What Evidence Exists for the Medical, Nutritional, and Surgical Management of SBS?

What Evidence Exists for the Medical, Nutritional, and Surgical Management of SBS?

Ezra Steiger, MD: The first presenter is Dr Steve McClave. Steve is Mr Everything in nutrition and nutrition support, but more importantly than that, he’s a Buckeye. So, read about Steve but listen to what he has to say. He’ll be starting off.

Stephen A. McClave, MD: Good evening, and thanks for joining us tonight. I’m excited about this because I learn a lot in these circumstances, and we’ve got some big boys up here to bounce the really hard questions off of.

My job tonight is to go over the basics of the physiology and the management of the patient with short bowel syndrome, SBS-101. If I do my job right, I will lay out a foundation and then we’ll bring in Steve O’Keefe for the heavy lifting, and he’ll take us through these exciting new agents and some of these studies.

These patients, I think, are the most complex patients the gastroenterologist sees or maybe any nutritionist sees. When I see one of these patients on my clinic list in the afternoon, I know my brain is going to hurt for 2 or 3 days afterwards because they’re so tough.

Let’s start with an overall organizational scheme, and I think this is appropriate to keep things in perspective. There are 3 types. Type 1 is a patient that’s had their entire colon and their ileum resected, and the jejunum is coming out into an ostomy and into a bag. Type 2, they’ve got the jejunum but it’s hooked anastomose to some portion of he colon, but the ileum and the ileocecal valve are completely gone. And in type 3, they have had resections of the small bowel but they end up with some ileum remaining, intact ileocecal valve, and then the entire colon. To put these 3 groups in perspective, small bowel is the name of the game in short bowel syndrome; the more you have, the better the absorption of food and calories and fluids and electrolytes.

If they, all 3, if you had 3 patients in front of you with all 3 subtypes and they had 100 cm of jejunum, a type 2 in comparison to type 1 because they’d have some colon, would be like having an extra 30 centimeters. If it’s a type 3, where they’ve got colon plus some ileum left, that’d be like having an extra 60 centimeters hooked onto the 100 centimeters of jejunum.

If you flip that around the other way, and look at gut autonomy, at what point would you lose gut autonomy and have to depend on TPN the rest of your life? Well, in type 1, when you get below 115 centimeters of jejunum, you’re talking about TPN. But in type 2, where if you got some of that colon, you can drop down all the way to 60 centimeters before you’re at risk for being on TPN the rest of your life. And with the ileum and a colon, you can get down to as little as 30 centimeters. So, these kind of put these groups in perspective.

Let’s talk about type 3 briefly and then we’re going to discard it, so we keep our mind free for type 1 and type 2. The reason we’re going to talk about it briefly is because this is an uncommon subtype. This is a Crohn’s patient, typical example, where you kind of whack away several times and remove sections of bowel, but they’re left at some point, with some ileum and an intact colon. The reason we’re going to dismiss these guys quickly, is that it’s fairly rare, but also it’s uncommon, but malnutrition is rare in these guys and they don’t often need specialized nutritional therapy. And the reason is because they have slower transit.

Polypeptide YY, which is the ileal brake, slows down intestinal transit and gives them time to absorb. They have an ileocecal valve which may provide a mechanical brake on intestinal transit, but clearly prevents bacteria from ascending the small bowel. And then because of the ileum and colon produce GLP-2, glucagon-like peptide-2, they will have better adaptation, longer villi, greater absorptive surface in the adaptation process.

Talk a minute about what adaptation involves. When you have a massive bowel resection, the remaining bowel will adapt in a process that can take one to two years. The folds in the small bowel that you can see with the naked eye will increase in size and increase the absorptive surface three-fold. The villi will grow longer in length. The number of enterocytes and their absorptive capacity will go up, increasing the surface area thirty-fold. And then on the individual epithelial cells, the little micro villi, like little hairs, that will increase and increase the absorptive surface 600 times.

Now, you need food in the lumina of the GI tract to do this, and there’s an interesting dilemma. The best adaptation, or the greatest effect is stimulated by intact foods, steak and potatoes, but we have these fancy semi-elemental formulas where the small peptides and MCT is absorbed more efficiently. So you think, “well why don’t we go to that?” It’s going to be absorbed more, but you would lose on that maximal stimulation from the intact steak and potatoes. So that’s a bit of an issue we have to deal with. And it’s not so much the food that’s so magic, it’s what they stimulate: bile, gastrin, GLP-2, are just some of the agents that stimulate this adaptation process. And it goes on for up to 1 to 2 years. At some point, that’s as good as it gets and we can’t expect absorption to be any greater.

Interesting comment though, the type 1s, the jejunostomy that comes out in a bag, no ileum, no colon, means their GLP levels are lower and adaptation may be less in that subtype.

