26 March 2016
A large thyroid gland presses on the trachea. This pressure may decalcify the tracheal cartilage (tracheomalacia), and produce some degree of narrowing [Dandekar et al, 2016]. This can cause difficulties during intubation for surgery, as well as after surgery [Agarwal et al, 2007]. Although pre-operative compression testing does not appear to reliably predict tracheomalacia [Agarwal et al, 2007], it can be a useful guide to increased awareness.
Kocher’s test is done during examination of the thyroid to rule out trachea narrowing (scabbard trachea). [Bhat, 2013] A “scabbard” trachea is a deformity of the trachea caused by flattening and approximation of the lateral wall, producing stenosis. It is called scabbard trachea because the trachea looks, radiologically, like a scabbard: the sheath of a sword.
The test is started by asking the patient to extend the neck, followed by asking the patient to take heavy deep breaths through the mouth continuously. After that, the examining physician compresses the swelling from the sides. The test is positive if there is the presence of stridor when the lateral lobes are pushed posteromedially with fingers [Bhat, 2013]. An 11-12 minute procedure of the examination can be viewed at .
The positive Kocher’s test is normally seen in scabbard trachea, which may occur in a large multinodular goiter or carcinoma of the thyroid.
When there is a long standing thyroid enlargement, the constant pressure of the thyroid gland on the trachea causes weakened tracheal rings. When the thyroid is being compressed during this test, the weakened trachea narrows, and this presents as stridor during compression of the thyroid (positive Kocher’s test). Due to the weakened tracheal ring, the patency of the trachea is mainly maintain by thyroid. This is important because after thyroidectomy, there is no support to trachea and so it may collapse, causing respiratory embarrassment. For this condition, temporary tracheostomy need to be done for 2-3 weeks. After 2-3 weeks, the trachea will regain its strength.
Tracheomalacia causing stridor is a rare complication after thyroid surgery [Lacoste et al, 1993; Findlay et al, 2011]. Nevertheless, it does occur, and may be commoner in countries where large endemic goiters are common [Agarwal et al, 2007; Abdel Rahim et al, 1999]. It may take the treating team by surprise and cause life-threatening respiratory distress [Tripathi and Kumari, 2008; Lee et al, 2011]. Surgeons should, therefore, be aware of the possibility of tracheomalacia when operating on large goiters. As regards the Kocher test, studies ([Agarwal et al, 2007, and others]) indicate that this test is only moderately reliable. A more reliable indicator of the need for tracheostomy may be the assessment of the tracheal cartilage at the time of surgery. The test is, of course, uncomfortable for the patient, and it can be debated whether it should be performed at all.
There are three interesting asides. One: Kocher’s sign (also known as Ramsay’s sign) is different fro the Kocher’s test described here. The sign refers to a retraction of the upper eyelid in Graves’ disease. Two: There is also a “Kocher’s testicular sign”! Three: Finally, did Kocher really describe the Kocher test? Plenty of books call it the Kocher test, but no book is able to provide an authentic reference.
- Abdel Rahim AA, Ahmed ME, Hassan MA. Respiratory complications after thyroidectomy and the need for tracheostomy in patients with a large goitre. Br J Surg 1999; 86: 88-90.
- Agarwal A, Mishra AK, Gupta SK, Arshad F, Agarwal A, Tripathi M, Singh PK. High Incidence of Tracheomalacia in Longstanding Goiters: Experience from an Endemic Goiter Region. World J Surg 2007;31:832-7
- Bhat MS, Chapter 6 Thyroid, Jaypee Brothers Medical Publisher (P) Ltd, India, 2013, pg 526
- Dandekar M, Kannan S, D’Cruz A. The thyroid and parathyroids. In: Lumley JSP, D’Cruz AK, Hoballah JJ, Scott-Connor CEH (editors) In: Hamilton Bailey’s Demonstrations of Physical Signs in Clinical Surgery, 19th edition. CRC Press, Boca Raton, 2016, p410.
- Findlay JM, Sadler GP, Bridge H, Mihai R. Post-thyroidectomy tracheomalacia: minimal risk despite significant tracheal compression.Br J Anaesth. 2011;106(6):903-6. doi: 10.1093/bja/aer062.
- Lacoste L, Gineste D, Karayan J, et al. Airway complications in thyroid surgery. Ann Otol Rhinol Laryngol 1993; 102: 441-6.
- Lee C, Cooper RM, Goldstein D. Management of a patient with tracheomalacia and supraglottic obstruction after thyroid surgery. Canadian Journal of Anesthesia 2011, 58:1029.
- Tripathi D, Kumari I. Tracheomalacia: A Rare Complication After Thyroi dectomy. Indian J Anaesth [serial online] 2008 [cited 2016 Mar 28];52:328-30. Available from: http://www.ijaweb.org/text.asp?2008/52/3/328/60644.