A Study of Novel Biomarkers of Kidney Dysfunction at Liver Transplant

Serum/plasma biomarkers: Approximately 10ml (3 teaspoons) of blood will be extracted to measure pre-specified biomarkers of renal injury including kidney injury molecule-1 (KIM-1), cystatin C and neutrophil gelatinase-associated lipocalin (NGAL). Samples will then be stored to facilitate measurement of additional biomarkers in the future.

Urinary biomarkers: A random urine sample will be obtained to measure urinary protein to creatinine ratio (uPCR), KIM-1 and liver-type fatty acid binding protein (L-FABP)

Cardiac bio-impedance - a non-invasive assessment of cardiac output, cardiac index and systemic vascular resistance index using the bio-impedence technique (Cardioscreen 1000 Medis) Cardiac bio-impedance is performed by attaching sticky electrodes to the participant's neck and thorax. These electrodes pass a very low, constant and alternating current (1.5 mA, 86 kHz) across the thorax, which is imperceptible to the patient. This provides beat by beat data on cardiac output and haemodynamic measurements.

"Aortic pulse wave velocity (APWV) a non-invasive measure of arterial function using oscillometric recordings to detail peripheral and central haemodynamics. This will be measured using two different techniques:~TensioMed Arteriograph: After a rest period a blood pressure cuff inflates and deflates twice on the arm. This takes \~3 minutes and should cause only mild, temporary discomfort. The test will routinely be performed in duplicate to ensure accuracy of results.~SphygmoCor: A pressure sensor is held over the radial pulse at the wrist to analyse the pulse wave. Then held over the carotid artery and/or femoral artery to assess the speed of the pulse wave through the body. The probe is similar to an ultrasound probe and should not cause any discomfort."

"OCT is a non-invasive imaging test which uses light waves to take cross sectional images of the back of the eye. Examination of the retinal and retinal nerve fibre layer thickness, macular volume, and choroidal thickness provides an assessment of generalised systemic microvascular injury. A strong correlation between choroidal thickness and renal dysfunction has previously been shown in patients with chronic kidney disease (Balmforth C et al, JCI Insight 2016).~The participant is asked to sit in front of the OCT machine and rest their chin on a support to keep it motionless. The equipment will then scan the eye without touching it. Scanning takes about 5 - 10 minutes."

"Magnetic resonance imaging using arterial spin labelling (ASL-MRI) This promising quantitative technique has the potential to identify dysregulated renal perfusion, stratify risk of AKI in pre-OLT patients, and to monitor alterations in renal haemodynamics in the post transplantation setting.~* We aim to recruit 5 participants with 'normal' renal function (eGFR≥60ml/min/1.73m2) and a further 5 participants with 'abnormal' renal function (eGFR\<60ml/min/1.73m2)~* ASL-MRI will be performed in this subgroup during the week of OLT assessment and then repeated at 6-weeks post transplantation in those participants who undergo OLT during the study period."