If she is having to receive blood all night and blood pressure is low, then likely it is due to internal bleeding. The scans are necessary to identify the source of bleeding. It could be a result of the surgery, perhaps the area wasn t sufficiently stitched up. An injury could also have occurred to another area during the surgery, such as a blood vessel or the ureter or bladder, and is continuing to bleed. She might also be experiencing an infection (sepsis) as the result of the inflamed appendix which can also cause weakness and low blood pressure. If there is active bleeding, they may need to do surgery to stop it, depending on what the scans show. Sepsis requires aggressive antibiotic treatment and control of blood pressure. These would be the primary complications most likely to cause her symptoms. Hope this answers your question.