll talk about both the pathophysiology of why this causes intestinal failure, as well as what potential causes of intestinal failure that fit into each of these groups. So the first...

Condition is short gut or a loss of intestinal length. And this is the most common cause of intestinal failure in adults. The mechanism is that there's a reduction in the mucosal surfaces that absorb nutrients, fluids and electrolytes. And it can also result in increased intestinal losses of fluids and electrolytes.

Restricted oral nutrition because of those intestinal losses, accelerated gastrointestinal transit time, and small bowel bacterial overgrowth, which all contribute to malnutrition in these patients. The most common cause of short gut is due to multiple resections due to conditions such as Crohn's disease, but it can also be due to a massive intestinal resection such as due to a vasculopathy such as mesenteric ischemia.

Other potential causes include radiation enteritis, complications of surgery, trauma, familial adenomyces polyposis requiring multiple resections, necrotizing enterocolitis, And in children, patients with gastroschisis, intestinal atresia, malformation or omphalociles can all result in short gut syndrome leading to intestinal failure. The second on that list of pathophysiological causes of intestinal failure is an intestinal fistula, which is basically a loss of a functional intestinal.

because you are bypassing otherwise normal functional intestine. So that primary pathophysiology of intestinal fistula causing... intestinal failure is that you're bypassing a large area of absorptive mucosal surface. You can also have additional mechanisms that contribute to malnutrition, such as intestinal losses of fluid and electrolytes.

a disruption of the bowel salt enterohepatic cycle, restricted oral or enteral nutrition because of bowel rest to decrease fistula output, and impaired... peristalsis and increased metabolic demands due to sepsis and inflammation that may be related to the fistula. Common causes of intestinal fistulas include inflammatory conditions such as Crohn's, diverticular disease, pancreatitis and radiation enteritis.

neoplastic conditions such as colon, ovarian and small bowel tumours, iatrogenic causes such as operations and percutaneous drainage. And infectious diseases such as tuberculosis and actinomycoses can also cause fistulas. So the third group is intestinal dysmotility.

The most common cause of intestinal dysmotility is a post-operative ileus, but you can also get chronic conditions such as chronic pseudo-obstructions and other neurological disorders leading to... intestinal dysmotility, such as Parkinson's disease, Chagas disease, medication-associated endocrine disorders, such as hypothyroidism and hypoparathyroidism. and collagen vascular diseases such as systemic sclerosis that can cause intestinal dysmotility.

And the mechanism by which this causes intestinal failure is that patients restrict their oral or enteral nutrition or may completely fast due to feeding related. exacerbation of their digestive symptoms or due to episodes of non-mechanical intestinal obstruction. The malabsorption can also lead to small bowel bacterial overgrowth increased intestinal secretions of fluids and electrolytes in obstructed segments.

and increased intestinal losses of fluid and electrolytes due to vomiting or diarrhea. And all these things can contribute to the intestinal failure experienced by these patients. The fourth group is mechanical obstruction. And we all know about this. This is where you get a complete obstruction in the bowel, which leads to patient...

unable to take oral intake. And they also get intestinal secretions of fluids and electrolytes that are increased in the obstructed segments and also have losses due to vomiting or gastric drainage causes. include intraluminal, intrinsic and extrinsic causes. So intraluminal are polypoid tumors, intersusception, gallstone ileus or foreign bodies.

Intrinsic wall lesions include stenosis or strictures that could be neoplastic, inflammatory or anastomotic in nature. And extrinsic includes adhesions, hernias, cancers. with peritoneal carcinomatosis, volvulus or congenital bands. And then the last group is extensive small bowel mucosal disease or a loss of intestinal absorptive capacity.

This can be a result of any inflammatory condition that reduces the function of the enterocytes, which means that they're not able to absorb as much as they should be able to. The inefficient absorption can also result in loss of nutrients and fluids and electrolytes through vomiting or diarrhea, and patients may also restrict their oral intake due to symptoms. Some potential causes of this include extensive Crohn's disease, sclerodoma, radiation enteritis and celiac disease and other...

