Can a tarlov cyst cause siatica and bowl and bladder issues?

Tarlov Cyst: http://en.wikipedia.org/wiki/tarlov_cyst group 1 - pain on tailbones that radiates to the legs with potential weakness; group 2 - pain on bones, legs, groin area, sexual dysfunctions, and dysfunctional bladder; group 3 - pain that radiate from the cyst site across hips to the lower abdomen; group 4 - no pain, just sexual dysfunction and dysfunctional bladder.

Yes: Tarlov cysts may compress your spinal nerves causing bowel and bladder dysfunction and sciatica. Fortunately they need to be very large and this is uncommon. Small tarlov cysts usually do not cause any neurological dysfunction.

Possible: Tarlov cysts are found within the sacrum and the nerves going to the bowel/bladder are exiting from there. So there could be a connection. Sometimes caudal epidural steroid injections can be helpful however if short-lived in rare situations surgery maybe performed to decompress these areas.