In fact, if we now come back to our type 1 and type 2, let’s compare the clinical differences between the two. In type 1, where all you’ve got left is a jejunostomy, the fluid and electrolyte losses are just all over the map and consume your efforts, particularly early on in the course. Because of what we were talking, with no ileum and colon and less GLP-2 levels, then this review by Nightingale says that adaptation is less. You get intestinal adaptation, but you don’t see real structural and functional changes, which is an odd comment. And he says that their change in nutrition and fluid needs, over time, are much less. Now, that’s what was a surprise to me and so for the big boys, I’m pitching this up to you guys. I’m surprised by that. I think they still get adaptation, but I think it’s clearly less than the other subtype.

In the type 2, the picture that predominates is a slow deterioration of nutritional status. One of my patients with this subtype of short bowel syndrome would lose about a half a pound per week. And every so often, in the first 2 years, I’d stop the TPN to see where we were in the adaptation process, and she was close to autonomy. If I went 3 months, 12 weeks, you divide 12 weeks by 2, she’d have lost 6 pounds. It was just like clockwork. These patients have higher GLP levels. They have higher levels of PYY, the ileal brake, so their intestinal transit is slower and they have more absorptive time, and so the jejunal absorption is better.

When you look at what point, as you whittle away at the small bowel, would you have to go to enteral tube feeds, it would be 150 cm in type 1, but you could get down to 100 cm in type 2 before you might need tube feeds through a PEG. And if you’re talking about TPN, it would be 100 cm in this group, 50 cm down in this group.

The nutritional management, the dietitians in this room, a bunch of you would be much better at this than me, but there’s some general principles to talk about. One is the polyphagia. They will eat more automatically and it’s because they’re absorbing a smaller percentage of the food that comes into the GI tract. So, the name of the game is to eat smaller, more frequent meals, to separate the solids from the liquids, drink the liquids between meals and just save enough to kind of wet your whistle when you’re eating a meal, when you’re sitting down to the snack-like meals. And the quantity of food we’re talking about can be huge. I sent one patient to Boston to one of their intestinal rehab programs, and they trained her to eat 6000 calories a day. Now, the only other people that eat that much on the planet are the Tour de France bicycle riders, and literally, it became work for her and she would be fatigued and she’d pretty soon sloop down to 5000 or 4000 calories a day and eating wasn’t so much fun anymore.

You’ve got to limit simple sugars and switch to complex carbohydrates, and protein should make up to 20% to 30% of your total calorie intake. And then what you do is think in your mind, are they the type 2 with a colon or type 1 without? And that is going to determine whether or not you have to add additional restrictions. Oxalate restrictions are important if the colon is intact because normally oxalate would come down, be bound by the calcium, get stuck in the stool, and come out the other end. But if you have unabsorbed fat that binds the calcium, then the oxalate gets absorbed and pretty soon you’re getting kidney stones. It’s not necessary in type 1, where there is no colon.

Restricting dietary products and lactose is probably more important in the colon. You’ll have less diarrhea, less cramping, less bloating; that may not be required nearly as much when there’s no colon. Fat restriction is controversial. I’m going to get to it on the next slide. General rule, if the colon is intact, restrict fat. If the colon is gone, don’t restrict fat, push it, they need it. But I’ll come back to that in a second and totally disagree with what I just said.

Soluble fiber, incredibly important if the colon’s intact. The reason why, the bacteria will ferment the fiber, produce short-chain fatty acids. It’s like getting an extra meal from the colon. You get colonic salvage of up to 500 calories a day. That’s obviously not a case, you don’t get colonic salvage in the type 1s, but fiber still might have a role in soaking up excess fluid. Electrolytes and oral rehydration solutions are important in both groups. It might be slightly more important with the colon.

And then an interesting addition to our dietary management is restricting foods that represent this FODMAP map group of agents. These are fermentable oligo-, di-, and monosaccharides and polyols; it sounds like something from the South, polyols. These are highly fermentable osmotic agents. They produce gas, distention, bloating, and cramping, and they contribute to the diarrhea. The big strategy in irritable bowel syndrome, you avoid these foods and their symptoms get better. And that’s a big consideration in short bowel if they have a colon. It’s a nice little trick in the back of your mind. It may not be as helpful in the type 1s.

Fat restriction, let’s come back to that because it’s a very controversial issue. The best patients that respond to fat restriction are the ones with just small ileal resections in which you have unabsorbed fat that would go into the colon, irritate the colonic epithelium and contribute to the diarrhea. You restrict the fat and that gets better. Ideally, in severe short bowel syndrome, by restricting fat you wouldn’t bind up as much calcium, magnesium, and zinc and you get better absorption. But what happens in actuality, is there is inherent value from the fat, even when you’ve got the colon intact. You need the caloric density. If you have to eat 5000 or 6000 calories a day, you can’t do that without some fat density.

