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Perioperative Nutrition

Nutritional care in GU reconstruction centers on identifying malnutrition, meeting actual intake deficits, choosing a safe feeding route and preventing refeeding complications. Low albumin and loss of muscle identify risk, but neither establishes that a graft or anastomosis will fail. Decisions about postponing surgery depend on the nutritional assessment, urgency and expected benefit of optimization.[1][2]

This is the perioperative workflow. Nutritional Assessment covers screening, examination, laboratory interpretation and body composition. See also Frailty, ERAS, Wound Healing and Bowel Anastomosis.

Why Nutrition Matters in GU Reconstruction​

Nutrition intersects the outcomes a reconstructive surgeon cares about.

  • Wound healing: energy, amino acids, vitamins and trace minerals are the substrate for fibroblast proliferation, collagen synthesis and epithelialization; deficiencies impair each step.[24]
  • Anastomoses and infection: malnutrition and underfeeding are risk factors for postoperative complications, and ESPEN treats nutritional therapy as mandatory for surgical patients at nutritional risk.[1]
  • Graft and flap take: buccal mucosa grafts and flaps depend on imbibition, inosculation and new vessel growth. It is reasonable to expect a catabolic patient to heal worse, but no urethroplasty-specific trial has shown that correcting a nutrition measure prevents graft failure.
  • Recovery: sarcopenia and frailty overlap with but are distinct from malnutrition. In older surgical patients, sarcopenia is associated with postoperative delirium and delayed recovery; in older patients undergoing major surgery, frailty is associated with poor postoperative outcomes.[49][1]

The working principle: screen every patient being considered for major elective reconstruction, and treat an identified deficit before the index operation when the surgical timeline allows.[1]

Assessment Before Major Reconstruction​

Screen early enough to intervene before elective surgery, then reassess when intake or clinical condition changes. Ask about weight trajectory, recent intake, swallowing, vomiting or diarrhea, restrictive diets, prior bowel or bariatric surgery, alcohol use and ability to obtain or prepare food. Examine for muscle and fat loss, edema and functional impairment.[1][2]

AssessmentAppropriate use
MUSTBest-supported screen in a 1,649-patient multicenter major-abdominal-surgery cohort (MUST analysis n = 1,614): sensitivity and specificity near 80% against SGA, with good prognostic validity[23]
NRS-2002ESPEN-associated screen combining nutritional status and disease severity; flagged only 24% of that cohort as at risk[23]
MNA-SFSuited to older adults; best discrimination on its ordinal scale (AUC 0.83) but flagged 58.6% as at risk, so follow an abnormal screen with assessment[23]
GLIMDiagnostic framework after screening: at least one phenotypic and one etiologic criterion
Weight, intake, muscle and functionEstablish the deficit and monitor recovery
Albumin / prealbuminPrognostic context influenced by inflammation, fluid balance, hepatic synthesis and renal/GI losses; not measures of body protein or adequate feeding

Do not prescribe albumin infusion, supplements or postponement solely to normalize a laboratory value. Hypoalbuminemia should prompt evaluation of its cause and overall surgical risk.[2]

ESPEN 2025 defines high metabolic risk by any one of: weight loss over 10–15% within six months, BMI below 18.5 kg/m², NRS-2002 of at least 5 or SGA grade C, or preoperative serum albumin below 30 g/L after excluding hepatic or renal dysfunction (a criterion also listed in ESPEN 2017).[1] ESPEN 2025 accepts hypoalbuminemia as a prognostic factor but attributes it mainly to disease severity and catabolism, not nutritional status.[1]

Nutrition and Wound Healing: The Reconstructive Evidence​

Most of the data below are observational and come from plastic and reconstructive cohorts. They identify who is at risk.

