Thursday, June 1, 2023
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Professor of Surgery, Department of Surgery, New York Medical College, Valhalla, New York; Staff Physician, Westchester Medical Center, Valhalla, New York
Of all the parts of the digestive tract, only the small bowel is absolutely essential for survival. Patients can survive total esophagectomy, gastrectomy, and colectomy, but loss of the entire small bowel is fatal without some sort of external support, such as total parenteral nutrition (TPN). The session discussed here from the American College of Surgeons 92nd Annual Clinical Congress focused on methods for increasing functional activity of the small bowel in circumstances when its function has been compromised.
Harry C. Sax, MD, Professor of Surgery, Brown Medical School, Providence, Rhode Island, opened the session with an overview of the problem.[1] He emphasized that intestinal failure has multiple causes -- not just adhesions -- and the main ones are:
Nutritional support is a critical component of the care of patients with intestinal failure. Stephen J. O'Keefe, MD, Professor of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, outlined the physiology and available therapeutic strategies. He reminded the audience that even after extensive loss of small bowel length, the function of the residual small bowel can improve over time.[2] As an example, clinicians have observed that after several months, many patients who require TPN can be supported either partially or totally with oral feedings.
The portions of the small bowel (duodenum, jejunum, and ileum) each have different functions, with digestion occurring mainly in the duodenum and water absorption in the ileum. Jejunal loss is not as serious as loss of the ileum. How much small intestine do we need to maintain a life? If there is a normally functioning colon, then the cutoff point is around 60 cm of small bowel. If the colon is absent or nonfunctioning, then about 115 cm of small bowel will be required to maintain life.
Monitoring the patient's weight is the best way to determine the adequacy of nutritional support. Patients require about 25 kcal/kg/day to maintain their weight. A key strategy is to encourage the remaining small bowel to work harder by increasing the caloric content of the diet, even at the risk for malabsorption -- because more nutrients will still be absorbed than lost.
With intestinal failure, however, fluid loss -- not inadequate digestion -- is the main problem. In regard to this, Dr. O'Keefe stressed an important point: Drinking water is bad! Allowing patients to consume large quantities of water will accentuate sodium loss. So instead of water, supply isotonic liquids. Soups supply liquid and contain nutrients and salt and can be an important part of the diet. Another simple but useful strategy is to divide dietary intake into several small meals rather than the customary 3 daily meals.
Dr. Thomas R. Ziegler, Associate Professor of Medicine, Department of Surgery and Medicine, Emory University, Atlanta, Georgia, discussed therapy with some of the newer agents that may increase the functional capacity of the remaining small bowel.
Growth hormone, for example, has received approval from the US Food and Drug Administration (FDA) for the management of short bowel syndrome.[3,4] Various treatment strategies with growth hormone and other agents are being tried in patients with short bowel syndrome. In one randomized controlled trial, a combination of an adequate diet plus growth hormone plus glutamine produced results that were superior to dietary therapy alone.[5] Another hormone, glucagon-like peptide (GLP)-2, may have a role in stimulating intestinal mucosal adaptation in patients with short bowel syndrome, although its mechanism of action is not completely clear.[6,7] This agent is now undergoing evaluation in a phase 3 trial.
A recent supplement to Gastroenterology summarized much of the available information about overall management, including drug therapy, of patients with short bowel syndrome.[8] Of note, however, a sustained effort should be made to wean patients from TPN without having to resort to additional therapeutic agents.
Because intestinal failure is so difficult to manage, are there preventive measures to reduce its occurrence? Dr. Jon S. Thompson, Professor and Section Chief of General Surgery Department of Surgery, University of Nebraska Medical Center, Omaha, Nebraska, discussed this problem. The known causes of intestinal failure are presented in the Table.[9,10]
| Cause | Percentage of Patients |
|---|---|
| Postoperative Resection (after previous surgery) | 25% |
| Irradiation following cancer | 24% |
| Vascular insufficiency with bowel ischemia | 22% |
| Crohn's Disease | 16% |
| Other causes | 13% |
He emphasized that preventive efforts should focus on minimizing the formation of adhesions, reducing technical error, and early diagnosis of ischemia. When operating for suspected bowel ischemia, it is sometimes difficult to determine the extent of compromised bowel; in this situation a conservative resection of potentially ischemic bowel followed by a "second-look" procedure may help salvage valuable portions of the bowel.[11]
When dealing with intestinal strictures in patients with short bowel syndrome, if possible, it is better to dilate or perform a stricturoplasty rather than to remove additional bowel.
He also reviewed surgical procedures for lengthening the small bowel, such as the Bianchi procedure or the serial transverse enteroplasty procedure (STEP) (Figure).
Figure. Diagram illustrating serial transverse enteroplasty (STEP) procedure. Multiple incisions are made and sutured with a surgical stapling instrument. The intestinal lumen becomes narrower but longer.[12]
Kareem M. Abu-Elmagd, MD, PhD, Professor of Surgery and Director, Intestinal Rehabilitation and Transplantation Center, University of Pittsburgh, Pittsburgh, Pennsylvania, closed the session with a discussion of transplantation.
Worldwide, 65 centers have performed approximately 1292 small bowel transplants, with a 5-year survival rate of 50% or better. The longest survival times are 13 years following small bowel transplantation and 16 years after combined small bowel and liver transplantation. It is difficult to perform a cost-effective analysis after transplantation, but it probably extends life and appears to be cost-effective.[13]
The prognosis after small bowel transplantation improved after the introduction of tacrolimus in 1990, but there are still problems related to the early diagnosis of rejection after transplantation. Currently, the most frequent source for donor small bowel is from cadavers, but living donors have also been used.[14]
Dr. Abu-Elmagd pointed out that at present, Medicare reimbursement for transplantation is only allowed for patients who are considered to be TPN failures. However, long-term TPN therapy often leads to liver failure, necessitating both bowel and liver transplantation. He hopes that the indications for small bowel transplantation will become wider.
Follow-up questions addressed by the panel included the following:
Key points from this session of management strategies for patients with intestinal failure included:
