NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #222

The Clinician’s Toolkit for the Adult Short Bowel Patient Part I: Nutrition and Hydration Therapy

The Clinician’s Toolkit for the Adult Short Bowel Patient Part I: Nutrition and Hydration Therapy

The care of patients with short bowel syndrome (SBS) varies nationwide. How do we know? Because we receive emails and phone calls from patients and clinicians all over the country (and even outside the country) desperate for help. SBS patients also present to clinic suffering with SBS (or undiagnosed SBS) with very little to no education provided to them. Patients just want a reasonable life back, and to take the best care of their health going forward; clinicians want to help their patients achieve just that. This article aims to address the most common diet and hydration issues that SBS patients struggle with and to provide clinicians with the tools to successfully improve both nutrition and hydration status as well as the overall health and well-being of the adult SBS patient.

Introduction

The gastrointestinal (GI) tract is an intricate and carefully orchestrated food-processing organ designed to digest and absorb the foods and beverages that enter it. Significant loss of the primary absorptive surface area resulting in short bowel syndrome (SBS) will require modifications to the oral diet for the remaining GI tract to compensate for this loss. SBS is defined as < 200cm or >75% of working small bowel (SB—not to be confused with SBS) lost.1 It is also described as an inability to nourish and hydrate an individual while consuming a normal diet and fluid intake. Luminal nutrients from food intake (or enteral infusion in some) are paramount to the GI tract adaptation process for those with SBS; these nutrients initiate the signaling in the GI tract through the secretion of enterohormones that control intestinal motility, absorption, and adaptation.2,3 The most common etiologies that can result in SBS in adults are found in Table 1.4,5

SBS is not just about the loss of SB absorptive surface area causing malabsorption, but encompasses all the regulatory processes that the diseased or resected SB segment controls such as: gastric emptying, motility and transit time, and gastric secretions.6,7 The loss of this “gut intelligence” results in:

  • Intestinal hurry making it difficult for nutrients to have enough time to be absorbed before being excreted
    Poor mixing of pancreatic and biliary secretions with ingested nutrients making digestion of fat particularly challenging
  • Too much acid entering the upper gut from gastric hypersecretion can denature pancreatic enzymes and destabilize bile salts rendering micelle formation ineffective
  • A diminished bile salt pool if too much ileum is resected as the bile salts will be lost in the stool instead of reabsorbed through enterohepatic circulation, and
  • Small intestinal bacterial overgrowth due to loss of the ileocecal valve, or areas of stricture, narrowing, or slowed motility. 

The SB primarily absorbs the vast majority of nutrients ingested. However, in addition to avid absorption of sodium and water, the colon can also absorb up to 500 calories per day through the generation of short chain fatty acids from fiber fermentation.8 Therefore, the presence of a colon can significantly improve the outcome of an individual with SBS and substantially improve survival. In most settings, recruitment of any remaining colon should be performed.
Given the complex malabsorptive disorder associated with SBS, it is difficult for patients to nourish and hydrate themselves without the help of diet modification and attention to oral hydration, selective use of medications, and when necessary, parenteral nutrition or intravenous fluids. Negotiating all aspects of care required of individuals with SBS challenges even the fittest of our patients and exhausts the rest. Patient and caregivers buy into a near fulltime job with honorary degrees in medicine, nursing, physical therapy, pharmacy, dietetics and more. Clinicians on the other hand (many without formal training or experience with SBS), suddenly find themselves in the role of air traffic control at Chicago O’Hare on a Friday night with serious weather approaching when dealing with the complexity that is SBS. Part I of this two-part series will address the most common diet and hydration issues seen in clinic that SBS patients struggle with and will provide clinicians with the tools to successfully improve both nutrition and hydration status, and in turn, overall health and well-being of the adult short bowel patient.

