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Cross-Sectional Anatomy of the Penis

Image: “Cross-Sectional Anatomy of the Penis” by philschatz. License: CC BY 4.0


Hypospadias

Definition

The term hypospadias refers to a congenital abnormality secondary to an abnormal formation of the urethra, the ventral aspect of the penis, and the foreskin. There is an abnormal opening of the penile urethra on the ventral surface of the penis. The condition occurs when the urethral folds do not fuse properly.

Epidemiology

Hypospadias is present in 1 in every 125 male children.

Pathogenesis

The etiopathogenesis is influenced by multiple factors. The most common are environmental factors implicated during pregnancy, like a predominantly vegetarian diet in the mother and exposure to female sex hormones, such as estrogen and progesterone.

Other risk factors include:

  • Abnormal sperm morphological characteristics from the father
  • Faulty spermiogenesis from the father, secondary to abnormalities of testes or scrotum
  • Low fetal birth weight
  • Maternal parity; primiparous at increased risk compared to multiparous
  • Maternal age

There is an aberrant complex interplay between epithelial and mesenchymal signaling pathways, which manifests as a displaced urethral outlet.

Clinical Presentation

More often, parents first diagnose hypospadias when the child has an abnormally directed poor urine stream or a misplaced urethral opening. Depending on the grade and severity of disjunction, the presentation varies from being minimally symptomatic to having gross penoscrotal defects.

Various clinical characteristics are summarized below.

Urethral meatal abnormalities Multiple variations have been enunciated, such as fissure, rigid, elastic, and with varied morphology and size.
Penile curvature Due to deficient ventral structures, downward penile curvature “chordee” is present.
Skin abnormalities The frenulum is absent. There is a presence of dorsal hood.
Bifid scrotum with penoscrotal transposition Observed in cases of perineal hypospadias.
Associated factors Hypospadias is associated with urinary tract structural aberrations, inguinal hernia, and un-descended testes.

Classification

Urologists have used liberal classifications for hypospadias over the years.

The significant relevant classifications are as follows:

Classification Description
Browne (1938) Most commonly used. The segregation is based on inspection and progressive proximal localization of the penile urethral opening. Accordingly, the various types are:

  • Glanular
  • Sub-coronal
  • Distal penile
  • Midshaft
  • Proximal penile
  • Penoscrotal
  • Midscrotal
  • Perineal
Schaefer (1950) Schaefer classified Hypospadiasis as Glanular, Penile, and Perineal variety. Avellan et al further segregated perineal into penoperineal, perineal, and perineal without bulb types.
Hadidi (2004) Hadidi et al. regrouped the categories described by Browne et al. as Glanular, Distal, and Proximal.
Smith (1938) This is the oldest and relatively simplest classification. There are three degrees of hypospadias corresponding to the three subsets in the Schaefer classification; namely, 1st degree is similar to glanular, 2nd degree to perineal, and 3rd degree to perineal.

Diagnosis

Hypospadias is mainly diagnosed clinically. Radiological imaging serves as an ancillary test to rule out complications and associated anomalies.

Therapy

Surgical treatment is the only option, and the implications extend far beyond cosmesis. The ideal time is between 6 to 18 months of age. All the layers of the penis around the meatus are reconstructed with delicate precision. The underlying principle is to reconstruct the meatus on the penis and remedy the deformed structures to ensure normal urination and sexual function.

Various surgical procedures performed are summarized as follows:

Surgery Explanation
“Snodgrass” tubularized incised plate urethroplasty (TIP) The most commonly performed procedure. Significant curvature with thin proximal skin is a contraindication.
MAGPI procedure Meant for glanular hypospadias, the presence of healthy proximal skin cover without chordee formation is a prerequisite.
“Mathieu” or perimeatal –based procedure Indicated in glanular hypospadias without an adequate measure of healthy proximal skin necessary for MAGPI.
Pyramid procedure Used in large granular defects without curvature.
Bracka two-stage hypospadias repair For posterior hypospadiasis.
GAP procedure Indicated in patients with wide and generous granular grooves.

More common than epispadias, hypospadias may result in urethral obstruction and cystitis.

Epispadias

Definition

The abnormal epithelial-mesenchymal opening of the penile urethra on the dorsal surface of the penis due to malpositioning of genital tubercle is termed as “Epispadiasis.” It is associated with abnormal abdominal wall defects such as exstrophy of the bladder. The same is known as “Exstrophy-epispadias complex.”

Presentation

Most neonates present with a bifid penis with urethral abnormalities, which necessitate surgical intervention emergently.

When chronic, males tend to develop an abnormal curvature of the penis: “chordee.”

Females present with an abnormal clitoris and urinary incontinence.

Treatment

Surgical intervention with a comprehensive repair of urethral meatal opening, penile shaft reconstruction, and associated mobilization of the corpora is complex. For optimum results, the patient should undergo genitourinary reconstruction within the first seven years of life. The most prevalent and tested intervention is the “Modified Cantwell-Ransley” approach. Other procedures performed include “Complete penile disassembly.”

Phimosis

Definition

Failure to retract the foreskin beyond the glans penis is termed as “phimosis.” This is a normal finding in children under five years of age.

Classification

Phimosis is segregated into congenital and acquired types; the latter is more common.  Acquired phimosis causes include poor hygiene, infection, inflammation, or trauma, leading to smegma accumulation and fibrosis.

Complications

The inability to retract the prepuce over the glans leads to the accumulation of smegma and secondary balanitis. A small risk of squamous cell carcinoma also exists.

Treatment

Phimosis is a relatively benign pathology with definite surgical treatment, namely circumcision. Circumcision has the additional benefit of decreasing the risk of spreading HPV and HIV.

Paraphimosis

Definition

Failure to advance the foreskin back over the glans after retraction is known as “paraphimosis.”

Paraphimosis is iatrogenic most of the time and follows faulty urethral catheterization techniques. It is also seen in congestive types of ischemia.

Complications

Retraction of a tight foreskin over the prepuce can lead to strangulation and infarction of the glans penis.

Treatment

Circumcision is the definitive treatment for paraphimosis. An emergency dorsal slit technique is also described.

Peyronie Disease

Definition

Also named “induratio penis plastica,” this disease is characterized by chronic inflammation, causing an increased thickness of tunica albuginea (CITA) surrounding the corpora cavernosa.

Presentation

Affecting about 5% of males, the presenting complaint is often disturbing abnormal penile curvature with subsequent trouble maintaining an erection.

An important differential diagnosis for these patients is the rupture of corpora cavernosa due to penile fracture.

Treatment

About 12% of patients demonstrate spontaneous regression. However, half of the patients can worsen considerably and require surgery. There is no unequivocal evidence of which treatment option is superior to others. Options include:

  • Vitamin E supplements
  • Interferon-alpha-2b
  • Collagenase injection
  • Pentoxyphylline
  • Dexamethasone

“Nesbit surgery” requires considerable expertise; hence, it is a last resort.

A penile prosthesis may be indicated in advanced cases.

Priapism

Definition

An abnormal, persistent, painful erection lasting for more than four hours or unrelated to sexual stimulation is “priapism.” It demands urgent attention.

Classifications

Type of priapism Explanation
Ischemic Ischemic priapism is a low flow, veno-occlusive condition with a non-sexual, persistent erection. This is an emergency. There is minimal cavernous blood flow. The corpora cavernosa are hard and painful to palpation. Simulating a compartment syndrome, ischemic priapism is associated with hypoxic, acidotic, hypercarbia cavernous blood gases. It is often associated with grave underlying disorders such as sickle cell disease or malignancy.
Non-ischemic Non-ischemic priapism is an arterial, high flow persistent, non-sexual erection with unregulated cavernous arterial inflow. The cavernous blood gas analysis is essential, not abnormal. Often associated with precedent trauma, non-ischemic priapism is not an emergency. The corpora cavernosa are neither rigid nor tender.

Stuttering (intermittent) priapism is characterized by recurrent, painful episodes of ischemic priapism.

Priapism is associated with SSD and the use of certain medications.

Treatment

Management of ischemic priapism requires urgent, rapid, and aggressive management. Immediate treatment comprises of corporal aspiration, intracavernosal phenylephrine injection followed by surgical decompression. Therapeutic aspiration is often the first maneuver performed.

Surgical shunts are advocated only after documented failure of intracavernous sympathomimetic drug injection trial. Various shunt surgeries described for ischemic priapism are listed below.

Shunt surgery Types
Open Proximal shunt Quackels (Corporo-spongiosal shunt)
Corporo-saphenous vein or superficial deep dorsal vein shunt Grayhack shunt

Barry shunt

Percutaneous distal shunt T-shunt (Corporo-glanular) shunt

Ebbehoj shunt (Corporo-glanular) shunt

Winter shunt (Corporo-glanular) shunt/td>

Open distal shunt Al-Ghorab shunt

Burnett “Snake “ maneuver

Penile prosthesis use is indicated in cases of extremely prolonged priapism for more than 72 hours, or in patients with multiple episodes of recurrent, refractory, ischemic priapism to facilitate regular sexual activity.

Treatment options for non-ischemic priapism are masterly inactivity with watchful waiting and cavernosal artery embolization.

Penile carcinoma in situ (CIS)

Variously known as Bowen disease, penile intraepithelial neoplasia, and erythroplasia of Queyrat; CIS potentially transforms into frank, invasive carcinoma. The diagnosis is purely histological with a meticulous search for the invasion of the basement membrane.

Treatment options for CIS can be summarized as follows:

  • For preputial local lesions: circumcision
  • Topical chemotherapy: with 5-fluorouracil as 5% base for local application
  • Radiotherapy
  • For non-invasive, small pathology: local excision
  • Laser: Nd:YAG and CO2 laser

About 46% of patients with squamous cell carcinoma of the penis have pre-existing penile lesions. The significant common lesions can be tabulated as follows:

Premalignant condition/Lesion Description
Leukoplakia Present in penile shaft
Bowenoid papulosis Presents as reddish papules
HPV 16 Prevalent in young men
Erythroplasia of Queyrat Presents as erythroplakia of glans.

Squamous cell carcinoma (SCC)

Introduction

The most common penile cancer is squamous cell carcinoma. It accounts for about 95% of all penile cancer. The other malignancies seen are summarized as follows:

Basal cell carcinoma
Mesenchymal tumors (about 3%): Kaposi sarcoma, Angiosarcoma
Malignant melanoma
Metastasis

Epidemiology

SCC is more common in Africa, Asia, and South America (almost 10% as against 0.5 per 1,00,000 in the USA) and is most likely due to the unequivocal influence of predominant HPV 16, 18 infections. IHC detects altered p16INK4a protein in these patients.

Risk factors

An elderly, unmarried male in his sixth decade with a history of late circumcision is prone to SCC. Other predisposing factors cited include promiscuous sexual behavior, multiple sex partners, tobacco use, and poor hygiene.

Distribution

The topographical distribution of SCC, along the penile length, is as follows:

Location Percentage
Glans 48% (most common)
Penile shaft Less than 2% (least common)
Glans and prepuce About 9%
Prepuce 21%
Coronal 6%

Lymphatic spread for SCC follows the regular drainage pattern of the penis. It transgresses the local limits and spreads to superficial nodes and then progressed to deep inguinal and, subsequently the external iliac lymph nodes.

Grading systems

There are two grading mechanisms available for SCC.

They are as follows:

Broders grading system:

Based on keratinization, mitosis predominance, and nuclear pleomorphism, SCC is segregated into four grades.

Maiche system score:

Based on five-year survival, there are three proposed levels:

Grade Five-year survival
Grade 1 80%
Grades 2 and 3 50%
Grade 4 30%

Jackson’s classification:

Stage Explanation
Stage I(A) Tumor localized to glans, prepuce, or both
Stage II(B) Tumor reaching to the shaft of the penis
Stage III(C) Tumor with resectable inguinal metastasis
Stage IV(D) Tumors with extension into adjacent structures, with inoperable inguinal metastasis or distant metastasis.

The standard AJCC staging for penile cancer is the TNM staging.

Various treatment options for penile cancer can be summarized as follows:

Treatment strategy Explanation
Penis preserving interventions Local excision with reconstruction

Glansectomy

Laser therapy

Radiotherapy

Brachytherapy

Partial/total amputation Partial excision decision has to be exercised with great caution in selected patients.
Surveillance for lymph node metastasis Low-risk patient with no vascular invasion
Early lymphadenectomy For high-risk patients or/with vascular invasion

Presence of any of the following factors after penile lesion excision and lymphadenectomy calls for adjuvant therapy:

  • Extranodal extension of disease
  • More than two metastatic inguinal nodes
  • Pelvic lymph node metastases

Distant metastases have dismal prognoses. Chemotherapy and palliative therapy are available treatment options with only about 30% response rate.

Summary

Penile disorders are a heterogeneous aggregation of conditions.

Hypospadias involves malposition of the urethral meatal opening on the ventral aspect of the penis. Treatment is essentially surgical. Many procedures have been described; the most commonly performed is TIP.

Epispadias is characterized by the dorsal opening of the urethral meatus. It is often associated with other genitourinary defects, such as bladder exstrophy. Surgical repair is often necessary before the patient reaches seven years of age.

Inability to retract the prepuce is known as “phimosis,” while failing to advance back the foreskin after retraction is termed as “paraphimosis.” Both conditions are definitively treated by circumcision.

Peyronie’s disease is a chronic inflammation of the tunica albuginea surrounding the corpora cavernosa in the penis, leading to abnormal curvature or indentation of the penis with subsequent difficult and often painful erection. While spontaneous regression is often described, about half of the patients need treatment.

Priapism is an abnormal, persistent, non-sexual erection. Ischemic priapism is a medical emergency. Non-ischemic priapism is often managed with careful observation.

Squamous cell carcinoma is the most common form of penile cancer. Penile cancer is often preceded by the presence of premalignant lesions. Local excision of these lesions can often evade the grave eventuality of SCC. Carcinoma in situ is a histological diagnosis and demands meticulous examination for basement membrane invasion. CIS can be treated by timely local intervention.

SCC is a frank, invasive, and most common penile cancer. Treatment is often tailored as per topographical distribution, local and distal progression, and lymph node status.

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