Constipation

A need for laxatives doesn’t mean there’s a bowel obstruction. People who are seriously ill often have trouble with bowel function. Laxatives are used to treat this before it has a chance to create a bowel obstruction.

Two main reasons why a person who’s ill may need a laxative are:

• Some cancers affect how the bowel works. Any tumor located near the bowel may press on it and make it difficult for the bowel to work properly. For example, ovarian cancer may do this because the ovaries are located near the bowel.
• Many medications affect how the bowel works. For example, opioid medications, such as morphine or Dilaudid, cause the bowel to slow down and not work well. Someone taking such medications needs to take a laxative also, in order to promote bowel movement.

As long as someone is passing regularly formed stools (stool consistency unchanged), and reasonably frequently (at least every three days), then it’s unlikely that person has a blocked bowel. A bowel obstruction produces abdominal pain that’s different from pain related to the underlying illness. It also produces nausea. The person is unlikely to pass any stool at all. At times there may be diarrhea or loose stool, as this can pass around a blockage. X-rays are often used to determine if someone has a bowel obstruction.

It’s important to contact a health care provider immediately if any of these symptoms appear:

• no bowel movement within three days;
• unusually high number of stools per day;
• blood in the urine, stool or anal area;
• no bowel movement within one day of taking a laxative;
• persistent cramps and vomiting.

In people with cancer, swelling of the stomach or abdominal area can have a few different causes.

• Fluid may collect in the area of the body containing the abdominal organs. This fluid is called ascites. It may result from the tumor causing the body to produce more fluid, or the tumor may be blocking the normal flow of fluid through the lymph and other body systems. Ascites can make someone feel bloated, uncomfortable and short of breath. If this does not bother the patient, it can be left alone. If there is discomfort, then the fluid sometimes can be drained. The draining of ascites from the abdominal cavity is called paracentesis. At times, medications can help the body eliminate the fluid. The medications often are not that helpful, because it’s not that there is too much fluid in the body, rather it is just collecting in the wrong places.
   
• Sometimes the bowels do not empty well. Stool may build up and gas may cause bloating. This can be due to constipation from opioids, from a general slowing of the bowels due to weakness, or a blockage of the bowel due to a tumor. In all these cases the patient usually has symptoms of constipation. Constipation from medication or slowed bowels can be treated with laxatives.
   
• As some illnesses progress, there can be swelling under the skin and in other body tissues. This is called edema.

Sometimes the causes of swelling can be treated and swelling decreased. For example, bowel functioning may be improved if a blockage is removed. At other times the cause of the swelling can’t be treated and it’s best to treat the symptoms associated with it. For example, if the swelling is causing shortness of breath, there are medications to ease this.

Constipation is a very common symptom in patients with advanced disease of any kind, including cancer. Patients at the end of life have many reasons for becoming constipated, including immobility, reduced fluid intake, and the use of a number of medications. Patients frequently need to have bowel movements in inconvenient and unfamiliar places, and in unnatural (non-physiologic) positions. Medications, especially opioids, contribute to constipation. Other medication causes of constipation include tricyclic antidepressants and diuretics, as well as anti-serotonin anti-nauseants, such as ondansetron and granisetron.

Investigating constipation includes paying attention to history, noting typical symptoms, such as anorexia, nausea, vomiting, abdominal pain, bloating, tenesmus and diarrhea (leaking past the fecal obstruction), as well as conducting abdominal and rectal exams. X-rays of the abdomen may be helpful to rule out obstruction. Bloodwork may be needed to rule out hypercalcemia, the most common metabolic cause of constipation in cancer.

Anticipating and preventing constipation, and treating it before it becomes severe, is always preferred. Long-standing constipation is more difficult to manage. Assuming there is no underlying bowel obstruction, treatment includes correcting reversible metabolic abnormalities and identifying offending medications that could be reduced or changed. As much as possible, allow regular bowel movements to occur after meals, in natural (physiologic) positions, in private surroundings.

Bulk-forming laxatives (such as fibre supplements) should usually be discontinued, as they require more fluid intake than many palliative care patients are able to consume. As well, opioids frequently limit intraluminal moisture, which is required for bulk-forming agents to be effective. Docusate is frequently prescribed as stool softener, but there is little evidence that it is effective.

Starting with a stimulant laxative (such as senna), then adding an osmotic laxative (such as lactulose) if needed, has been an accepted approach. More recently, based on evidence, guidelines[1] suggest the use of polyethylene glycol (PEG) marketed as Lax-A-Day, Restoralax and others. PEG can be mixed in a favourite drink or sprinkled on food. PEG may cause less cramping than other laxatives.

If the rectum is full of stool, a low enema may be helpful to get things going. If the stool is hard and impacted, manual disimpaction with extra analgesia before the procedure may be required. Once constipation is resolved, the regular use of laxatives helps to prevent recurrence of this problem.

A special situation results when severe opioid-induced constipation does not respond to the usual agents described above. In this scenario, using subcutaneously injected methylnaltrexone may be helpful.

Reference

1. Librach L, et al. Consensus recommendations for the management of constipation in patients with advanced, progressive illness. J Pain Symptom Manage. 2010;40(5):761-773.

Other references

Fraser Health. Hospice Palliative Care Program Symptom Management Guidelines: Bowel Care. Surrey, BC; 2006.

Winnipeg Regional Health Authority Palliative Care Program. Constipation Assessment and Management Algorithm. Winnipeg, MB; 2012.

Woelk C. The hand that writes the opioid… Can Fam Phys. 2007;53:1015-1017.