Albumin as a Risk Marker​

CohortFinding
ACS-NSQIP plastic surgery, 200,015 patientsAlbumin ≤3.3 g/dL: any 30-day complication 36.5% vs 10.4% with higher albumin. In the adjusted model, higher albumin concentration was associated with lower odds of a complication (OR 0.460, 95% CI 0.375–0.564).[25]
NSQIP autologous breast reconstruction, 10,865 proceduresWound complications 16% with obesity plus albumin below 3.5 g/dL, vs 9.2% for obesity alone or hypoalbuminemia alone[26]
NSQIP head-and-neck free flap, 3,038 patientsAlbumin below 3.5 g/dL: flap failure 6.3% vs 2.1% (OR 3.37, 95% CI 1.38–8.21); death OR 3.98 (1.70–9.63)[27]
NSQIP free tissue transfer, 34,571 patients (albumin available in 16,250)Frailty (mFI-5) and hypoalbuminemia each independently predicted complications; the two together predicted outcomes better than either alone[28]

Protein​

Protein supplies the substrate for collagen, angiogenesis and immune function. For malnourished patients planning elective GI surgery, the ASCRS/SAGES guideline notes that oral supplements targeting 1.2–1.5 g/kg/day for 1–2 weeks have been associated with fewer complications .[3] Body-contouring guidance after massive weight loss cites 60–120 g/day.[38]

A retrospective cohort of 200 non-bariatric full abdominoplasty patients compared protein supplementation (at least 1.2 g/kg/day as whey isolate or hydrolyzed collagen, started within 24 hours and continued at least 14 days) with none. Dehiscence was 6% versus 17% (P = .018), seroma 9% versus 18% (P = .048) and time to complete healing 16.8 versus 20.5 days. Surgical site infection (4% versus 10%) did not differ significantly. The design is observational and single-procedure.[29]

Micronutrients​

Evidence for vitamins and minerals is wound-type specific. A systematic review of 36 studies (2,339 patients) found benefit reported for vitamin C and zinc in pressure ulcers, zinc in venous ulcers, vitamins A, D and E in diabetic ulcers and burns, and vitamin E in hypertrophic scars; it found no official recommendation for routine supplementation.[30]

NutrientWound-healing roleWhere trials report benefit[30]
Vitamin CCollagen hydroxylation, neutrophil function, antioxidantPressure ulcers
ZincDNA and protein synthesis, cell divisionPressure ulcers, venous ulcers, burns
Vitamin AEpithelial differentiation, inflammatory modulationBurns, diabetic ulcers
Vitamin DImmune modulation, tissue repairBurns, diabetic ulcers

An exploratory randomized trial in 21 men undergoing Lichtenstein hernia repair gave arginine 14 g, glutamine 14 g, vitamin C 1,250 mg and zinc 55 mg daily from 14 days before to 14 days after surgery, on top of about 1.5 g/kg/day protein in both arms. Wound-fluid procollagen (CICP) rose from day 1 to day 2 only in the supplemented group and was 49% higher on day 2 (P = .10), and the serum collagen marker PRO-C5 fell postoperatively only in controls.[31]

Applying This in GU Reconstruction​

  • Urethroplasty and grafts: treat measured malnutrition, weight loss or poor intake before elective grafting. There is no urethroplasty-specific trial of albumin or protein optimization.
  • Bowel-containing reconstruction: malnourished patients carry higher morbidity, so apply the ESPEN pathway below. See Bowel Anastomosis.[1]
  • Free flaps (gracilis, DIEP, ALT, fibula for phalloplasty): screen for frailty and malnutrition together.[27][28]

Preoperative Optimization​

  • Address a measured intake deficit: food fortification, dietitian support and a balanced oral nutritional supplement (ONS) when ordinary food is insufficient. ESPEN recommends an ONS that matches the deficit in calories, protein and micronutrients before major abdominal surgery in malnourished or high-metabolic-risk patients.[1] A commonly used protein target in malnourished elective GI surgical patients is 1.2–1.5 g/kg/day for 1–2 weeks; choose the dosing weight and modify the target for renal disease, obesity, catabolism and other individual factors.[3]
  • Severe malnutrition or high metabolic risk. ESPEN 2025 recommends preoperative nutrition even if surgery must be postponed (grade A, strong consensus) and suggests considering 10–14 days (grade B).[1] Current high-risk criteria include marked weight loss, BMI below 18.5, NRS at least 5 or SGA C, or serum albumin below 30 g/L after excluding hepatic or renal dysfunction. Albumin denotes metabolic or surgical risk, not a stand-alone malnutrition diagnosis.[1][2]
  • Use oral or enteral delivery when feasible. ESPEN recommends preoperative PN only for severe malnutrition or high metabolic risk when oral/enteral nutrition is not feasible (grade A); a 10–14-day period, with a minimum of seven days, can be recommended for that selected group (GPP).[1]
  • Correct identified deficiencies: avoid routine high-dose zinc, vitamin A or other micronutrient combinations without an indication.
  • Combine nutrition with risk-adjusted prehabilitation: exercise and management of smoking, alcohol use, symptoms and comorbidities should fit the available surgical timeline.[1]

