Fecal impaction is a condition in which the stool becomes hardened and stuck in the rectum, making it difficult or even impossible to pass. It is usually caused by chronic constipation, which can be due to many different factors. Constipation can be caused by a lack of dietary fiber, inadequate fluid intake, certain medications, and medical conditions such as diabetes or hypothyroidism. Inactivity can also contribute to constipation. Other causes of fecal impaction include rectal prolapse and rectocele.