utter confusion; chaos; pandemonium
Describes a situation where everything is turned upside down, with people running around in a panic or great excitement. Often used for large-scale disorder or frantic activity.
With the news of the fire, the office was thrown into utter confusion.
Because of the sudden blackout, the station was in chaos.
大騒ぎ means a big uproar or commotion, but 上を下への大騒ぎ emphasizes the topsy-turvy, chaotic nature of the confusion.
てんやわんや is a more colloquial and onomatopoeic way to describe a chaotic scramble, while 上を下への大騒ぎ is a set phrase with a more formal or literary feel.
A set phrase literally meaning 'a big uproar of up and down', i.e., everything turned upside down. The exact origin is uncertain, but it vividly depicts a scene of total disorder.