How do you approach work-up for a patient suspected for monoclonal gammopathy of renal significance for whom renal biopsy is contraindicated?  

Not very many reasons that a renal biopsy could not be done, but I would consider doing a bone marrow biopsy if the free light chain ratio was significantly abnormal, i.e. a ratio of 3 or greater. A reminder that in renal failure, both light chains may be elevated, but the ratio in benign processes ...

I agree entirely with @Ann Mohrbacher. In short, I'd biopsy whatever I could. Depending on the clinical circumstances, fat-pad aspiration would be reasonable to rule out AL amyloidosis as the specific type of MGRS. In general, I'd recommend a complete rule-out of AL amyloidosis regardless for sure s...