A Word about Anti-motility Medications

While diet and hydration therapy are critical for the success of the SBS patient, most will also require antimotility medications to slow intestinal transit and optimize digestion and absorption of nutrients and fluids in the SB. Often, providers simply prescribe these medications with a flexible dosing schedule of two, three or four times daily. However, taking antimotility medications consistently in a scheduled fashion 30-60 minutes prior to meals will slow gastric emptying, improve digestion, and allow increased nutrient and fluid contact time with intestinal mucosa for increased absorption and reduced stool output.9 There are some patients who will benefit from liquid antimotility agents or crushing the tablet to increase efficacy of the medication. The clinician should discuss proper timing of antimotility medications with meals when talking to SBS patients about diet and hydration. It is imperative for SBS patients to understand why providers might order these medications and how to administer the drugs to optimize absorption. Part II of this series will provide more in-depth information about medication use and abuse in the SBS patient.10

Diet and Nutrition Therapy

Because different sections of the GI tract have different responsibilities, understanding normal anatomy and physiology, with knowledge of the patient’s remaining GI anatomy, will help the clinician tailor the diet to the individual SBS patient. A crucial role of the dietitian is to translate alterations in digestion and nutrient absorption after a bowel resection into a meal plan that not only meets the individual’s preferences and lifestyle but is also presented in a manner that the patient can understand. The patient must be informed of not only what they need to avoid, but more importantly, what they can eat, and the amount and frequency of meals and snacks. Clinicians should ideally start with a good 2 to 3-day diet record of what is normally consumed and then tailor the meal plan—it may feel less like taking things away when readjusting the diet that the patient is familiar with. Expertise in the SBS diet highlights the role of the dietitian as an invaluable team member to these patients. 

The SBS diet is quite similar for those with and without a colon, however, there are some important differences. Table 2 lists the general SBS diet guidelines and Table 3 provides recommendations specific to remnant anatomy. 

About Dietary Oxalate Restriction in SBS

Oxalate kidney stones are of concern for individuals with SBS and some colon in continuity. In the normal GI tract, dietary calcium and oxalate bind to form an insoluble complex that passes unabsorbed in the stool.12 However, when dietary fat is malabsorbed, the fat will preferentially bind to calcium leaving oxalate free in the gut lumen. Free, unbound oxalate passes into the colon where it is readily absorbed across the mucosa into the bloodstream, is then filtered by the kidney, and can bind to blood calcium forming insoluble calcium-oxalate kidney stones.13 As oxalate is not absorbed by the SB, calcium oxalate stones are only expected to occur in the setting of a colon in continuity (although patients without a colon are at higher risk for dehydration and therefore stone formation).14

Kidney stones are not only extremely painful to pass, but if left in the kidney can lead to end stage kidney disease. The last thing someone with SBS needs is reliance on hemodialysis or a kidney transplant. Prevention of calcium-oxalate kidney stones is the best approach. Limit dietary fat in those with a colon. Be mindful that treating bile acid malabsorption with bile acid binders can worsen fat malabsorption, further enhancing oxalate absorption in the colon. Work to balance bile salt sequestration and dietary fat restriction. Of note, for those with > 100 cm of terminal ileum lost (or dysfunctional due to disease), the normal compensatory increase in bile acid synthesis cannot keep up to maintain the intraluminal bile acid pool. As a result, these patients should not be put on bile acid sequestrants or steatorrhea will worsen.15

The best defense against kidney stone formation is to flush the oxalate through the urinary tract by maintaining a urine output > 1500 mL/day.16 A calcium citrate supplement taken with meals will correct metabolic acidosis, if present, and in addition, the calcium will bind free oxalate in the intestinal lumen to prevent absorption. Avoid using calcium carbonate in the setting of acid suppression (proton pump inhibitor or H2-receptor antagonist); the calcium will not solubilize at the higher pH, making it unavailable to bind oxalate.6 A low oxalate diet on top of the SBS diet becomes very restrictive and should only be necessary once a patient has “earned it” by developing a kidney stone or hyperoxaluria. A 24-hour urine collection for volume and urine oxalate can help decipher need for dietary oxalate restriction and increased daily urine volume is warranted when there is concern for calcium oxalate kidney stone formation.

Essential Fatty Acids

Essential fatty acids (EFA) are required for health and development. Good sources of EFAs are plantbased oils such as sunflower, soybean, and walnut. Those with SBS who are dependent on parenteral nutrition and receiving less than 1 g soy-based lipid emulsion/kg/week are at risk of developing EFA deficiency.1 Clinical signs of EFA are dry, scaly, or red patches of skin. Assessment for EFA deficiency (triene-tetraene ratio on a fatty acid panel) is suggested as part of the routine monitoring of micronutrient levels.

