CHAPTER 20 Intestinal Segments in Urology
True/False: Ileal conduit is the standard form of urinary diversion.
True. The ileal conduit was described in 1950 by Bricker and has remained a standard urinary diversion against which others are judged (Bricker, 1950).
Which type of surgical urinary diversion is considered the “optimal” form of urinary reconstruction?
Currently centers of excellence recommend that an orthotopic bladder be offered to most patients as the primary form of urinary reconstruction. Patients with advanced age or comorbidity should generally have an ileal conduit (Hautmann et al., 2007). Patients with prostatic urethral involvement should be considered for a conduit or a continent abdominal diversion.
List the contraindications to an ileal conduit.
Short bowel syndrome, inflammatory small bowel disease, and previous extensive radiation to the ileum.
List the 3 types of diversion.
• Abdominal diversion such as ureterocutaneostomy, ileal or colonic conduit, and various forms of a continent pouch.
• Urethral diversion which includes various forms of gastrointestinal pouches attached to the urethra as a continent, orthotopic urinary diversion (neobladder, orthotopic bladder substitution).
• Rectosigmoid diversions, such as uretero(ileo-)rectostomy.
Does the type of urinary diversion affect outcome for muscle invasive bladder cancer?
No. In a recent study Yossepowitch et al. (2003) compared cancer control and patterns of disease recurrence in neobladder and conduit patients. No cancer-specific survival difference could be identified between the 2 groups when adjusting for the pathological stage.
Does the type of diversion affect the chance of a urethral recurrence following cystectomy for bladder cancer?
Stein et al. demonstrated that at long-term follow-up urethral tumor recurrence occurs in approximately 7% of men following cystectomy for bladder cancer. Involvement of the prostate with tumor and the form of urinary diversion were significant and independent risk factors for urethral tumor recurrence. Patients undergoing orthotropic diversion have a lower incidence of urethral recurrence (4%) compared with those undergoing cutaneous diversion (8%). These results maybe confounded by selection bias since those at higher risk of urethral recurrence were offered a cutaneous diversion compared to those with orthotopic diversion.
What is/are the absolute contraindication(s) to continent urinary diversion?
Absolute contraindications to continent urinary diversion are compromised renal function with serum creatinine levels above 1.50 to 2.00 mg/dL, severe hepatic dysfunction, and patients in whom urethrectomy is indicated (usually because of urethral involvement by transitional cell carcinoma (TCC)) (Studer et al., 1998).
A patient is considered for a continent diversion. His serum creatinine exceeds 2.0 mg/dL. How should he be evaluated to determine whether he is a candidate?
Criteria for candidacy for a continent diversion include the ability to achieve a urine pH of 5.8 or less following an ammonium chloride loading test, a urine osmolality >600 mOsm/kg in response to water deprivation, a glomerular filtration rate >35 mL/min, and no more than minimal proteinuria. These tests are helpful in patients desiring continent diversion with borderline renal functions (ie, serum creatinine between 1.50 and 2.00 mg/dL).
Does extensive pelvic disease, a palpable mass, or positive lymph nodes preclude the use of neobladder because of the high propensity for pelvic recurrence or distant relapse?
No. Convincing evidence suggests that a patient with an orthotopic diversion tolerates adjuvant chemotherapy less well. Local recurrence may be more problematic with a neobladder, but conversion to an ileal conduit if this occurs is a reasonable option. Patients can anticipate normal neobladder function until the time of death (Hautmann and Simon, 1999).
True/False: Continent urinary diversions are better than incontinent diversions in terms of quality of life (QOL).
False. Published evidence does not support an advantage of one type of reconstruction over the others with regard to QOL (Hautmann et al., 2007). Although the QOL studies have not demonstrated an advantage of orthotopic bladder replacement, many urologists believe that the QOL is improved. Patients usually prefer this option when offered.
What are the surgical principles for bladder reconstruction?
• High volume
• Low pressure
• Continence mechanism
• Anti reflux mechanism
List the 8 most common complications specific to continent urinary diversions.
• Stomal stenosis: The incidence of stomal stenosis in continent cutaneous urinary diversions is determined by the different continence mechanisms employed. The incidence of stomal stenosis as defined by difficulty catheterising may be as low as 1.5% for plication anti reflux mechanisms to as much as 54% in Mitrofanoff conduits.
• Incontinence: The incidence of incontinence is hard to report since its definition varies significantly between studies. If assessed strictly as the presence of ANY leakage, incontinence rates of up to 28% are reported but such strict criteria are seldom used. Daytime continence rate is generally 5% to 10% greater than the nighttime continence rate. Studer et al. (2006) report that the continence rate is 92% during the day and 79% during nighttime after 1 year.
• Calculi: These are a frequent encounter in urinary diversions and augmentations and are related to the presence of infection, stasis, mucus, and exposed staples.
• Anastomotic urinary leakage: It ranges between 2% and 10%.
• Anastomotic strictures: These can occur secondary to excessive tension, ischemia, recurrent malignancy, radiation, and failure to achieve mucosal coaptation during surgery. In addition to these factors, the creation of an anti reflux mechanism also increases the risk of stricture at the uretero-bowel anastomosis.
• Incomplete voiding: All forms of continent diversion carry with them an inherent risk of incomplete voiding requiring the utilization of clean intermittent self-catheterisation (CISC).