The food is more palatable, and guess what, it has lower osmolarity when you’ve got fat in it and you remember, we’re absorbing a percentage of the fat that we take in, and so if you don’t restrict fat, you’ll less likely get essential fatty acid deficiency. But here’s the big reason and this is something GG Boyd taught me early in my career. When you have severe short bowel syndrome and you’ve got some colon, you restrict the fat, you can’t tell the difference in the diarrhea. So don’t restrict it. What we usually will say is you’ve got to use a normal amount of fat if the colon’s there, if it’s not there, you can actually go for it on the fat.

Fluid and electrolytes. This is crazy. These patients are between a rock and a hard place. They’re hosed if they drink hypotonic fluids like water or unsweet tea and they’re equally hosed if they drink hypertonic fluids like soft drinks or fruit juices. So, you have to avoid the hyperosmolar drinks and limit the hypotonic fluid. One of my worst patients to manage worked in a school, and she could not go past the drinking fountain without hitting it and taking a big slug of water. And I could not get her to do the oral rehydration solutions.

Spread your fluids throughout the day, but some patients you just have to have runs of saline on a daily basis. One of my patients manages a farm, and he doesn’t need TPN more than 3 nights a week, but he has to get a run of saline everyday at lunch; and in the hot weather in the summer, he sometimes has to get ia couple of bags in.

Now here’s some crazy things. This review by Nightingale said add salt to liquid feeds so that you get the concentration of sodium to 100 and osmolar near 300, and he said, “And use salt tablets sometimes to help manage the symptoms of dehydration and orthostasis.” I’ve talked to all my buddies that I can think of in short bowel and nobody does that that.

The other crazy thing he says is, use Florinef to try and handle the orthostasis and the dehydration. Florinef is a mineralocorticoid we use in Addison’s disease where the adrenal glands aren’t putting out enough mineralocorticoid, you’d give Florinef to hold onto the sodium in the water with it. It’s a little bit crazy because that will also, that would contribute to the hypomagnesemia and make that worse. And that’s one of the biggest problems you have with their fluid and electrolytes. And then the oral rehydration solutions are very important.

Now this is how it works when you drink water. If you’re drinking hypotonic fluids like water or unsweet tea, you have only got one mechanism to absorb the water and that’s passive diffusion, where there’s more water in the lumen and less in the cell and you’ll move a little bit of water in there. The World Health Organization in these cholera epidemics found that if they brought a water truck into a village where there was cholera, they couldn’t change the mortality. But if they brought bags of glucose powder and salt and added it to whatever water they had, then they reduced the mortalities from cholera. And that’s because the glucose and salt bring in 3 more active pumps and you can pump more water against the gradient and they do better.

Here’s why they have trouble with the soft drinks and fruit drinks, is the hyperosmolar effect. The osmolarity of the tissue and therefore the wall and the blood is around 290 or 300. Soft drinks are twice that, and cranberry juice that looks like it ought to be healthy, is 4 times the osmolarity. That’s a killer for patients like this.

Now look what happens when a patient with severe short bowel syndrome drinks 250 cc’s of coke or a soft drink.They take it into the stomach, and before it ever gets out of the stomach, osmolar receptors in the duodenum will hold it there until it gets isosmotic.

What does that mean? It will actively secrete fluid and sodium into the lumen of the GI tract to get the osmolarity down to its isosmotic. It goes into the small bowel, you still get more absorption, more secretion of fluid, and sodium. You get some absorption below that, but the net effect after drinking 250 cc’s of Coca Cola is to get 600 cc’s out the other end with a loss of 15 milliequivalents of sodium. Can you imagine that, you’re trying to wet your thirst and you end up losing more than you took in.

Hypomagnesia is one of the biggest problems that I have trouble controlling, and there are a couple of caveats here. First of all, remember that magnesium, 60% is bound to albumin. So, if the albumin levels are low, it’s kind of like calcium, you have to actually correct for the low albumin number and I have an equation for calcium, I don’t have one for magnesium. So just because it’s a little bit low, if the albumin’s low, the active amount of magnesium may be okay. But usually, magnesium is a huge problem in severe short bowel because the magnesium is chelated or bound by the unabsorbed fatty acid. And then when they’re dehydrated and you’re not keeping up with the decreased volume status you’ll affect the adrenal glands and you’ll get a secondary hyperaldosteronism. It’s trying to hold onto the sodium and pull the fluid in that way. Because of that effect, you will dump magnesium through the kidneys.