Conditions that can affect the small bowel mucosa include microvillus atrophy, intestinal epithelial dysplasia, severe food allergies in children, and chemotherapy-related enteritis.

So I'm just going to spend a little bit of time talking about a couple of important nutrients that are absorbed at different points of the gastrointestinal tract. and also about what you might find if specific parts of the gastrointestinal tract are resected. So in general, most of the absorption of nutrients in the gastrointestinal tract occurs in the small bowel. The colon is essentially responsible for reabsorbing fluid.

It also absorbs potassium and can absorb calories through digested carbohydrates and also absorbs short-chain fatty acids. So splitting the small bowel up into a couple of the different areas and what micronutrients they're responsible for, the duodenum absorbs calcium and iron. The duodenum and the jejunum are responsible for absorbing amino acids, some carbohydrates such as monosaccharides. as well as fatty acids and the fat-soluble vitamins A, E, D, and K.

The ilium is responsible for absorbing bile salts and also the distal ilium absorbs vitamin B12. And the water-soluble vitamins and zinc are absorbed both in the jejunum and the ilium. So how much bowel, small bowel, do you have to have left before you have intestinal failure or short gut?

It really does depend on the person and it is quite difficult to actually measure intraoperatively. There's no clear description on how you should hold the bowel and whether you should measure the mesenteric or the anti-mesenteric border, etc. But in general... If you leave less than 180 centimeters of small bowel, that's pretty bad. And the likelihood is that they're going to develop intestinal failure. If you lose the ileum and...

only have the jejunum left then this causes more malabsorption than if you leave the ileum. The ileum has better adaptation than the jejunum. And if you leave and end jejunostomy, this is one of the worst prognosis in terms of intestinal failure. These patients lose lots of salt and fluids and they don't absorb much nutrition.

If you lose the ileum as well, then you're going to get vitamin B12 deficiency if you lose a distal 60 centimetres. And if you lose all of the ileum, then you lose the ability to reabsorb bile acids and you can get... bile acid malabsorption, which leads to fat-soluble vitamin malabsorption, secretive motor diarrhea. and can also lead to kidney stones because you get increased oxalate absorption as the fat in the bowel attaches to calcium and then that gets reabsorbed. In terms of...

The colon, as I've mentioned, the colon does absorb fluids as well as potassiums and salts and can absorb some calories through digestive carbohydrates. So if you have the whole colon left, it's the equivalent of having an... extra 50 centimeters of small bowel. So if you had 100 centimeters of small bowel and then you had a intact colon, those patients may actually not end up with short gut syndrome in the longer term.

For those patients, you would put them on a high-carbohydrate diet because the colon can absorb up to 50% energy requirements on a carbohydrate diet. And the colon can also absorb excess fluids. So if a patient with an endogenostomy has an opportunity to have intestinal continuity restored and the colon is intact, it can actually absorb even up to six liters of excess fluid. per day which can help a lot with the fluid and salt balance for those patients.

So let's talk about the three different stages of intestinal failure and what the management is of patients during these three different stages. So the first phase is the acute intestinal failure or hyper secretory phase. The second phase is the adaptation phase. And the third phase is the chronic intestinal failure or stabilization phase. So phase one, as I mentioned, is acute intestinal failure or the hypersecretory phase. And this occurs in the first four to eight weeks postoperatively.

In this phase, patients lose large volumes of fluid electrolytes and have significant malabsorption. Up to 7 litres a day is secreted by the stomach duodenum. pancreas, liver and small intestine. And usually six liters of this are reabsorbed proximal to the ileocecal valve and a further about a liter in the colon. So lack of absorption of this fluid leads to large volume losses with copious diarrhea or a high output stoma or fistula, depending on the patient's anatomy.

