Can Hypercalcaemia Cause Small Bowel Obstruction?
Hypercalcaemia does not directly cause mechanical small bowel obstruction, but it can cause adynamic ileus (functional obstruction) through metabolic disturbance, which presents with similar symptoms of bowel obstruction including abdominal distension, vomiting, and constipation. 1
Mechanism of Bowel Dysfunction in Hypercalcaemia
Hypercalcaemia causes functional bowel obstruction (adynamic ileus), not mechanical obstruction. The distinction is critical:
- Adynamic ileus and colonic pseudo-obstruction are caused by lack of enteric propulsion and can result from metabolic disturbances including hypercalcaemia 1
- Mechanical small bowel obstruction (90% of cases) is caused by adhesions, hernias, and neoplasms—not metabolic derangements 1
Clinical Presentation
Hypercalcaemia produces gastrointestinal symptoms that mimic bowel obstruction:
- Nausea and vomiting are common manifestations of moderate hypercalcaemia (calcium 11-12 mg/dL) 2
- Abdominal pain frequently occurs with moderate hypercalcaemia 2
- Constipation is a recognized manifestation, particularly in severe cases 3
- Severe hypercalcaemia (>14 mg/dL) can cause vomiting, dehydration, and altered mental status 3
Case Evidence
A documented case demonstrates the severity: A 63-year-old woman with severe hypercalcaemia (17.7 mg/dL) presented with abdominal distension and vomiting, developing toxic megacolon requiring emergency subtotal colectomy 4. This illustrates that hypercalcaemia can cause life-threatening bowel dysfunction, though this represented colonic pseudo-obstruction rather than mechanical small bowel obstruction.
Diagnostic Approach
When evaluating a patient with suspected bowel obstruction and hypercalcaemia:
- Rule out mechanical obstruction first through imaging (CT scan) 1
- Check serum calcium, albumin, intact PTH, creatinine, and phosphorus 5
- Assess for hypercalcaemia as the cause if mechanical obstruction is excluded 1
- In constipation cases, rule out both bowel obstruction AND hypercalcaemia 1
Management Implications
Treatment of the underlying hypercalcaemia typically resolves the functional bowel obstruction:
- Initial therapy consists of aggressive intravenous hydration with normal saline 3, 6
- In the documented case, hypercalcaemia corrected within 24 hours with 8L of 0.9% NaCl in the first 12 hours, with calcium dropping from 17.7 to 8.2 mg/dL 4
- Bisphosphonates (zoledronic acid or pamidronate) should be added for severe or symptomatic hypercalcaemia 3
Common Pitfalls
- Do not assume all bowel obstruction symptoms represent mechanical obstruction—metabolic causes like hypercalcaemia must be considered 1
- Hypercalcaemia in children with Williams syndrome requires monitoring every 4-6 months until age 2, as it commonly presents with vomiting and constipation 1
- Dehydration can both cause and result from hypercalcaemia, creating a vicious cycle 2, 4
- In dialysis patients, avoid hypercalcaemia as it may be nephrotoxic and worsen renal function 1