3.3 Urinary Diversions: Ileal Conduit, Continent Cutaneous Reservoirs & Neobladders

Urinary Diversions: Ileal Conduit, Continent Cutaneous Reservoirs & Neobladders

Urinary diversion is indicated when the native urinary bladder must be bypassed or removed due to malignancy, neurogenic dysfunction, or severe radiation trauma. Because intestinal segments are repurposed to transport or store urine, the Certified Ostomy Care Nurse (COCN) must master the surgical architecture, mucus physiology, ureteral stent protocols, continence mechanisms, and complex metabolic alterations inherent to urinary diversions.

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Urinary Tract Anatomy & Indications for Surgical Diversion

The urinary system comprises the bilateral kidneys, retroperitoneal ureters, urinary bladder (composed of the detrusor muscle, trigone, and ureteral orifices), and urethra.

Primary Indications for Radical Cystectomy and Urinary Diversion

• Muscle-Invasive Bladder Cancer: Urothelial (transitional cell) carcinoma invading the muscularis propria (Stage T2–T4a) or high-grade non-muscle-invasive bladder cancer refractory to intravesical Bacillus Calmette-Guérin (BCG) immunotherapy.
  • Radical Cystectomy in Males: Removal of bladder, prostate, seminal vesicles, distal ureters, and regional pelvic lymph nodes.
  • Anterior Pelvic Exenteration in Females: Removal of bladder, urethra, uterus, fallopian tubes, ovaries, anterior vaginal wall, distal ureters, and pelvic lymph nodes.
• Neurogenic Bladder Dysfunction: Spina bifida (myelomeningocele), quadriplegia, or advanced multiple sclerosis with high-pressure detrusor sphincter dyssynergia causing refractory hydronephrosis and progressive renal failure.
• Refractory Radiation Cystitis & Trauma: Severe radiation necrosis with intractable hemorrhage, severe interstitial cystitis, intractable incontinence, or irreparable vesicovaginal / urethrorectal fistulas.

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Non-Continent Urinary Diversion: The Ileal Conduit (Bricker Loop)

First described by Dr. Eugene Bricker in 1950, the ileal conduit remains the most common and robust urinary diversion performed worldwide.

                 [Kidneys]
                 /       \
        (Left Ureter)   (Right Ureter)
                \         /
                 \       /
           +-------------------+
           |  Isolated Ileal   |  <--- 15-20 cm segment of ileum
           |     Conduit       |       (Mesenteric blood supply intact)
           +---------+---------+
                     |
             [Everted Bud Stoma]  <--- 1.5 to 2.5 cm spout in RLQ
                     |
             [Urostomy Pouch]     <--- Continuous urinary collection

Surgical Construction Principles

1. Segment Isolation: A 15 to 20 cm segment of distal ileum is isolated with its mesenteric vascular pedicle intact. Crucially, the segment is harvested at least 15 cm proximal to the ileocecal valve to preserve active vitamin B12 and bile acid absorption.
2. Bowel Continuity: Gastrointestinal continuity is re-established via an end-to-end or side-to-side ileal anastomosis (enteroenterostomy).
3. Ureteroenteric Anastomoses:
   • Bricker Technique: The left ureter is brought through the sigmoid mesentery to the right side; both ureters are implanted separately into the anti-mesenteric border of the conduit in an end-to-side fashion.
   • Wallace Technique: The medial edges of both ureteral ends are spatulated and sutured together side-to-side, and the resulting common plate is anastomosed to the open proximal end of the conduit.
4. Stoma Maturation: The distal end of the conduit is brought through the right rectus abdominis muscle and matured as an everted 1.5 to 2.5 cm protruding bud stoma.

Alternative: Colon Conduits

When the ileum is compromised by prior high-dose pelvic radiation therapy, extensive adhesions, or short bowel syndrome, a segment of sigmoid colon, transverse colon, or jejunum may be isolated as a conduit. Sigmoid conduits allow non-refluxing tunneling anastomoses but carry higher mucus viscosity.

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Intestinal Mucus Secretion and Patient Management

Because the ileal segment retains its native histological structure, mucosal goblet cells continue to secrete thick, gelatinous mucus into the urine for the lifetime of the patient.

