What is the diagnosis for a patient presenting with new onset urinary or bowel retention, saddle anesthesia, and decreased anal sphincter tone on digital rectal examination?

The presentation of new onset urinary or bowel retention, saddle anesthesia, and decreased anal sphincter tone strongly suggests cauda equina syndrome. This condition occurs due to compression of the cauda equina, which comprises the nerve roots at the lower end of the spinal cord.

In cauda equina syndrome, the compression can lead to significant neurological deficits, particularly affecting the pelvic organs and lower limbs. The symptoms of urinary retention and bowel dysfunction arise because the nerves that supply these functions can be compromised. Saddle anesthesia specifically refers to loss of sensation in the areas that would sit on a saddle—essentially the perineal area, which by itself is a crucial sign of potential nerve root damage. Decreased anal sphincter tone on digital rectal examination indicates a loss of neurological control over the anal sphincter, further supporting this diagnosis.

In contrast, conditions like spinal stenosis and lumbosacral sprains/strains may lead to back pain or radicular symptoms but typically do not cause the specific combination of symptoms seen in cauda equina syndrome. Spinal compression fractures can also lead to pain and possible radiculopathy, but they would not necessarily cause the urinary and bowel symptoms along with saddle anesthesia. Thus,