Fasting and Carbohydrate Drinks​

For elective adults without increased aspiration risk, clear liquids, including clear carbohydrate drinks, may be taken until two hours before anesthesia; solids and non-clear liquids such as milk products, meal-replacement drinks and enteral formulas generally require at least six hours, while a large fatty meal may require eight hours or longer. Preprocedural tube feeding may not need to stop when a cuffed tracheostomy or tracheal tube already secures the airway.[42] Follow the anesthetic plan for obstruction, delayed gastric emptying, emergency surgery or other increased-risk situations.[1][3]

A protocolized carbohydrate drink (maltodextrin-type complex carbohydrate, given the evening before and up to two hours before anesthesia) may improve comfort and the metabolic response before major abdominal surgery. ESPEN grades this B/0; ASCRS/SAGES gives a weak recommendation for colorectal surgery patients without diabetes.[1][3] A Cochrane review of 27 trials found about 0.3 day shorter stay and no difference in overall complications, and a 2025 meta-analysis of 44 trials in major elective non-cardiac surgery found 0.56 day shorter stay (95% CI 0.02–1.10).[1][3][40] Do not prescribe carbohydrate drinks indiscriminately in suspected gastroparesis or poorly controlled diabetes. GLP-1 or GIP therapy requires the additional assessment below.

Immunonutrition: What Changes Practice​

Immunonutrition adds selected substrates such as arginine, omega-3 fatty acids and nucleotides to standard nutrition. GI-cancer trials and meta-analyses underpin the ESPEN 2025 grade B recommendation to offer it preoperatively or perioperatively around major tumor surgery, for five to seven days before surgery in GI cancer. That recommendation predates the phase 3 SWOG cystectomy report.[1]

GI-Cancer Evidence​

AnalysisPopulationResult
Khan 2023 meta-analysis37 RCTs, 3,793 patientsInfectious complications OR 0.58 (0.47–0.72); SSI OR 0.65 (0.52–0.81); anastomotic leak OR 0.67 (0.47–0.93); length of stay 1.94 days shorter. Benefit was seen with preoperative or perioperative dosing and independent of nutritional status[32]
Adiamah 2019 meta-analysis16 RCTs, 1,387 patients, preoperative ImpactInfectious complications (n = 1,387): OR 0.52 (95% CI 0.38–0.71); hospital stay (n = 995): 1.57 days shorter (95% CI 0.66–2.48 days shorter); no detected effect on noninfectious complications (n = 1,303) or mortality (n = 955)[33]
Ricci 2023 component network meta-analysis87 studies, 8,375 patients, major abdominal surgeryBest morbidity result: perioperative enteral/oral arginine, glutamine and PUFA, OR 0.32 (0.10–0.98), moderate certainty with a wide interval; effects on mortality, infection and stay were uncertain[34]

Effect size varies with the control arm (isocaloric standard supplement versus unsupplemented diet) and with industry sponsorship, and is smaller against an equivalent calorie and protein control.[3]

Radical Cystectomy — SWOG S1600, 2026​

Specialized immunonutrition did not significantly reduce the primary complication outcome compared with standard ONS. This double-blind phase 3 trial randomized 203 patients at 13 US centers; 178 contributed to the primary analysis. Both groups received matched calorie and protein supplements for five days before and five days after cystectomy.[4]

Primary 30-day resultSpecialized immunonutritionStandard ONS
Any complication56/90 (62.2%)51/88 (58.0%)

The odds ratio was 1.18 (95% CI 0.64–2.18). High-grade (Clavien-Dindo III–V) 30-day complications were 11.1% versus 12.5% (OR 0.86, 0.34–2.17). Intervention-related adverse events, most often nausea, occurred in 31/91 (34.1%) versus 18/88 (20.5%; P = .06). Separately, postoperative UTI occurred in 29/90 (32.2%) versus 15/88 (17.0%; P = .02); the authors cautioned that this individual complication difference may be random variation.[4] Severe malnutrition was excluded.[4] Two-year survival numerically favored immunonutrition (overall survival 87.4% versus 78.2%) but the difference was not statistically significant.[4]

Prioritize adequate nutrition.