• Clinical Reassurance: Patients and family members often mistake white, stringy mucus threads in the urine for pus or infection. The COCN must reassure the patient that mucus production is an expected, normal physiological process.
• Hydration Therapy: Patients must maintain a daily fluid intake of 2,000 to 3,000 mL (2 to 3 liters/day) unless medically contraindicated. High fluid intake keeps mucus diluted, preventing mucus plug formation that can obstruct the stoma lumen or occlude the urostomy pouch drainage valve.
• Night Drainage System: Connecting the pouch to a bedside gravity drainage container overnight prevents urine accumulation, backpressure on the kidneys, and adhesive seal degradation.

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Ureteral Stents: Purpose, Monitoring & Removal Protocols

During conduit construction, flexible plastic catheters (e.g., 6–8 Fr single-J or double-J ureteral stents) are placed through the conduit and anastomoses into each renal pelvis.

  Left Renal Pelvis  ==[Stent 1]==> Through Conduit ===> Drains outside stoma
  Right Renal Pelvis ==[Stent 2]==> Through Conduit ===> Drains outside stoma

Clinical Functions of Ureteral Stents

• Maintain lumen patency across the ureteroenteric anastomoses during the acute postoperative inflammatory phase.
• Prevent anastomotic occlusion from localized mucosal edema, tissue spasm, or blood clots.
• Prevent urinary extravasation (leakage) into the retroperitoneum while the delicate suture lines heal.

Monitoring and Stent Care

• Independent Output Tracking: Verify that urine drains freely from each stent. An abrupt decrease in output from one stent signals potential kink, dislodgement, or clot occlusion.
• Patency Verification: Never forcefully flush a ureteral stent. If occlusion is suspected, gentle aspiration or low-pressure irrigation ($<5\text{ mL}$ sterile saline) requires a specific physician order.
• Removal Timing: Ureteral stents typically remain in place for 7 to 14 days postoperatively, allowing sufficient anastomotic healing before removal in the clinic or prior to hospital discharge.

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Continent Cutaneous Urinary Diversions: Indiana Pouch & Alternatives

Continent cutaneous urinary reservoirs store urine internally in a surgically constructed low-pressure bowel pouch, eliminating the need for an external appliance.

Indiana Pouch Architecture

• Internal Reservoir: Constructed from the cecum and ascending colon (approximately 25–30 cm). The colon segment is detubularized along its antimesenteric border and folded/reconfigured into a spherical, low-pressure, high-capacity reservoir (holding 600 to 800 mL).
• Continence Mechanism: The terminal ileum (10–12 cm) is plicated (tapered) to narrow its caliber. Continence is maintained by the intrinsic resistance of the reinforced, plicated ileocecal valve and the tightened efferent ileal limb.
• Stoma: The narrow ileal conduit terminates as a small, flush, coin-sized stoma in the right lower quadrant or recessed within the umbilicus.

                 [Indiana Pouch Construction]

               +-------------------------------+
               |     Detubularized Cecum /     |
               |        Ascending Colon        |  <--- Low-Pressure Reservoir
               |       (Holds 600-800 mL)      |
               +---------------+---------------+
                               |
                   [Plicated Ileocecal Valve]  <--- Continence Mechanism
                               |
                   [Tapered Terminal Ileum]    <--- Efferent Channel
                               |
                        [Flush Stoma]          <--- Clean Intermittent
                                                    Catheterization (CISC)

Alternative Cutaneous Reservoirs

• Mainz Pouch I: Utilizes cecum combined with loops of ileum to create a larger spherical reservoir with a tapered ileal or appendiceal stoma.
• Kock Urostomy: Constructed entirely from detubularized ileum utilizing an intussuscepted ileal nipple valve for continence.

Catheterization and Postoperative Regimen

1. Postoperative Drainage (Weeks 1–4): A large-bore cecostomy tube (e.g., 22–24 Fr Malecot catheter) remains on gravity drainage for 3 to 4 weeks. A pouchogram (contrast fluoroscopy) is performed at 3–4 weeks to confirm absence of extravasation before the catheter is clamped and removed.
2. Clean Intermittent Self-Catheterization (CISC) Protocol:
   • Initial Schedule: Catheterize every 2 to 3 hours around the clock.
   • Maintenance Schedule: Gradually extend intervals to every 4 to 6 hours (4–6 times/day). Never exceed 6 hours, as overdistension ($>800\text{ mL}$) can cause ischemic damage to the pouch wall and valve incompetence.
   • Catheter Selection: 14 to 16 Fr straight or coudé-tip catheter lubricated with water-soluble lubricant.
3. Mucus Irrigation: Daily or twice-daily irrigation with 30 to 60 mL of sterile saline or water is required to evacuate thick colonic mucus plugs.

