Explore lower urinary tract anatomy, ureter pathology including UPJ obstruction, urothelial carcinomas, calculi, and sclerosing retroperitoneal fibrosis.
--- DISORDERS OF THE LOWER URINARY TRACT — PART 1 --- CLINICAL ANATOMY Definition: The renal pelves, ureters, urinary bladder, and urethra (except the terminal portion) are lined by a special transitional epithelium called urothelium . Structure: - Composed of 5–6 cell layers with oval nuclei and linear nuclear grooves - Surface layer = large, flattened "umbrella cells" with abundant cytoplasm - Bladder Wall Layers — ⚠️ Know This: - Muscularis mucosa — wisps of smooth muscle in the lamina propria; discontinuous - Detrusor muscle (muscularis propria) — deeper, well-defined, larger bundles - Bladder cancers are staged based on invasion of the detrusor muscle — the two must not be confused - Obstructed urine flow → ↑ intravesical pressure → bladder musculature hypertrophy - Clinical Relationships: - Ureters are entirely retroperitoneal → retroperitoneal tumours or fibrosis can entrap and obstruct them - Women (middle-aged/older): pelvic support relaxation → uterine prolapse → bladder floor descends → cystocele (bladder protrudes into vagina; fails to empty properly during micturition) - Men: prostate lies posterior/inferior to bladder neck → prostatic enlargement = major cause of urinary tract obstruction - --- - URETERS - --- A. CONGENITAL ANOMALIES Incidence: Found in ~2–3% of all autopsies; most clinically insignificant. UPJ (Ureteropelvic Junction) Obstruction: - Most common cause of hydronephrosis in infants and children - In children: preferentially affects males ; bilateral in 20% of cases; often associated with other anomalies; minority have agenesis of the contralateral kidney - In adults: more common in women ; most often unilateral - Cause: abnormal smooth muscle bundle organisation OR excess collagen deposition at UPJ OR (rarely) extrinsic compression by abnormal renal vessels - --- B. TUMOURS AND TUMOUR-LIKE LESIONS Benign Tumours: - Rare; generally of mesenchymal origin - Fibroepithelial polyp — tumour-like lesion; common in children; composed of loose, vascularised connective tissue overlaid by urothelium - Malignant Tumours: - Primary malignant ureteral tumours resemble those of the renal pelvis, calyces, and bladder - Majority are urothelial carcinomas - Peak incidence: 6th–7th decade of life → cause obstruction of the ureteral lumen - Commonly occur concurrently with urothelial carcinomas of the bladder or renal pelvis - --- C. OBSTRUCTIVE LESIONS Overview: - Intrinsic and extrinsic lesions may obstruct ureters → hydroureter, hydronephrosis, pyelonephritis - Unilateral obstruction → proximal intrinsic or extrinsic causes (e.g., stones, neoplasms) - Bilateral obstruction → distal causes (e.g., nodular hyperplasia of the prostate) - Intrinsic Causes: - Calculi — typically of renal origin; usually ≤5 mm; impact at narrowings (UPJ, iliac vessel crossing, bladder entry) → excruciating renal colic - Strictures — congenital or acquired - Tumours — urothelial carcinomas; rarely benign tumours/fibroepithelial polyps - Blood clots — from massive haematuria due to renal calculi, tumours, or papillary necrosis - Neurogenic — interruption of neural pathways to the bladder - Extrinsic Causes: - Pregnancy — physiologic smooth muscle relaxation OR uterine fundus pressure on ureters at the pelvic brim - Periureteral inflammation — salpingitis, diverticulitis, peritonitis, sclerosing retroperitoneal fibrosis - Endometriosis — pelvic lesions with scarring - Tumours — cancers of rectum, bladder, prostate, ovaries, uterus, cervix; lymphomas; sarcomas - --- D. SCLEROSING RETROPERITONEAL FIBROSIS Definition: Rare fibrotic proliferative inflammatory process that encases retroperitoneal structures → causes hydronephrosis . Epidemiology: - Middle to late age; more common in males - Aetiology: - Subset linked to IgG4-related disease → elevated serum IgG4; fibroinflammatory lesions rich in IgG4-secreting plasma cells; affects multiple organs - Other causes: drug