Right flank pain but normal kidney function?

[FurballsMom]

About three years ago I was hospitalized with renal failure.  I had been very nauseous for about two weeks and had gotten to the point where I couldn't even hold down plain water.  After I was hospitalized came the flank pain, like the worst pain in my life and the worst nausea ever.  I normally drink plenty of water, so except for this extreme nausea causing me to be unable to hold down water at the time, none of the doctors can figure out why my kidneys failed or why my body showed signs of extreme dehydration, even though I was putting out normal amounts of urine.  I am once again experiencing the familiar right flank pain that I know is kidney spasms and feeling nauseous.  Yet, when I went to the ER all the blood tests showed normal kidney functioning.  When the kidney spasms, I would place the rate of pain between a 6 on the low end of the scale to an 8 on the high end of the scale.  So, it's not the 10 plus I had when I was hospitalized about three years ago, but it's still quite painful.

I am sensitive to pain medications, so the only pain medications my body seems to be able to handle are the NSAIDS, which I obviously should avoid if I'm having kidney issues of any kind.  All other pain medications make me very sick, including Tylenol.

The doctors never did figure out what led to the kidney function issues about three years ago.  I went in the ER, because I certainly didn't want a repeat of what had happened before, because even after I had been released from the hospital about three years ago, it took me a whole month to really recover.  The nausea was so unbearable, even after I was released.  So, I naturally thought they might have released me too soon.  But, they said that my kidney functioned had recovered well enough to be released.  

All they could find wrong with me this time was mild dehydration.  But, this still leaves me wondering why so much kidney pain and why so much nausea?  I'm left thinking that the only reason I haven't thrown up is because I haven't felt like trying to push my luck in eating when I'm feeling so nauseous.  And, if I'm so good at drinking fluids, why do I keep ending up with dehydration?  If my kidney function tests normal, why am I still experiencing so much pain and nausea?  This is confusing.

No, there is absolutely no possibility of pregnancy.