Interpreting Earlier Evidence​

  • Cochrane 2019: eight cystectomy trials (500 patients) of mostly small, dated design. The immunonutrition comparison rested on 29 patients; the 90-day complication estimate was RR 0.31, 95% CI 0.08–1.23, with low certainty. The interval includes no benefit. In one 157-patient trial, parenteral nutrition increased 30-day complications compared with oral nutrition (RR 1.40, 1.07–1.82; low certainty).[5]
  • Khaleel 2021, 204 patients (retrospective, single institution): preoperative oral arginine-based immunonutrition was associated with less postoperative infection (25% versus 45%; adjusted OR 0.35) and less TPN use (17.3% versus 35.6%; OR 0.38), with no significant difference in high-grade complications, readmission, ileus or length of stay.[35]
  • Hamilton-Reeves 2018 pilot RCT, 29 men: five days of specialized immunonutrition before and after cystectomy shifted the Th1/Th2 balance toward Th1, had 42.8% lower plasma interleukin-6 on postoperative day 2 than the standard oral nutritional supplement group and prevented the postoperative fall in plasma arginine.[36]
  • Amer 2026, 74 patients: a combined calorie and protein and immunonutrition pathway improved recovery measures (time to flatus 39.6 versus 64.8 hours; length of stay 7.8 versus 10.6 days; wound healing 14.2 versus 15.5 days; better skeletal muscle preservation at 30 days), but the primary overall complication outcome was not significantly different (54% versus 68%; P=.236).[6]
  • INCyst: the cited publication describes a planned 232-patient trial.[7]

Choosing and Starting Nutrition Support​

Oral food or ONS first, then enteral tube feeding when oral intake is inadequate, then PN when oral or enteral delivery is contraindicated or insufficient.[1]

Clinical situationPractical approach
Awake, hemodynamically stable and tolerating intake after surgeryResume oral intake early; routine waiting for flatus is unnecessary
Unable to meet needs orally, especially with malnutrition or expected prolonged inadequate intakeConsider EN within 24 hours when safe; select access according to anatomy and aspiration risk
Expected inability to eat for at least five days, or already below 50% of energy needs for over seven daysBegin nutrition therapy promptly
Oral/EN delivery remains below 50% of requirements within three to four daysESPEN 2025 recommends supplemental PN to address the deficit
Oral/EN contraindicated, particularly with severe malnutritionStart PN as soon as feasible with appropriate metabolic precautions

Severe shock, suspected bowel ischemia, obstruction, uncontrolled GI bleeding or an unsuitable intestinal fistula may preclude EN. Most postoperative patients who require tube feeding can use a balanced standard polymeric formula; recent bowel surgery alone does not mandate an elemental formula.[1]

ESPEN recommends starting EN within 24 hours when calories cannot be met orally, particularly when oral energy and protein intake is expected to stay below 50% for the next seven days. In malnourished or high-metabolic-risk patients, start EN at 10–30 mL/h and advance only while electrolytes stay stable; reaching the caloric target can take up to five days. Weigh intraoperative nasojejunal or jejunostomy access for esophagectomy, total gastrectomy and pancreatoduodenectomy; it is rarely relevant to GU reconstruction. Malnourished patients needing tube feeding beyond four weeks warrant PEG or jejunal access.[1]

Why Early Supplemental PN Is Selective​

In Gao 2022, 230 adults after elective major abdominal surgery were randomized to supplemental PN on day 3 or day 8. Eligibility required NRS-2002 at least 3, EN at or below 30% of the energy target on day 2, and an expected stay longer than seven days. Infection occurred in 10/115 (8.7%) versus 21/114 (18.4%), respectively; absolute difference 9.7 percentage points (95% CI 0.9–18.5). Length of stay and noninfectious complications were not significantly different.[8]

Pelvic exenteration. Hogan et al. randomized 87 patients after pelvic exenteration, all with a nasogastric tube and continuous parenteral nutrition, to early trophic enteral feeding (20 mL/h via the nasogastric tube until upgraded to free fluids) or standard nasogastric suction. Postoperative ileus was significantly less frequent with early enteral feeding in the per-protocol analysis (P = .036), though time to first bowel movement did not differ between arms; regression analysis separately found that a longer postoperative restriction from an oral diet was associated with a longer time to first bowel movement and more postoperative complications. Hogan et al.’s pelvic-exenteration estimate has uncertain applicability to uncomplicated GU reconstruction; feeding depends on bowel viability, aspiration risk, hemodynamic status and tolerance.[41]

