You can do the liver biopsy or genetic test. for disease diagnosis. For renal transplant, only a combined one!

Managing these patients is not always straight forward and it does partly turn on the underlying genetics as outlined in this excellent monograph from the Mayo Clinic-

http://www.mayomedicallaboratories.com/articles/communique/2013/07-hyperoxaluria-oxalosis/index.html

If the patient proceeds t ocombined  liver kidney transplantation attention needs to be paid to managing the oxalate load post transplantation. This requires attention to hydration if you have immediate function of the renal allograft or with dialysis if there is delayed graft function, to prevent oxalate deposition in the new kidney.

Thanks for posting such an interesting question. The following multidisciplinary  management strategy is highly suggested:

1. Confirm the diagnosis: genetic mutational analysis of AGXT gene should confirm the diagnosis in most cases. Nevertheless,if no mutation could be identified (because the mutation lies in a promoter or other regulatory sequence) in highly suspected cases on clinical basis, one should resort to the cumbersome enzymatic assay for levels of AGT and GRHPR activity.

2. Check pyridoxine sensitivity status.

3. Intensive dialysis strategies prior to transplantation to clear plasma oxalate levels and to limit systemic involvement, such as daily sessions of high-flux dialysis. 

4. Combined liver and kidney transplantation, whether simultaneous or sequential depending largely on the expertise of the center. nevertheless sequential Tx, starting with the liver, gives a sufficient time window for aggressive dialysis to remove the excessive oxalate load prior to transplanting the new kidney. It all boils down to the surgical expertise at your center.

Thanks for your thoughts, how does pyridoxine sensitivity status help at this stage when his organ had failed, as we don't have access to AGXT gene mutation analysis, we would not be able do. He is on aggressive dialysis regime, waiting for a suitable donor to shot and we will be putting both liver and kidney same time