What causes lower back pain that radiates to lower abdomen accompanied with symptoms like sweating, vomiting, loose stool and chills?

Kidney infection: There is a high chance that you may have a gastroenteritis accompanied by a kidney infection. Depending on your age this can be caused by multiple other factors. In the elderly you can have a reduced blood supply to the gut causing mesenteric ischemia. You will need to see a doctor as soon as possible to investigate further.

Colon infection.: That sounds to be an infection in the colon. Something like colitis, or diverticulitis. Could be appendicitis. Could even be mesenteric ischemia. Or acute gastroenteritis. Likelihood of a given diagnosis would depend on the specific patient in question, of course.