So the initial management for stage one is resuscitation and intravenous correction of fluids and electrolytes. The next step is to... Identify reversible factors that could be contributing, such as intra-abdominal sepsis or an anastomotic leak. If there is sepsis, then it needs to be controlled with source control, which may be a combination of re-operation or radiological drainage and antibiotics.

infections are treated especially if there's a fistula as these will influence the likelihood of the fistula closing and also infection leads to increased metabolic demands and puts the patient into a catabolic state which obviously affects their nutrition.

Patients should be put on acid suppression with a PPI. In the first six months of short gut syndrome, patients have... hypergastronemia and excess acid secretion, which lowers the small bowel pH and reduces the efficacy of digestive enzymes and can contribute to secretion of fluids and high output stomas as well. as lead to ulcers. In addition, patients should have their nutrition optimized. So patients should have a dietician involved early.

They may need total parenteral nutrition, especially in the short and sometimes in the longer term. And if possible, enteral feeding should be started early to maximize the likelihood that the gut will adapt. increase its absorptive capacity and reduce the likelihood of long-term TPN reliance. In this phase, you want to also be looking and assessing about whether this is likely a condition that's going to resolve or likely to be a longer term condition. And if you can define the anatomy.

especially documenting at the time of surgery what the gut lengths are that are remaining and their integrity, assessing disease burden, inflammatory bowel disease. Rule out reasons why fistula might not be healing, such as a distal obstruction, foreign body or malignancy. Consider endoscopy and gastrographin follow-through to identify what the anatomy is and if the patient has an open abdomen, making sure that the patient's getting adequate wound care and fistula care if they have a fistula.

I mentioned adaptation just now so I'll briefly talk about that. Intestinal adaptation is a combination of both structural and functional changes that occur in the gastrointestinal tract. after surgery that results in short gut. And it's a combination of both macroscopic and microscopic changes. These occur better in the ileum than in the jejunum.

And some of the changes include that the bowel dilates and elongates, which increases the surface area. The transit time through the gastrointestinal tract slows down. The gastrointestinal villi in the mucosa get longer to increase the absorptive area. And there's epithelial hyperplasia and expansion of microvilli. There's an increase in the number of enterocytes and the muscle wall thickness increases. And there's also upregulation of the brush border membrane.

enzyme activity, permeability, and the number of transporters also increase. And intestinal adaptation is maximized by starting feeding early and making sure that any sepsis is treated.

So let's get back on track and talk about stage two or the adaptation phase of intestinal failure. So this is where those structural and functional changes occur to the remaining small bowel and colon, which is that adaptation I just talked about. In this phase, the management principles are to establish oral feeding in a slow, stepwise manner over weeks to months.

And the type of diet will depend on whether the colon is present or absent. So in general, if the colon is present, you want to have a higher carbohydrate. diet and you want to restrict oxalate so you don't get those oxalate renal stones. And if the colon is present, you can use oral rehydration solutions. Or you can also give hypotonic fluids. You just want to avoid hypertonic, such as fruit juice, those sorts of things, as they will cause diarrhea.

Soluble fiber supplements can also be helpful if patients have a colon in continuity because the colon can use this as a calorie source and also decreases water losses because the colon can absorb more fluid. And it also slows gastric emptying and gastrointestinal transit as well. If the colon is not present, then you don't have to focus so much on carbohydrates as the main energy source. There's a more even balance of carbohydrates, fats, and proteins.

But these patients should have oral rehydration solutions such as St. Mark's solution and you should be avoiding hyper and hypotonic oral solutions. You don't need to restrict oxalate. In this phase, you want to start introducing drugs and other treatments that we have to try to increase the absorbent capacity of the gastrointestinal tract.

So I've already mentioned a PPI and this should be continued for six months, which is that hyper secretory phase, but then it should be stopped to avoid small bowel intestinal overgrowth. Patients can be started on liparamide, which is a drug that reduces motility and intestinal secretions. And they can have up to 16... milligrams per day according to the box, but the ESPN guideline says you can actually go much higher than that.

And you can also add codeine if loperamide is ineffective, which also reduces motility. And that can be given as 15 to 60 milligrams twice or three times a day. But there is a risk of addiction when using codeine. Patients can also be trialed on octreotide, which can be used if patients are needing a lot of intravenous fluid to maintain their fluid status.

