Good evening Wendy,I am very sorry to hear about Lula's deterioration and passing. Now I truly do not think that her deterioration is as easily determinable as you what you are asking. The reason is because Lula had a chronic issue with her kidneys (which obviously I cannot appreciate the type or severity having not seen her bloods nor knowing her history), so already from the start we know this isn't a simple situation and instead her passing was more likely to be multi-factorial.Now if we consider the antibiotic, Convenia is a cephalosporin antibiotic (which is an antibiotic type we use very commonly) and is on that is only partially excreted via the kidney. That said, if she already had severe kidney compromise, then any drug that has kidney based excretion could stress the kidney and damage it further. So, if her kidneys were already severely damaged, then this wouldn't have been an ideal treatment (nor would any drug that is excreted by the kidney) and could have played a partial role in her kidney failure (only a partial one though since she would need to already have severe kidney disease first to be in a position of vulnerability to be so affected by such a drug).That said, in the case of Convenia, when we refer to the drug companies research we find very little evidence of the drug negatively impacting the kidney. There was a report of one cat (on a low dose study) in all their study cats having a notable change to her kidney values after being treated with this drug. And even when the studies went on to giving high doses (22.5X the normal dose Lula would have received), there was no report of kidney damage or failure. Therefore, while any kidney excreted drug could have pushed precariously severe kidney disease over the edge, it is unlikely that this one specific injection was purely to blame for her sudden deterioration.So, in this case, it is doubtful that the Convenia caused kidney failure on its own. If she was already suffering with severe kidney dysfunction, then this could have pushed her over the edge but otherwise we'd have to consider other causes or her playing down her kidney disease as kitties so often do when they are unwell.Please take care,Dr. B.