specimen in pee?

Hello ladies, I'm due in September and I had symptoms of an uti last week so I called my doctor and they told me to come in so they could test my urine. So I went in and the test came back negative, doctor proceed to tell me that sometimes our bodies can tell us before it actually happens so she put on medication. But I just had a baby 10 months old (August 2016) And ended up having preeclampsia and had to be induced then an emergency c section. Doctor called me back yesterday and said they found specimen in my pee that after I finish my medication they needed to see me. So my question is what exactly is specimen? I've done research but I'm still not understanding?