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.
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/diarrhea, restrictive diets, prior bowel/bariatric surgery, alcohol use and ability to obtain or prepare food. Examine for muscle and fat loss, edema and functional impairment.[1][2]
| Assessment | Appropriate use |
|---|---|
| MUST or NRS-2002 | Validated screening options; use the tool appropriate to the setting rather than applying one study's sensitivity or prevalence to every population |
| MNA-SF | An option for older adults; follow an abnormal screen with assessment |
| GLIM | Diagnostic framework after screening: at least one phenotypic and one etiologic criterion; not itself a substitute for the initial screen |
| Weight, intake, muscle and function | Establish the deficit and monitor recovery; obesity does not exclude malnutrition |
| Albumin / prealbumin | Prognostic 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. Its association with complications in plastic-surgery and free-flap cohorts does not prove that increasing albumin prevents GU graft failure.[2]
Preoperative Optimization
- Address a measured intake deficit: food fortification, dietitian support and a balanced oral nutritional supplement (ONS) when ordinary food is insufficient. A commonly used protein target in malnourished elective GI surgical patients is 1.2–1.5 g/kg/day; choose the dosing weight and modify the target for renal disease, obesity, catabolism and other individual factors.[3]
- Severe malnutrition / high metabolic risk: ESPEN 2025 supports preoperative nutrition even when elective surgery must be postponed; consider 10–14 days. Historical ESPEN high-risk criteria include marked weight loss, BMI below 18.5, NRS at least 5 or SGA C, or albumin below 30 g/L after excluding hepatic/renal insufficiency. The albumin criterion denotes metabolic/surgical risk, not a stand-alone malnutrition diagnosis.[1][2]
- Use oral/enteral delivery when feasible. Preoperative PN is reserved for severe malnutrition/high metabolic risk when these routes cannot meet needs; ESPEN suggests 10–14 days, with a minimum of seven, in that selected group.[1]
- Correct identified deficiencies: avoid routine high-dose zinc, vitamin A or other micronutrient combinations without an indication. A small mechanistic wound study is not sufficient evidence for a universal graft-healing supplement regimen.
- 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 patients without increased aspiration risk, standard guidance allows clear liquids until two hours and a light meal until six hours before anesthesia; fatty/heavy meals require longer fasting. Follow the anesthetic plan for obstruction, delayed gastric emptying, emergency surgery or other increased-risk situations.[1][3]
A protocolized carbohydrate drink may improve comfort and metabolic response before major abdominal surgery. It does not guarantee fewer major complications and should not be prescribed indiscriminately in suspected gastroparesis or poorly controlled diabetes. GLP-1/GIP therapy requires the additional assessment below.[1]
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 around major tumor surgery. Effects vary with procedure, timing and whether the control receives equivalent calories/protein. That broader recommendation predates the phase 3 SWOG cystectomy report.[1]
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/protein supplements for five days before and five days after cystectomy.[4]
| Primary 30-day result | Specialized immunonutrition | Standard ONS |
|---|---|---|
| Any complication | 56/90 (62.2%) | 51/88 (58.0%) |
The odds ratio was 1.18 (95% CI 0.64–2.18). Severe malnutrition was excluded. This result does not establish equivalence, test supplements against no supplementation, or establish benefit in severely malnourished patients. Exploratory survival findings do not justify prescribing it for cancer control.[4]
For cystectomy counseling, prioritize adequate nutrition; specialized formulations should not be presented as proven superior to standard ONS.
Interpreting Earlier Evidence
- Cochrane 2019: 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.[5]
- Amer 2025, 74 patients: a combined calorie/protein and immunonutrition pathway improved some recovery measures, but the primary overall complication outcome was not significantly different (54% vs 68%; P=.236). The bundle cannot isolate the effect of immunonutrition.[6]
- INCyst: the cited publication describes a planned 232-patient trial. A protocol is not an efficacy result; do not assign benefit or a firm publication date from it.[7]
Evidence from cystectomy or GI cancer should not be assumed to demonstrate benefit in routine urethroplasty, prosthetic surgery or prolapse repair.
Choosing and Starting Nutrition Support
Oral food/ONS → enteral tube feeding when oral intake is inadequate → PN when oral/enteral delivery is contraindicated or insufficient. Route and timing depend on physiology and the intake deficit, not simply the postoperative day.[1]
| Clinical situation | Practical approach |
|---|---|
| Awake, hemodynamically stable and tolerating intake after surgery | Resume oral intake early; routine waiting for flatus is unnecessary |
| Unable to meet needs orally, especially with malnutrition or expected prolonged inadequate intake | Consider 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 days | Begin nutrition therapy promptly rather than waiting for further deterioration |
| Oral/EN delivery remains below 50% of requirements within three to four days | ESPEN 2025 recommends supplemental PN to address the deficit |
| Oral/EN contraindicated, particularly with severe malnutrition | Start 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. A functioning bowel alone does not establish that feeding is safe. 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]
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%) vs 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]
This supports filling a substantial deficit in selected at-risk patients. It does not support automatic PN on postoperative day 3 after an uncomplicated reconstruction.
