6.Assessingorgan’s condition (2,590 words) Posttransplantation, kidneys may function instantly, require a period of recoverywith no function, require a period of recovery with impaired function, or neverwork at all.
Immediate function depends on the general health of the donor /kidney characteristics but also on the time of ischaemia plus the additionalharm caused during death and organ retrieval. As there is the option of dialysis in order to deal with the initialgraft dysfunction the main focus is to reduce the primary non-function (PNF). 16 Theperfect kidney derives from a young age donor, without comorbidities prior toshort terminal illness, controlled DCD, with an immediate death when harvestingis performed and prompt laparotomy, cannulation of the aorta, perfusion andexcellent appearance on retrieval. If the ischaemia time is minimised thosekidneys ought to work instantly without need to undergo special tests onviability etc. However, the vastmajority of organs do not belong to the above group.
Their viability requiresassessment in order to identify those at greater risk of delayed function oreven potential non-function that would allow better selection and matching fortransplantation. This would also permitinterventions in order to improve the organ’s condition (reconditioning) – seerelevant chapter. It is estimated that 12 – 18 percent ofkidneys are abandoned because of issues with regards to their functional statuspost transplantation. 50 I believe that further optimisation of viabilityassessment tools will lead to reduction of above figure and also more accuratelydetermine which kidneys must be discarded. The research in the field of viabilityassessment & evaluation of organs’ condition has focused on; Machine perfusion dynamics; – Machineperfusion pressures- Machineperfusion flow rate- Resistanceindices- Machineperfusate biomarkers Imaging related;- Dopplerultrasonography and renal scintigraphy – DynamicMRI using the Ktrans technique Biopsy involvement; – ‘Pirani’ – Banff, and – CADI (chronicallograft damage index) scores- Composite scorescombining donor hypertension and creatinine with histological scoring Other; – RapidSampling Microdialysis for parenchyma assessment- Kidneyperfusate and urine biomarkers- Clinicaldonor risk scores One of the key advantages of MP that makes itattractive to the transplant surgeons is the fact that it permits graftviability & quality assessment before the transplantation itself. As mentioned key part of this is the machineperfusion dynamics such as flow, resistance etc and several well recognisedbiomarkers within the perfusate.
It hasbeen concluded that although these can predict to an extent the subsequentgraft function, so far, they can’t be used alone on decision making on whetherto accept or reject an organ 6. Machine perfusion pressures 8 When developing machine perfusion as a mode oforgan preservation researchers noticed that when the perfusion pressure wasgoing up and at the same time the flow rate was decreasing this was a sign thatgraft failure is pending 51. However, at the same time low pressures areresponsible for suboptimal perfusion. On the other hand, very high pressureswere demonstrated to cause shear stress an endothelial injury. Porcine kidneyspreserved at higher pressures prior to transplantation they had higher expressionof von Willebrand factor from their endothelial cells.
This marker is commonlypresent in the endothelial cells of the kidneys of patients suffering fromhypertension or AKI /CKD 52, 53. Lastly kidneys perfused at 25 mmHg comparedto 30 mmHg have greater preservation of their structural integrity and quickerfunctional recovery as demonstrated by repeat renal function evaluation posttransplantation 53. The majority ofresearch on perfusion pressures has been undertaken on porcine models.
TheNewcastle group recommended perfusion pressures of