Parenteral Nutrition: Prescription and Safety​

Peripheral or central describes venous access; supplemental or total describes how much nutrition PN provides. These are separate decisions. Peripheral PN can bridge a short deficit when osmolarity, volume and venous tolerance permit: ESPEN suggests it for supplementary PN expected to last under seven days, formulations above about 900 mOsm/L are poorly tolerated peripherally, and dextrose should not exceed 10% to limit thrombophlebitis.[1][22] Central access permits more concentrated admixtures but adds insertion, infection and thrombosis risks; ESPEN asks that a central line placed solely for PN be justified by the expected duration.[1]

What the Prescription Must Specify​

ComponentCheck before prescribing
Energy and amino acidsAn average adult needs about 25–30 kcal/kg and 1–2 g/kg protein; use a predictive equation and a dietitian, and adjust for current oral/EN intake, organ function and refeeding risk. Amino acids come as 3–20% solutions, and excess protein raises renal load. Count energy from dextrose fluids and propofol[22]
Dextrose3.4 kcal/g in 2.5–70% solutions, usually 70–85% of non-protein energy. Keep infusion at or below 5–7 mg/kg/min in adults who are not critically ill and 4 mg/kg/min or less in the critically ill to limit hyperglycemia[22]
IV lipid10%, 20% and 30% emulsions provide 1.1, 2.0 and 2.9–3.0 kcal/mL. Lipid supplies essential fatty acids and energy; set the dose from the total energy prescription and product label instead of treating 30% as a universal ceiling. The SMOFlipid adult label permits up to 60% of total energy requirements, subject to its other dose and rate limits. Check product, dose, infusion rate, allergies, triglycerides and other lipid sources.[22][16]
Electrolytes / fluidRenal function, urine and GI losses, acid–base state, existing replacement and admixture compatibility
Vitamins / trace elementsDaily provision as appropriate, deficiency treatment and adjustment for losses or organ dysfunction
AdministrationVerified access, pharmacy-compatible formulation, pump, filter and line-care protocol

Typical daily additives for a two-in-one adult formulation (individualize for losses, renal and hepatic function):[22]

AdditiveUsual daily amount
Sodium, potassium1–2 mEq/kg each
Calcium10–15 mEq
Magnesium8–20 mEq
Phosphorus20–40 mmol (also relevant to refeeding prevention)
Adult multivitamin10 mL daily, with or without vitamin K
Trace elementsChromium, copper (0.3–0.5 mg), manganese, selenium (60–100 mcg), zinc (3–5 mg); give copper and manganese conservatively in hepatic dysfunction and consider extra zinc with high small-bowel losses; iron is not routinely included

A three-in-one admixture contains dextrose, amino acids and lipid; a two-in-one contains dextrose and amino acids with lipid administered separately. ESPEN prefers all-in-one bags to multiple-bottle systems. Nutrition-support and pharmacy review should reconcile the complete prescription and monitoring plan.[1][22]

Lipids, Liver Tests and Warfarin​

  • SMOFlipid is a mixed soybean, MCT, olive and fish-oil emulsion used as a source of calories and essential fatty acids in PN. The adult label recommends 1–2 g/kg/day (maximum 2.5 g/kg/day); for direct infusion, start at 0.2 mL/kg/h for 15–30 minutes and do not exceed 0.5 mL/kg/h.[16] Known hypersensitivity to fish, egg, soybean, peanut or any ingredient, and severe lipid-metabolism disorders with triglycerides >1,000 mg/dL, are contraindications. Measure triglycerides before and during treatment; stop the adult infusion if levels exceed 400 mg/dL, and use a lower starting dose and smaller titration steps when pretreatment levels are elevated.[16] The 1 g/kg/day figure for soybean-oil emulsions is not a ceiling for every IV lipid product.[16][22]
  • Omegaven is a fish-oil emulsion whose US indication is pediatric PN-associated cholestasis, not prevention of that condition or routine adult postoperative PN.[11]
  • Abnormal liver tests on PN require assessment for sepsis, biliary disease, drugs, overfeeding and intestinal failure. Avoid overfeeding, treat infection and retain oral/EN intake when safe. Long-term PN may require cycling and lipid adjustment with the nutrition team.
  • Do not automatically omit vitamin K because a patient takes warfarin. Vitamin K-containing multivitamins and lipid products can affect anticoagulation; keep intake consistent where possible and monitor INR to guide warfarin adjustment.[11][12]