Parenteral Nutrition: Prescription and Safety
Peripheral/central describes venous access; supplemental/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. Central access permits more concentrated admixtures but adds insertion, infection and thrombosis risks. Use the actual product's osmolarity limits and the expected duration; central access does not remove metabolic or compatibility limits.[1][11]
What the Prescription Must Specify
| Component | Check before prescribing |
|---|---|
| Energy and amino acids | Individual requirements, current oral/EN intake, organ function and refeeding risk; account for energy from dextrose fluids and propofol |
| Dextrose | Grams, infusion rate and glucose response; do not give an identical glucose load to every patient |
| IV lipid | Product, dose, infusion rate, allergies, triglycerides and other lipid sources |
| Electrolytes / fluid | Renal function, urine and GI losses, acid–base state, existing replacement and admixture compatibility |
| Vitamins / trace elements | Daily provision as appropriate, deficiency treatment and adjustment for losses or organ dysfunction |
| Administration | Verified access, pharmacy-compatible formulation, pump, filter and line-care protocol |
A three-in-one admixture contains dextrose, amino acids and lipid; a two-in-one contains dextrose and amino acids with lipid administered separately. Nutrition-support and pharmacy review should reconcile the complete prescription and monitoring plan.[1]
Lipids, Liver Tests and Warfarin
- SMOFlipid is a mixed soybean/MCT/olive/fish-oil emulsion used as a source of calories and essential fatty acids in PN. Follow its adult label and triglyceride monitoring; there is no universal 1 g/kg/day ceiling for every IV lipid product.[16]
- Omegaven is a fish-oil emulsion whose US indication is pediatric PN-associated cholestasis, not prevention of that condition or routine adult postoperative PN. It is not interchangeable with a standard adult lipid prescription.[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; infant cholestasis statistics do not predict adult outcomes.
- 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/prealbumin should not be used as targets proving adequate nutrition.[2][9][16]
If feeds are interrupted while insulin remains active, prevent and monitor for hypoglycemia with the diabetes/nutrition team. PN discontinuation needs an individualized glucose/insulin plan; a blanket instruction that PN must never be stopped abruptly is inappropriate. Investigate catheter infection, thrombosis, fluid overload and metabolic disturbance promptly.[13]
Refeeding Syndrome
Refeeding can cause dangerous phosphate, potassium and magnesium shifts and increased thiamine demand after prolonged undernutrition. Assess risk before oral, enteral or parenteral feeding, including calories in IV dextrose. Normal initial electrolytes do not exclude depleted stores.[9]
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/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/medication history). Alcohol use or a diuretic alone is not the whole definition.[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; a single phosphate threshold is not a universal diagnostic definition.[9]
Use One Coherent Protocol
| Element | ASPEN 2020 adult consensus approach |
|---|---|
| Initial feeding | 10–20 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 deficits | Delay initiation or escalation until severely low phosphate, potassium or magnesium is corrected; reassess less severe deficits before increasing calories |
| Thiamine prophylaxis | 100 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 |
| Electrolyte monitoring | Baseline 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 deterioration | Replace by established protocols; reduce calorie/dextrose delivery when levels fall precipitously or resist correction; consider stopping nutrition in life-threatening deterioration |
| Clinical monitoring | Vitals, fluid balance, daily weight and cardiorespiratory monitoring when unstable |
These are prevention/management recommendations, not a Wernicke encephalopathy treatment regimen. Give thiamine promptly, but do not delay emergency glucose treatment of hypoglycemia; see Thiamine.[9]
NICE uses a different high-risk regimen: at most 10 kcal/kg/day initially (5 in extreme risk), with oral thiamine 200–300 mg/day for the first ten days and additional vitamins. Its potassium/phosphate/magnesium estimates are not automatic orders in renal failure or when levels are high; oral and IV magnesium doses differ. Follow a complete institutional protocol rather than mixing these doses with ASPEN's schedule.[10]
GLP-1 / GIP Medicines and Surgery
Aspiration Planning
The ADA 2026 framework individualizes management by indication, glycemia, drug/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. Medication withholding does not guarantee an empty stomach.[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 vs 25.0% after continuing. The absolute difference was 21.9 percentage points (90% CI 7.0–36.7); the trial stopped early. This was elective upper endoscopy under moderate sedation/monitored anesthesia care in stable users, not a trial of all major operations.[14]
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/bowel preparation had the primary event. That subgroup does not isolate or prove the effect of a liquid diet. Patients with retained contents were asymptomatic, so symptom screening alone cannot exclude risk.[14]
Nutrition and Wound Healing
Ask about appetite, actual protein/energy intake, vomiting, weight-loss rate and muscle/function. GLP-1 treatment does not automatically cause protein malnutrition. Investigate a demonstrated deficit and coordinate nutrition and prescribing care; albumin differences alone do not prove the mechanism of wound complications.[2]
Current wound studies are observational and differ in population. Aschen's matched study concerned patients with diabetes and reported lower dehiscence; Lee's TriNetX non-diabetic plastic-surgery cohort reported higher wound complications; Koenig's panniculectomy series reported more delayed healing and fewer seromas. These findings do not establish that continuing or stopping a GLP-1 medicine improves healing after GU reconstruction.[17][18][19]
GU Reconstruction and Follow-up
- Cystectomy/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, not supplements alone.
