Sacral Nerve Stimulation for Anal Incontinence and Bowel Control

140 patients (7 study groups, up to 20 implanted patients per study group) Fecal Incontinence groups: Main Inclusion Criteria: * Fecal incontinence (defined as incontinence to solid or liquid stool \> 1 / week); * Failed biofeedback or medical therapy; Groups 1 - 5 patients with: * Group 1) Circumferentially intact external anal sphincter, no previous surgery; * Group 2) Circumferentially intact external anal sphincter after surgical repair; * Group 3) Rectal prolapse repaired with a rectopexy; * Group 4) Spinal injury including disc prolapse; * Group 5) Sigmoid or partial rectal resection with colorectal or coloanal anastomosis Constipation groups: Main Inclusion Criteria: * Chronic constipation (defined as \</= 2 weekly bowel movements; and/or \>25% of bowel movements required straining; and/or \>25% of bowel movements patient did not feel empty afterwards) with symptoms more than 1 year * Failed biofeedback or medical therapy; Groups 6 - 7 patients with: * Group 6) Idiopathic slow transit constipation as proven on colonic transit studies; * Group 7) Normal colonic transit studies but chronic constipation due to either pelvic floor dysfunction or disordered defecation.