Monitoring​

Track the amount actually delivered, tolerance, fluid balance, weight, glucose, renal function, sodium, potassium, magnesium and phosphate. Check triglycerides with IV lipids and liver tests during PN; frequency depends on acuity, initiation, recent changes and stability. Albumin and prealbumin should not be used as targets proving adequate nutrition.[2][9][16]

If enteral feeds stop while insulin remains active, IV dextrose may be given for the duration of insulin action to prevent hypoglycemia. Adding insulin to the parenteral nutrition bag is the safest way to prevent hypoglycemia if parenteral nutrition is stopped or interrupted.[13]

Refeeding Syndrome​

Refeeding can cause dangerous phosphate, potassium and magnesium shifts and increased thiamine demand after prolonged undernutrition: carbohydrate triggers insulin release, which drives these ions into cells. Assess risk before oral, enteral or parenteral feeding, including calories in IV dextrose. Normal initial electrolytes do not exclude depleted stores.[9]

Manifestations include arrhythmia and heart failure, respiratory weakness or failure (phosphate-dependent diaphragmatic function), fluid overload and edema, and neurologic change from thiamine depletion, including Wernicke encephalopathy. It can occur with oral, enteral or parenteral feeding.[9][22]

Recognize Risk and Deterioration​

NICE high risk requires one major criterion (BMI below 16, weight loss over 15% in 3–6 months, negligible intake over 10 days, or low potassium, phosphate or magnesium), or two lesser criteria (BMI below 18.5, weight loss over 10% in 3–6 months, negligible intake over five days, or the specified alcohol or medication history).[10]

ASPEN's consensus diagnostic framework uses a fall in one or more of phosphate, potassium or magnesium within five days of reintroducing or substantially increasing calories: 10–20% mild, 20–30% moderate, and over 30% and/or associated organ dysfunction due to these shifts or thiamine deficiency severe. Interpret changes clinically and consider other causes; ASPEN’s definition uses changes in phosphate, potassium or magnesium.[9]

Use One Coherent Protocol​

ElementASPEN 2020 adult consensus approach
Initial feeding10–20 kcal/kg in the first 24 hours or 100–150 g dextrose; count all carbohydrate sources and advance by about one-third of goal every 1–2 days as tolerated
Severe electrolyte deficitsDelay initiation or escalation until severely low phosphate, potassium or magnesium is corrected; reassess less severe deficits before increasing calories
Thiamine prophylaxis100 mg before feeding/dextrose, then 100 mg/day for 5–7 days or longer in severe starvation, chronic alcohol use or other high-risk circumstances; provide multivitamins [9]
Electrolyte monitoringBaseline potassium, magnesium and phosphate; every 12 hours for the first three days in high-risk patients, more frequently if clinically necessary
Falling levels or clinical deteriorationReplace by established protocols; reduce calorie/dextrose delivery when levels fall precipitously or resist correction; consider stopping nutrition in life-threatening deterioration
Clinical monitoringVitals, fluid balance, daily weight and cardiorespiratory monitoring when unstable

These are prevention and management recommendations, not a Wernicke encephalopathy treatment regimen. Give thiamine promptly, but do not delay emergency glucose treatment of hypoglycemia; see Thiamine.[9]

NICE recommendation 1.4.8 says to consider, for people at high risk of refeeding problems, starting at no more than 10 kcal/kg/day (5 in extreme risk, such as BMI below 14 or negligible intake for over 15 days), increasing to full needs over four to seven days, with oral thiamine 200–300 mg/day immediately before and during the first ten days of feeding and a balanced multivitamin or trace-element supplement. Its likely requirements are potassium 2–4 mmol/kg/day, phosphate 0.3–0.6 mmol/kg/day and magnesium 0.2 mmol/kg/day IV (0.4 oral). These are estimates and not automatic orders in renal failure or when pre-feeding levels are high. Follow a complete institutional protocol rather than mixing these doses with ASPEN's schedule.[10]

