(P 383) PRE-OPERATIVE SPLIT RENAL FUNCTION RADIONUCLIDE IMAGING IN SURGICAL PLANNING FOR MULTI-VISCERAL RESECTION OF RETROPERITONEAL SARCOMA: A RETROSPECTIVE COHORT STUDY

Objective: Multi-visceral resection (MVR) for retroperitoneal sarcoma (RPS) often includes en-bloc nephrectomy. Split renal function (SRF), measured by a radionuclide scan that uses dimercaptosuccinic acid (DMSA scan), is currently considered a useful pre-operative renal imaging modality to assess both the contribution of the ipsilateral kidney (to be resected) and the sole remaining kidney following surgery, to pre-operative renal function. However, there is limited evidence to support the role of DMSA and we therefore sought to retrospectively assess the influence of this imaging modality in surgical planning and decision making.

Methods: A retrospective cohort study was conducted at the Birmingham Sarcoma Service based at the Queen Elizabeth Hospital. 217 patients were referred for DMSA imaging between 2010 – 2024. Distribution of DMSA SRF, was correlated with other imaging, co-morbidity, biochemical renal tests and clinic letters. A SRF difference of ≥ 10% has been considered significant in the literature and was implemented in this study.

Results: Forty-seven out of 217 (22%) patients did not receive surgery. Five patients were excluded due to insufficient data. Nineteen patients out of the remaining 165 patients (12%) undergoing en-bloc MVR had a contralateral DMSA SRF ≤ 45% [split renal function difference (SPRFD) ≥ 10%]. 28% was the lowest contralateral SRF DMSA undergoing en-bloc MVR (SPRFD 44%). Furthermore, in line with en-bloc nephrectomy, an expected significant decline was detected in eGFR pre-operatively, to post-operatively (2 days post-MVR) [eGFR: 77.1, 63.9 respectively, p< 0.05, one-way ANOVA with Tukey’s HSD] with a slight improvement in eGFR three to five years post-MVR [eGFR 65.5 p=0.647]. The latterly improved renal function explained by normalisation of the surgical stress response and adaptive changes in the remaining kidney. In those failing to progress to MVR, the following was categorised; pre-operative death (30%), inoperable RPS (21%), metastasis (18%), patient refusal (9%), abandoned operation (6%). Unfavourable DMSA SRF was responsible for none of the cases failing to progress to MVR, with patient refusal and pre-operative deaths the specific respective reasons in a total of two patients with poor DMSA SRF specifically cited in pre-operative planning clinic letters. Finally, one patient, was noted to have a bilateral nephrectomy resected en-block with the sigmoid colon, (SRFD 26%), with subsequent placement on haemodialysis, whilst four patients progressed to MVR despite incalculable SRF on DMSA due to significant tumour dependent displacement of the kidneys causing one kidney to be superimposed onto the other.

Conclusion: Pre-operative DMSA, whilst routinely requested in some specialist centres appears to have little bearing on whether patients are declined or proposed for MVR of RPS and is not an effective use of resource. However, this is retrospective data and the subtle influence of potentially unfavourable DMSA imaging on decision-making is difficult to define with accuracy.