Continuous data were summarized as medians with interquartile ranges, while categorical data were presented as counts and percentages. Differences between groups for continuous outcomes were assessed using the unpaired non-parametric Kruskal-Wallis test. For categorical data, the chi-squared test was used, and Fisher’s exact test was applied for groups with small sample sizes. Post hoc pairwise comparisons were conducted to identify which groups differed from one another. Wilcoxon rank-sum tests were used for continuous outcomes, and Chi-squared tests were used for categorical outcomes. To assess the impact of ERAS protocols on length of stay multivariable Cox regression models were used with a frailty term (random effect) for transplant centre. For this analysis each centre was considered a single cluster, even if the use of ERAS protocols varied at the patient-level. This hierarchical strategy accounts for the clustered nature of the data, whilst allowing adjustment for patient-level variables (including recipient, transplant and donor factors). For these analyses, LOS was treated as a time-to-event variable, with discharge being the event (with higher hazard ratios indicating faster discharge). All analyses were performed in R version 4.2.1 (R Project for Statistical Computing).

Eighteen adult kidney transplant centres across the United Kingdom participated in the study, of a possible 24. Each hospital submitted a centre-reported perioperative care pathway questionnaire which detailed whether they had a formal ERAS programme and what the standard elements of pre-, intra-, and post-operative care included, Table 1. This allowed us to categorise the centres. One hospital had an informal ERAS programme when they began the CRAFT study data collection, however, during the study period initiated a separate trial which brought in a formal ERAS programme. As such this hospital is treated as two separate centres throughout our descriptive analyses (Centre E − informal – to represent the patients prior to the trial starting, and Centre E – formal to represent the patients after the trial started). Another hospital, Centre K had an informal ERAS programme for living donor kidneys but no ERAS programme for deceased donor kidneys recipients. This centre was also treated as two “separate centres” within our descriptive analyses to ensure the difference in ERAS protocoled care was accounted for. Of the 20 separate centres, n = 5 had a formal ERAS protocol, n = 7 considered themselves to have informal ERAS care and n = 8 had no specific ERAS programme.

213 transplants took place across the 20 centres during the 30-day study timeframe (15th January – 15th February 2024). Donor and recipient demographics were compared between centres that defined themselves as a formal ERAS centre, an informal ERAS centre a non-ERAS centre. Data completeness for this study was 99.8% and so a missing value analysis was not undertaken.

Donor demographics were comparable between groups with regards to donor sex, donor age, donor type (live/DBD/DCD), UK Donor Risk Index [16], HLA mismatch, and hypothermic machine perfusion. Warm ischaemic time (WIT) and cold ischaemic time (CIT) were also similar between the two groups.

Live donor transplants accounted for 34.9% (n = 37) or transplants performed in formal ERAS centres, 46.8% (n = 22) of transplants performed in an informal ERAS centre and 30.1% (n = 31) transplants performed in centres with no ERAS programme. The UK donor risk index (UKDRI) was calculated for all donors. There was comparable donor risk grafts utilised by formal ERAS centres (Median 1.4, IQR 0.7–1.6), when compared to informal centres (Median 1.4, IQR 1.1–1.7) and non-ERAS centres (Median 1.2, IQR 1.0–1.6), p = 0.615, Table 2. There were also a comparable number of donors having a renal transplant pre-emptively (defined as prior to the start of dialysis) in centres with a formal ERAS programme (n = 11, 17.5%), compared with informal centres (n = 10, 21.3%) and non-ERAS centres (n = 17, 16.5%). CIT was also comparable between those with a formal, informal or no ERAS programme, p = 0.213, Table 2.

Donor Terminal eGFR was statistically significantly lower (p = 0.040) in centres with an informal ERAS programme when compared to those with a formal programme and no programme at all, Table 2. NRP was also noted to be statistically significantly less likely to be utilised in the formal ERAS programme (p = 0.041).

There was no significant difference in any other recipient demographics between comparator groups. This included analysis of age, sex, body mass index (BMI - categorised by the WHO classification) [17], WHO performance status, number of previous transplants, urological pathology, anatomy, and immunosuppression regime, Table 3. Indicating that the groups were well matched.

Prospective data was collected on intra- and peri-operative management to better understand how care was actually being delivered, alongside how centres had reported that they delivered care in the site survey.

