Internal and external urinary diversion

This chapter closes with an account of the principles of this important subject, and includes indications, the methods employed and their attendant problems, and some operative details.

Indications

Diversion of the urine may be either a temporary expedient to relieve distal obstruction, or a permanent procedure when:

(1) the bladder has been removed; (2) the sphincters of the bladder have been damaged or have lost their normal neurological control; (3) there is an incurable fistula; (4) there is an irremovable obstruction; and (5) in late cases of ectopia vesicae.

Methods of urinary diversion

The urinary tract may be diverted at most sites extending from the kidney, the ureter, the bladder and the urethra or it may involve the creation of new structures such as an ileal or colonic conduit, continent diversions or bladder substitutions (Fig. 65.55). The diversion may be achieved by any of the following methods, but the choice in each case will be decided largely by the primary disease, patient comorbidity and motivation:

 

       pyelostomy on nephrostomy (now carried out percutaneous­ly by means of interventional percutaneous nephrostomy —Chapter 62) on catheter drainage (or urethrostomy);

cutaneous uneterostomy or the use of indwelling ‘double J’ pigtail ureteric stents;

       suprapubic cystostomy (with indwelling catheter);

cutaneous vesicostomy (cystostomy);

       ureterosigmoidostomy: (1) in continuity; (2) making a rectal bladder and colostomy; or (3) creating a rectal reservoir;

external diversion of urine by a number of surgical techniques. The following problems may occur: (1) collection of the urine; (2) stricture formation at any anastomosis; and (3) reflux and reabsorption of urinary solutes. The problems of infection are intimately related to all three;

internal urinary diversion by means of bladder replacement.

Collection of urine

Catheters

In the past, indwelling catheters have been used for permanent diversion. They invariably result in bacteriuria and carry a risk of infection, and they often become blocked by phos­phate encrustation. Temporary nephrostomy drainage is very useful in the management of patients with acute upper tract obstruction. For temporary cutaneous ureterostomy drainage, the tubes should be of soft silicone.

Bladder drainage. In elderly patients unfit for prostatectomy and in some terminal cases of carcinoma of the prostate, an indwelling silicone urethral Foley catheter changed every 3 months is a satisfactory method of drainage. Other methods include the use of prostatic urethral stents passed under ultrasound or direct vision to hold open the prostatic urethra and bladder neck.

Cutaneous stomas

Suprapubic vesicostomy or urethrostomy. Collection from a formal suprapubic vesicostomy (cystostomy) is unsatisfactory because the local incisions result in skin creases which make it difficult to apply a water-tight collecting appliance.

Cutaneous ureterostomies. These are very liable to stricture formation. In addition, two openings (Fig. 65.55d) and appliances add to the patient’s burden. Mobilisation of the ureters and the making of a central abdominal stoma may be useful in children with grossly dilated ureters as a temporary measure (Fig. 65.55e).

Ileal or colonic conduit. At present, the most generally useful form of external diversion is to implant each ureter with as little mobilisation as possible into an isolated segment of gut (ileum on colon), which conducts the urine onwards to a cutaneous stoma (Fig. 65.55a). Urine is then collected in an ileostomy bag. This form of diversion limits infection and avoids the problems of reabsorption of urine as contact time with the mucosa is minimal. In some cases in which the pelvic area has been subjected to radiation, the lower ureters may be unhealthy. A high division with insertion of the ureters into an ileal loop above the root of the mesentery may be wiser (Fig. 65.56).

Siting of stoma. The site for the stoma must be chosen before operation in consultation with a stoma care therapist. The site of the future stoma is marked indelibly on the skin.

Colon and rectum

The advantage of diverting urine into the colon is that no collecting apparatus is necessary (Fig. 65.55b and f). Clearly, however, the anal sphincter must be competent. Before ureterosigmoidostomy is undertaken, the patient must prove that he or she can control at least 200 ml of fluid in the rectum. The disadvantage of the operation is that the renal tract is exposed continuously to infection from the faeces. This can be minimised by performing some type of antireflux procedure or by establishing a terminal left iliac colostomy, and closing the upper rectum to make a rectal bladder (Fig. 65.55c). This prevents the urine refluxing retrogradely round the colon to the caecum. diminishes reabsorption (see below) and protects renal function. Cancer can develop at long­standing ureterocolic junctions (Fig. 65.57). More recent developments include the formation of a detubularised sigmoid segment that provides a low-pressure reservoir in continuity.

Stricture formation

Ureterosigmoidostomy was first used by Chaput (1894). Subsequent modifications included those made by Coffey and Grey Turner. In these methods, the ureters were cut obliquely and pulled into the gut by a stitch — the ends were not stitched to the gut wall. Stenosis was common. Nesbit, Cordonnier and Leadbetter all recognised that these strictures could be prevented by anastomosing mucosa to mucosa.

Reflux of urine and reabsorption of urinary solutes

Re flux of urine

High-pressure activity within a segment of gut can cause reflux of infected urine at high pressure to the kidneys. In the long term this can cause renal impairment.

Reabsorption of urinary solutes

  This depends upon the following factors: (1) the area of bowel which is exposed to urine; and (2) the length of rime for which the urine is in contact with the bowel epithelium.

