Endoscopic Diagnosis and Treatment in Urethral Pathology (eBook)

Handbook of Endourology

Petrisor Aurelian Geavlete (Herausgeber)

eBook Download: PDF | EPUB

2015 | 1. Auflage
236 Seiten
Elsevier Science (Verlag)
978-0-12-802455-3 (ISBN)

Handbook of Endourology contains five focused, review-oriented volumes that are ideal for students and clinicians looking for a comprehensive review rather than a whole course. Each volume is easily accessible through eBook format. Topics covered review both the endourological diagnosis and treatment of prostate, urethral, urinary bladder, upper urinary tract, and renal pathology. All chapters describe the most recent techniques, review the latest results, and analyze the most modern technologies. In the past ten years, the field of endourology has expanded beyond the urinary tract to include all urologic minimally invasive surgical procedures. Recent advancements in robotic and laparoscopic bladder surgery make this one of the fastest moving fields in medicine. As current textbooks are too time-consuming for busy urologists or trainees who also need to learn other areas of urology, this collection provides quick references and over 4000 images that are appropriate for fellows as well as those teaching in the field.

Offers review content for urologists in training and 'refresher' content for experts in endourology
Explores new surgical techniques and technology through review-level content, extensive images of pathologies, and abundant videos of techniques
Includes over 500 images and videos per volume; images and videos taken from the more than 4,000 endourologic procedures performed annually at the editor's hospital

Chapter 1

Anatomy of the Urethra

Răzvan Mulţescu

Emanuel Alexandrescu

Bogdan Geavlete

Abstract

The male urethra, like the female one, is divided into several parts, each with distinct anatomical landmarks. Due to its longer length and to the presence of the prostate, these landmarks are much more evident in the male urethra. Another difference between the male and the female urethra is that the former, besides its urinary role, also intervenes in the reproductive function through the passage of semen during ejaculation.

Keywords

urethra

urethral meatus

male

female

posterior

sphincter

1.1. Male urethra

1.1.1. Descriptive Anatomy

The male urethra, like the female, is divided into several parts, each with distinct anatomical landmarks. Due to its longer length and to the presence of the prostate, these landmarks are much more evident in the male urethra. Another difference between the male and the female urethra is that the former, besides its urinary role, also has a reproductive function in the passage of semen during ejaculation.

The male urethra is 17.5–20 cm long and is divided into two distinct regions: anterior and posterior. The line of demarcation between the two segments is represented by the external striated urethral sphincter or the urogenital diaphragm, passed at this level by the urethra (Moore et al., 2005).

The posterior urethra is divided into the prostatic and the membranous urethra, while the anterior urethra is divided into the penile and the bulbar urethra.

The external urethral meatus (urinary meatus) represents the distal limit of the male urethra; it is shaped as a 6 mm long vertical slot and is one of the narrowest segments. The penile urethra, the longest and the most mobile part of the urethra, is surrounded by the corpus spongiosum, is approximately 15 cm long, and has a homogeneous diameter of 6–7 mm, with the exception of the fossa navicularis. The openings of the periurethral glands (or Littre glands), which are located in the submucosal tissue, are found at the level of the penile urethral mucosa. The mucus secreted by these glands is incorporated into the semen during ejaculation. The Lacunae of Morgagni (the urethral lacunae), where the glands of Littre open, are small depressions or recesses found on the surface of the mucosa of the penile urethra.

The largest of these recesses, which is called the lacuna magna (or the sinus of Guérin), is located on the upper part of the fossa navicularis and is occasionally noticed during endoscopic exams (Dyson, 1995).

The second segment of the anterior part is the bulbar urethra, which has a higher diameter compared with the penile urethra. Some anatomical classifications overlooked this segment of the male urethra, including in the penile part. The bulbar urethra starts at the level of the suspensory ligament of the penis, passes through the bulb, being surrounded by the bulbocavernosus muscle, and ends in the distal part of the external sphincter.

The posterior urethra is located between the urogenital diaphragm and the neck of the bladder.

The membranous urethra is the shortest and the less distensible part of the male urethra. With the exception of the urinary meatus, this is also the segment with the smallest diameter. Like the bulbar urethra, its direction is obliquely downward and forward, being slightly curved with the concavity directed forward and upward. Anterior to the membranous urethra, the dorsal vein of the penis enters the pelvis between the transverse and the arcuate pubic ligaments, while the bulbourethral Cowper glands are located posterior and lateral. The membranous urethra is 12–20 mm long and is surrounded by the fibers of the external striated urethral sphincter.

