Bladder, prostate and testis

Bladder: position, peritoneum and rupture

• Empty, it lies in the pelvis behind the pubis; as it fills it rises into the abdomen, lifting the peritoneum off the anterior wall, so a suprapubic catheter stays extraperitoneal. In infants the bladder lies largely in the abdomen.
• Peritoneum covers only the superior surface. A blow to a full bladder bursts the dome: intraperitoneal rupture, contrast outlines bowel loops. A pelvic fracture tears the base or neck: extraperitoneal rupture, contrast spreads in the retropubic space.
• Development: the cloaca is divided by the urorectal septum; the anterior urogenital sinus forms the bladder and urethra, so the transitional epithelium (urothelium) is endodermal. The trigone is first formed by incorporation of the mesonephric ducts (mesoderm), later covered by endoderm. The urachus (allantois remnant) runs from the dome to the umbilicus; a patent urachus leaks urine at the umbilicus.
• The trigone is smooth because its mucosa is bound to the muscle. A paraureteric diverticulum above the ureteric orifice weakens the tunnel and causes reflux.
• In women the bladder base lies on the cervix and anterior vagina. After prolonged obstructed labour, the fetal head crushes the bladder base and vagina against the pubis; the ischaemic tissue sloughs a week or so later, giving a vesicovaginal fistula with continuous leakage of urine per vagina (stress incontinence leaks only on effort).
• Lateral wall tumours lie over the obturator nerve: diathermy can make the thigh adduct. Lymph from the lateral wall goes to external iliac nodes.

Micturition

• Filling: sympathetic (T11–L2, hypogastric) relaxes the detrusor (beta-3) and closes the bladder neck (alpha-1); the pudendal nerve (S2–S4) keeps the external sphincter contracted.
• Voiding: stretch afferents run to the pontine micturition centre, which triggers the pelvic splanchnic (parasympathetic S2–S4) outflow: acetylcholine on M3 receptors contracts the detrusor while the sphincters relax. The cortex (medial frontal lobe) gives voluntary control.
• A lesion above the pons gives an uninhibited bladder; a cord lesion between pons and sacral cord gives detrusor–sphincter dyssynergia; a sacral or cauda equina lesion gives a large atonic bladder with overflow.

Bladder imaging and tumours

• Commonest bladder cancer: urothelial (transitional cell) carcinoma. Risk factors: smoking (commonest), aromatic amines in dye, rubber and leather work (2-naphthylamine, benzidine), cyclophosphamide, phenacetin. It shows as an enhancing filling defect, often multifocal (field change).
• Squamous cell carcinoma follows chronic irritation: Schistosoma haematobium, stones, long-term catheters (squamous metaplasia first). Adenocarcinoma arises at the dome from the urachal remnant or in bladder exstrophy.

Male urethra

• Hypospadias: failure of the urethral (urogenital) folds to fuse on the ventral penis, so the meatus opens on the underside. Epispadias is a dorsal opening linked to bladder exstrophy (abnormal genital tubercle position).
• Posterior urethral valves: dilated, elongated posterior urethra ending abruptly on micturating cystourethrogram; antenatally a thick bladder with a keyhole proximal urethra and hydronephrosis.
• Penile fracture with intact Buck fascia: bruising confined to the shaft. At radical prostatectomy the dorsal venous complex bleeds; continence then depends on the external sphincter.

Female urethra

• About 4 cm, opening just in front of the vagina: short length and proximity to vagina and anus explain coital cystitis.
• Pubourethral ligaments hold the mid-urethra (a sling replaces them in stress incontinence). Skene glands (prostate homologue) lie beside the meatus.

Prostate and seminal vesicles

• Neurovascular bundles lie posterolaterally (5 and 7 o'clock); tumour bulging through the capsule there invades them. Lymph drains to internal iliac and obturator nodes; venous spread to the spine via the vertebral plexus gives sclerotic metastases.
• A large gland lifts the bladder base: fish-hook ureters on urography. Alpha-1 agonists (pseudoephedrine) can precipitate retention.
• Seminal vesicles provide most semen volume and its fructose (alkaline); the prostate adds acid phosphatase, PSA and citrate. After vasectomy the ejaculate is almost unchanged in volume but contains no sperm, which is confirmed on semen analysis because residual sperm persist for weeks. Low-volume, acidic, fructose-negative azoospermia means ejaculatory duct obstruction or absent vesicles.
• Sperm granuloma: a small tender solid nodule at the cut end of the vas after vasectomy, from sperm leaking and provoking a foreign-body granulomatous reaction; it can bridge the gap and allow recanalisation.

Testis, cord and scrotum

• Spermatogenesis takes about 64–74 days, plus about 2 weeks of transit in the epididymis, where sperm gain motility. Sertoli cells (FSH, inhibin) support it; Leydig cells (LH) make testosterone.
• Histology: the vas deferens has a small star-shaped lumen, pseudostratified columnar epithelium with stereocilia and a very thick three-layered muscle wall; the epididymis has the same epithelium with taller stereocilia but only a thin muscle coat.
• Normal ultrasound: homogeneous medium echoes; the mediastinum testis is a bright posterior band. Tiny cysts there are benign tubular ectasia of the rete testis.
• Layers from outside: skin, dartos, external spermatic fascia (external oblique), cremaster (internal oblique), internal spermatic fascia (transversalis fascia), tunica vaginalis, then tunica albuginea. The ilioinguinal nerve runs through the inguinal canal outside the spermatic cord; the genital branch of the genitofemoral nerve is inside it.

• Torsion: bell-clapper testis; early pain felt at the umbilicus (T10); absent flow on Doppler.
• The pampiniform plexus cools the testis by countercurrent exchange; a varicocele warms it and impairs fertility. A new non-emptying left varicocele suggests a left renal tumour.
• Testis lymph drains to para-aortic nodes; scrotal skin to superficial inguinal nodes.

• Klinefelter syndrome (47,XXY): small firm testes, long legs, gynaecomastia, azoospermia; FSH and LH high, testosterone low.

Penis, erection and priapism

• Erection: parasympathetic (pelvic splanchnic), nitric oxide raises cGMP and relaxes cavernous smooth muscle; emission: sympathetic (T10–L2); ejaculation: pudendal.

• Penile Doppler with good arterial peak velocity but high end-diastolic flow means venous leak.

Remember Peripheral zone for cancer, transition zone for hyperplasia. Dark blood is ischaemic and urgent; bright blood is a fistula.

Exam trap A pelvic fracture tears the membranous urethra; a fall astride tears the bulbar urethra.

Exam trap Continuous leakage after obstructed labour is a vesicovaginal fistula, not stress incontinence.

How FCPS asks about this

• Germ layer of bladder epithelium: endoderm of the urogenital sinus.
• Constant urinary leakage a week after obstructed labour: vesicovaginal fistula from pressure necrosis.
• Nerve in the inguinal canal but outside the cord: ilioinguinal nerve.
• Hypospadias: failed fusion of the urethral folds.
• Commonest bladder cancer and squamous type cause: urothelial carcinoma (smoking, aniline dyes); squamous with schistosomiasis.
• Radiosensitive testicular tumour: seminoma; AFP in a child under 3 points to yolk sac tumour.
• Priapism with bright red blood after straddle injury: cavernosal artery to sinusoid fistula.