Review of Incidence and Management of Chylous Ascites After Small Bowel TransplantationUniversity of Nebraska Medical Center, Intestinal Rehabilitation and Liver/Small Bowel Transplant Programs, Omaha, Nebraska Correspondence: Rebecca A. Weseman, RD, CNSD, LMNT, University of Nebraska Medical Center, Intestinal Rehabilitation and Liver/Small Bowel Transplant Programs, 983285 Nebraska Medical Center, Omaha, NE 68198-3285. Electronic mail may be sent to Bweseman{at}nebraskamed.com.
Nutrition management of intestinal transplant recipients continues to be a
challenging and essential component of the early postoperative care of this
patient population. The absorptive capacity of the graft can be affected by
immunologic and nonimmunologic factors, including enteric lymphatic
disruption, preservation injury, central denervation, viral enteritis,
systemic infections, and rejection. Chylous ascites, the extravasation of
milky chyle into the peritoneal fluid, defined by elevated triglycerides
levels of The goal of intestinal transplantation is to free patients from their dependence on receiving parenteral nutrition (PN), to restore nutrition autonomy, and to allow for removal of central venous catheters which carry the potential complication of life-threatening infections. As clinical advancements have been made in this population, nutrition feeding protocols have also evolved. However, there remains limited evidence on the most appropriate type of enteral or oral feeding regimens and rates for advancement of these feedings in order to achieve autonomy from PN.1 PN support has continued to be the primary source of nutrition in the early posttransplant period until bowel function is restored, evidenced by ostomy output and resolution of postoperative ileus. Discontinuation of PN is achieved in most patients in the first 4–6 weeks posttransplant as enteral nutrition support is achieved; this is generally transitioned to full oral nutrition by 6–8 weeks in the adult recipients. Longer periods of enteral nutrition support are common in pediatric recipients due to oral aversion or acquired eating disorders.2 It appears that regeneration of the lymphatic system must occur to allow for the absorption of long-chain triglycerides. Posttransplant chylous ascites does occur; however, the frequency appears to be low. This review will attempt to address the following questions:
The absorptive capacity of the graft can be affected by immunologic and nonimmunologic factors, including enteric lymphatic disruption, preservation injury, central denervation, viral enteritis, systemic infections, and rejection.2 Chylous ascites, the extravasation of milky chyle in to the peritoneal fluid, defined by elevated triglycerides levels of 218–8100 mg/dL, can occur as a result of trauma, obstruction, or interruption of the lymphatic system.3 The end products of lipid absorption in the enterocytes are chylomicrons and very-low-density lipoproteins (VLDL). These end products diffuse into the central lacteal of the villus and are transported by the lymphatic system to the circulatory system. Although carbohydrates and proteins are absorbed by the small intestine and transported to the liver by the portal venous system for processing, long-chain fats are transported by the lymphatic system. The regeneration of the lymphatic system after small intestinal transplantation (including graft retrieval, transport, and enteric lymphatic disruption) is required to allow for long-term enteral fat absorption and preservation of fat-soluble vitamin absorption. Without regeneration of the lymphatic system, the potential for the development of chylous ascites after small bowel transplantation is increased. Chylous ascites or chylothorax can also result after thoracic duct injury. As the surgical procedure with extensive retroperitoneal dissection for multivisceral transplant could result in thoracic duct injury, this potentially could lead to chylous leak. Currently, it is unclear whether multivisceral (ie, combined liver, pancreas, and small bowel) transplants may lead to an increased incidence of chylous leak vs isolated small bowel transplantation. The actual incidence of chylous ascites after small bowel transplantation reportedly is minimal.4,5 Reyes and colleagues5 at the Pittsburgh transplant program reported that chylous ascites occurred in only 4 of 58 intestinal transplant recipients between 1990 and 1997.
It has been said that there is a commonly observed "mutual adaptation" that results between the transplanted graft and the native bowel that may allow for reconstitution of the intestinal lymphatics.2 Lymphatic system regeneration appears to be essential for the absorption of chylomicrons. In animal models, there is evidence that lymphatic drainage repair begins within 2 weeks after intestinal transplantation and is complete within 6 weeks.6–12 During this time frame, the body reportedly compensates by forming collaterals around the lymphatics of the vascular anastomosis and not as a result of an increase in absorption into the mesenteric venous system of the graft. Fecal fat studies in pediatric intestinal transplant recipients have shown that near-normal fat assimilation is generally present within 8 weeks posttransplant. By this time, the majority of patients are tolerating full enteral nutrition. In 1 study, coefficients of lipid absorption were evaluated in patients receiving enteral nutrition support for between 43 and 1032 days after transplantation.10 There were no primary disaccharidase deficiencies. The mean coefficient of lipid absorption was 86% ± 12%. However, vitamin E absorption was not demonstrated until about 160 days posttransplant. Whether dietary lipid intake should be restricted within the first 1–4 weeks after transplantation is unknown, as fecal fat studies were not conducted in this study.
