Had CT scan for stones, came back clear. Low back pain. Nurse says low back wld not show on CT scan? Wld spinal tumor show up from CT of area? Confused

True. The ct abdomen/pelvis stone protocol studies image different structures, than would be imaged in a dedicated ct lumbar spine study. If there is concern for the back, then another imaging study is needed, i.e. Mri or ct.
Yes. Yes a spinal tumor would be seen on a ct of the spine, however MRI is mush more useful to look at soft tissue structures, nerve roots, disks, spinal fluid, etc. Usually MRI gives a better evaluation of spinal conditions. You may want consider that as well.