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AN48.1-8 | Pelvic wall and viscera — Part 2

Pelvic Viscera — Urinary Bladder, Uterus, Ovary, Rectum, Prostate (AN48.1)

Urinary Bladder:
- Empty: tetrahedral, entirely in the pelvis (behind pubic symphysis)
- Full: rises into the abdomen (peritoneum stripped off → extraperitoneal approach for suprapubic cystostomy)
- Relations: superior — loops of small intestine; posterior (male) — rectum, seminal vesicles, vas deferens; posterior (female) — uterus (vesicouterine pouch)
- Blood supply: Superior + inferior vesical arteries (from internal iliac)
- Nerve supply: Parasympathetic (S2–S4 via pelvic splanchnics) → detrusor contraction; Sympathetic (L1, L2 via hypogastric plexus) → internal urethral sphincter closure + detrusor relaxation

Uterus:
- Positions: Anteverted + anteflexed (normal); retroverted + retroflexed (10–20% women)
- Ligaments: Round ligament (to inguinal canal → labium majus); Broad ligament (double fold of peritoneum); Uterosacral ligament (to sacrum — supports cervix); Cardinal/Mackenrodt ligament (cervix to lateral pelvic wall — main support)
- Relations: Anterior — vesicouterine pouch, bladder; Posterior — rectouterine pouch (pouch of Douglas) = most dependent part of peritoneal cavity
- Blood supply: Uterine artery (crosses ureter 2 cm lateral to cervix — "water under the bridge")

Ovary:
- Almond-shaped, ~3 × 1.5 × 1 cm
- Held by: Suspensory ligament of ovary (infundibulopelvic ligament — carries ovarian vessels from aorta/IVC); Ligament of ovary (to uterus); Broad ligament (mesovarium)
- Blood supply: Ovarian artery — arises from aorta at L2 (same as testicular artery — both are gonadal vessels)
- Lymphatics drain to para-aortic nodes at L2 — not to inguinal nodes (important for metastatic spread)

Rectum:
- Follows curvature of sacrum; 12–15 cm long; 3 lateral bends (peritoneal reflections)
- Peritoneal relations: Upper 1/3 covered anteriorly and laterally; middle 1/3 covered anteriorly only; lower 1/3 — no peritoneal cover (below peritoneal reflection)
- Pouch of Douglas = rectouterine pouch (female) / rectovesical pouch (male) — lowest point of peritoneum; fluid/pus/blood collects here
- Blood supply: Superior rectal artery (inferior mesenteric), middle rectal (internal iliac), inferior rectal (pudendal — perineal)

Prostate:
- Walnut-sized gland around the bladder neck and proximal urethra
- Lobes (McNeal zones): Peripheral zone (70% — most PCa); Central zone (25%); Transition zone (5% — site of BPH)
- BPH affects the transition zone (periurethral glands) → compresses urethra → LUTS (frequency, hesitancy, poor stream, nocturia, overflow incontinence)
- Prostate cancer starts in the peripheral zone → felt as hard nodule on DRE; spreads to bone (osteoblastic metastases) via Batson's venous plexus
- Blood supply: Inferior vesical artery (internal iliac)
- Digital Rectal Examination (DRE): Through anterior rectal wall → feel prostate anteriorly; in women → feel cervix, uterus, pouch of Douglas

Neurological Basis of Automatic Bladder (AN48.6)

Normal micturition circuit:

Component	Location	Function
Pontine micturition centre (PMC)	Brainstem	Coordinates detrusor contraction + sphincter relaxation
Cortical control	Frontal lobes	Voluntary suppression/initiation
Sympathetic	T10–L2 (hypogastric nerve)	Bladder filling: detrusor relaxation + IUS closure
Parasympathetic	S2–S4 (pelvic splanchnics)	Voiding: detrusor contraction + IUS opening
Somatic	S2–S4 (pudendal nerve)	EUS contraction (voluntary)

Automatic (reflex/spastic) bladder:
- Occurs after complete spinal cord lesion above the sacral cord (above S2)
- Disrupts cortical + supraspinal inhibition
- Result: bladder fills → stretches → triggers reflex detrusor contraction → involuntary voiding without warning
- Bladder capacity reduced; high intravesical pressure → risk of VUR (vesicoureteric reflux) and upper tract damage

Autonomous (atonic/flaccid) bladder:
- Lesion at or below S2–S4 (conus medullaris, cauda equina, pelvic splanchnics)
- No reflex arc intact → bladder overfills → overflow incontinence (dribbling)
- Large capacity, low pressure; risk of UTI from stasis

Suprapubic cystostomy (AN48.5 applied):
- Indication: urinary retention when urethral catheterisation fails (BPH, urethral stricture, trauma)
- When the bladder is full, it rises above the pubic symphysis; peritoneum is stripped anteriorly → extraperitoneal approach is safe
- A trocar is inserted 2–3 cm above the pubic symphysis in the midline into the distended bladder

Applied Anatomy — Key Clinical Conditions (AN48.5, AN48.7, AN48.8)

Retroverted uterus: The uterus is tilted backward instead of forward; the fundus faces the pouch of Douglas. Present in 10–20% women. Usually asymptomatic; may cause dysmenorrhoea or dyspareunia. Diagnosed on bimanual examination — cervix points anteriorly, fundus posteriorly.

Uterine prolapse: Descent of the uterus through the vagina. Caused by weakness of the Cardinal (Mackenrodt) ligament + uterosacral ligament + levator ani. Common in Indian multiparous women. Grades: 1st (cervix descends into vaginal canal), 2nd (cervix at introitus), 3rd (procidentia — uterus completely outside). Treated by pelvic floor repair or vaginal hysterectomy.

Haemorrhoids (AN48.5):

Type	Location	Drainage	Pain
Internal	Above pectinate (dentate) line	Superior rectal vein → portal	Painless (no somatic innervation)
External	Below pectinate line	Inferior rectal vein → IVC	Painful (somatic innervation from inferior rectal nerve)

Tubal (ectopic) pregnancy: Fertilised ovum implants in the uterine tube (most common site — ampulla). Rupture of the ectopic causes haemoperitoneum — blood collects in the pouch of Douglas → posterior vaginal fornix tenderness (pouch of Douglas tenderness). Managed by salpingectomy or salpingostomy.

Tubal ligation: Fallopian tubes are accessed through a small suprapubic incision (minilaparotomy) or laparoscopically → ligated, clipped, or divided near the isthmus. Vasectomy: vas deferens identified in the spermatic cord at the neck of scrotum → divided and ligated.

Structures palpable on DRE (male): Prostate anteriorly (median sulcus, lobes, seminal vesicles above), rectal mucosa, sacrum and coccyx posteriorly, ischiorectal fossa laterally.
On vaginal examination: Cervix, anterior and posterior vaginal fornices, body of uterus (with combined abdominal hand), rectouterine pouch (pouch of Douglas) posteriorly.