Page 153 Guide to Pain Management in Low-Resource Settings

Abdominal Cancer, Constipation, and Anorexia 141

enemas will help to evacuate the feces. If the rectum is Why do opioids induce
found to be empty and collapsed, fecal impaction is not constipation?
probable, then oral fecal expanders (combined with per-
istaltic stimulants) should be used. To understand opioid-induced constipation, we have
to remember that peristaltic movement is the con-
Which etiologies apart from the sequence of longitudinal contractions of the smooth
cancer must be considered? muscles proximal to descending food and intestinal
compliance. Th e excitatory motoneurons in the intes-
Certain factors infl uence the motility of the colon. Th e tines responsible for longitudinal contractions have
most important “extrinsic” factor is pharmacotherapy cholinergic innervation. Since opioids have anticholin-
(e.g., opioids and all anticholinergic drugs such as an- ergic eff ects, they inhibit peristaltic movements. Addi-
tidepressants, calcium, and aluminum-containing ant- tionally, opioids enhance local concentrations of 5-HT
acids), and the most important “intrinsic” factor are and norepinephrine, thereby reducing the secretions of
plexopathies (e.g., with autonomous neuropathy in dia- the intestinal wall, which further impedes movement of
betes or Parkinson disease). Dehydration, immobiliza- the feces. A central peristalsis-reducing eff ect from the
tion, hypokalemia (e.g., as a result of diuretic therapy), opioids may add to the problem. Although opioid use is
and physical weakness are additional factors. Th e latter one of the most frequent causes of constipation, there
conditions are the main reasons for constipation in gas- is no evidence-based treatment protocol or prophylaxis
troenterological cancer patients in addition to the direct protocol for this therapeutic situation, but it is advisable
eff ects of the cancer tissue growth (obstruction and in- to always use a prophylaxis to prevent opioid-induced
fl ammation). Sometimes overlooked, depression and constipation, whether constipation is already present or
anxiety disorders, which have a higher incidence in can- not.
cer patients, may be another predisposing factor.
Do all patients with constipation
What are the specifi c risk require special laxative therapy,
factors for cancer patients to get and what would be the most simple
constipated? treatment algorithm?

• Dehydration, e.g., following repeated vomiting As usual, simple solutions are the best. Specifi c laxative
• Reduced nutritional intake due to cancer-related therapy is only indicated in special situations, one of the
anorexia most important one being the prophylactic treatment of
• Multiple surgical or diagnostic manipulations opioid-induced constipation.
(e.g., barium use for radiology is a potent consti- “Unspecifi c” techniques to reduce constipation
pating agent) may be eff ective if used in combination, e.g., fi ber-rich
• Gastrointestinal metastasis nutrition, regular daily activities, colonic massage, and
• Continuous opioid medication suffi cient oral hydration. Unfortunately, the eff ective-
• Coanalgesics with anticholinergic eff ects (e.g., tri- ness of this prophylactic regimen is limited if opioids or
cyclic antidepressants and anticonvulsants) other constipation-causing medications are used. Addi-
• Chemotherapeutics (e.g., vinca alkaloids) tionally, in most cases it will be not appropriate in pa-
• Hypercalcemia (frequent with osseous metasta- tients who will be unable to follow such a diet and ac-
sis) tivities most of the time. Th erefore, constipating drugs
• Immobilization in inpatient treatment (plus loss should be limited to those that are absolutely necessary.
of privacy, causing a “psychological inhibition” of If therapy cannot be done without these drugs, specifi c
normal defecation) regimens should be instituted in every patient, starting
• Uncontrolled pain (from surgery or the cancer with a stepwise approach. Th e fi rst step would be lo-
itself), depressive disorders, and anxiety (causing cally available laxatives, e.g., dried and crushed pawpaw
“arousal” of sympathetic stimulation with conse- seeds (1–5 teaspoons daily, at bedtime) combined with
quent reduction of bowel motility) vegetable oil (1 teaspoon daily) or alternative remedies