• Tumor formation: Current evidence, although low level and limited to small case series and case reports, suggests that ureterosigmoidostomy urinary diversion increases the risk of malignancy. This risk is difficult to quantify and appears related to time, being almost unheard of in the first 15 years following diversion. Following ileocystoplasty, continent cutaneous urinary diversion, and orthotopic neobladder formation, there have been isolated reports of malignancy at the anastomotic site but these are almost universally found in patients having had surgery for chronically inflamed or tuberculous bladders. The intrinsic risk of malignancy in patients undergoing surgery for noninflammatory, benign condition, for example detrusor overactivity appears to be no greater than for the age-matched population; however, patients should be warned regarding possible symptoms of malignancy (hematuria) and appropriately investigated whether these can occur. Annual surveillance has been advocated by some although the time of initiation remains a matter for debate.
• Mucus production
Describe several surgical techniques of maintaining continence in a pouch.
• Nipple valve principle where the valve protrudes into the reservoir cavity and as the reservoir fills, the valve is compressed preventing incontinence.
• The Flap valve technique relies on the proximal segment of the continence channel running on the inner wall of the reservoir. As the reservoir fills, the channel is compressed preventing incontinence. The most popular type of flap valve is the appendix implanted into the reservoir (Mitrofanoff principle).
Is a continent diversion better than conduit diversion for maintaining upper tract function?
Not necessarily. The only prospective randomized trial is reported by Kristjansson et al. (1995a, b). In this trial, 2 types of conduit diversions (ileal [n = 18] and colonic [n = 20]) and cecal continent diversion (n = 8) were used for the treatment of patients. For the statistical analysis, the combined outcome measures of the ileal and colonic conduit diversions (n = 38) were compared to the outcome measures of the cecal continent diversion. There were no statistically significant differences in the relative risks of upper urinary tract infection, number with uretero-intestinal stenosis, incidence of glomerular filtration rate deterioration (of more than 25%), and renal scarring. The confidence intervals were all wide, however, and did not rule out clinically important differences.
In terms of metabolic consequences, what bowel segment is preferably used for bladder reconstruction and why?
Ileum is preferred to colon for bladder reconstruction. Chloride absorption and bicarbonate excretion are more pronounced in the colon, which leads to a higher risk of hyperchloremic metabolic acidosis, particularly in the presence of renal impairment (Davidsson et al., 1994).
What is the advantage of stomach over other intestinal segments for urinary diversion?
Stomach is less permeable to urinary solutes, it acidifies the urine, it has a net excretion of chloride and protons rather than a net absorption of them, and it produces less mucus.
True/False: The jejunum is a good option as an intestinal segment for urinary intestinal diversion.
False. The jejunum is usually not employed for reconstruction of the urinary system, because its use often results in severe electrolyte imbalance.
What are the preferred methods of urinary diversion in patients with history of pelvic irradiation and why?
In patients with pelvic irradiation, it is preferable to avoid using the ileum because it is the bowel segment that is most affected by pelvic radiation. The preferred method of diversion is either a colon conduit or a continent cutaneous pouch using the colon (eg, Indiana or Mainz pouch) (Leissner et al., 2000; Ravi et al., 1994).
Which part of colon is the most appropriate segment as a colon conduit in patients undergoing a total pelvic exenteration?
Sigmoid colon. No bowel anastomosis needs to be made.
What is the contraindication to the use of sigmoid colon in addition to disease of the segment and extensive pelvic irradiation?
If the internal iliac arteries have been ligated and the rectum has been left in situ, use of the sigmoid colon is contraindicated. It may result in sloughing of the rectum or its mucosa.
What are the contraindications to the use of colonic segments?
Inflammatory large bowel disease and severe chronic diarrhea.
Which part of the gut is most suitable for bladder replacement?
Unclear. Two randomized trials (Chen 2009; Khafagy, 2006) compared between 2 different bowel segments (ileal and ileocolonic; Chen 2009 and ileal and ileocaecal; Khafagy, 2006) in the treatment of patients with bladder replacement. A Cochrane Meta analysis did not show any difference in daytime incontinence or nighttime incontinence, renal function deterioration, or any other complication. Thus at present no conclusion can be drawn.
What are the main advantages of an ileocecal pouch (Indiana pouch)?
The main advantage is, clearly, continence. In addition, the terminal ileum remains in the fecal stream (with the exception of the distal 15 cm), and it is avoided, especially following pelvic radiation.
Where are the 3 vulnerable points involving the vascular supply to the colon located?
Sudeck critical point is located between the junction of the sigmoid and superior hemorrhoidal arteries with the midpoints between the middle colic and right colic arteries. Between the middle colic and left colic arteries are tenuous anastomotic areas. If the colon were transected in these regions, the anastomosis might be at risk because of compromised blood supply.
What are the most common aerobic organisms in the bowel?
Escherichia coli and Streptococcus faecalis.
What are the most common anaerobic organisms in the bowel?
Bacteroides species and Clostridium species.
True/False: A mechanical bowel preparation reduces the concentration of bacteria as well as the total number.
False. The mechanical preparation reduces the amount of feces, whereas the antibiotic preparation reduces the bacterial concentration.
What are the common adverse effects of antibiotic bowel preparation?
Diarrhea. Pseudomembranous enterocolitis, monilial overgrowth resulting in stomatitis, malabsorption of protein, carbohydrate, and fat are the other disadvantages.
True/False: The main reason for detubularization of the bowel segment used in urinary diversion is altering the shape of the reservoir from spherical to ellipsoid.
False. Detubularized bowel segments provide greater capacity at lower pressure and require a shorter length of intestine than do intact segments; shape is of secondary importance (Colding-Jorgensen et al., 1993).
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