Which Statistical Test to use for my project - Comparing two ranked lists, 2 groups

I have a project comparing two medical treatments - 1) Treat a Presentation and 2) Treat after Growth.

I am comparing the groups based on the number of complications experienced after each treatment. For each patient (in each group) it was noted if the experienced 1 or more of 18 complications. The complications are in order of severity 1 being the worst (death) and 18 being the least (UTI). How do I create a weighed list/average (i.e. which multipliers) and then compare the two groups - which stat test(s). I do not want to compare individual complications between the two groups, but I want a model that takes the weighted average into account. Sample size is 42 (trust me if I had more I would use them...this is a university hospital study and that is all we have between 2005 and 2013 that fit our criteria).

Thank you.