Severe Constipation. Fecal impaction typically indicates that stool has collected in your rectum and formed a large bolus or ball of stool. This typically requires "disimpaction" which is digital (with a finger) removal of this stool. This can in fact require sedation. Ironically severe impaction can cause fecal incontinence or soilage from liquid stool leaking around the large bolus of stool.
All stopped up. Fecal impaction is when the stool within the rectum becomes hard to the point that it "clogs" the rectum. This can be very uncomfortable and causes pain and bloating. Sometimes it can be severe enough that it causes the intestines to rupture which can be life-threatening. For this reason it is important to treat constipation before it worsens to the point of fecal impaction!