Page 161 Guide to Pain Management in Low-Resource Settings

Osseous Metastasis with Incident Pain 149

two-thirds of all demonstrated sites of bone metastases characteristically described as dull in character, con-
are painless. Many nerves are found in the periosteum, stant in presentation, and gradually progressive in in-
and others enter bones via the blood vessels. tensity. Pain increases with pressure on the area of in-
Microfractures occur in bony trabeculae at the volvement. Th ese characteristics are fully described by
site of metastases, resulting in bone distortion. Th e the patient, so the condition should be investigated as
stretching of periosteum by tumor expansion, mechani- probable osseous metastasis with bone pain.
cal stress on the weakened bone, nerve entrapment by Th e gnawing pain described by the patient is
the tumor, or direct destruction of the bone with a con- characteristic sign suggesting neuropathic elements. It
sequent collapse are possible associated mechanisms. is radicular in distribution (L2/3) and unilateral, sug-
Th e weakening of bone trabeculate and the release of gesting an origin from the lumbosacral spine. Pain is
cytokines, which mediate osteoclastic bone destruction, usually bilateral when originating in the thoracic spine
may activate pain receptors. and is exacerbated in certain positions that the patient
Th e release of algesic chemicals within the mar- usually tries to avoid. Straight leg raising, coughing,
row probably accounts for the observation that pain and local pressure can exaggerate the pain, while pain
produced by tumors is often disproportionate to their may be relieved by sitting up or lying absolutely still.
size or degree of bone involvement. A secondary pain Weakness, sphincter impairment, and sensory loss are
may be caused by reactive muscle spasm. Nerve root in- uncommon at presentation, but they develop when
fi ltration and the compression of nerves by the collapse the disease progresses in the compressive phase, and
of osteolytic vertebrae are other sources of pain. should be prevented.
In osseous metastasis, hypercalcemia, i.e., el-
Clinical presentation evated plasma levels of ionized calcium, is inevitable. As
half of the calcium is albumin-bound, the total calcium
Case study value should be adjusted for the albumin level to cor-
A female patient, aged 63 years, came to the pain clinic rectly evaluate the calcemic status. Renal function, in-
with vague aching pain in the lower back, which she has cluding urea and electrolytes, should be checked. Symp-
had for 3 months, accompanied by gnawing pain in the toms occur with calcium values exceeding 3 mmol/L,
middle of her right thigh, particularly on standing up and their severity is correlated with higher values. In
or walking. Pain scoring by the patient defi ned the pain elderly and very ill patients, very slight increases of ion-
at rest as 4, and pain on walking as 6, on a 10-cm line. ized calcium plasma levels may be symptomatic.
Th e back pain has been steadily increasing during this • A shortened QT interval on the electrocardio-
time, and now she lies in bed all the time to prevent her gram may be evidenced. Increases in urinary cal-
pain from increasing further. Her back pain was great- cium levels are caused by the release of calcium
ly reduced by NSAIDs. Th e patient has had radical left into the circulation secondary to an increased
breast surgery due to breast cancer, followed up by radio- bone resorption.
therapy. On examination, there was clear tenderness on • Urinary excretion of hydroxyproline, a major
the lumbar spine, at the second lumbar vertebra, and on constituent of type I collagen, is an indirect mea-
the medial part of the lower third of the right thigh. sure of increased bone turnover. Both urinary hy-
Pain may be vague or absent because osseous droxyproline/creatinine and calcium/creatinine
metastasis may be painless. However, any vague pain ratio have been used to monitor the eff ects of
in a patient with a history of treated cancer should be bisphosphonate treatment.
taken seriously and thoroughly investigated. Bone pain • Hypercalcemia is associated with pain, nausea,
usually results from osteolytic bone metastases. Pain as vomiting, anorexia, constipation, weakness, de-
a symptom is present in about 50% of patients. Th e fi ve hydration, polyuria, mental disturbances, and
most frequently involved sites are the vertebrae, pelvis, confusion. Symptoms can mimic those associ-
ribs, femur, and skull. Pain develops gradually during ated with diseases or conditions. Gastrointestinal
a period of weeks or months, becoming progressively symptoms are often mistaken for opioid eff ects or
more severe. Th e pain usually is localized in a particular are potentiated by opioid-related symptoms, and
area, such as the back and the lower third of the femur, neurological symptoms are often attributed to ce-
and is often felt at night or on weight bearing. Pain is rebral metastases. Hypercalcemia complicates the