Thyroidectomy has a 30-day complication rate of 7.7%. Hypocalcemia is one possible complication affecting 13.2% of cases and can be permanent (> 6 months) or transient. Hypocalcemia can be severe, causing cardiac arrhythmias, tetany, seizures, laryngospasm, Farh’s syndrome, and death. There are risk factors for post-thyroidectomy hypocalcemia, namely central neck dissection, identification/handling of parathyroid glands during surgery, and inflammatory thyroid diseases. Additionally, according to the PROSPERO systematic review, obesity is associated with post-thyroidectomy hypocalcemia.
Dr. Cleere et al. from Galway, Ireland, published this year in BJS the results of the PROSPERO systematic review of 19547 patients submitted to total or near-total thyroidectomy, including 196 patients with a history of bariatric surgery (BS). In this study, post-thyroidectomy hypocalcemia was defined as symptoms (paresthesia, muscle cramps, tetany), need for intravenous calcium administration, or biochemical demonstration of hypocalcemia. Of the 196 patients with a history of BS, 118 had a malabsorptive procedure (113 gastric bypasses, 5 biliopancreatic diversions), and 98 had a restrictive surgery (57 gastric bandings, 41 sleeve gastrectomies). Comparing the group with a history of BS with the group without BS, the rate of central neck dissection was similar. However, only a small number of reports conducted this analysis, which is a drawback of this systematic review.
The overall incidence of hypocalcemia was 13.2% (2583 patients). A previous BS was significantly associated with hypocalcemia after total or near-total thyroidectomy. Post-thyroidectomy hypocalcemia occurred in 30.6% and in 13.0% of patients with and without BS, respectively (p=0.005). Additionally, patients submitted to gastric bypass were more likely to have post-thyroidectomy hypocalcemia (38%) than those who had a restrictive procedure (23%), p=0.02. Why are these data so important? Obesity is a pandemic in the western world, and BS emerged as a miraculous solution to treat obesity-resistant to medical/dietary options while reversing comorbidities like hypertension, diabetes, and hyperlipidemia. However, doctors must be aware of the life-long complications which come with BS because it disrupts a normal upper gastrointestinal tract and causes biochemical changes. BS causes changes in the metabolism of calcium and fat-soluble vitamins (including vitamin D). It also reduces gastric acidity, which decreases nutrient solubility, and patients will usually have a lower oral intake of calcium and vitamin D. BS is another disease by itself.
Why is gastric bypass more likely to promote post-thyroidectomy hypocalcemia? Calcium is absorbed in the duodenum and proximal jejunum, segments that are bypassed by the malabsorptive procedure. After a gastric bypass food only mixes with bile and pancreatic juices at the alimentary channel, which reduces the absorption of vitamin D and causes secondary hypocalcemia. If a patient had a BS, it is paramount to know which was the procedure (mal-absorptive versus restrictive) to understand the increased risk of post-thyroidectomy hypocalcemia. PTH synthetic analog (teriparatide) failed to improve calcium levels. Revision of the gastric bypass (what was done is not presented) also failed. The use of pancrelipase improved calcium levels in gastric bypass patients. One study showed that prophylactic supplementation immediately after total thyroidectomy avoided hypocalcemia.
The authors say, "it is evident (…) that the management of post-thyroidectomy hypocalcemia in the BS population should be more aggressive than in patients without a history of BS". BS patients with hypocalcemia after total thyroidectomy will need lifelong high-dose calcium supplementation. However, there is no ideal management strategy. That is why closer surveillance of calcium levels is paramount in BS patients who endorsed a total or near-total thyroidectomy.
Because the risk of post-thyroidectomy hypocalcemia is higher in BS patients, they may not be suitable for ambulatory or one-day surgery settings. Great to hear that! That is very important because it is common to see doctors and administrators increasing numbers of ambulatory surgery without clinical criteria, aiming only at saving money. We must never forget that it is the patient who is or is not suitable for ambulatory, not the disease itself. We must eliminate sentences like: "this gallbladder is ok for ambulatory"; "that hernia is suitable for ambulatory setting". We treat patients with a complex set of characteristics and comorbidities, in whom a surgical procedure will disrupt the fragile balance that sustains their health status. Surgeons must be true doctors, properly advise those in charge, and not behave as surgery ignorant administrators.
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Dr. Carlos Eduardo Costa Almeida
General Surgeon
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