Volume of intraoperative fluid provided was compared between our groups. Centres with a formal ERAS protocol gave statistically significantly (p < 0.001) large fluid volumes (2,800 mL IQR: 2,000–3,900) when compared with informal ERAS centres (2,000 mL IQR: 1,500–2,950) and non-ERAS centres (2,000 mL IQR: 1,500–2,950), Figure 1A. Most patients (55.9%, n = 116) received TAP block analgesia with or without continuous infusion, intraoperatively. Patients in a centre with no ERAS programme were statistically significantly less likely to use a TAP block than those with a formal/informal programme (p = 0.012) Figure 1C. Patient controlled analgesia was utilised in 96.7% of transplants (n = 206). Of the seven patients who did not receive a PCA they were all within a single informal ERAS centre which was statistically significant (p < 0.0001), Figure 1D. Patients who received formal ERAS care were statistically significantly more likely to go back to the ward post-operatively (50.8%, n = 32), as were those who underwent informal ERAS care (76.6%, n = 36) when compared to those without an ERAS programme (43.7%, n = 45), p < 0.0001, Figure 1E where they were more likely to go to the high dependency unit. Those who underwent formal or informal ERAS care were also statistically significantly less likely to have a surgical drain inserted (p = 0.009). 60.3% of formal ERAS patient (n = 38) had a drain inserted, 57.4% (n = 27) in an informal centre and 78.6% (n = 81) in centres with no ERAS programme, Figure 1H. Comparable rates of peripheral vasopressor use (p = 0.106), Figure 1B, urethral catheterisation (p = 0.302), Figure 1F, and ureteric stenting (p = 0.847), Figure 1G, was seen in all centres.

Patients in centres with a formal ERAS protocol had earlier catheter removal (4.3 days IQR: 3.4–5.1) than those with an informal programme (4.8 days IQR: 4.1–5.5) and comparable catheter removal to centres with no-ERAS (4.3 days IQR: 3.7–4.9) protocol, Figure 2A (p = 0.036). Oral diet was introduced at a later stage in recipients who underwent a formal ERAS protocol (12.7%, at 24 h or more) when compared to centres with an informal programme (6.4%) or no ERAS programme (0%) (p = 0.015), Figure 2F. Centres with no ERAS protocol had a statistically significant shorter period of time post-operatively until documentation of bowel movement (2.8 days, IQR: 2.1–3.7), when compared to formal centres (3.8 days, IQR:2.6–4.2) and informal centres (3.3 days, IQR:2.2–4.9) (p = 0.040) Figure 2I. Patients in a formal ERAS centre had their PCA taken down earlier (1.7 days IQR: 0.8–2.6) when compared to centres with informal programmes (1.8 days IQR:1.3–2.7) and non-ERAS centres (1.9 days IQR:1.7–2.7), this reached statistical significance but is unlikely to be clinically significant given the actual values (p = 0.036), Figure 2B. The time from operation to re-introducing oral fluids (p = 0.370) Figure 2C, and IV fluids being taken down (p = 0.084), Figure 2D was comparable. Days until drain removal was also comparable (p = 0.504), and on average centres were removing drains after 3.6 days, Figure 2E. There were comparable outcomes when analysing the number of days from operation to mobilisation, those in a formal ERAS program mobilised at 1.3 days (IQR: 0.8–2.1), an informal programme 1.0 days (IQR: 0.7–1.6) and no ERAS programme 1.1 days (IQR: 0.8–1.9) (p = 0.185), Figure 2G. They also returned to baseline mobility at comparable timeframes, 3.2 days for patients in a formal ERAS programme (IQR: 2.1–4.9), 3.7 days in the informal programme (IQR: 2.5–4.9) and 3.3 days for patients with no ERAS programme (IQR: 2.5–4.6), (p = 0.861), Figure 2H. Patients in the non-ERAS centres opened their bowels sooner than patients in formal ERAS centres (p = 0.040), Figure 2I.

