Unit 07 — Urogenital System · Question Bank

Position

• Paired retroperitoneal organs, lying on the posterior abdominal wall on either side of the vertebral column.
• Left kidney: T11–L2/3. Right kidney: T12–L3. Both renal hila at L1.
• Right kidney lies lower because the liver occupies the right hypochondrium. Left kidney is slender; right is broader and shorter. (TMU Slide 10)

Surface Relations

• Posterior: Diaphragm (upper pole), quadratus lumborum, psoas major, transversus abdominis; crossed by the 12th rib (and 11th on the left).
• Right kidney anterior: Liver (large area), 2nd part of duodenum (medial), right colic (hepatic) flexure (lower pole).
• Left kidney anterior: Stomach, spleen, tail of pancreas, left colic (splenic) flexure, descending colon.
• Suprarenal glands lie above both kidneys, separated by loose connective tissue.

Coverings (inner to outer)

• Fibrous capsule — tough, peels off easily in a normal kidney.
• Adipose (perinephric) capsule — fatty layer; buffer protection; reduced in cachexia → nephroptosis.
• Renal fascia (Gerota's fascia) — anterior and posterior layers; sends trabeculae to fibrous capsule for fixation.

Structure: Cortex and Medulla

• Renal cortex: Outer, reddish-brown; contains renal corpuscles (glomerulus + Bowman's capsule) and proximal/distal convoluted tubules. Also projects between pyramids as renal columns (of Bertin).
• Renal medulla: Inner, paler; consists of 15–20 renal pyramids. Each pyramid apex = renal papilla (perforated by papillary foramina opening into a minor calyx). Contains loops of Henle and collecting ducts.

Collecting System

• Minor renal calyces (7–8, cup-shaped) → Major renal calyces (2–3) → Renal pelvis → Ureter.

Blood Supply

• Renal arteries: Direct lateral branches of the abdominal aorta at L1. Right renal artery is longer (crosses posterior to IVC).
• Each renal artery divides into segmental arteries (5 segments: upper, upper anterior, lower anterior, lower, posterior) — end arteries (no anastomoses → infarction if occluded).
• Renal veins drain into the IVC. Left renal vein is longer (crosses anterior to the aorta). The left gonadal and left suprarenal veins drain into the left renal vein.

General

The ureter is a muscular tube (~20–30 cm, diameter 0.5–1.0 cm) running from the renal pelvis to the posterior wall of the bladder. It is divided into three parts.

Three Parts

• Abdominal part: Descends on psoas major, crossed anteriorly by the gonadal vessels. Right ureter related to the descending duodenum; left ureter related to the descending colon.
• Pelvic part: Enters the pelvis at the bifurcation of the common iliac artery (at the pelvic brim). In males, the vas deferens crosses anterior to the ureter (“water under the bridge”). In females, the ureter is crossed anteriorly by the uterine artery (“water under the bridge” — important in hysterectomy to avoid ureteric injury).
• Intramural (VUJ) part: 1.5 cm, runs obliquely through the bladder wall; opens at the superolateral angle of the trigone.

Three Constrictions (mnemonic: P–I–V)

• 1. PUJ — pelvi-ureteric junction, where the renal pelvis narrows to become the ureter.
• 2. Iliac vessel crossing — where the ureter crosses the superior aperture of the lesser pelvis over the iliac vessels.
• 3. VUJ / intramural part — narrowest constriction, as the ureter passes through the bladder wall.

Clinical: Renal Calculi

• Stones formed in the renal collecting system (calcium oxalate most common) may descend the ureter. They preferentially arrest at the three constrictions, causing sudden severe ureteric (renal) colic — loin-to-groin pain, haematuria, nausea/vomiting.
• VUJ (narrowest) = most common impaction site; causes hydronephrosis and hydroureter above the obstruction.
• Obstruction at the iliac crossing can mimic appendicitis (right) or ovarian pathology (left) due to referred pain.
• Management: analgesia (NSAIDs/opiates), hydration; stones <5 mm usually pass spontaneously; >10 mm require ureteroscopy or ESWL.

Overview

The male urethra is 17–20 cm long, extending from the internal urethral orifice of the bladder to the external urethral orifice at the tip of the glans penis. It has three parts. (TMU Slides 63–67)

Three Parts

• Prostatic part (2.5 cm): Widest and most dilatable part. Contains the urethral crest (posterior midline ridge); the verumontanum (colliculus seminalis, site where ejaculatory ducts open); and openings of 16–32 prostatic ducts. “Posterior urethra” includes prostatic + membranous.
• Membranous part (1–2 cm): Shortest and narrowest part. Passes through the urogenital diaphragm. Surrounded by the external urethral sphincter (skeletal muscle, voluntary; pudendal nerve). Most vulnerable to rupture in pelvic fractures.
• Spongy (cavernous) part (~15 cm): Longest part. Enclosed in the corpus spongiosum of the penis. Has two dilatations: the bulbous portion (proximally) and the navicular fossa (just before the external orifice, in the glans). The bulbourethral glands (Cowper's glands) open into the proximal spongy urethra.

