__What symptoms or diagnoses do you think could show a “Kidney Tubules syndrome” at play?__
If I understand the expression correctly, the word "kidney tubules syndrome" refers to kidney collecting-tubules (fluid collection in the body) while another conflict is in repair phase.
The __main symptom__ I would expect is __weight gain__ without consuming more food. Maybe some CM doctors would give a diagnosis such as obesity and not differentiate between fat and water.
In the regeneration phase, the body sends fluid to the cells to transport everything necessary for repair. If the cells are already full of water, this could lead to pain because the cells are overly full. Healing will be prolonged, possibly painful, or more dangerouse if the healing peak will be a heart attack or a slipped disk in the spine.
Possibly the client has unusually strong cravings for salty food.
Possibly headaches because of Hamer herds in the brain and little space because everything is filled with water.
CM might also diagnose kidney cancer, because of finding more cells to help retain water.
The client drinks a lot but hardly urinates.

__What symptoms or diagnoses could show a "Brain Stem Constellation" at play?__
I would expect the client to be in a shut-down mood. Very low on the autonomic ladder. The client might suffer from constipation. Maybe CM doctors would diagnose depression.
The client might be perplexed and disorientated. Feel numb, shut down and collapsed. The client might also not be very sensitive to pain and feel the same pain less than others.
The biological reason for this constellation is to slow the client down. To make him observe and wait. To learn a lesson before acting.
So the findings could be a vegetative state, confusion, bewilderment, or Alzheimer's disease. The client might be unable to take decisions and might hoard or collect things. Generally, I would expect the client to be slow and not capable of taking information in.