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Memokath 051

New Procedures

4

The stent

Ureter strictures from a scar or a tumour

lead to blockage of the kidneys.This is

usually managed by either ureteric JJ stents

that need changing every few months, or

invasive reconstructive surgery.

As a minimally invasive but long-lasting

solution, the Memokath 051

TM

stent

has recently been introduced. It is a

thermo-expandable nickel-titanium alloy

spiral with a thermo-sensitive ‘shape

memory’ as it softens at < 10˚C but

returns to a pre-formed shape when

warmed to > 50˚C, allowing easy insertion

and removal. In addition, it has a closed

tight spiral structure which prevents

urothelial in-growth, and thus again

facilitates easy removal if required.This

is a significant advantage in comparison

with previously used metallic stents.

Insertion of the Memokath 051

TM

is,

in time and invasiveness, comparable

to the insertion of a JJ stent.The procedure

takes 20-50 minutes, patients leave the

hospital the day of the procedure and

most of them return to normal activities

within a few days.

Our experience

We treated 42 renal units in 38 patients

(20 females), mean age 55.7 years (23-84).

Strictures were benign in 29 and malignant

in 9 cases, and bilateral in 4.

There were no peri-operative complications.

The average hospital stay was 1.5 days.

The average indwelling time of an individual

Memokath was 8 months.The overall success

rate was 84%. After a mean follow-up

period of 17.5 months (1-44) there were

27 (65%) stents in situ. In 8 (19%) cases,

spontaneous resolution of the ureteric

stricture was revealed. 7 (16%) cases

were treatment failures, which were

managed with insertion of JJ stents

and/or open surgery. Causes included

stent encrustation and anterograde

or retrograde stent migration. In 6

(18%) patients, the Memokath had

to be exchanged at least once during

follow-up.

Can we afford it?

For the UK we developed a cost-

comparison model between JJ and

Memokath stent insertion which

showed that, in the first year, the

Memokath is ~ 400 GBP less expensive

than treatment with regular exchanges

of JJ stent. From the 2nd year after stent

insertion, the annual savings through

Memokath amount to ~ 4000 GBP.

Conclusions

Since this is a novel stent, there is

not much literature available as yet.

However, the data available correspond

nicely with our own experience as

outlined above.The Memokath 051

TM

stent seems to be an attractive cost-

effective treatment option for both

benign and malignant ureteric strictures.

Insertion, removal and/or exchange of

the Memokath 051

TM

stent is easy and

it can be easily removed in contrast

to previously used metallic stents. It

is well tolerated by patients, who do

not experience lower urinary tract

symptoms or loin pain.There is no

need for frequent replacement. From

our own experience, we discourage

its usage in active stone formers.

Interestingly, a 20% rate of spontaneous

stricture resolution could be related

with the insertion of the Memokath

stent, but further studies are warranted.

MR noor buchholz

Consultant Urological

Surgeon

Director of Endourology

& Stone Services, Barts

andThe London NHS Trust

UK – London EC1A 7BE

Tel: +44 (0) 20 7601 8394

Fax: +44 (0) 20 7601 7844

Email:

[email protected]

A novel long-term thermo-expandable ureteric metal stent

Fig 1: bilateral Memokath 051

TM

after

embolization and partial necrosis of

bladder

Fig 2: long right Memokath 051

TM

in idiopathic

stricture

Fig 3: short left Memokath 051

TM

in stricture after

uretero-vaginal fistula from previous hysterectomy

Benign strictures (29)

• Iatrogenic (post stone manipulation)

4

• Gynaecologic injury

3

Uretero-vaginal fistula

2

• Pelvic inflammatory disease (BIL)

1

• Retroperitoneal/para-aortic fibrosis

2

• Pelvic endometriosis

1

• Crohn’s disease

1

• Simple (idiopathic) strictures

12

in transplant kidney

1

• Vesico-ureteric anastomosis stricture

5

in transplant kidneys

4

Bilateral after re-implantation

1

• Single kidneys

3

• Bilateral strictures

4

Malignant strictures (9)

• Rectum CA

2

• Cervix CA

3

• Prostate CA

2

• Colon CA

1

• Breast CA (retroperitoneal

1

lymphadenopathy)

Table 1.

Causes of benign and malignant strictures