"I've got just the one kidney..." Just The One: Diagnosis & Inquiry

     I've got 
just the one kidney. Yep! Only the one.
     Were I, 
somehow, to lose it, why, then I'd have none.
     I've got 
just the one kidney, a snap-bean-shaped curve
     I could 
sever in twain, had I requisite nerve.

     I've got 
just the one kidney. Time was, I had two.
     So: why 
vanish'd the second...? I'm sure I've no clue.
     I've got 
just the one kidney. What caused this, I'm told,
     was a 
tumble I took when but half a week old.

     I've got 
just the one kidney. Some claim they've got three.
     How I 
wish I own'd extras, but, hey...that's just me.
     I've got 
just the one kidney. (I scarf kidney pie
     when I 
breakfast in Brighton, nor've never known why.)

     I've got 
just the one kidney. It's one I can't spare.
     For as 
long as I've got it, I'm walking on air.
     I've got 
just the one kidney. Friends boast they've a few,
     to which, 
someday, they'll stake me. How many have you...?