Is this correct? A right and left retrograde pyelogram were performed.

It's hard for me to tell because I don't know "a right and left retrograde pyelogram" is.

If it's two things, "were" would be correct.

If it's one thing, "was" would be correct.

Looking over the sentence again and trying to figure this out, I had some thoughts.

If it said "A right and a left retrograde pyelogram were proformed" (with the word "a" before the word "left"), then "were" would seem correct.

If the word "a" is not placed in that position, and hyphens were used to connect the words "right-and-left", then "was" would seem correct.

So now I'm curious. Do you know if the author is talking about one thing called "a right-and-left retrograde pyelogram" or two things, "a right and a left retrograde pyelogram"?

I assess from the question that it's two things. Plump for 'were'.

For 'were' to be correct it should state: "A right, then a left blah...were performed." Otherwise 'right and left' should become a compound adjective, meaning 'was' would be right. My advice would be avoid ambiguity: tell the reader if it is one action or two, then you answer your own question.

A pyelogram is a roentgenograph produced by pyelography, which is the science or technique of making photographs of the kidneys, renal pelves, and ureters by means of x=rays, after the injection of an opaque solution.