The prostatic urethra is 25–30 mm long, is the largest and most distensible part of the male urethra, and has an almost vertical position inside the prostate, which it passes from the base up to its apex. A longitudinal elevation called verumontanum or urethral crest is located on the posterior wall of the prostatic urethra (Fig. 1.1).

Figure 1.1 Endoscopic appearances of the verumontanum.

The verumontanum is 15–17 mm long and 3 mm in height and has a structure made from muscle and erectile tissues (Kobelt). Small depressions are located on both slopes of the verumontanum into which the prostatic ducts open. The extremity of the verumontanum has a median elevation called the seminal colliculus, into which the ejaculatory ducts and the prostatic utricle open (Dyson, 1995; Moore et al., 2005).

Histologically, the urethra is composed of mucosa and the submucosal connective tissue, which connects to different surrounding structures. The fossa navicularis has a nonkeratinized stratified squamous epithelium, while the rest of the urethral mucosa is a transitional columnar epithelium similar to the rest of the urinary epithelium. The submucous layer is made from erectile vascular tissue surrounded by a layer of circular smooth muscle fibers.

1.1.2. Endoscopic Anatomy

Identification of different urethral segments during urethroscopy is based on anatomical landmarks and on changes in the caliber and the trajectory that are specific to each segment.

The first endoscopic landmark of the penile urethra is the fossa navicularis, a dilated part located at the level of the penile glans and noticed immediately after passing the urethral meatus. This is a frequent location of urethral strictures.

The rest of the penile urethra is inspected after passing through the fossa navicularis, focusing on the appearance of the mucosa, vascularization, distensibility, and any changes in diameter. There are no other peculiar endoscopic elements up to the level of the bulbar urethra.

The appearance of the mucosa is relatively flat, pinkish in color, without any sudden changes in diameter (Fig. 1.2). These characteristics may be altered by different diseases. In urethritis the mucosa is red, hyperemic, with a tiger-like appearance (Fig. 1.3), edematous (Fig. 1.4), and sometimes with annulary stacked narrowings (Fig. 1.5).

Figure 1.2 Endoscopic appearance of the penile urethra.

Figure 1.3 Tiger-like hyperemic mucosa in urethritis.

Figure 1.4 Edema of the urethral mucosa.

Figure 1.5 Large stacked stenoses in patients with urethritis.

White deposits and areas of necrosis can be seen in certain infections, such as the very rare tuberculous infections (Fig. 1.6).

Figure 1.6 Tuberculous lesions in the urethra.

The bulbar urethra is identified during endoscopy by changes from a homogeneous diameter and relatively straight character of the spongious part to a higher caliber and oblique position of the next urethral segment (Fig. 1.7).

Figure 1.7 Endoscopic appearance of the bulbar urethra in its (a) distal and (b) proximal part.

In order to pass this difficult region during endoscopy, a combination of progression and gradual tilting of the cystoscope is required, with the aim of elevating its distal part. For this reason, the bulbar urethra is the place where most injuries occur during urethrocystocopy and, implicitly, the most frequent location of iatrogenic urethral strictures.

The membranous urethra has the same oblique position as the bulbar urethra, is small in length and diameter, and is less distensible. Passing this segment during endoscopy is difficult for all these reasons. The external striated sphincter, which is located at the level of the membranous urethra, has an endoscopic appearance of a circular narrowing of the lumen, with radial mucosal folds (Fig. 1.8). During a dynamic study this sphincter opens and closes, acting like a diaphragm.

Figure 1.8 Endoscopic appearance of the external urethral sphincter.

After passing the external sphincter, the prostatic urethra, which is the largest part of the male urethra, is next. The lower limit of this segment is the verumontanum (Fig. 1.9), with the openings of the ejaculatory ducts seen during endoscopy.

Figure 1.9 The lower part of the prostatic urethra, marked by the verumontanum.

The prostatic urethra is delimited laterally by the two prostatic lobes (Fig. 1.10).

Figure 1.10 Endoscopic appearance of the prostatic urethra, between the two prostatic lobes.

The shape and dimensions of the prostatic urethra may vary, depending on the patient’s age and on the eventual presence of prostate pathology. In the...

Erscheint lt. Verlag	27.11.2015
Sprache	englisch
Themenwelt	Medizin / Pharmazie ► Medizinische Fachgebiete ► Chirurgie
	Medizinische Fachgebiete ► Innere Medizin ► Endokrinologie
	Medizin / Pharmazie ► Medizinische Fachgebiete ► Urologie
	Studium ► 1. Studienabschnitt (Vorklinik) ► Biochemie / Molekularbiologie
	Naturwissenschaften ► Biologie ► Humanbiologie
ISBN-10	0-12-802455-0 / 0128024550
ISBN-13	978-0-12-802455-3 / 9780128024553

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