My iguana passed away yesterday

Question
QUESTION: I adopted a 15 year old iguana from my brother, in which I have had for about 5 months.  Up until the last month, she was great and playful.  She recently stopped eating, moving, and going to the bathroom.  She drank a little.  I put her outside numerous times for the sun to help.  A couple of times, she got in her water bowl. I took her to the vet and found out she had a swollen tongue.  They didn't know if she had parasites or what else was wrong, but they gave me medication for her tongue.  Yesterday, I put her in the sun while was gone, with her water bowl right next to her.  When I came home, I found her passed away.  She was located halfway in her waterbowl with her nose in the water.  I feel absolutely horrible and feel so guilty of not being able to help her.  I don't know if she got stuck and couldn't get out of the water because she was sooooo weak.  I wanted to get an autopsy but don't know if I can live with myself knowing for sure if she drowned.  What are reasons for her sickness in the first place.  Symptoms were: swollen tongue, not eating, barely drinking, barely moving, not going to the bathroom.  She was always in the sun so I don't think it was calcium related.  Please give me ideas on what happened because I have no idea.

ANSWER: Hi Sharla,
I am so very very sorry for your loss.
What you are describing sounds like she had kidney disease.
As to the water, I have heard many many people that have had elderly and or sickly iguanas that have done the same thing. It makes us wonder if this is how they end their life in the wild...
I would have the necropsy done as I think they will find that she had kidney disease and a whole host of other problems.  15 years is still a good life for an iguana...Yes, some are living beyond that but there are still way to many that are dying in less than 1/2 that age.  
Again, I am very sorry for your loss.  Know that she had a wonderful 5 months being loved and cared for by you.

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QUESTION: Are there certain reasons why she may have had kidney disease.  Did I not give her enough water?  Did she suffer?  Is there anything I could have done?  Do you think she drowned or gave up?  
Thanks in advance for any help to ease my pain because she just looked miserable and I didn't know what else to do.

Answer
Hi Sharla,
If it was kidney disease or actually any other disease, its safe to say it was nothing you did as that in most cases, its a very slow progression of the disease over a period of time.
Yes, there are things that can cause death with no signs at all, and also very quickly....same as with humans.  Blood clots, tumors, etc can all strike reptiles very quickly. I actually lost a very young leopard gecko in November..she was about 7 yrs old...she was fine the night before...eating, etc... and she was gone the next morning. Her gallbladder ruptured.
I don't think she drown or gave up...I think it was her time and she was just plain worn out. I would say she just closed her eyes and was at peace.  You need to take that same peace and know you did all you could for her.
many times, I think we try so very very hard to extend their lives beyond what is meant for a particular ig and in extending their life, I sometimes fear that even though on the outside, they look ok..on the inside they are hurting and we just can't see it. Again, I am sorry for your loss.