exposures (ergot derivatives, β-adrenergic blockers), inflammatory conditions (vasculitis, diverticulitis, Crohn disease), malignancies (lymphomas, urinary tract carcinomas) - Most cases: no obvious cause → idiopathic (Ormond disease) - Morphology (Histology): - Fibrous tissue with prominent infiltrate of lymphocytes (often with germinal centres), plasma cells (frequently IgG4+), and eosinophils - Treatment: - Initially: corticosteroids - If resistant → ureteral stents or surgical ureterolysis (freeing ureters from surrounding fibrosis) - --- - URINARY BLADDER - --- A. CONGENITAL ANOMALIES Vesicoureteral Reflux: - Most common and serious congenital bladder anomaly - Predisposes to ascending pyelonephritis and loss of renal function - Abnormal connections between bladder and vagina/rectum/uterus → congenital vesicouterine fistulae - Diverticula: - Pouch-like invaginations of the bladder wall; 6 weeks in the absence of infection or other identifiable cause. Features: - Intermittent, often severe suprapubic pain; urinary frequency; urgency; haematuria; dysuria - Cystoscopy: mucosal fissures + punctate haemorrhages (glomerulations) - Histology: nonspecific; mast cells often increased in submucosa (significance uncertain) - ⚠️ Main role of biopsy = rule out CIS , which clinically mimics interstitial cystitis - Some cases: chronic mucosal ulcers → Hunner ulcers (late/classic/ulcerative phase) - Late course: transmural fibrosis → contracted bladder - Treatment: largely empiric - Malakoplakia: Definition: Distinctive chronic inflammatory reaction from acquired defects in phagocyte function ; arises in setting of chronic bacterial infection (mostly E. coli, occasionally Proteus); increased frequency in immunosuppressed (e.g., renal transplant recipients). Morphology: - Cystoscopy: soft yellow, slightly raised mucosal plaques (~3–4 cm) - Histology: aggregates of large foamy macrophages + occasional multinucleate giant cells + lymphocytes - Macrophage cytoplasm: granular due to phagosomes stuffed with bacterial debris (defective phagolysosome function) - Pathognomonic finding: Michaelis-Gutmann bodies — laminated mineralized concretions from calcium deposition in enlarged lysosomes within macrophages - Similar lesions described in: colon, GI tract, brain, lungs, bones, endometrium, kidneys, prostate, epididymis - Polypoid Cystitis: - Inflammatory lesion from irritation of bladder mucosa — most commonly from instrumentation/indwelling catheters - Urothelium thrown into broad bulbous polypoid projections due to marked submucosal oedema - ⚠️ May be mistaken for papillary urothelial carcinoma — both clinically and histologically - --- C. METAPLASTIC LESIONS Cystitis Glandularis and Cystitis Cystica: - Common lesions in which nests of urothelium ( von Brunn nests ) grow downward into the lamina propria - Central cells undergo metaplasia: - - Cystitis glandularis → cuboidal/columnar appearance - Cystitis cystica → retract to form cystic spaces lined by flattened urothelium - Often coexist → referred to as cystitis cystica et glandularis - Variant: goblet cells present → epithelium resembles intestinal mucosa ( intestinal/colonic metaplasia ) - ⚠️ Extensive, multifocal intestinal metaplasia = precursor to adenocarcinoma - Squamous Metaplasia: - Response to chronic injury → urothelium replaced by nonkeratinizing or keratinizing squamous epithelium - Distinguish from: glycogenated squamous epithelium normally found at the trigone in women (this is normal) - ⚠️ Extensive multifocal keratinizing squamous metaplasia = precursor to squamous dysplasia, CIS, and invasive squamous cell carcinoma - Classic example: bladder schistosomiasis → squamous metaplasia → squamous cell carcinoma in endemic areas - Nephrogenic Adenoma: - Unusual lesion; may not be true metaplasia - Evidence from renal transplant recipients: caused by implantation and growth of renal tubular cells at sites of bladder mucosal erosion - Overlying urothelium focally replaced by cuboidal epithelium → may assume papillary growth - Usually <1 cm; larger lesions can