CHAPTER 21 Urinary Diversion and Undiversion
What is the electrolyte abnormality most commonly seen when stomach is used in the urinary tract? What are signs and symptoms that result from these electrolyte disturbances and how is this often treated?
Hypochloremic metabolic alkalosis. This is secondary to the HCl secretion by the stomach segment, involving the H+/K+ ATPase secretory mechanism of the gastric mucosa.
When it is fully manifested, lethargy, respiratory insufficiency, seizures, and ventricular arrhythmias may occur. These manifestations are typically preceded by vomiting resulting in dehydration.
Patients are generally successfully treated with an H2 blocker to reduce proton secretion by the gastric segment and rehydration. In life-threatening circumstances, arginine hydrochloride infusion has been employed to rapidly restore acid–base balance. When H2 blockers are ineffective, proton pump inhibitors (PPIs) have been successfully used. In rare cases when PPIs are ineffective and the life-threatening metabolic alkalosis persists, the gastric segment must be removed.
What is the electrolyte abnormality most commonly seen when jejunum is used in the urinary tract?
Hyponatremic, hypochloremic, and hyperkalemic metabolic acidosis. This has been termed the “jejunal conduit syndrome.” These disorders result from an increased secretion of sodium chloride and water leading to dehydration and increased reabsorption of potassium and hydrogen from both the conduit and kidneys (due to increased renin–angiotensin system from hypovolemia). This syndrome can be quite debilitating, resulting in nausea, anorexia, lethargy, fever, and even death. The more proximal the segment used, the more likely the syndrome is to develop, secondary to the increased surface area available, due to increased villi and microvilli. The jejunum should be used only when there are no other acceptable segments available for use.
What is the electrolyte abnormality most commonly seen when ileum or colon is used in the urinary tract? What are signs and symptoms that result from these electrolyte disturbances and how is this often treated?
Hyperchloremic metabolic acidosis. This is caused by the substitution of ammonium for sodium in the Na/H transport. Therefore, ammonium chloride is absorbed into the bloodstream in exchange for carbonic acid (CO2 and H2O).
Common signs and symptoms include easy fatigability, anorexia, polydipsia, and lethargy. Those with ureterosigmoidostomies also may have an exacerbation of diarrhea.
Alkalinization with oral sodium bicarbonate is effective in restoring normal acid–base balance though it may produce significant intestinal gas. Oral citrate may also be used. Chlorpromazine and nicotinic acid inhibit cAMP and thereby impede chloride transport.
What is the cause of the altered sensorium occasionally associated with intestinal conduits?
Magnesium deficiency, drug intoxication, or abnormalities of ammonia metabolism. This should be treated with drainage of the urinary intestinal diversion (foley or rectal tube), administration of neomycin (to reduce the enteric ammonia load), minimizing protein intake, and treating the underlying condition.
What commonly used drugs can be reabsorbed in intestinal diversions after excretion from the kidneys and result in toxic serum levels?
Phenytoin, methotrexate, lithium carbonate, and theophylline may be reabsorbed in their original form from intestinal diversions and lead to toxic serum levels.
True/False: Incontinent urinary diversions are generally associated with fewer metabolic abnormalities.
True. Given the longer dwell time of urine in contact with the intestinal segment used, both neobladders and continent urinary diversions are associated with a higher risk of electrolyte and metabolic abnormalities.
True/False: Mechanical bowel preparation results in a reduction in bacteria per gram of enteric contents.
False. Mechanical bowel preparation will reduce the total number of bacteria in the gut, but not their concentration.
Which portion of the small intestine is typically used for ileal conduit formation?
An ileal segment is selected 10 to 15 cm from the ileocecal valve, which is usually 20–25 cm in length.
Which portions of the small intestine should one avoid using for diversion in patients with history of pelvic radiation?
The last 2 inches of the terminal ileum, which is often fixed in the pelvis by ligamentous attachments, and the 5 feet of small bowel beginning approximately 6 feet from the ligament of Treitz, the mesentery of which is the longest of the entire small bowel. As such, this portion of the small bowel can descend into the pelvis.
What is the most common stomal complication following urinary diversion?
Stomal stenosis. The incidence is reported to be 20% to 24% for ileal conduits and 10% to 20% for colon conduits. Other complications include bleeding, bowel necrosis, dermatitis, parastomal hernias, and stomal prolapse.
Which segment of bowel is most suitable for nonrefluxing ureterointestinal anastomoses?
Colon. Numerous anastomoses (Leadbetter and Clarke, Goodwin, Strickler, and Pagano) employ the seromuscular strength of the tenia to create a backing for the submucosal tunnel needed for the antireflux procedure.
What type of ureteroileal anastomosis carries the highest risk of ureteral stricture?
Antirefluxing ureteroileal anastomosis. In general, antirefluxing anastomoses carry a higher risk of stricture that persists for the life of the conduit. Although open and endourological methods of repair have been successful, open repair carries a higher success rate (approximately 75% vs 60% for endourological methods).
What is the most common site of ureteral stricture after ileal conduit formation not at the ureteroileal anastomosis?
The left ureter as it crosses over the aorta. As the left ureter crosses over the aorta and underneath the inferior mesenteric artery, it is both extrinsically compressed and angulated, which may result in stricture formation. In addition, aggressive stripping of the periureteral adventitia may result in vascular compromise at this level, also predisposing to stricture.