Hydrating the SBS Patient

Attaining adequate hydration can be very difficult for patients with end ileostomies;17 it is even more difficult for those with SBS with SB stomas (without a colon in continuity). Renal impairment in the short bowel patient has been well documented.18,19 Most clinicians are aware that individuals with SBS will have difficulty meeting nutritional requirements without diet modification, selected medications, and possibly parenteral nutrition. What is not so apparent is how well they can achieve hydration goals or what hydration goals are for an individual patient. Although serum laboratory values provide clues, they are not the most reliable criteria to assess hydration status; some are only abnormal when significant volume contraction occurs, or worse, acute kidney injury. It is therefore incumbent upon the clinician to ensure both nutrition and hydration adequacy (see Table 4 for signs and symptoms). Clinicians should always ask:

  1. Can the patient nourish themselves?
  2. Can the patient hydrate themselves?
  3. How will each of the above be monitored to ensure success?

to have patients periodically measure their 24hour urine volume to ensure they can make a minimum of 1000-1200 mL/day. Keep in mind, there is nothing wrong with making more urine (ask any nephrologist), but there is a lot wrong with not making enough. Another promising measure of adequate hydration status is a morning spot urine sodium.20 For those with kidney stones, collaboration with the managing nephrologist or urologist may help to determine the appropriate 24-hour urine volume for a particular patient. Remember, the goal for hydration is to protect kidney function and prevent end stage renal disease and future dialysis-dependence.

Hydration Management

Unfortunately, more than one SBS patient has been advised to “just drink more” when they have presented to clinic or the emergency room with dehydration as healthcare providers have presumed the patient was just not drinking enough. However, the true problem in SBS is the lack of absorptive surface area for both salt and water; that their remaining bowel just cannot absorb enough of the fluid consumed. In fact, a vicious cycle of drinking (often hypotonic or hypertonic fluids) can develop in SBS patients who experience an uncontrollable desire to constantly drink fluids. This is caused by chronic, severe, dehydration. In the same way that the patient malabsorbs food and feels constantly hungry (as they are starving); the same is true for the patient who cannot sufficiently absorb enough fluid; they feel constantly and insatiably thirsty. When a patient feels thirsty, they are already dehydrated. Hence, the cycle is perpetuated by drinking more fluids, aggravating diarrheal losses, leading to more thirst, and more drinking yet. Furthermore, there are patients who, no matter what they drink (including oral rehydration solutions [ORS]), only add to their stool or ostomy losses and worsen dehydration. Some patients just need IV fluids, at least until enough adaptation occurs. It is very important for clinicians to identify these patients before deterioration of their renal function occurs. See Table 5 for common scenarios patients report or experience.

Table 6 illustrates the experience of one such patient who thought she was supposed to drink a lot because she had a high output stoma (she was drinking primarily oral rehydration therapy, some water, and 6 ounces of coffee). Her oral fluid intake was reduced every 2 weeks with no other changes to demonstrate to her how much her drinking was driving her unwanted high ostomy output. This underscores how important it is to not only have patients record what they are eating, but what, and how much they are drinking.

Maintaining euvolemia and sodium balance while ingesting common oral liquids can be dependent on the presence or absence of a colon. With a colon segment in continuity, many SBS patients can tolerate hypotonic fluids without excessive fluid losses.21 However, without a colon in continuity, high ostomy outputs are commonly encountered when excess fluid losses result from consuming either hypertonic or hypotonic fluids. Table 7 lists common types of beverages based on their tonicity. It is not enough to suggest to a SBS patient what to drink, but equally as important to teach how to drink, especially how much to drink. It is recommended that in SBS, patients drink small amounts of fluids with meals to ease passage of the food bolus. However, the majority of fluid intake should come from sipping all day long between meals as fluids are more efficiently absorbed when consumed in small amounts, frequently, and between meals.22 Some patients need to be educated on this behavior. A smaller volume of liquid prevents a surge of fluid in the small intestine. This surge can reduce fluid absorption rates through the SB as opposed to absorption.23 In particular, for those with a SB ostomy, excessive fluid intake or drinking too fast (regardless of the fluid type), will lead to a significant loss of fluid, further worsening dehydration. Therefore, good practice is to advise patients of their daily fluid volume goal (which is patient dependent) and encourage sipping these fluids over the course of a day. Until urine output is adequate and stable, 24-hour urine volume should be measured and monitored to optimize volume status and protect kidney function. It may be necessary to demonstrate to patients how the oral fluids they are consuming drive stool output. This can be accomplished by asking the patient to decrease oral fluid intake to only 500mL over 24 hours and have them measure both urine and stool/ostomy output to illustrate the effect of the limited oral fluid intake. However, do not try this without a mechanism to ensure hydration of the patient. Oral Rehydration Solutions (ORS)

