A fecal impaction is a solid, immobile bulk of feces that can develop in the rectum as a result of chronic constipation. A related term is fecal loading which refers to a large volume of stool in the rectum of any consistency. Fecal impaction is a common result of neurogenic bowel dysfunction and causes immense discomfort and pain. Treatment of fecal impaction includes laxatives, enema, and pulsed irrigation evacuation (PIE). Signs and symptoms
Symptoms include chronic constipation. There can be fecal incontinence and paradoxical overflow diarrhea (encopresis) as liquid stool passes around the obstruction. Complications may include necrosis and ulcers of the rectal tissue. Abdominal pain and bloating could also be present depending on the severity of the condition. Loss of appetite can also occur. Causes
There are many possible causes; for example, physical inactivity, not eating enough fiber, dehydration, and holding in bowel movements. Medications such as opioid pain relievers (fentanyl, buprenorphine, methadone, codeine, oxycodone, hydrocodone, morphine, hydromorphone, etc.) and certain sedatives that reduce intestinal movement may cause fecal matter to become too large, hard and/or dry to expel. Specific conditions, such as irritable bowel syndrome, certain neurological disorders, paralytic ileus, gastroparesis, diabetes, dehydration, enlarged prostate gland, distended colon, ingested foreign object, inflammatory bowel diseases such as Crohns disease and colitis,  and autoimmune diseases such as amyloidosis, celiac disease, lupus, and scleroderma can cause constipation. Hypothyroidism can cause chronic constipation because of sluggish, slower, or weaker colon contractions. Iron supplements or increased blood calcium levels are also potential causes.
This may take 24 to 48 hours for it to take effect, and it is not well suited to cases where the impaction needs to be removed immediately due to risk of complications or severe pain. Enemas (such as hyperosmotic saline) and suppositories (such as glycerine suppositories) work by increasing water content and stimulating peristalsis to aid in expulsion, and both work much more quickly than oral laxatives. Because enemas work in 2–15 minutes, they do not allow sufficient time for a large fecal mass to soften. Even if the enema is successful at dislodging the impacted stool, the impacted stool may remain too large to be expelled through the anal canal. Mineral oil enemas can assist by lubricating the stool for easier passage. In cases where enemas fail to remove the impaction, polyethylene glycol can be used to attempt to soften the mass over 24–48 hours, or if immediate removal of the mass is needed, manual disimpaction may be used. Manual disimpaction may be performed by lubricating the anus and using one gloved finger with a scoop-like motion to break up the fecal mass. Most often manual disimpaction is performed without general anaesthesia, although sedation may be used. In more involved procedures, general anaesthesia may be used, although the use of general anaesthesia increases the risk of damage to the anal sphincter. If all other treatments fail, surgery may be necessary. An easier, more comfortable, and more efficient method to enema and manual disimpaction is to use pulsed irrigation evacuation (PIE).