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Urinary Diversion: Surgical Principles and Complications

Definitions and Classification of Urinary Diversion

Classification of Urinary Diversion

• According to the place of reconstruction: orthotopic (replacing the bladder) or heterotopic (at another place)
• According to the intestinal segments used: ileum, ileocecal junction, or colon.
• According to urine leakage: continent or incontinent urinary diversions.

Common Used Urinary Diversions:

• Orthotopic continent urinary diversion: urinary diversion replaces the bladder and is connected to the urethra with an intact sphincter. Examples: ileum neobladder (Studer or Hautmann technique).
• Heterotopic continent urinary diversion: a continent reservoir (pouch) is emptied with intermittent catheterization. Examples: MAINZ pouch 1, continent ileal pouch.
• Heterotopic incontinent urinary diversion: the ureters are brought out to the skin directly or with an interposed intestinal segment. Examples: ureterocutaneostomy, ileal conduit, colon conduit.

Principles of Continent Urinary Diversion

Reservoir volume:

Detubularization of intestinal segments is the solution for the construction of large-volume reservoirs with low reservoir pressures, without strong reabsorption, or reflux to the kidneys. A U-shaped detubularization doubles the reservoir volume compared to the tubular intestinal segment. W-shaped or S-shaped detubularization can triple the volume.

Reabsorption of urinary components:

A primary function of the bowel is the reabsorption of water and electrolytes; this is undesirable in urinary diversions. Cl⁻ is absorbed by ileal mucosa in exchange for HCO₃⁻, Na⁺ is absorbed in exchange with H⁺. Because more Cl⁻ than Na⁺ is typically absorbed, and thus more HCO₃⁻ than H⁺ is secreted, hyperchloremic metabolic acidosis results. The additional absorption of ammonium (NH₄⁺) exacerbates the acidosis. Reservoirs from the ileum have minor advantages over reservoirs from the colon in terms of storage pressures and reabsorption of urinary components. Patients with healthy kidneys can compensate for the electrolyte changes. However, a decreased GFR can cause problems concerning H⁺ and electrolyte excretion. Therapy consists of oral alkalinization with potassium or sodium bicarbonate.

Specific Contraindications for Continent Urinary Diversion

• All continent urinary diversion:} Crohn disease, ulcerative colitis, renal insufficiency (GFR &li;60–80 ml/min), poor compliance, low life expectancy.
• Orthotopic continent urinary diversion: defective sphincter muscle, urothelial carcinoma involvement of membranous urethra, prostate, or bladder neck.
• Heterotopic continent urinary diversion: the patient cannot catheterize himself.

Step-by-Step Surgical Techniques of Urinary Diversion

Preoperative patient preparation:

Please see the section on radical cystectomy.

• Ileal conduit
• Colon conduit
• Ureterocutaneostomy
• Ileum neobladder (Studer)
• Ileum neobladder (Hautmann)
• Continent heterotope urostoma (Mainz-Pouch I)

Postoperative Care after Urinary Diversion

General measures:

• Early mobilization
• Intensive respiratory therapy
• Thrombosis prophylaxis
• Laboratory tests (hemoglobin, electrolytes, creatinine)
• Regular physical examination of the abdomen and incision wound.

Analgesia:

The avoidance of opiates is essential for a rapid gastrointestinal recovery; a prerequisite for this is peridural anesthesia and the administration of nonsteroidal analgesics or COX2 inhibitors.

Diet advancement:

After laparotomy, a so-called "physiological" paralytic ileus develops. The duration of postoperative atony differs depending on the clinical situation and the extent of surgical therapy. Early oral feeding shortens the period of postoperative intestinal atony, and a prophylactic gastric tube is not helpful. 

Remove the nasogastric tube after surgery. Allow small sips of clear liquids after surgery. Small amounts of clear liquids and yogurt on postoperative day one. If the patient feels well, allow amounts of clear liquids, yogurt and bread starting postoperative day two. Chewing gum speeds up the recovery time. The diet is increased after overcoming the postoperative gastrointestinal atony.

Drains:

Minimal 1–2 days, remove when the drainage volume is below 100 ml/d. In patients with high drainage volume, check ureteral stents and catheters for patency and determine creatinine concentration if a urinary leakage is suspected.

Catheters:

MJ ureteral stent for ten days, and the reservoir catheter stays until radiologically documented sufficiency, but at least 14 days. A pouch or neobladder must be regularly irrigated via the catheter to remove the mucus of the intestinal mucosa.

Acid-base balance:

After urine storage begins in continent urinary diversions, regular determinations of blood pH, base excess, and electrolytes from venous blood are necessary. The base excess should not drop below -2.5 mmol/l.

Vitamins:

Regular lifelong substitution of vitamin B12 is necessary after using the distal ileum.

Complications of Urinary Diversion

Surgical Complications

Please see the section on radical cystectomy for the surgical complications.

Acid-base balance:

A decreased GFR may cause problems regarding proton and electrolyte excretion (see above). The typical disorder when using ileum or colon is the formation of hyperchloremic metabolic acidosis. Therapy consists of oral alkalinization with potassium or sodium bicarbonate. The base excess should not fall below -2.5 mmol/l.

Drug toxicity:

Drugs that are absorbed by the gastrointestinal tract and excreted by the kidneys may reach toxic levels due to continent urinary diversion. Catheter drainage of the reservoir is necessary to prevent toxicity, especially in adjuvant chemotherapy.

Urinary tract infections:

There is an increased incidence of bacteriuria, pyelonephritis or septic episodes. Increased bacterial colonization is caused by the decreased ability of the intestinal epithelium compared to the urothelium to prevent it.

Mucus formation:

Mucus may interfere with emptying the urinary reservoir and cause urinary retention. Simple hydration is adequate for prevention; oral administration of ACC is not helpful.

Urinary stone formation:

Mucus and urinary tract infections predispose to the formation of infection stones.

Malabsorption:

The loss of terminal ileum or a short bowel syndrome (due to complications) can cause vitamine B12 deficiency and loss of bile acids. Macrocytic anemia, neurologic symptoms, and diarrhea develop. Resection of the ileocecal valve favors bacterial colonization of the small intestine, this can lead to diarrhea, osteomalacia and other vitamin deficiency symptoms.

Osteomalacia:

Osteomalacia arises from metabolic acidosis, vitamin D resistance, and renal calcium loss.

References

  Deutsche Version: Grundlagen der Harnableitung