A. Rudin1, T. McKenzie1, G. B. Thompson1, D. Farley1, M. Richards1 1Mayo Clinic,Division Of General Surgery,Rochester, MN, USA
Introduction:
Hypoparathyroidism is the most common complication after a total or near-total thyroidectomy (T-NT). Intraoperative evaluation of parathyroid viability has been limited to visual inspection. Parathyroid function has been confirmed with postoperative lab values. Indocyanine green fluorescence angiography (ICGA) is a new adjunct that has been used in surgical procedures to assess blood flow. This study evaluated the utility of ICGA compared to visual inspection to predict parathyroid function, guide auto-transplantation and potentially decrease permanent hypoparathyroidism.
Methods:
This was a single center retrospective study of patients who underwent T-NT between January 2015 and June 2016. All patients were screened for hypercalcemia and those with hyperparathyroidism were excluded. Patients who had ICGA were compared to T-NT patients without ICGA. All patients had a PTH level on postoperative day 1. Parathyroid blood supply was scored based on ICGA as none, intermediate or normal. Visual blood supply was either viable or non-viable. Glands with no ICGA uptake were auto-transplanted. Data was analyzed to assess the frequency of auto-transplantation and incidence of hypoparathyroidism between groups. ICGA was also compared to visual inspection of the parathyroid glands.
Results:
112 patients underwent T-NT, 25 with ICGA and 87 without. Auto-transplantation was more common in the ICGA group at 36% compared to 13% in the control (p=0.015). The mean postop day 1 PTH in the ICGA group was 22 vs. 21 in the control group (p= 0.30) (normal 15-65 pg/ml). 22 out of 25 patients with intraoperative ICGA had at least one parathyroid gland with normal ICGA uptake, and 3 with intermediate update. There was no correlation with postoperative PTH levels (p=1.0). 14 of 25 patients with intraoperative ICGA had at least two parathyroid glands with normal ICGA uptake, which correlated to postoperative PTH levels >=15 in 12 patients and PTH <15 in 2. There was no difference when compared to patients with less than 2 normal ICGA glands (n=11, p=0.08)(note: <2 normal includes patients with ICGA intermediate glands). There were 83 parathyroid glands identified in the ICGA group. Visual and ICGA assessment of normal blood flow were 66/84(78%) and 52/84(61%) respectively. There were 8 glands (9%) that would have undergone auto-transplantation based on visual inspection that had adequate blood supply on ICGA. Hypoparathyroidism was present in 32 out of 87 controls (37.5%) and 8 out of 25 (32% in the ICG group). No cases of permanent hypoparathyroidism were identified in either group.
Conclusion:
ICGA is a novel technique that may improve the assessment of parathyroid gland blood supply compared to visual inspection. ICGA can guide more appropriate auto-transplantation without compromising postoperative parathyroid function. At least two vascularized glands on ICGA may predict postoperative parathyroid gland function.