Briefly describe the Bricker ureterointestinal anastomosis.
The Bricker anastomosis is a refluxing end-to-side anastomosis. It involves spatulating the distal end of the ureter, and stitching the full thickness of the bowel to the full thickness of the ureter. This anastomosis boasts both technical ease as well as a low complication rate (see the figure).
Briefly describe the Wallace ureterointestinal anastomosis.
The Wallace anastomosis is a refluxing end-to-end anastomosis. Different techniques are described, but the concept is that the ureteral ends are spatulated and sewn together into a common opening. This “common ureter” is then anastomosed to the end of the intestinal segment used. It has a lower stricture rate due to the wide anastomosis, but is not recommended for patients with extensive carcinoma in situ or a high likelihood of recurrence in the ureter. Recurrence in the distal aspect of one ureter could block the egress of both ureters, causing bilateral obstruction (see the figure).
What is the generally accepted cut-off value of serum creatinine at which continent diversions and orthotopic neobladders are no longer considered?
2.0 mg/dL. Due to the extended dwell time of urine in contact with the intestinal segments used, continent diversions and orthotopic neobladders should be considered only for those patients with good renal function.
What renal parameters must be met to consider continent diversion in a patient with serum creatinine greater than 2.0 mg/dL?
Urine pH 5.8 or less after ammonium chloride load, urine osmolality of 600 mOsm/kg or greater with water deprivation, glomerular filtration rate (GFR) greater than or equal to 35 mL/min, and minimal protein in the urine.
What percent of patients with normal preoperative creatinine and GFR who undergo conduit diversion develop renal deterioration?
Approximately 18% of patients with ileal conduit diversion will have progressive renal deterioration, which may lead to death from renal failure in approximately 6% of patients. 13% of patients with nonrefluxing colon conduits will show progressive deterioration.
What long-term effects can urinary intestinal diversion have on the bony skeleton?
Osteomalacia. Osteomalacia (or renal rickets) has been reported most commonly with ureterosigmoidostomy, but also with colon and ileal conduits, and ileal ureters. It is thought to be secondary to acidosis, vitamin D resistance, and excessive calcium loss by the kidney.
What type of reservoir requires nocturnal emptying?
Ureterosigmoidostomy. Although all continent reservoirs may require nocturnal emptying to prevent overdistention, the increased risk of metabolic acidosis from ionized transport of ammonium via the Na+/H+ antiport in ureterosigmoidostomy necessitates nocturnal emptying.
True/False: Approximately 75% of urine specimens from ileal conduits are infected.
True. Intestine, in contrast to urothelium, generally lives symbiotically with bacterial flora. Most patients have no sequelae from their chronic bacteriuria, and are not treated unless they develop symptoms.
What bacterial infections from conduits or continent diversions should be treated?
Cultures dominantly positive for Proteus, Pseudomonas, or Klebsiella species should be treated. Proteus and Pseudomonas infections have been linked to upper tract deterioration, and all 3 organisms are urea-splitting, making patients infected with these organisms more likely to form stones.
What is the urinary diversion procedure that puts the patient at the highest risk for development of carcinoma of the intestinal segment?
Ureterosigmoidostomy. Following ureterosigmoidostomy, as many as 40% of patients will develop tumors at the ureterosigmoid anastomosis given sufficient time. About half of the tumors are adenocarcinoma and the rest are benign polyps. The mean latency period between ureterosigmoidostomy and the diagnosis of tumor is 26 years.
If performing undiversion following ureterosigmoidostomy, what must be done to minimize the risk of tumorigenesis?
The distal ureteral stumps must be removed from contact with the colonic epithelium. Adenocarcinoma has been reported to occur when the ureterointestinal anastomoses were left in situ, even when the diversion is defunctionalized.
Briefly describe the Mitrofanoff procedure.
The Mitrofanoff procedure is the creation of a continent, catheterizable urinary diversion. It is usually performed with the appendix, which is anastomosed to the conduit (or bladder) in a tunneled fashion (similar to a ureteroneocystostomy). The other end of the appendix is brought out to the anterior abdominal wall, and is utilized for clean intermittent catheterization.
In patients who have received extensive pelvic radiation, which intestinal segment is preferred for creation of a conduit?
The transverse colon. Given its position within the abdominal cavity, it is the most likely unaffected by previous pelvic radiation.
What is the blood supply of the appendix?
The appendiceal artery, a branch usually off of the ileocolic artery, which arises from the superior mesenteric artery.
What is the source of continence for orthotopic neobladders?
In both the male and female, the preserved striated external sphincter is the source of continence. Daytime continence rates of greater than 95% can be expected if this mechanism is surgically spared.
What are the 2 phenomena thought to be responsible for nocturnal enuresis following orthotopic neobladder procedures?
First, the spinal reflex arc that recruits external sphincter contraction is gone, as the native bladder (and therefore the afferent nerves) has been removed. The other hypothesis is that there is a significant re-absorption and re-circulation of urinary constituents and metabolites that stimulate increased urinary volume, resulting in nocturnal enuresis.
Briefly describe the ureterointestinal anastomosis described by Studer and colleagues.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