The biochemical changes associated with urinary diversion are due to a combination of reabsorption of chloride and urea, and progressively diminishing tubular function as a result of chronically impaired tubular function due to pyelonephritis. Diarrhoea with loss of potassium-containing mucus may exacerbate the loss of potassium. The typical changes of a hypenchloraemic acidosis with potassium deple­tion occur frequently in patients with uneterosigmoid diversion. When severe, the patient develops loss of appetite, weakness, thirst and diarrhoea. Coma may ensue. Mild acidosis, unrecognised oven a long period, produces osteomalacia. Bone pain and even pathological fracture can occur. Renal impairment from pyelonephritis and reabsorption from the mucosa are seen less frequently after ileal or colonic conduit formation, continent urinary diversion or orthotopic bladder substitution. In particular, they are seen very infrequently except in patients with pre-existing renal impairment and unsatisfactory emptying of the urinary reservoir.

Treatment

Prevention. Patients should be instructed to empty the rectum or continent reservoir or neo-bladder 3-hourly by day. In cases of ureterosigmoidostomy where acidosis is present a rectal tube should be inserted at night to drain the urine continuously. The patient should take a mixture of potassium citrate and sodium bicarbonate t.d.s. (2 g of each, either as crystals or as tablets). Regular serum biochemical analyses, including calcium, are required.

Established hyperchloraemic acidosis is usually associated with marked dehydration and the mainstay of treatment is intravenous saline. The patient may be given small doses of sodium bicarbonate to half-correct the pH deficit if it is severe and additional intravenous potassium. This should be coupled with appropriate systemic antibiotic treatment.

Operative details

Bowel preparation is by means of 3 litres of balanced polyethylene glycol solution (Golytely or Kleanprep). The abdomen is opened by a lower midline incision. The patient is then placed in the Tnendelenberg position.

Ureterocolic anastomosis

The right ureter is sought at the pelvic brim and dissected towards its entry into the bladder. The ureter is divided and its distal stump ligated; the proximal end is trimmed obliquely and split for 1 cm. An incision 3 cm long is made in the anterior wall of the colon and the peritoneal and muscular coats are divided, but not the mucous membrane. An incision is made into the extreme lower end of the exposed mucous membrane and the full thickness of the ureteric wall is joined by interrupted 4/0 chromic catgut sutures to the mucosal opening. The incision in the outer coats of the bowel is approximated over the ureter. A drain is left down to the area. The left ureter is implanted into the colon above in a similar manner. A full-sized Foley’s catheter is inserted through the anus no further than the rectal ampulla and the balloon is inflated, which permits urine output to be measured.

Uretero-ileostomy (ileal loop conduit)

A coil of ileum, approximately 15—20 cm long and 30 cm from the ileocaecal valve, with its blood supply intact, is isolated. The left ureter is brought behind the mesorectum. The ureters may be joined to the ileum either end-to-side or end-to-end after anastomosing of the distal spatulated ureters to form a plate (Wallace). The ileal loop is tacked lightly to the peritoneum of the posterior abdominal wall at the level of the pelvic brim. The distal end of the coil is brought out through an incision at the site which had been identified before operation; a disc of skin and far is removed, a cruciate incision is made in the fascia and the muscle is split. The stoma is made about 2—3 cm long. It is evaginated initially by means of four sutures passing through the skin, the ileal loop as it passes through the opening, and the cut edge of the ileum (Fig. 65.57).

Bladder replacement

Over the past decade, various techniques have become available to form a near spherical urinary reservoir out of various lengths of bowel which are detubularised. These may consist of ileum, ileum and caecum on sigmoid colon. The ureters can then be reimplanted in these reservoirs in an antireflux manner and the reservoir can then be anastomosed to the membranous urethra in the male (Figs 65.20,65.21,65.22 and 65.23 and 65.53). These reservoirs usually need to be emptied by means of CISC. The results are good in selected younger men after radical cystectomy.

Continent urinary diversion

A similar concept is used in the construction of continent diversions. A urinary reservoir is made as described above and the ureters are attached to the reservoir. A continence mechanism is then made to connect the reservoir to the skin. This is the complication prone part of the operation. The continence mechanism may be made of an invaginated loop of ileum supported by three rows of staples (Kock pouch) or made from the appendix buried in an antireflux manner in a submucosal tube (Mitrofanoff; Fig. 65.58) or a length of ileum can be made into a tube (of similar size to the appendix) after excision of the antimesenteric ileum and buried in a submucosal tunnel in an antireflux way. Clearly, these operations are complex, with the potential for increased postoperative complication.

Bladder substitution and augmentation

In patients with contraction of the bladder due to tuberculosis or with neuropathic dysfunction and a small bladder capacity, the bladder may need to be augmented. Similar techniques to those used to perform a bladder replacement can be utilised to make a near-spherical pouch from detubularised bowel which can then be attached to the tnigone or bladder neck after a near-total cystectomy (Figs 65.20,65.21,65.22 and 65.23). The ureters are then reimplanted. The facility to provide a continence mechanism must be available if needed in the neuropathic patient. This may comprise an artificial urinary sphincter on a colposuspension in the female.