Urgent diagnosis for sister. how could she have diverticultitis if no tests to show diverticulosis?

Good question...: All it takes for diverticulitis is one diverticulum. Colonoscopy may not see the diverticular openings if they are small. Ct scan may also not see diverticula if small. Contrast enema is probably best to see the degree of diverticulosis. However, if none are seen, perhaps alternate diagnoses shuold be considered, including irritable bowel and other causes of inflammation.

One begets other.: Sometimes a doctor will treat a patient on the presumption that he or she has diverticulitis, but technically one could not have diverticulitis without diverticulosis so at some point the presence of such needs to be confirmed with CT or colonoscopy.