Gastrointestinal surgery, malabsorptive conditions, and postoperative hypocalcemia after neck surgery.

Background: Postoperative hypocalcemia is a common complication of thyroid and parathyroid surgery. Patients with prior gastric bypass face increased risk of postoperative hypocalcemia, but the impact of other malabsorptive conditions is not well understood. In this study, we evaluated the relationship between multiple medical and surgical malabsorptive states and hypocalcemia after thyroid and parathyroid surgery.

Methods: We performed a retrospective cohort study of patients who underwent total thyroidectomy and/or parathyroidectomy in Optum's deidentified Clinformatics Data Mart Database (2004-2022). Patients were categorized as having surgical (foregut/midgut: gastrectomy, intestinal bypass, enterectomy, enterostomy, pancreatectomy, or hindgut: colectomy/colostomy) or medical (Crohn or Celiac disease) malabsorptive conditions. The primary outcomes were early (<7 days) and late (7-365 days) postoperative hypocalcemia. Logistic regression was performed to determine the associations between malabsorptive conditions and outcomes.

Results: Of 25,400 patients (56.9% total thyroidectomy, 40.8% parathyroidectomy, and 2.4% both procedures), 4.0% had a pre-existing malabsorptive condition. Early postoperative hypocalcemia occurred in 8.8% of patients, and late hypocalcemia in 18.3%. Thyroidectomy was associated with a greater likelihood of hypocalcemia than parathyroidectomy (odds ratio: 1.22; P < .001). Pancreatectomy was associated with twice the adjusted odds of postoperative hypocalcemia (odds ratio: 2.27; P = .031) across both procedures. Patients with prior foregut/midgut surgery were at higher risk after total thyroidectomy (odds ratio: 1.65, P = .002). This association was significant in late (odds ratio: 1.82, P < .001) rather than early hypocalcemia (odds ratio: 1.33, P = .175). Hindgut surgery and medical malabsorption did not demonstrate such associations.

Conclusion: Prior foregut and midgut resections may predispose patients to postoperative hypocalcemia, particularly in patients undergoing total thyroidectomy.