Final answer:
Pyelitis is an infection of the renal pelvis and calyces, often stemming from a urinary tract infection, and it could lead to acute renal failure or stage 5 chronic kidney disease.
Step-by-step explanation:
The disruption in homeostasis known as pyelitis, is actually an infection of the renal pelvis and calyces. This is not exclusive to any specific age group and is not directly caused by a virus or poor hygiene in children, nor is it the aftermath of a severe upper respiratory infection. Pyelitis, or more correctly pyelonephritis, is often a complication resulting from a urinary tract infection. This condition can lead to various complications, including acute renal failure or advancing to stage 5 chronic kidney disease if not properly treated.