And patients should be trialed for a period of a few weeks. And if it's not improving the situation, then the drug should be stopped. Side effects or downsides of octreotide include that patients can get tachyphylaxis. It's expensive. can cause gallstones and also is usually given as a subcutaneous injection. Antibiotics are another thing that we can use for small bowel bacterial overgrowth, which can either be diagnosed clinically...

with a patient with lots of bloating or with a carbohydrate breath test. So this is where you give patients lactulose and then you do a breath test and patients should have a peak of methane and hydrogen at three hours when the... Lactulose gets to the colon, but this peak is earlier if there's lots of small bowel bacteria. And small bowel bacterial overgrowth also results in low B12 levels because the bacteria use the B12 themselves.

And the treatment is a broad-spectrum antibiotics for two weeks. And then the last medication, which I hadn't heard of before and I haven't seen used, is a GLP-2 analog called Tegglutide. It's given as a subcutaneous injection and it's a type of growth hormone which apparently encourages gastrointestinal tract adaptation.

Once the patient is being established on oral intake, you want to slowly wean the TPN and monitor their calorie intake, symptoms, hydration, and electrolytes. And you want to stop the TPN once they're having sufficient.

intake enterally. And you also need to monitor these patients for micronutrient deficiencies. In terms of the phase two or adaptational phase, you want to consider intestinal reconstruction after six months and you want to make sure that the patient is nutritionally replete before you do any further surgery.

And the last phase of intestinal failure is the stabilization phase or chronic intestinal failure. Maximal adaptation of the gastrointestinal tract can take up to one to two years. And after that time, you have to try and figure out how you can get that patient living as normal a lifestyle as possible at home.

Intestinal rehabilitation aims to restore bowel function through nutrition, pharmacological measures like we've talked about and or surgery. And it really does require a specialized team with lots of experience. If a patient has irreversible chronic intestinal failure, they may require lifelong TPN, which is usually supported to be provided at home.

The survival rates are 63% at five years and complications include catheter-associated infections, loss of venous access, and the development of liver failure, which can be due to the... TPN itself and it's called intestinal failure associated liver disease. Intestinal transplantation is really reserved for patients who have A risk of death due to life-threatening complications of TPN or the underlying gastrointestinal disease.

And the five-year survival of an intestinal transplant is only 54%. So really, if a patient is doing well on home TPN, you wouldn't be thinking about a transplant. And it seems that these are pretty rare. There's only been a few thousand of these performed ever.

The indications for transplant are recurrent catheter-associated bloodstream infections, intestinal failure-associated liver disease, Complications of venous thrombosis or frequent episodes of dehydration where fluid losses exceed the maximum infusion rates. And this can be done as a small bowel transplant with a combined liver transplant if required. There are other types of surgery for short gut syndrome, which really...

are mostly done in young patients and children and don't have a lot of evidence in adults. Some of the options include reversing small bowel segments in order to... slow down intestinal transit and increase absorption. tapering the small bowel and then lengthening, which can be done either as a Bianchi technique or a longitudinal intestinal lengthening and tailoring procedure, which is where you basically...

divide the bowel along its long axis and then retubularize it and then sequentially join the two bits that you end up with. Or a step procedure, which is called serial transverse enteroplasty procedure. which is where you kind of zigzag the bowel and you staple the dilated bowel on a zigzag and then re-anastomose the lumen, which leads to increased length. But this, as I've said, doesn't really have good outcomes in adults.

More importantly, really, is if possible, once you get the patient to a nutritionally replete state and after the adhesions have had time to relax, that you would restore continuity, especially in the presence of a proximal enterocutanus. fistula or a stoma, which should increase their absorbative capacity.

And that completes this episode on intestinal failure. I hope that was helpful and giving you a little bit of a framework for how you might approach a question on this for the exam. Please remember to rate, leave me a review and subscribe to the podcast. It makes it easier for others to find and I do love reading your reviews. It's time to close up.

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