Surgical Anatomy of the Prostate Sphincter Complex 8

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Surgical Anatomy of the Prostate Sphincter Complex

Lutz Trojan, Maurice-Stephan Michel

Introduction – 72 Anatomy – 72 Innervation – 74 Identification – 75

Injury of the Prostate Sphincter Complex – 75 References – 75

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Hohenfellner_L4F-2sp.indd 71 23.06.2005 17:56:3423.06.2005 17:56:34

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The knowledge on the anatomy of the external sphincter has increased over the years. The image of a plane muscular layer distal to the prostate, as often described in textbooks on pelvic anatomy, is not correct (⊡ Fig. 8.1).

its ventral parts with an extension over the ventral aspects of the prostate [1, 2]

(⊡Figs. 8.2a, c, 8.3).

▬ Heterogenous prostate shapes [2] (e.g.

donut vs. croissant shape) result in diffe-

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⊡ Fig. 8.1. Incorrect image of the external sphincter. The sphincter is often described as a muscular disc distal to the prostate.

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⊡ Fig. 8.3. Illustration of the male striated urethral sphincter (sagittal view). The sphincter (8) extends on the ventral aspects of the prostate. Note that in the sagittal view no sphincter but a midline fibrous raphe (21) is present in the dorsal aspects of the periurethral region distally from the apex of the prostate (2). From [4] (by permission of Mayo Foundation for Medical Education and Research. All rights reserved)

⊡ Fig. 8.2A–C. Illustration of the male striated urethral sphincter (reconstruction of the embryological situation). The sphincter extends over the ventral aspects of the prostate (A, C, left lateral view) and has an omega-like shape (B, dorsal view). Red: sphincter, white: bladder neck and urethra, yellow: prostate. From [1]

A B C

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⊡ Fig. 8.4A–D. Different prostate shapes and the consecutive heterogeneous relation of the apex and the external sphincter. The shape of the prostate can occur as a crescent (A) or a donut (C). In the sagittal view (B, D) the rela- tion of the prostate (black) and the sphincter area (red) with different prostate shapes is illustrated. A, C from [4];

A B

C D

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Identification

▬ The sphincter should be identified and evaluated in every cystoscopy and surgical procedure.

▬ The external sphincter should be identified and evaluated at the beginning of the dia- gnostic or surgical procedure: initially the sphincter and its relation to the prostate is not compromised by multiple passages and/or constant placement of an instrument.

Even the first passage of a shaft results in a detonization of the external sphincter.

▬ The prostate sphincter complex can be identified by the endourological view.

▬ During the procedure, the easiest method is a pull-back manoeuvre of the instrument from the prostatic urethra: the external sphincter is seen as a mucosal bulge narrowing the lumen of the urethra.

▬ In case of i.v. sedation of the patient, active activation of the sphincter by the patient can help to identify the sphincter: ask the patient to simulate the interruption of micturition.

▬ Nesbit sign, a pullback manoeuvre of the instrument from the prostatic urethra into the membranous urethra with a consecutive gentle push-forward towards the prostate facilitates identification of the proximal edge of the external sphincter by radial mucosal crinkles which are located between the distal end of prostate and the proximal edge of the external sphincter.

Injury of the Prostate Sphincter Complex

▬ Injury of the prostate sphincter complex results in incontinence.

▬ Injury of the external sphincter can occur as a result of cutting but also can be caused by coagulation lesions (development of heat in the region of the apex).

▬ Injury of the dorsal aspects are not as severe as a damage of the ventral or lateral parts of the sphincter due to the omega-shape of the sphincter.

▬ One has to differentiate between stress incontinence and a postoperative urge incontinence. The latter is not due to and= injury of the sphincter complex, mostly transient, and can be treated by a anticholinergic therapy. A urinary tract infection, which can cause urge incontinence, should be ruled out.

▬ Reports on the rate of incontinence vary around 0.4% [3].

▬ Pelvic floor training can improve the conti- nence situation.

▬ Medical treatment of stress incontinence after injury of the prostate sphincter complex is usually insufficient. New drugs such as duloxetine (serotonin reuptake inhibitor, initially used as antidepressants) are current- ly under investigation to treat stress incontinence.

▬ Injection of microspheres (dextranomer/

hyaluronic acid copolymer) and artificial sphincter implantation are the secondary, operative options.

References

1. Yucel S, Baskin LS (2004) An anatomical description of the male and female urethral sphincter complex. J Urol 171:1890–1897

2. Myers RP, Goellner JR, Cahill DR (1987) Prostate shape, external striated urethral sphincter and radical prostatectomy: the apical dissection. J Urol 138:543–550 3. Mebust WK, Holtgrewe HL, Cockett AT, Peters PC

(1989) Transurethral prostatectomy: immediate and postoperative complications. A cooperative study of 13 participating institutions evaluating 3,885 patients.

J Urol 141:243–247

4. Myers RP (1991) Male urethral sphincteric anatomy and radical prostatectomy. Urol Clin North Am 1:211–

227

5. Myers RP (1994) Radical prostatectomy. Urol Clin North Am 2:8