What Causes Urinary Retention After A Spinal Fusion Surgery?

My wife has had a spinal fusion recently had a ct scan as maybe possible nurological damage she recently had facet joint injection but is at present laid up most of time cannot stand for long periods of time has not been out of house for three weeks awaiting results but this is why I m asking the question about Bowell movement and urination that with stool movement she has to help it along by pressing on the area between the vagina and anus plus when urinating she has to press her stomach to release the retained fluid I am very concerned as she has just told me she already has drop foot with no strength in her left foot problems with elevation and slight paralysis for example numbness in feeling please help