Nutrition before Crohn's disease surgery: what the 2024 AGA expert guidance advises

A 2024 American Gastroenterological Association (AGA) Clinical Practice Update on diet and nutritional therapies in inflammatory bowel disease (IBD) addresses, among other topics, nutrition for patients with Crohn's disease who are heading for surgery ^[2]. Its stated aim is to provide best practice advice statements, primarily to clinical gastroenterologists, while emphasizing the identification and treatment of malnutrition ^[2]. The authors note that guidance about diet in IBD is often controversial and a source of uncertainty for many physicians and patients ^[2]. They also note that dietary restrictions, along with the clinical complications of IBD, can result in malnutrition, which they describe as an underrecognized condition in this population ^[2].

What kind of guidance this is

The update is an expert review commissioned and approved by the AGA Clinical Practice Updates Committee and the AGA Governing Board ^[2]. It underwent internal peer review by that committee and external peer review through the standard procedures of the journal Gastroenterology ^[2]. Its best practice advice statements were drawn from a review of existing literature combined with expert opinion ^[2]. Because it was not a systematic review, the authors did not formally rate the quality of evidence or the strength of the statements ^[2]. Several of the statements most relevant to surgery are phrased with "may" rather than as firm recommendations ^[2].

Finding malnutrition first

The update advises that all patients with IBD be screened regularly for malnutrition by their provider, by assessing signs and symptoms including unintended weight loss, edema and fluid retention, and loss of fat and muscle mass ^[2]. When these are observed, it states that a more complete evaluation for malnutrition by a registered dietitian is indicated ^[2]. It states that serum proteins are no longer recommended for identifying or diagnosing malnutrition, because they lack specificity for nutritional status and are highly sensitive to inflammation ^[2].

Micronutrients are handled separately. The AGA advises monitoring all patients with IBD for vitamin D and iron deficiency, and monitoring for vitamin B12 deficiency in those with extensive ileal disease or prior ileal surgery, such as resection or an ileal pouch ^[2]. It also advises that outpatients and inpatients with complicated IBD be co-managed with a registered dietitian, especially those with malnutrition, short bowel syndrome, enterocutaneous fistula or more complex nutrition therapies such as parenteral nutrition, enteral nutrition or exclusive enteral nutrition ^[2]. The update describes registered dietitians as an essential part of the interdisciplinary team for nutrition assessment and management in IBD ^[2].

Exclusive enteral nutrition before elective surgery

The update discusses exclusive enteral nutrition (EEN) using liquid nutrition formulations ^[2]. It states that EEN may be an effective therapy in malnourished patients before elective surgery for Crohn's disease, with the aims of optimizing nutritional status and reducing postoperative complications ^[2]. The authors describe new data in Crohn's disease supporting enteral liquid nutrition to help induce remission and correct malnutrition in patients heading for surgery ^[2]. The abstract does not report the size of any effect on postoperative complications ^[2].

The same statements place EEN in a broader role. The AGA describes EEN as an effective therapy for inducing clinical remission and endoscopic response in Crohn's disease, with stronger evidence in children than in adults ^[2]. It adds that EEN may be considered as a steroid-sparing bridge therapy for patients with Crohn's disease ^[2]. The Crohn's disease exclusion diet, which the update calls a type of partial enteral nutrition therapy, may be effective for inducing remission and endoscopic response in mild to moderate Crohn's disease of relatively short duration, according to the update ^[2].

Parenteral nutrition in defined situations

The update states that parenteral nutrition plays a critical role in patients with IBD facing acute or chronic intestinal failure, and it names the situations in which it may be used or is suggested ^[2].

• In patients with an intra-abdominal abscess or phlegmonous inflammation that limits the ability to achieve optimal nutrition through the digestive tract, short-term parenteral nutrition may be used to provide bowel rest before surgery, to decrease infection and inflammation as a bridge to definitive surgical management, and to optimize surgical outcomes ^[2].
• The AGA suggests parenteral nutrition for high-output gastrointestinal fistula, prolonged ileus and short bowel syndrome ^[2].
• It also suggests parenteral nutrition for patients with IBD and severe malnutrition when oral and enteral nutrition have been tried and failed, or when enteral access is not feasible or is contraindicated ^[2].
• For patients with IBD and short bowel syndrome, the update advises that long-term parenteral nutrition be transitioned whenever possible to oral intake and customized hydration management, meaning intravenous electrolyte support and/or oral rehydration solutions, to decrease the risk of long-term complications; it notes that glucagon-like peptide-2 agonists can facilitate this transition ^[2].
• Intravenous, in the MedlinePlus definition, means within a vein, most often referring to medicines or fluids given through a needle or tube inserted into a vein so that they enter the bloodstream right away ^[4].

Everyday diet and strictures

Outside these specialized therapies, the AGA advises that, unless contraindicated, patients with IBD follow a Mediterranean diet rich in fresh fruits and vegetables, monounsaturated fats, complex carbohydrates and lean proteins, and low in ultraprocessed foods, added sugar and salt ^[2]. It is explicit that no diet has consistently been found to decrease the rate of flares in adults with IBD ^[2]. Patients with symptomatic intestinal strictures may not tolerate fibrous raw fruits and vegetables because of their texture, and the update suggests careful chewing and cooking or processing produce to a softer consistency ^[2].

Planning around pregnancy

A separate 2024 AGA expert review on pregnancy-related gastrointestinal and liver disease used the same approach, a literature review plus expert opinion without formal evidence ratings ^[3]. It states that clinical remission before conception, during pregnancy and postpartum is essential for improving pregnancy outcomes in IBD ^[3]. It advises that procedures and other interventions to optimize maternal health should not be withheld solely because a patient is pregnant, and that they be individualized after weighing risks and benefits ^[3]. It also states that birth for a pregnant patient with complex IBD should be coordinated by a multidisciplinary team, preferably in a tertiary care center ^[3].

Points for the pre-surgical conversation

• The update describes assessing nutritional status clinically, by weight change, fluid status and muscle and fat loss, rather than by serum protein levels ^[2].
• Vitamin D and iron are named monitoring targets for all patients with IBD, and vitamin B12 for those with extensive ileal disease or prior ileal surgery ^[2].
• For malnourished patients with Crohn's disease facing elective surgery, the update states that EEN may be an effective therapy ^[2].
• Parenteral nutrition is described for named complications, and for severe malnutrition when oral and enteral nutrition have failed or enteral access is not feasible ^[2].

Limitations

The AGA statements combine literature review with expert opinion and carry no formal evidence grades, so they are not equivalent to recommendations from a graded systematic review ^[2][3]. The abstract reports no effect sizes for preoperative EEN, and the update itself notes that evidence for EEN in inducing remission is stronger in children than in adults ^[2]. Key statements on preoperative EEN and short-term preoperative parenteral nutrition are framed with "may" rather than as firm statements ^[2]. This explainer draws on the published abstracts and does not assess the individual studies behind each statement ^[2][3].