A 65-year-old woman comes to the emergency department due to a 2-week history of constipation and abdominal pain. The patient also has urinary frequency and constant thirst. Her medical history is significant for persistent atrial fibrillation treated with diltiazem and rivaroxaban, hypertension treated with hydrochlorothiazide, and hypothyroidism treated with levothyroxine. There has been no recent change in any of these medications. In addition, the patient was diagnosed with osteoporosis 3 months ago; she declined treatment with bisphosphonates and instead opted to treat only with over-the-counter vitamin and mineral supplements. She does not use tobacco or alcohol. On physical examination, temperature is 36.8 C (98.2 F), blood pressure is 120/70 mm Hg, pulse is 90/min and irregular, and respirations are 12/min. Mucous membranes are dry, and the abdomen is soft and nontender without rebound tenderness or rigidity. Bowel sounds are decreased but present. Bedside dipstick urinalysis is within normal limits. Which of the following is the most likely cause of this patient's current symptoms?

Question

A 65-year-old woman comes to the emergency department due to a 2-week history of constipation and abdominal pain.  The patient also has urinary frequency and constant thirst.  Her medical history is significant for persistent atrial fibrillation treated with diltiazem and rivaroxaban, hypertension treated with hydrochlorothiazide, and hypothyroidism treated with levothyroxine.  There has been no recent change in any of these medications.  In addition, the patient was diagnosed with osteoporosis 3 months ago; she declined treatment with bisphosphonates and instead opted to treat only with over-the-counter vitamin and mineral supplements.  She does not use tobacco or alcohol.  On physical examination, temperature is 36.8 C (98.2 F), blood pressure is 120/70 mm Hg, pulse is 90/min and irregular, and respirations are 12/min.  Mucous membranes are dry, and the abdomen is soft and nontender without rebound tenderness or rigidity.  Bowel sounds are decreased but present.  Bedside dipstick urinalysis is within normal limits.  Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

11ec25c8_d3b2_30c3_bc81_73a07d6f67b7_MD0003_00 This patient has typical symptoms of hypercalcemia, including abdominal pain, constipation, and polydipsia. In light of initiation of over-the-counter supplements for osteoporosis 3 months ago, her symptoms are likely due to milk-alkali syndrome (MAS). MAS is caused by excessive intake of calcium and absorbable alkali (eg, calcium carbonate preparations used in patients with osteoporosis). The resulting hypercalcemia causes renal vasoconstriction and decreased glomerular blood flow. In addition, inhibition of the Na-K-2Cl cotransporter (due to activation of calcium-sensing receptors in the thick ascending loop) and impaired antidiuretic hormone activity lead to loss of sodium and free water. This results in hypovolemia and increased reabsorption of bicarbonate (augmented by the increased intake of alkali). Medications that raise the risk of MAS include thiazide diuretics, ACE inhibitors/angiotensin II receptor blockers, and nonsteroidal anti-inflammatory drugs. In addition to hypercalcemia, metabolic findings in MAS include hypophosphatemia, hypomagnesemia, metabolic alkalosis, and acute kidney injury. Parathyroid hormone levels are suppressed. (Choice A) Diltiazem is a calcium channel blocker that can cause constipation, but it does not cause other symptoms of hypercalcemia (ie, polyuria and polydipsia). (Choice B) Diabetic ketoacidosis can be the initial presentation of type 1 diabetes mellitus and presents with polyuria, polydipsia, and weight loss. However, new onset of type 1 diabetes is uncommon in older individuals, and urinalysis would show glucose and ketones. (Choice C) Hypothyroidism can cause constipation but is unlikely to lead to hypercalcemia and would be accompanied by other findings (eg, weight gain, cold intolerance, fatigue). Hyperthyroidism (and excessive replacement of levothyroxine in hypothyroidism) can cause mild hypercalcemia due to increased bone turnover but is unlikely to cause constipation. (Choices E) Thiazides can be associated with mild hypercalcemia due to increased calcium reabsorption in the distal tubule, but severe, symptomatic calcemia as seen in this patient would be extremely unlikely due to thiazide therapy alone. In addition, there is no indication that her thiazide dose has changed. (Choice F) Excessive doses of vitamin A can increase bone turnover and lead to abdominal pain and hypercalcemia; however, hypercalcemia is usually mild, and vitamin A toxicity would also manifest as dry skin, headache, and blurry vision. Educational objective: Milk-alkali syndrome is caused by excessive intake of calcium and absorbable alkali. It can be seen in patients taking calcium bicarbonate for osteoporosis. Clinical findings include symptomatic hypercalcemia, metabolic alkalosis, and acute kidney injury. References: Antacids, altered mental status, and milk-alkali syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/23431478) Milk alkali and hydrochlorothiazide: a case report. (http://www.ncbi.nlm.nih.gov/pubmed/21738535)

A 65-Year-Old Woman Comes to the Emergency Department Due to a 2-Week