AuSPEN's 2025 consensus describes a separate adult inpatient approach for patients meeting at least two of four risk criteria: unintentional weight loss over 10% in three months or moderate-to-severe malnutrition; fasting or limited intake for at least seven days; problematic alcohol use; or gastrointestinal losses.[48] With close electrolyte and clinical monitoring and supplementation as needed, it advises starting at 50% or more of estimated energy requirements and reaching goal within 24–72 hours if medical monitoring is available.[48] It advises pausing advancement after an electrolyte decrease of more than 30% from baseline that is outside the normal range until levels stabilize; for critically ill patients, it defers to existing critical-care nutrition guidance.[48]

GLP-1 / GIP Medicines and Surgery​

GLP-1 receptor agonists (semaglutide, liraglutide, dulaglutide) and the dual GIP/GLP-1 agonist tirzepatide are now a common preoperative exposure. They affect candidacy (weight loss can move a patient into a lower obesity class) and risk (appetite suppression, delayed gastric emptying, and possible protein and micronutrient deficits).

Aspiration Planning​

Ask about GLP-1/GIP use at every preoperative visit; patients often do not volunteer "weight-loss injections." FDA added pulmonary-aspiration warnings to the US labels of these drugs in 2024.[45] The current WEGOVY and MOUNJARO labels describe postmarketing aspiration during general anesthesia or deep sedation despite reported fasting; both state that evidence is insufficient to determine whether temporarily withholding the drug or changing fasting reduces retained gastric contents.[46][47]

The multisociety guidance of October 2024 (ASA, AGA, ASMBS, ISPCOP and SAGES) replaced the 2023 ASA consensus advice to hold weekly agents for a week before elective surgery. It states that most patients may continue their GLP-1 RA when delayed-gastric-emptying risk is not elevated, after assessment of dose escalation, higher doses, weekly dosing, GI symptoms and comorbidities that slow gastric emptying. If the team decides to withhold therapy because of an unacceptable safety profile, the guidance suggests holding daily agents on the day of surgery or weekly agents for one week; the optimal interval is unknown.[20] A liquid diet for at least 24 hours before the procedure is an option when delayed gastric emptying is a concern; the team may also adjust the anesthetic plan. Point-of-care gastric ultrasound can help when retained contents are suspected.[20] For GLP-1 RA users without significant gastrointestinal symptoms or another cause of delayed gastric emptying, the 2025 SPAQI consensus recommends continuing therapy (grade B), consuming only clear liquids for 24 hours before anesthesia (grade B), and stopping clear liquids with at least 10% glucose eight hours before anesthesia or those with less than 10% glucose four hours before anesthesia (both grade C).[21] Follow the anesthesia department's protocol.[21]

The ADA 2026 framework individualizes management by indication, glycemia, drug and dose, GI symptoms, procedure, urgency and anesthesia. Options include a 24-hour liquid nutrition protocol, gastric ultrasound where appropriate and full-stomach precautions. If holding treatment is expected to worsen glycemia, establish an alternative plan.[13]

OCULUS 2026: 68 patients were randomized and 60 included in the prespecified interim analysis; clinically significant residual gastric contents occurred in 3.1% after holding one dose versus 25.0% after continuing. The absolute difference was 21.9 percentage points (90% CI 7.0–36.7); the trial stopped early.[14] This was elective upper endoscopy under moderate sedation or monitored anesthesia care in stable users.[14]

In the 35 patients having upper endoscopy alone, the event rate was 46.7% when continuing versus 5.0% when holding one dose. All events prevented adequate endoscopic examination; no aspiration events occurred, but the trial was too small to establish aspiration safety. None of the 25 patients undergoing concurrent colonoscopy after clear liquids or bowel preparation had the primary event. Patients with retained contents were asymptomatic.[14] A September 2026 prospective UK cohort observed perioperative regurgitation or aspiration in 19/1,348 GLP-1-exposed patients (1.41%) versus 57/45,691 unexposed patients (0.12%); aspiration itself occurred in 2 and 16 patients, respectively, and 10 of the 19 exposed patients' events occurred during emergence.[43] A 2025 meta-analysis of observational studies did not detect an association with pulmonary aspiration alone (OR 1.04, 95% CI 0.87–1.25; low certainty).[44] The newer cohort could not adjust for patient-level confounding.[43]

Nutrition and Wound Healing​

Ask about appetite, actual protein and energy intake, vomiting, weight-loss rate and muscle and function. Investigate a demonstrated deficit and coordinate nutrition and prescribing care.[2]

Current wound studies are observational and differ in population, and the signal is mixed.

