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Year : 2013  |  Volume : 1  |  Issue : 2  |  Page : 37-40

Pyramidal lobe on 99m technetium thyroid scan: Incidence, origin and association with thyroid function

1 Department of Radiology, Section of Nuclear Medicine, The Aga Khan University Hospital, Karachi, Pakistan
2 Department of Nuclear Medicine, Dr. Ziauddin Medical University, Karachi, Pakistan
3 Dow University of Health Sciences, Karachi, Pakistan

Correspondence Address:
Maseeh uz Zaman
Department of Radiology, Section of Nuclear Medicine,The Aga Khan University Hospital, Karachi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2320-3846.125033

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Purpose: The purpose of the study is to find out the incidence of pyramidal lobe (PL), its position in relation to thyroid and correlation with functioning status of thyroid gland. Materials and Methods : This was a retrospective study conducted in Nuclear Medicine Section, Department of Radiology, Aga Khan University Hospital, Karachi, Pakistan. We evaluated radionuclide thyroid scans performed with technetium-99m pertechnetate from March 2009 to May 2013. As per our departmental protocol, patients were used to swallow 100-150 cc water to wash away secreted esophageal activity and minimizing the possibility of false positive results. Patients with diagnosis of thyroiditis or history of any thyroid surgery were excluded. Presence and position of PL (arising from isthmus or either lobe of thyroid), presence or absence of cold or hot nodule (s), total thyroid uptake and thyroid function test performed within 4 weeks of thyroid scan were noted. Results: A total of 1116 thyroid scans qualified inclusion criteria of the study. PL was appreciable in 156 patients with overall incidence of 14% and an annual incidence of 3.5%/year (P < 0.05). Mean age of the population was 40 ± 12 years and female: Male was 113:43 (P < 0.05). Mean thyroid uptake was 14 ± 9% (P > 0.05). PL had origin from left thyroid lobe in 72 (46%), from the right thyroid lobe 58 (37%) and from the isthmus in 26 (17%) (P < 0.05). 135 (86.5%) patients were toxic (P < 0.05) while 15 (9.6%) euthyroid and 6 (3.8%) were hypothyroid (P > 0.05). Conclusion: We conclude that the incidence of PL on thyroid scanning was 14% with predominance for the female gender, left lobe origin and diffuse toxic goiters. An adequately performed thyroid scan would ensure completeness of thyroidectomies and avoid per-operative inconvenience to surgeons due to false positive scan results.

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