Three Strictures (narrowings)

• Internal urethral orifice (bladder neck)
• Membranous part (urogenital diaphragm)
• External urethral orifice (narrowest point of the entire urethra)

Three Dilatations

• Prostatic part
• Bulbous portion of the urethra
• Navicular fossa

Two Curvatures

• Subpubic (fixed) curvature: Concavity faces anterosuperiorly, below the pubic symphysis; cannot be straightened.
• Prepubic (mobile) curvature: Concavity faces posteroinferiorly, in the pendulous penis; can be straightened by lifting the penis against the abdominal wall — this is done when passing a urethral catheter.

Clinical Relevance

• Urethral catheterisation: Lifting the penis straightens the prepubic curvature. The catheter must negotiate the subpubic curvature and the three strictures.
• Urethral rupture: The membranous urethra is most commonly torn in pelvic fractures (blood at the external meatus, inability to void = do NOT catheterise).
• Urethral stricture: Narrowing (post-infection, post-trauma) most commonly at the membranous or bulbous urethra → obstructive symptoms.
• Catheter tip position: The external orifice is the tightest point to pass through.

Position

The prostate is a single firm gland (~4×2×3 cm, 20 g) lying in the lesser pelvic cavity, immediately below the neck of the bladder and above the urogenital diaphragm. It surrounds the superior (prostatic) part of the urethra. Its base is related superiorly to the bladder neck; its apex rests on the urogenital diaphragm. Posteriorly it is related to the rectum, separated by the rectovesical fascia (Denonvilliers' fascia) — enabling digital rectal examination. In males, the neck of bladder is firmly attached to the prostate. (TMU Slide 52)

Structure

• Composed of glandular and muscular tissue, enclosed in a fibrous capsule with a surrounding prostatic sheath.
• Has 16–32 excretory ducts opening into the prostatic urethra on either side of the verumontanum.
• Older anatomical description: five lobes (anterior, posterior, median/isthmus, two lateral).

Zones (McNeal Classification)

• Peripheral zone (~70%): Posterior and lateral; palpable on DRE; site of ~70% prostate cancers. A hard nodule on DRE suggests malignancy. PSA elevated.
• Transitional zone: Bilateral around the proximal urethra; site of BPH.
• Central zone (~25%): Surrounds ejaculatory ducts; rarely diseased.

BPH vs Prostate Cancer

• BPH (benign prostatic hyperplasia): Hyperplasia of transitional zone glands and stroma. Compresses the prostatic urethra → lower urinary tract symptoms (LUTS): hesitancy, poor stream, terminal dribbling, incomplete emptying, nocturia. Gland is uniformly enlarged and rubbery on DRE. PSA mildly elevated. Treatment: alpha-blockers (tamsulosin), 5-alpha reductase inhibitors (finasteride), TURP (transurethral resection of prostate).
• Prostate cancer (adenocarcinoma): Usually arises in the peripheral zone. Hard, irregular nodule on DRE. PSA significantly elevated. Spreads via: lymphatics (iliac/obturator nodes) and blood (to bone — osteosclerotic metastases, especially in the lumbar spine and pelvis). Staging by Gleason score. Treatment: radical prostatectomy, radiotherapy, ADT (androgen deprivation therapy).

Position and Shape

• Paired endocrine glands lying on the anteromedial aspect of the upper poles of both kidneys, retroperitoneal, enclosed within the renal fascia (Gerota's fascia) but separated from the kidneys by connective tissue (so they do not descend with a ptotic kidney).
• Right suprarenal gland: Pyramidal (triangular); medially related to the IVC; posteriorly to the bare area of the liver.
• Left suprarenal gland: Crescentic (semilunar), larger; lies along the medial border of the left kidney; related anteriorly to the pancreas, stomach, and splenic vessels.

Blood Supply

• Superior suprarenal arteries (from inferior phrenic artery)
• Middle suprarenal arteries (directly from abdominal aorta at L1)
• Inferior suprarenal arteries (from renal arteries)
• Venous drainage: right suprarenal vein → IVC directly (short, important in adrenalectomy); left suprarenal vein → left renal vein.

Cortex — Three Zones (GFR mnemonic)

• Zona Glomerulosa (outer) → Aldosterone (mineralocorticoid). Regulated by renin-angiotensin-aldosterone system (RAAS) and serum K+. Effect: Na+ retention, K+ excretion in the kidney. Excess → Conn's syndrome (primary hyperaldosteronism): hypertension, hypokalaemia.
• Zona Fasciculata (middle, largest) → Cortisol (glucocorticoid). Regulated by ACTH from anterior pituitary. Effects: gluconeogenesis, anti-inflammatory, immunosuppressive. Excess → Cushing's syndrome; deficiency → Addison's disease.
• Zona Reticularis (inner) → Androgens (DHEA, androstenedione). Regulated by ACTH. Contributes to pubic/axillary hair in women; excess → congenital adrenal hyperplasia (CAH), virilisation.

Medulla

• Composed of chromaffin cells (modified postganglionic sympathetic neurons). Innervated by preganglionic sympathetic fibres (greater splanchnic nerve, T5–T9).
• Produces adrenaline (epinephrine) (~80%) and noradrenaline (norepinephrine) (~20%).
• Released in the “fight or flight” response: increased heart rate, BP, blood glucose, bronchodilation.
• Phaeochromocytoma: chromaffin cell tumour; classically presents with episodic hypertension, headache, palpitations, sweating. Biochemical diagnosis: elevated urine metanephrines. Treatment: surgical excision after alpha-blockade.