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Orthotopic Neobladders (Studer & Hautmann Pouches)

An orthotopic neobladder substitutes the resected bladder with an internal ileal reservoir placed in the native anatomical pelvis and anastomosed directly to the native urethral stump, preserving normal transurethral voiding without a cutaneous stoma.

Surgical Construction (Studer Pouch)

• Constructed from 54 to 60 cm of detubularized distal ileum.
• 40 to 44 cm of the distal segment is opened and folded into a spherical reservoir (the "neobladder").
• An intact 12 to 16 cm proximal isoperistaltic afferent limb is preserved without detubularization, into which the ureters are implanted to provide anti-reflux protection.
• The inferior aspect of the pouch is anastomosed to the membranous urethra and external striated urethral sphincter.

Voiding Retraining and Physiology

• Absence of Detrusor Innervation: The neobladder lacks autonomic stretch receptors and parasympathetic motor innervation. The patient feels no "urge to void"; fullness is perceived as vague lower abdominal fullness, bloating, or pelvic heaviness.
• Voiding Technique: To empty the neobladder, the patient must:
  1. Completely relax the pelvic floor musculature (external sphincter).
  2. Perform a sustained, gentle Valsalva maneuver (abdominal wall straining) or apply manual suprapubic pressure (Credé maneuver).
• Timed Voiding Schedule: Void strictly every 2 to 3 hours during the day and every 3 to 4 hours at night (setting an alarm clock) to prevent chronic overdistension, urinary retention, and bilateral hydronephrosis.
• Nocturnal Incontinence: Occurs in 20% to 30% of patients due to the loss of the spinal guarding reflex during deep sleep (the smooth muscle neobladder has no autonomic tone to signal the external sphincter).

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Metabolic, Electrolyte & Acid-Base Complications

When intestinal mucosa is exposed to urine, transport proteins that evolved for nutrient and electrolyte absorption continue to function, leading to predictable systemic metabolic abnormalities.

[Urinary Solutes in Lumen]
    NH4+ (Ammonium)  ========================> [Active Mucosal Uptake] ===> Systemic Circulation
    Cl- (Chloride)   ========================> [Active Mucosal Uptake] ===> Hyperchloremia
                                                       |
                                            [Reciprocal Secretion]
                                                       v
    HCO3- (Bicarbonate) <===================== [Mucosal Loss]          ===> Systemic Base Deficit
    H+ (Hydrogen)       <===================== [Mucosal Loss]          ===> Metabolic Acidosis

Hyperchloremic Hypokalemic Metabolic Acidosis

The most frequent metabolic complication in ileal and colonic diversions (ileal conduits, Indiana pouches, neobladders):

• Mechanism: The intestinal brush border exchanges urinary ammonium ($NH_4^+$) and chloride ($Cl^-$) for systemic bicarbonate ($HCO_3^-$) and hydrogen ($H^+$). Reabsorption of $NH_4^+$ and $Cl^-$ causes hyperchloremia, while intestinal bicarbonate loss causes a systemic base deficit.
• Potassium Wasting: Renal excretion of ammonium and osmotic fluid shifts lead to progressive hypokalemia.
• Bone Demineralization: Chronic metabolic acidosis triggers bone buffering, releasing calcium carbonate and calcium phosphate from the skeleton. This leads to osteomalacia, osteoporosis, hypercalciuria, and calcium phosphate nephrolithiasis.
• Medical Management:
  • Mild: Oral sodium bicarbonate tablets (1–2 grams TID) or sodium/potassium citrate (Bicitra / Shohl's solution).
  • Refractory: Chlorpromazine or nicotinic acid (inhibits intestinal mucosal chloride transport).

Segment-Specific Metabolic Alterations

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Clinical Traps & Exam Pearls

Caution: Exam Trap: Never obtain a urine specimen for culture and sensitivity directly from an existing urostomy pouch bag. Pouch urine is heavily colonized with skin and intestinal bacteria. Always remove the appliance, clean the stoma with sterile saline, and catheterize the conduit lumen using a sterile 14 Fr straight catheter inserted 2 to 3 inches.

Note: Practice Tip: In neobladder patients presenting with acute lethargy, confusion, or weakness, always check serum electrolytes and venous blood gas. Hyperchloremic metabolic acidosis and acute urinary retention are frequent underlying causes.