Sunday, June 17, 2012

The Cohen procedure (step by step operations series)

The Cohen procedure (step by step operations series)

INDICATIONS

If the patient has recurrent breakthrough infections, or if there are signs of continued deterioration of the renal substance, radical treatment should be offered. Surgery consists of re-implanting the ureters into the bladder.

The aim of these treatments is to stop the VUR; this does not necessarily mean that the progression of renal damage is halted, or that further UTIs are prevented. In cases where the reflux has caused severe damage to the kidney (relative function <10%), a nephroureterectomy may be the best option. The choice between surgical or endoscopic correction of reflux is an individual matter, each technique having its protagonists.



Figure 1

The patient lies supine on the operating table; a small sheet placed under the sacrum is useful to flatten the abdomen. A right-handed surgeon should stand on the left side of the patient, with the scrub nurse on the left of the surgeon. The two assistants should stand on the right side of the patient. A transverse suprapubic incision is made, 2 cm above the pubic symphysis, in the lower abdominal crease.

Figure 2

The subcutaneous tissues are incised, exposing the rectus sheath, which is opened vertically in the midline (dotted line). Both recti are separated and the peritoneum gently pushed upwards.

Figure 3

A Dennis-Browne retractor is inserted. The lateral blades retract the recti and the upper and lower blades retract the skin and subcutaneous tissues.

Figure 4

The anterior wall of the bladder is incised vertically and two or three stay sutures placed on each side to expose the bladder. To expose the trigone, one or several swabs are put inside the bladder and retracted upwards with a Deaver retractor held by the second assistant. A 3/0 or 4/0 absorbable suture isplaced at the lowest point of the vesicotomy, to prevent splitting of the incision downwards into the bladder neck and the urethra.The blades of the Dennis-Browne retractor should not be placed within the bladder for three reasons: (i) retraction is vigorous and may damage the bladder; (ii) access to the laterovesical spaces may be difficult; and (iii) the bladder wall loses its natural mobility, rendering the procedure more difficult. It is essential to avoid rigid retraction and to maintain the natural suppleness of the tissues.The trigone is now well exposed and an infant-feeding tube (usually 4 F) is inserted into each ureter. A stay suture is placed around each ureteric orifice and tied over the feeding tube. The first assistant holds this staysuture with mild traction.

Figure 5

The ureteric orifice is circumcised with diathermy (cutting and coagulation current should be very low) and the distal 2 cm of ureter can be mobilised with diathermy alone (these 2 cm will be excised later).



Figure 6

It is essential to enter the correct plane between the bladder and the transparietal ureter, commencing below the orifice. Sharp scissors should be avoided and Reynolds scissors make this procedure much easier. The tip of the Reynolds scissors elevates the muscle fibres that attach the ureter to the bladder musculature. These fibres are grasped with fine forceps, coagulated and divided. The fibres should be coagulated some distance from the ureter, to avoid damaging its blood supply.




Figure 7

The dissection continues progressively, circumferentially until the ureter is completely freed.




Figure 8

The peritoneum is visible at the end of this dissection and should be teased away from the ureter. In boys the vas deferens may lie close to the ureter at this point, and care must be taken to avoid damaging it. A similar procedure can be used for the opposite ureter. 

In cases of ureteric duplication, both ureters are dissected together and should not be separated, thus avoiding damage to their blood supply.In some cases the ureteric hiatus is wide and should be narrowed by one or two absorbable sutures, to prevent the formation of a bladder diverticulum. These sutures should narrow the hiatus, but still allow the free movement of the ureter and not restrict or constrict it.



Figure 9

The submucosal tunnel is then formed; it is usually a horizontal tunnel, crossing the midline of the posterior surface of the bladder, just above the trigone.



Figure 10

The length of the submucosal tunnel should be at least five times the ureteric diameter (Paquin’s rule) and, if this cannot be fulfilled, modelling of the ureter should be considered. In this case, the calibre of the ureter may be reduced by excising a strip of ureter (Hendren’s technique



Figure 11

The calibre of the ureter may also be reduced by infolding the ureter (Kalicinski’s technique and the length of the modelled segment should not exceed the length of the submucosal tunnel.


Figure 12

The site of the new ureteric orifice is selected and the bladder mucosa lifted from the underlying bladder muscles with a pair of Reynolds scissors, starting either from the hiatus or from the new ureteric orifice. Again, sharp scissors should be avoided; Reynolds scissors are ideal because their tips are blunt. 
The tunnel should be wide enough to allow easy insertion of the ureter, with no constriction.

A similar procedure can be used for the opposite ureter in case of bilateral reimplantation. The construction of the lowest tunnel which crosses the trigone can cause slight bleeding, and lifting the mucosa 
is slightly less easy.A pair of artery forceps or a right-angle is inserted through the tunnel, the stay suture grasped and gently pulled to draw the ureter into place, taking care not to twist or kink it.

Figure 13

The last 2 cm of ureter is excised and the ureteric opening spatulated with a pair of angled Potts scissors.

Figures 14 and 15

The 5/0 absorbable suture anchors the ureter to the bladder muscles and the ureterovesicostomy is completed with interrupted 6/0 absorbable sutures.



Figure 16

For some surgeons, an infant feeding tube or JJ stent or ‘Blue Stent’ is inserted into the reimplanted ureter and exteriorized through the bladder wall, the rectus muscle and the skin, using the punch of a suprapubic 
catheter. The feeding tube is left in position for 2 days, or for 10 days if the ureter has been re-modelled.There is no consensus on the efficacy of drainage of the reimplanted ureter and some authors do not leave any drainage. The bladder is drained either by a transurethral catheter for 5 days or by a suprapubic catheter.

Figure 17

The bladder is closed with a 3/0 or 4/0 suture (interrupted or continuous). The pre-vesical and subcutaneous spaces are drained by a suction drain. The abdominal wall, the subcutaneous tissues and the skin are then 
closed.


POSTOPERATIVE CARE

The child is usually hospitalized for 5 days; the ureteric stent is removed after 2 days (or 10 days if the ureter has been re-modelled). The bladder catheter is removed at 5 days. Both suction drains are usually removed on the second day. Bladder spasms are common and oral oxybutynin can be useful to reduce the
discomfort.The type of antibiotic prophylaxis varies widely among surgical 
teams. Pain is controlled with diclofenac suppositories.
















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