The concern of enteric lymphatic disruption has led to the clinical dilemma of determining the most appropriate type of enteral feeding. Traditional intestinal posttransplant enteral feeding regimens used very-low-fat enteral formulas after the resolution of the postoperative ileus. The intention was to avoid the development of chylous ascites because it was thought the lymphatic system required a period of time to regenerate before the graft could function physiologically to absorb a diet with normal fat composition. As experience has evolved in bowel transplantation, some transplant centers have verbally reported good tolerance in some patients to the initiation of a polymeric formula that includes 30% of the total calories as fat (25% medium-chain triglycerides).2 When chylous ascites is diagnosed, nutrition therapy for chylous ascites traditionally includes limiting the consumption of enteral long-chain triglycerides until the thoracic duct spontaneously repairs.3
There is little evidence to support specific enteral support or oral feeding practices after small bowel transplantation, although the goal is to use the gastrointestinal tract as soon as possible. Early feeding is defined as beginning when the postoperative ileus resolves and stomal output is evident, generally within 3–7 days posttransplant.1,10,13 Nutrition protocols vary by centers regarding the timing and type of specialized nutrition support (eg, PN, enteral nutrition), as well as when an oral diet is initiated.1,2,9,14–17 One survey evaluated the feeding protocols of the 5 most active small bowel transplant centers in the United States. Highly modified feedings (elemental ± low-fat) were commonly used in the early posttransplant period due to the fear of nonimmunologic injury, procurement and transport, and theoretically potential food allergies related to immunosuppression.1 Several centers reported that they used diluted, half-strength or three-quarters-strength low-fat elemental formulations. Enteral formulas are diluted in order to provide a formula that is isotonic or is low in osmolality to reduce the possibility of osmotic diarrhea. On the other hand, the University of Pittsburgh Medical Center and Pittsburgh Children's Hospital reported initiating small volumes of full-strength polymeric, normal-fat-content enteral feedings within 3–7 days of transplant. The use of enteral formulations with higher osmolality, theoretically, may lead to an increase in stomal output, which could be misinterpreted because increased outputs are associated with graft rejection. If low-fat elemental formulas are used, they are advanced to age-appropriate whole-protein formulas according to the individual's tolerance. Transitions to oral feedings are monitored closely to facilitate weaning of tube feedings. Many patients who begin receiving low-fat enteral formulas advance to standard polymeric formulations containing a greater provision of fat within a few weeks.1 Because absorption of medium-chain triglycerides is not through the lymphatic system, one would theorize that there may be a benefit to using enteral formulas containing medium-chain vs long-chain triglycerides. However, according to Winkelaar and colleagues, 18 there appears to be no advantage for the absorption of medium-chain triglycerides after transplantation in an animal model.18 However, these findings were based on enteral diets that were very low in fat compared with normal diets.
According to a review of the available literature, it appears the reported incidence of chylous ascites after small bowel transplantation is low. Nutrition therapies, including the use of low-fat enteral feedings and limitation of fat intake as the oral diet advances, are sometimes used; prophylactic modalities are used by some centers to avoid the potential complication of chylous ascites. When this complication occurs, advancements in either oral diet or enteral support may be delayed. Ultimately, this may lead to a prolonged requirement for PN support that is associated with increased rates of infections and metabolic complications. Despite the lack of a clear understanding regarding the regeneration of the lymphatic system after small bowel transplantation, in clinical practice, regeneration seems to begin 1–2 weeks after transplantation, with most patients consuming a normal diet within 6 weeks of transplantation.
Nutrition in Clinical Practice, Vol. 22, No. 5,
482-484 (2007)
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200 mg/dL, can occur as a result of trauma, obstruction, or
interruption of the lymphatic system. It seems the incidence of chylous
ascites after small bowel transplantation is low; however, this may be due in
part to the limitation of enteral long-chain triglycerides in the early
posttransplant period of 2–6 weeks. After this time frame, clinical
evidence suggests that fat assimilation normalizes. In the event that chylous
ascites develop as a posttransplant complication, limitation of oral or
enteral nutrition support to a very-low-fat regimen may be required, or
parenteral nutrition (PN) will need to be provided until clinical status
improves. Long-term posttransplant, lymphatic regeneration generally occurs
and the majority of intestinal transplant recipients achieve the ultimate goal
of nutrition autonomy. 
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