The primary outcome measured in this study was the length of stay (days since transplant) and no statistically significant differences on univariate analysis were observed between formal ERAS centres, or informal ERAS centres when compared with non-ERAS units (p = 0.746). The average length of stay in centres with a formal ERAS programme was 6.0 days (5.0–11.5), 7.0 days (5.0–10.5) in centres with informal ERAS and 6.0 (5.0–10.5) days in centres without an ERAS protocol, Figure 3A. A comparable rate of post-operative complications (categorised using the Clavien-Dindo Grading system) (p = 0.604), were observed. 14.3% (n = 9) patients in the formal ERAS programme had a Grade 3 or higher Clavien-Dindo complication, comparable to the 17% (n = 8) in the informal ERAS programme and 12% (n = 12) in centres with no ERAS programme, Figure 3B.

The recipients also had comparable rates of readmission at 30 days. In centres with a formal ERAS programme 14.3% (n = 9) patients were readmitted, 17% (n = 8) in centres with informal ERAS programmes and 19.4% (n = 20) in centres without an ERAS programme (p = 0.721), Figure 3C. Median eGFR 30 days post-operatively was also comparable. In formal ERAS centres median 30 days eGFR was 41.5 mL/min/1.73 m² (IQR: 29.0–59.0), 47.0 mL/min/1.73 m² in informal centres (IQR: 33.5–61.5) and 46.0 mL/min/1.73 m² (IQR: 32.5–56.0), (p = 0.469), Figure 3D. Univariate analyses were also performed delineating recipients who received a graft from a deceased donor (DBD/DCD graft) and those who received a graft from a living donor. These models showed comparable time until discharge irrespective of whether the centre described themselves as having a formal ERAS protocol, and informal protocol or no ERAS protocol. This trend was similar in both deceased and live donors (Figure 4).

A multivariable model was created to analyse the impact of ERAS protocols within the context of other recipient and donor factors including type of transplant (DBD/DCD/Live Donor) as well as patient frailty (based on the WHO performance status), Table 4. In the multivariable hierarchical Cox regression model, ERAS status was statistically significantly associated with length of stay (Wald p = 0.030). This was demonstrated by a lower HR for discharge (formal ERAS aHR = 0.753, 0.543–1.045, p = 0.090 and informal ERAS aHR = 0.628, 0.435–0.906, p = 0.013; Table 4); adjusted length of stay was longer in the centres with ERAS programmes compared to those without ERAS programmes. The multivariable models also demonstrated patients with WHO performance status ≥1 (frailer patients) had longer LOS, Table 4. A sensitivity analysis adjusting for pre-emptive transplant as a confounder was performed which demonstrated similar results. A further sensitivity analysis was performed excluding the two centres which used a mixture of ERAS and no ERAS; results were in keeping with the model in Table 4. Finally, we repeated the model shown in Table 4, instead categorising ERAS status into “formal ERAS” versus “no formal ERAS” (combining the “no ERAS” and “informal ERAS” groups). There was no significant difference in length of stay between “formal ERAS” and “no formal ERAS” (aHR = 0.888, 0.647–1.219, 0.462).

The main limitation of our study is its observational nature, consequently assessments of causality cannot clearly be made. Additionally, we acknowledge that the follow up period, is limited: the study was actively recruiting for 30 days and had a further 30 days of follow up which is a relatively short time period. This was deliberately chosen to be pragmatic, as our contributors were trainees who often move centre during training. Despite this, we had well matched cohorts across 20 different centres with over 200 patients and for the majority of patients a 30 days follow up period is more than adequate to capture outcomes of interest in the early postoperative period that were of interest in this scenario e.g., length of stay, readmission and complications. The study was designed as a prospective service evaluation study which allowed for multiple centres to be involved due to the simpler registration and approval processes. Again, this was a pragmatic decision, as the real world costs associated with running a multicentre randomised control trial of an ERAS protocol would be prohibitive, not to mention challenging to ensure adherence. As such, this is the largest prospective study to date assessing the role of ERAS care in renal transplantation, which provides a clear snapshot of perioperative practice across the UK and potential insights for future improvements.

In conclusion, while intraoperative ERAS principles have been widely integrated into routine kidney transplant care, formal ERAS protocols were not associated with significant improvements in post-transplant outcomes. This study found few centres offered prehabilitation strategies. Future efforts should focus on identifying high-risk patient populations and implementing prehabilitation strategies to enhance recovery and reduce complications. Further research is needed to explore how this would impact patient outcomes specifically within transplant patients and how we can achieve the same culture change for preoperative care that we have seen in the perioperative care setting to further optimize transplant outcomes effectively.