This story disturbs me too.
Unfortunately, I think it plays out too often for too many people. I have birds like this referred to me fairly often when things go wrong. The most disturbing part to me is, why the first vet didn't refer Churchil to the avian vet you now take your lovebird to (or another, if others are in the area) on that Saturday, or even Thursday night or Friday, when things went wrong.
You said the original reason for the visit was loose droppings. This can be caused by a lot of things, from stress to kidney or other disease, to eating too much watermelon (or other wet foods). Not too much for good health, too much to avoid loose droppings. When there is a medical problem, birds often drink excessively, so this is a very non-specific symptom. The vet didn't run any tests, I assume – especially bloodwork.
There is actually a long list of things that can cause kidney failure. Infection, nutrition, cancer, toxins, the list goes on from there.
The FIRST thing that should be done with a case like this is to rule out kidney disease and find out about the general health of the bird. This requires gathering information beyond that obtained with a physical exam. Birds compensate extremely well for low-grade, chronic problems and can hide these problems for some time before the process overwhelms them and they can no longer hide it.
The only injections I can imagine that the vet would be justified in giving with only the history of loose droppings and an otherwise unremarkable physical would be antibiotics for a suspected bacterial infection. Bacteria does like to take advantage of a weakened bird, so their use is appropriate to prevent secondary infection, as well as to treat a possible primary infection (like in the kidneys), that may have been the cause of the loose droppings. Some bacteria are sensitive to certain antibiotics, and others are sensitive to other antibiotics, so perhaps the vet wanted to “cover all the bases” by giving two kinds of antibiotics. This is known as “shotgun medicine” and is only practiced when there is no choice – usually when the client refuses to spend the money for diagnostics to discover the real reason for the symptoms. It is also appropriate when diagnostic tests will take some time to get the results. Covering the bacterial possibilities while waiting for test results is a good idea in cases like this. At this time, continuing antibiotics should be sent home to give – not just a single injection. If there was bacteria involved, then a single injection would not be enough
So to answer one of your questions, yes, one way or another, it is usually possible to detect kidney disease. Bloodwork usually shows an elevated uric acid level if the kidneys are badly affected. Mildly affect kidneys may not show this increase, but bloodwork can help to rule out most other causes for the symptoms. Bacterial cultures can be taken to see if there is abnormal, possible disease-causing bacteria present in the GI or the respiratory system. An x-ray can be taken to rule out other things.
If those diagnostics don't reveal the answer and the symptoms persist, there are more advanced diagnostics, like endoscopy, that can be (and are routinely) employed. Once a diagnosis is made, then the ability to effectively treat the problem depends on the degree of damage and the actual cause. Some things can be completely cured. Some may not be cured, but can be managed so the patient has a longer life with good quality. Some require medical treatment, some surgical. There is a vast array of possibilities.
Poor Churchil was not given the chance to find out.
As for the “reaction”, this may have been an allergic reaction – the likelihood depends on the exact drugs he was given. If he was given the “usual” antibiotics given birds, the likelihood of an allergic reaction is low. Reactions don't have to be allergic in nature. If he was suffering near end-stage kidney failure and compensating well enough that the only symptoms he had were the loose droppings, then just the stress of the visit, coupled with getting injections of any kind could have been enough to put him over the threshold and make him get very sick very quickly.
When this happened, IMO, he should have been taken to a qualified avian vet to respond to this, rather than taken home with other medicine to “see how he does”. On Saturday, when he got worse, he definitely should have been referred.
So to answer the question, “did he lie”, I doubt if he was trying to deceive you – HE thought nothing could have been done. In my opinion, a LOT could have been DONE, but I don't have enough information to know if Churchil could have been saved or not. I do know that he was NOT given a chance to find out before he died.
I would highly recommend that you request copies of all medical records from this vet on Churchil. This is your right to obtain them. All notes he made, information on all meds given, hospital records and notes on what they did while he was there. Also, a report from the vet that did the necropsy at the university, including any histopathology reports (if this was even done). If you get this information and share it with me, I will help you decide whether this vet should be reported to the Board of Veterinary Examiners in your state for review of the case.
I feel strongly that he MAY have neglected giving Churchil reasonable care, including the opportunity of a referral to a more qualified avian vet.