Is bariatric surgery in patients following renal transplantation safe and effective? A best evidence topic.

Obesity is common amongst patients with renal transplants (RT). It is associated not only with generic obesity-related complications including diabetes, but also with higher rates of graft rejection and loss. A Best Evidence Topic in surgery was written according to a structured protocol: this is a systematic review of the literature, suitable when the quality of available evidence is low. The question addressed was: is weight-loss surgery (WLS) safe and effective in patients that have had a previous renal transplant? Three prospective case series and one multicentre retrospective study were identified, together reporting on a total of 112 patients who underwent WLS after RT. Eighty-seven patients underwent open WLS and 25 patients underwent laparoscopic operations of which 11 had sleeve gastrectomy and 14 RYGB. Percentage excess weight loss was highly variable between the studies, ranging from an average of 30.8%-75% at 12 months. One graft rejection occurred within 30 days of surgery. All studies were limited by lack of suitable comparison group, short follow-up and heterogeneity in type of bariatric procedure and approach. To date, there is limited evidence to suggest that bariatric surgery is safe and has good short-term outcomes for selected obese patients post-renal transplant.

Radiofrequency-induced small bowel thermofusion: an ex vivo study of intestinal seal adequacy using mechanical and imaging modalities.

BACKGROUND: Bipolar radiofrequency (RF) induced tissue fusion is believed to have the potential to seal and anastomose intestinal tissue thereby providing an alternative to current techniques which are associated with technical and functional complications. This study examines the mechanical and cellular effects of RF energy and varying compressive pressures when applied to create ex vivo intestinal seals. METHODS: A total of 299 mucosa-to-mucosa fusions were formed on ex vivo porcine small bowel segments using a prototype bipolar RF device powered by a closed-loop, feedback-controlled RF generator. Compressive pressures were increased at 0.05 MPa intervals from 0.00 to 0.49 MPa and RF energy was applied for a set time period to achieve bowel tissue fusion. Seal strength was subsequently assessed using burst pressure and tensile strength testing, whilst morphological changes were determined through light microscopy. To further identify the subcellular tissue changes that occur as a result of RF energy application, the collagen matrix in the fused area of a single bowel segment sealed at an optimal pressure was examined using transmission electron microscopy (TEM). RESULTS: An optimal applied compressive pressure range was observed between 0.10 and 0.25 MPa. Light microscopy demonstrated a step change between fused and unfused tissues but was ineffective in distinguishing between pressure levels once tissues were sealed. Non uniform collagen damage was observed in the sealed tissue area using TEM, with some areas showing complete collagen denaturation and others showing none, despite the seal being complete. This finding has not been described previously in RF-fused tissue and may have implications for in vivo healing. CONCLUSIONS: This study shows that both bipolar RF energy and optimal compressive pressures are needed to create strong intestinal seals. This finding suggests that RF fusion technology can be effectively applied for bowel sealing and may lead to the development of novel anastomosis tools.