They are BACK PUMPS.
You are suffering from back pumps. It's a side from some steroids.
It's not your liver. Unless your POOP is tan, like peanut butter and your eyes are yellow.
Your liver is located under your right rib cage in FRONT.
It's not your Kidneys unless your piss is brown. The pain would be more to the sides.
If you lower back hurts right above your belt line, a few inches east or west of center, like you've been picking cotton for a week, and hurts when you load the dishwasher, you have back pumps. :aargh:
Water, potassium, taurine, lay on your back between sets...
They are a nuisance, but it's part of the plan.
I get them from superdrol, Dbol, Tbol, and Drol. Your dose of 20 is good, IMO.