StudyPopulationWound signal
Aschen 2025 (Ann Surg)Type 1 or 2 diabetes, 35,020 matched proceduresActive GLP-1 RA prescription was associated with less 180-day dehiscence (RR 0.71, 0.58–0.88) and hematoma (RR 0.44, 0.22–0.89); no significant overall difference in infection or bleeding. In matched urinary procedures, 180-day bleeding was 0.7% versus 0.3% (P = .045).[17]
Lee 2026 (TriNetX)Patients without diabetes, smoking, peripheral vascular disease, nutritional/metabolic/endocrine disease or cancer history undergoing panniculectomy, abdominoplasty or breast reductionHigher 30-day rates of a composite of surgical wound infection, breakdown, or dehiscence with GLP-1 RA use: abdominoplasty 9.8% vs 3.6% (P = .001), panniculectomy 4.7% vs 2.7% (P = .05), breast reduction 2.6% vs 1.3% (P = .035)[18]
Koenig 2026373 non-bariatric panniculectomies (81 users; all patients had at least one year of follow-up)More delayed healing (18.5% vs 7.5%), fewer seromas (4.9% vs 14.0%); no difference in infection or hematoma[19]

One proposed reconciliation is that glycemic control dominates in patients with diabetes, whereas in non-diabetic patients taking the drug for weight loss, appetite suppression may create a protein deficit that impairs collagen synthesis. This is a hypothesis. In a 30-versus-30 pilot of breast implant explantation with mastopexy, users had lower albumin (4.06 versus 4.22 g/dL) and prealbumin (23.5 versus 25.6 mg/dL), but complication differences were not significant.[39] In the Koenig cohort, users' prealbumin was higher.[19]

Candidacy and Nutritional Planning​

In a retrospective TriNetX cohort of 5,618 DIEP flap patients with 90-day follow-up, 212 had class I or II obesity and GLP-1 exposure before matching. After matching, this group had fewer revisions than class I or II obese non-users (P = .037) and class III obese non-users (P = .046), with no detected difference in dehiscence.[37] The analogous question for GU work (fistula repair, urethroplasty, sacrocolpopexy, AUS or IPP, phalloplasty) is open.

Because these drugs suppress appetite and slow gastric emptying, plan protein intake deliberately. Body-contouring guidance recommends individualized protein timing plans, spacing protein through the day in small frequent meals, and correcting micronutrient deficiencies (iron, B12, vitamin D, calcium, folate, thiamine) before surgery, and notes that many patients fall short of the 60–120 g/day protein targets.[38]

Practical checklist: ask about GLP-1/GIP use; screen intake, weight-loss rate and muscle function; treat an identified protein or micronutrient deficit; agree a hold-or-continue and fasting plan with anesthesia; and document baseline weight and trajectory before elective body-contouring or abdominal-wall procedures. For GLP-1 RA therapy held perioperatively, SPAQI suggests resuming it once the usual diet returns (grade E for inpatients, grade B for outpatients).[21]

GU Reconstruction and Follow-up​

  • Cystectomy or diversion: assess intake, hydration, renal function, stoma or catheter function and GI recovery. Recurrent vomiting or failure to thrive needs evaluation for surgical and medical causes.
  • Bowel-containing urinary reconstruction: monitor metabolic complications and B12 according to segment, resection, renal function and follow-up findings. Bicarbonate and B12 are given according to individual need. See Urinary Acidifiers & Alkalinizers and Vitamin B12 Supplementation.
  • Urogynecologic procedures: the AUGS-IUGA ERAS consensus rates fasting for 6 hours (solids) with clear fluids up to 2 hours before surgery, and chewing gum to reduce ileus, as high-level-evidence components; early tolerated oral intake belongs in the same pathway.[15]
  • Urethroplasty, fistula and flap surgery: treat identified malnutrition and deficiency, but do not use albumin alone to predict failure, choose a technique or mandate delay.

Before discharge, document intake targets, the supplement and feeding plan, hydration and symptom advice, laboratory monitoring where indicated, and who will reassess recovery.

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