O'Keeffe, Derek

OBJECTIVE Inferior petrosal sinus (IPS) sampling (IPSS) is a diagnostic procedure used to guide diagnostic localization of imaging-negative adrenocorticotropic hormone (ACTH)–secreting pituitary microadenomas. However, the efficacy of IPSS has been suboptimal at accurately lateralizing the adenoma, reducing surgical cure rates and leading to unintended pituitary dysfunction due to the added exploration. One rationale for the occasional imprecision is the existence of additional petrosal sinus collateral channels that connect the IPS bilaterally, which may lead to false localization results during sampling. The aim of this study was to explore a potential connection between normal anatomical variation in the angioarchitecture of the IPSs and the ACTH results obtained in subsequent IPSS tests. METHODS A retrospective review was performed on all cases between 1998 and 2013 involving patients at a single institution who underwent IPSS for radiographically equivocal pituitary microadenomas. Cases were reviewed for tumor laterality noted on either operative or pathology reports, as well as the presence of angiographic evidence of cross-filling between the sinuses. In addition, ACTH levels from the right and left IPSs were documented at baseline and at 2, 5, and 10 minutes after corticotropin-releasing hormone (CRH) administration. A ratio of the change in ACTH levels measured at the time of maximal response (10 minutes) versus the levels measured at the initial response (2 minutes) was computed for each patient and compared between patients by their angiographic cross-filling status. RESULTS There were 41 patients with a histopathologically confirmed right- or left-sided ACTH-secreting pituitary microadenoma who underwent preoperative IPSS. Among these patients, 28 (68%) showed angiographic evidence of cross-filling between the IPSs, and 13 showed no cross-filling. On average, ACTH levels increased by a factor of 3.91 ± 0.77 in the contralateral IPS in patients with angiographic cross-filling, compared with a factor increase of only 1.80 ± 0.27 in patients without cross-filling (p = 0.014). In comparison, ACTH levels increased by a factor of 2.01 ± 0.57 in the ipsilateral IPS in patients with cross-filling, and by 8.78 ± 7.30 in those without cross-filling (p = 0.373). CONCLUSIONS The presence of angiographic cross-filling, suggestive of a greater degree of vascular channel networking between the right and left IPS, is a significant factor influencing the measured rates of change of ACTH in IPSS and may impact the specificity of this test to accurately determine microadenoma laterality in the preoperative setting.

SummaryBackgroundThyroid ultrasound to assess for nodular growth is commonly performed during the follow‐up of patients with benign thyroid nodules, with the goal of identifying patients with a missed diagnosis of thyroid cancer. The objective of this study was to summarize the evidence regarding the diagnostic accuracy of growth during follow‐up of benign thyroid nodules for thyroid cancer.MethodsWe searched multiple electronic databases using a search strategy designed by an experienced medical librarian from inception to March 2015. Eligible studies included patients with benign thyroid nodules assessed for growth during follow‐up and evaluated for thyroid cancer either by surgical histology or a repeat fine needle aspiration biopsy. Reviewers working independently and in duplicate recorded data and assessed each study.ResultsThe seven eligible studies lacked safeguards against bias and generated results that were imprecise with wide confidence intervals and inconsistent across studies. This warrants very low confidence in these results. The odds of nodule growth in patients with thyroid cancer on histopathology over these odds in patients without thyroid cancer (diagnostic odds ratio) was 0·58 (95% CI: 0·26–1·3); the diagnostic odds ratio was 2·2 (95% CI: 0·26–18) when an abnormal repeat biopsy was the reference standard.ConclusionThe body of evidence linking nodule growth with thyroid cancer during the follow‐up of benign nodules warrants very low confidence. In the era of high‐value health care, the commonplace practice of following benign thyroid nodules with serial ultrasound assessment of growth to diagnose cancer can be questioned, calling for imminent evaluation.