Assistant principals aid the principal in the overall administration of the school. Some assistant principals hold this position for several years to prepare for advancement to principal jobs; others are career assistant principals.n larger school systems, a principal is often assisted by someone known as a vice-principal (Republic of Ireland: deputy principal) or assistant principal.
Causes. Pressure on the bladder during delivery is the main cause of a ruptured bladder, although a weakness in the bladder wall may make it susceptible to a rupture. In older horses, a ruptured bladder may be caused by an accident or related to a urinary obstruction.
Other possible causes of hydronephrosis include: 1  Blood clots in the kidney or ureter. 2  Narrowing or stricture of the urinary tract due to injury, infection, birth defects or surgery.3  Nerve or muscle problems that affect the kidneys or ureters.4  Urinary retention due to an inability to empty the bladder.ther possible causes of hydronephrosis include: 1  Blood clots in the kidney or ureter. 2  Narrowing or stricture of the urinary tract due to injury, infection, birth defects or surgery.