Cobb's collar(also known as a Moormann's ring) is an uncommon finding on a paediatric voiding/micturating cystourethrogram (VCUG), but an indentation of the bulbar urethra is seen in more than half of boy's who are cystoscoped, as the narrow represents two different phenomena3-4.
One is a congenital urethral obstruction which is thought to be due to incomplete widening of the urogenital diaphragm and is a membrane with a central hole without any connection to the verumontanum. Video-endoscopic recording correlated with radiological imaging now better define anatomy and pathology that has also been given the names of Young's type III valves, congenital stricture and prolapsed Type III valves.
Apart from the fibrous type of obstruction, the other type of anomaly seen, and represented in both the paper from Cobb and that by Moormann 5, is due to contraction of the lower end of what is now known to be a tubular external sphincter, the bottom end of which can on occasion obstruct the passage of a catheter and the contrast. The resultant appearance is that of a funnelling change, rather than a sharp demarcation. There can be a variable morphological degree of narrowing due to variation of the prominence of the lower end of the sphincter and fluctuation in the degree of contraction.
Cobb's collar is associated with syringoceles 6; the latter being a cystic dilatation of the Cowper's gland duct.
- 1. Cobb B, Wolf JJ, Ansell J. Congenital stricture of the proximal urethral bulb. J Urol 1968; 99: 629–31
- 2. Moormann J. Congenital bulbar urethral stenosis as a cause of diseases of the urogenital junction. Urologe A 1972; 11: 157–60
- 3. Dewan PA, Keenan RJ, Morris LL et-al. Congenital urethral obstruction: Cobb's collar or prolapsed congenital obstructive posterior urethral membrane (COPUM). Br J Urol. 1994;73 (1): 91-5. Pubmed citation
- 4. Dewan PA, Goh DG, Crameri J. Cobb's collar. Pediatr. Surg. Int., 1995 10(4): 243-246
- 5. Cranston D, Davies AH, Smith JC. Cobb's collar-a forgotten entity. Br J Urol. 1990;66 (3): 294-6. Pubmed citation
- 6. Dewan PA. A study of the relationship between syringoceles and Cobb's collar. Eur. Urol. 1996;30 (1): 119-24. Pubmed citation