- Bowel-containing urinary reconstruction: monitor metabolic complications and B12 according to segment, resection, renal function and follow-up findings. Preserving a fixed terminal-ileum length does not guarantee normal absorption; bicarbonate and B12 are individualized rather than automatic for every pouch. See Urinary Acidifiers & Alkalinizers and Vitamin B12 Supplementation.
- Urogynecologic procedures: early tolerated oral intake and appropriate fasting belong within the AUGS/IUGA ERAS pathway. Major abdominal-cancer effect sizes should not be applied directly to an uncomplicated vaginal prolapse or sling operation.[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/feeding plan, hydration and symptom advice, laboratory monitoring where indicated, and who will reassess recovery.
References
1. Weimann A, Bezmarevic M, Braga M, et al. "ESPEN Guideline on Clinical Nutrition in Surgery — Update 2025." Clin Nutr. 2025;53:222–261. doi:10.1016/j.clnu.2025.08.029
2. Evans DC, Corkins MR, Malone A, et al. The use of visceral proteins as nutrition markers: an ASPEN position paper. Nutr Clin Pract. 2021;36:22–28. doi:10.1002/ncp.10588.
3. Irani JL, Hedrick TL, Miller TE, et al. "Clinical Practice Guidelines for Enhanced Recovery After Colon and Rectal Surgery (ASCRS/SAGES)." Dis Colon Rectum. 2023;66(1):15–40. doi:10.1097/DCR.0000000000002650
4. Hamilton-Reeves JM, et al. Immune-enhancing nutrition and outcomes after radical cystectomy: a randomized clinical trial. JAMA Netw Open. 2026;9:e2623622. doi:10.1001/jamanetworkopen.2026.23622. Full text.
5. Burden S, Billson HA, Lal S, Owen KA, Muneer A. Perioperative nutrition for the treatment of bladder cancer by radical cystectomy. Cochrane Database Syst Rev. 2019;5:CD010127. doi:10.1002/14651858.CD010127.pub2
6. Amer ML, Amer AR, Elnasharty SF, et al. Impact of perioperative nutrition on recovery after radical cystectomy: a randomised trial. BJU Int. 2025. doi:10.1111/bju.70094
7. Derré L, Crettenand F, Grilo N, et al. The role of preoperative immunonutrition on morbidity and immune response after cystectomy: protocol of a multicenter randomized controlled trial (INCyst trial). Trials. 2024;25(1):687. doi:10.1186/s13063-024-08536-5
8. Gao X, Liu Y, Zhang L, et al. "Effect of Early vs Late Supplemental Parenteral Nutrition in Patients Undergoing Abdominal Surgery: A Randomized Clinical Trial." JAMA Surg. 2022;157(5):384–393. doi:10.1001/jamasurg.2022.0269
9. da Silva JSV, Seres DS, Sabino K, et al. ASPEN consensus recommendations for refeeding syndrome. Nutr Clin Pract. 2020;35:178–195. doi:10.1002/ncp.10474.
10. NICE. Nutrition support for adults: oral nutrition support, enteral tube feeding and parenteral nutrition. CG32, recommendations 1.4.6–1.4.8. Guideline.
11. Fresenius Kabi. Omegaven prescribing information. US label, revised 2025. DailyMed.
12. INFUVITE ADULT prescribing information. Section 5.4: decreased anticoagulant effect of warfarin. DailyMed.
13. American Diabetes Association Professional Practice Committee. 16. Diabetes care in the hospital: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S339-S355. doi:10.2337/dc26-S016
14. Ahmad AI, Garg S, Jacobs J, et al. Holding vs continuing GLP-1/GIP agonists before upper endoscopy. JAMA Intern Med. 2026. doi:10.1001/jamainternmed.2026.0027
15. AUGS-IUGA Joint Clinical Consensus Statement on enhanced recovery after urogynecologic surgery. Int Urogynecol J. 2022;33(11):2921-2940. doi:10.1007/s00192-022-05223-4
16. Fresenius Kabi. SMOFlipid prescribing information. US label. DailyMed.
17. Aschen SZ, Zhang A, O'Connell GM, et al. Association of perioperative glucagon-like peptide-1 receptor agonist use and postoperative outcomes. Ann Surg. 2025;281(4):600-607. doi:10.1097/SLA.0000000000006614
18. Lee CC, Newland M, Yau A, Chroneos R, Johnson TS. Impact of GLP-1 agonist on surgical wound complications following plastic and reconstructive surgery: a propensity matched cohort large database analysis. Plast Reconstr Surg. 2025. doi:10.1097/PRS.0000000000012703
19. Koenig ZA, Rashid S, Hobbs GR, Uygur HS. Perioperative GLP-1 receptor agonist use and surgical outcomes in nonbariatric abdominal panniculectomy: a 10-year retrospective analysis. Plast Reconstr Surg. 2026;157(4):645-655. doi:10.1097/PRS.0000000000012405