Final answer:
A kidney that moves downwards upon standing is termed a ptotic kidney or ren ptosis, which occurs due to abnormal kidney mobility and can lead to complications.
Step-by-step explanation:
A kidney that moves down or descends when the patient stands up is referred to as a ptotic kidney or ren ptosis. This condition occurs when there is an abnormal mobility of the kidney within the abdomen. Normally, kidneys are relatively fixed in their position in the back of the abdominal cavity, secured by surrounding structures and tissues. However, conditions such as loss of surrounding fatty tissue, weakening of supporting structures, or congenital anomalies can result in increased mobility leading to nephroptosis.
It is important to diagnose and understand the implications of a ptotic kidney as it may potentially lead to complications such as ureteral kinking, obstruction, and pain.