In those SBS patients without a colon, additional sodium is often required since every liter of stool output contains 90-110mEq of sodium (2 g sodium or 1 teaspoon table salt).24 However, this amount of salt is usually unpalatable, so consumption of salty foods and ORS is necessary to effectively replace sodium losses. Water absorption in the SB is dependent on the sodium-glucose co-transport system which draws glucose and sodium across the epithelial membrane in equimolar fashion, while allowing for water absorption via paracellular passage.25 Commercial and homemade ORS recipes are based on this premise, and therefore, need similar concentrations of sodium and glucose to allow for water absorption and ultimately hydration of the individual. See Table 8 for examples of commercial ORS (and ORS recipes that can be made at home).

ORS, while lifesaving in many, is not a panacea for all patients with SBS. When starting ORS, it is advisable to have the patient sip 1-2 cups throughout the day while tracking 24-hour urine output. If urine output increases without significant increase in stoma or diarrheal output, then it is ok to slowly increase the daily ORS volume to somewhere between 1-2 liters/day. However, if slowly sipping ORS throughout the day leads to significantly increased stoma output (without a concomitant increase in urine output, or worse, a decrease in urine production), then the ORS trial has failed, and the patient should reduce the consumption of ORS. Before declaring an ORS trial a failure, make sure the patient is slowly sipping the ORS throughout the day and not rapidly consuming the solution just to finish it.

Vitamins and Minerals

Many SBS patients will require vitamin and mineral supplementation throughout their lifetime. The sites of remaining bowel, health of the bowel, intestinal transit time, and nutrient quality of the habitual diet will influence the need for supplementation. Micronutrients of concern, specific to SBS, include fat soluble vitamins (A, D, E, and K), vitamin B12, folate, calcium, magnesium, zinc, iron, copper, and selenium.26 Rapid intestinal transit, chronic vomiting, and parenteral multivitamins less than five days a week (if parenteral support dependent), may necessitate water-soluble vitamin supplementation. The exception to this rule is for vitamin B12; all SBS patients will need routine monitoring for vitamin B12 deficiency by checking both serum B12 and methylmalonic acid on a periodic basis. This is an area ripe for study.27

Table 9 lists examples of oral vitamin and mineral supplements that might be needed by those with SBS. Remember, micronutrient absorption can improve with bowel adaptation and therefore, lifelong monitoring of serum vitamin and mineral levels, as well as a periodic nutrition focused physical exam are essential for the SBS patient. Clinicians monitoring micronutrient levels must recognize that inflammation, acute illness, and hypoproteinemia, can alter transport protein concentrations leading to factitious serum and plasma levels making results difficult to interpret.29,30 It is critical that clinicians do not rely solely on biochemical interpretations to develop micronutrient treatment strategies when a deficiency is suspected. 

Bone health is an excellent example of the need for comprehensive assessment to determine the need for supplementation. Since calcium, vitamin D, and magnesium absorption are often suboptimal in those with SBS, periodic DEXA scans are recommended to evaluate bone density to guide therapy and prevent metabolic bone disease (Table 10).1

Conclusion

Maintaining both nutrition and hydration status are central components to the care of patients with SBS. Failure to attend to these key issues puts the SBS patient at risk for malnutrition, weight loss, nutrient deficiencies, dehydration (with or without electrolyte disarray), nephrolithiasis, and, worse-case scenario, for acute kidney injury, and over time, loss of renal function. With careful education regarding principles of nutrition and hydration, this will set the SBS patient on a path to ensure good health and protection of their renal function. Lifelong monitoring and support from a healthcare team are necessary in all SBS patients as management goals can change over time. Table 11 provides a summary of common clinical blunders and the suitable solution in the care of SBS patients. See Table 12 for SBS-related resources for the clinician.

References

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