A 66-year-old man comes to the office due to several weeks of severe constipation and increasing back pain. The patient notes that he has always had regular bowel movements; however, for the last 2 months, he has required over-the-counter laxatives to produce any stool. During this period, he has also had increasing pain in his lower back. He has had no trauma to that area. There is no radiation down the legs, bowel incontinence, or lower extremity weakness. The patient takes lisinopril for hypertension and ibuprofen as needed for back pain. He does not use tobacco or alcohol. Temperature is 36.1 C (97 F), blood pressure is 134/80 mm Hg, and pulse is 78/min. Mucosal pallor is present. He is anicteric. Cardiopulmonary and abdominal examinations are normal. Rectal examination reveals a smooth, nonenlarged prostate. The stool is negative for occult blood. Strength and reflexes are intact in his lower extremities. Laboratory results are as follows: Which of the following is the best explanation for this patient's constipation?

Question

A 66-year-old man comes to the office due to several weeks of severe constipation and increasing back pain.  The patient notes that he has always had regular bowel movements; however, for the last 2 months, he has required over-the-counter laxatives to produce any stool.  During this period, he has also had increasing pain in his lower back.  He has had no trauma to that area.  There is no radiation down the legs, bowel incontinence, or lower extremity weakness.  The patient takes lisinopril for hypertension and ibuprofen as needed for back pain.  He does not use tobacco or alcohol.  Temperature is 36.1 C (97 F), blood pressure is 134/80 mm Hg, and pulse is 78/min.  Mucosal pallor is present.  He is anicteric.  Cardiopulmonary and abdominal examinations are normal.  Rectal examination reveals a smooth, nonenlarged prostate.  The stool is negative for occult blood.  Strength and reflexes are intact in his lower extremities.  Laboratory results are as follows:  Which of the following is the best explanation for this patient's constipation?

Quizplus · Accepted Answer

11ec25c8_d423_1ae7_bc81_ebd40edde5fe_MD0003_00 This patient with constipation, back pain, and laboratory evidence of anemia, renal insufficiency, and hypercalcemia likely has multiple myeloma (MM). MM is a plasma cell neoplasm that commonly presents with manifestations related to bone marrow infiltration (bone pain, fractures, hypercalcemia, anemia) or elevations in serum monoclonal protein (renal insufficiency). At the time of diagnosis, approximately 25% of patients with MM have hypercalcemia. Typically, this is a result of osteolytic bone destruction by the neoplastic plasma cells. Although hypercalcemia may be asymptomatic with a calcium level <12 mg/dL, fatigue, constipation, and depression are common. This patient's constipation is likely a result of hypercalcemia. Patients with suspected MM should have serum/urine protein electrophoresis (M-spike), a peripheral blood smear (rouleaux), and a serum free light chain analysis. If these screening tests suggest MM, diagnosis can be confirmed by bone marrow biopsy. (Choice B) Hormonal causes of constipation include hypothyroidism and hyperparathyroidism (causing hypercalcemia). However, in an elderly patient, the cluster of renal insufficiency, anemia, and hypercalcemia are far more commonly associated with MM. (Choice C) Irritable bowel syndrome (IBS) is associated with abdominal pain and altered bowel habits. The laboratory findings in this patient would not be consistent with IBS. (Choice D) Mechanical causes of constipation are usually associated with pain and bloating. If severe, nausea and vomiting may result. This patient's examination (normal abdominal/prostate/occult blood examination) and laboratory findings make a mechanical cause less likely. (Choice E) Ibuprofen and lisinopril do not commonly cause constipation. (Choice F) Many neurologic conditions can affect colonic transit resulting in constipation. However, given the patient's laboratory findings, including hypercalcemia, this would be less likely. Educational objective: Hypercalcemia is common in patients with multiple myeloma. It is caused by osteolytic bone destruction. Fatigue, constipation, and depression are common symptoms of mild hypercalcemia. References: Multiple myeloma/hypercalcemia. (http://www.ncbi.nlm.nih.gov/pubmed/17634143)

A 66-Year-Old Man Comes to the Office Due to Several