Journal of Pediatric Urology (2009) 5, 122e125

Mitrofanoff continent catheterizable conduits:Top down or bottom up?

J. Berkowitz, A.C. North, R. Tripp, J.P. Gearhart, Y. Lakshmanan*

Division of Pediatric Urology, Brady Urological Institute, Johns Hopkins Medical Institutions, Baltimore, MD, USA

Received 4 June 2008; accepted 5 November 2008Available online 10 December 2008

KEYWORDSBladder exstrophy;Urinary bladder calculi;Bladder catheterization

* Correspondence to: Yegappan Lakof Michigan, Department of PediatBoulevard, Detroit, MI 48201, USAfax: þ1 313 993 8738.

E-mail address: ylaksh@gmail.com

1477-5131/$34 ª 2008 Journal of Peddoi:10.1016/j.jpurol.2008.11.003

Abstract Objective: During augmentation and Mitrofanoff procedures, conduits are usuallyimplanted into the posterior bladder wall. Anatomical considerations may necessitate ananterior conduit. To compare the relative drainage efficiency in patients with posterior andanterior conduits, we studied their rates of bladder stone formation and urinary tract infection(UTI).Materials and methods: A retrospective chart review identified exstrophy patients who under-went augmentation and Mitrofanoff between 1991 and 2003. Patients with 3 years or greaterfollow-up were included. Fifty-four patients fit this criterion, with a conduit implanted ante-riorly (33) or posteriorly (21). We compared rates of bladder stone formation and UTI. Stomalrevisions and the status of the bladder neck were also noted.Results: Stone formation and UTI rates were higher in the anterior conduits, although only UTIshowed a statistically significant difference. Patient demographics were similar between thetwo groups, including age and sex. The rates of stomal complications and the bladder neckstatus were also similar.Conclusions: Patients with anterior conduits had an increased risk of UTI and bladder stoneformation compared to those with posterior conduits, although this was not significant inthe case of bladder stone rate. This may indicate sub-optimal bladder drainage and shouldbe addressed with careful preoperative counseling and close follow-up.ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

shmanan, Children’s Hospitalric Urology, 3901 Beaubien. Tel.: þ1 313 745 5588;

(Y. Lakshmanan).

iatric Urology Company. Publishe

Introduction

The Mitrofanoff principle has revolutionized urinary tractreconstruction in both the adult and pediatric patient. Firstdescribed in 1980 [1], it has been used in a wide variety ofbladder diseases including spina bifida, pelvic malignancy,neuropathic bladder and the exstrophyeepispadiascomplex. The Mitrofanoff principle involves using theappendix or tapered enteric segment to drain the bladder

d by Elsevier Ltd. All rights reserved.

Mitrofanoff continent catheterizable conduits 123

via a cutaneous stoma. The conduit is typically sewn intothe posterior wall of the bladder. Since then, others havedescribed modifications of this technique to fit uniquepatient populations and situations. Keating et al. [2] wasthe first to report a series describing a ‘seromusculartrough’ technique which can be used in cases whereadequate backing is not available to create the flap valvecontinence mechanism in the native bladder. It involvesimplanting the conduit into a seromuscular trough anteri-orly along the augmented portion of bladder. This tech-nique was later dubbed a ‘serosal hammock’. Anotheranteriorly placed modification includes implantation intothe tenia of the colonic segment used for augmentation.

Complications of enterocystoplasty are well-known andhave been described previously. They are mainly related topoor emptying [3] and include UTI, bladder stone forma-tion, stomal problems, metabolic complications and renaldamage. The ability to easily catheterize and efficientlydrain the bladder with each attempt can decrease the rateof the aforementioned complications. We hypothesizedthat anteriorly placed conduits are less efficient at bladderdrainage due to the effects of gravity and their position atthe top of the augmented bladder. We examined patientswith the exstrophyeepispadias complex who underwentbladder augmentation and Mitrofanoff procedure at ourinstitution and compared the drainage efficiency betweenthe anterior and posterior conduits using UTI and bladderstone formation as indicators of poor bladder emptying.

Patients/methods

An Institutional Review Board approved retrospective chartreview identified exstrophy patients who underwent surgeryfor augmentation and Mitrofanoff conduits between 1991and 2003. Only patients with 3 years or greater continuousfollow-up at our institution were included. Fifty-fourpatients fit this criterion, with a conduit implanted anteri-orly (33) or posteriorly (21). We compared rates of bladderstone formation and UTI between these groups. In addition,stomal revisions and the status of the bladder neck werenoted. Indications for surgery were those patients who hadpoorly growing bladders with small capacity, poor sphinc-teric function and refractory incontinence. Patients withspina bifida and cloacal exstrophy were excluded as their co-existent anatomical problems and decreased mobility putthem at a higher baseline risk for stone formation. Thestoma is placed at the neo-umbilicus. The postoperative

Table 1 Patient demographics and complication rates.

Anterior

Total number 33Mean age (range) 9.1 years (5e17)Male/female 24 (72.7%)/9 (27.2%)Bladder stones 16 (48.4%)UTI 12 (36.3%)Stomal complications 14 (42.2%)Bladder neck: closed/open 26 (78.8%)/7 (21.2%)

N/S Z not significant.

bladder irrigation protocol at our institution begins onpostoperative day 5 with 60 cc normal saline daily. Thisvolume is increased by 60 cc every week until 240 cc isreached. Patients are monitored with renal and bladderultrasound, pre- and post-void, every 3 months for the firstyear, and every 6 months thereafter.

Bladder stones were diagnosed by ultrasound, CT scan orduring cystoscopy, and were usually treated with percuta-neous lithotripsy. UTI was diagnosed by patient complaintsof foul smelling urine, fever, chills and nausea, with posi-tive urine culture. Stomal complications were defined aspatient complaints of difficulty or pain with catheterizing,inability to catheterize, and those requiring stomal revisioneither for stenosis at the skin level or deeper in thechannel. When needed, bladder neck closure was per-formed at the time of bladder augmentation.

P values for continuous variables were calculated usingthe Student t-test, and the Chi-square test was used fornon-continuous variables. Statistical significance wasconsidered at P< 0.05.

Results

The rate of UTIs was higher in the anterior group (36.3%)compared to the posterior group (9.5%), with a statisticallysignificant difference. Except for two that were compli-cated UTIs requiring hospitalization, the majority of theseinfections were treated with oral antibiotics. Bladder stonerate was also higher in the anterior conduit group (48.4%),although this was not statistically significant (Table 1).Other patient demographics, including gender and patientage at the time of surgery, were similar between the twogroups. Further, stomal complications and bladder neckstatus (open vs closed) were not statistically differentbetween the groups. Most stomal complications were at theskin level and were resolved with minor revisions (Table 2).In the group with anteriorly placed conduits, 12 had smallbowel augments while 21 had colonic augments. In theposterior group, 20 of 21 had small bowel augments. In theanterior group, of the 16 patients with stones, 10 had largebowel and six had small bowel augments. In the posteriorgroup, of the six patients with stones, one had a largebowel augment and five had small bowel augments. For UTIrates, of the 12 patients that had UTIs in the anterior group,four had small bowel augments and eight had large bowelaugments. In the posterior group, of the two patients withUTIs, both had small bowel augments.

Posterior P Value

2110 years (3e38) N/S14 (66.7%)/7 (33.3%) N/S6 (28.5%) P Z 0.22 (9.5%) P< 0.0110 (47.6%) N/S13 (61.9%)/8 (38.1%) N/S

Table 2 Complication details.

Anterior(33)

Posterior(21)

Stomal complications 14 10Patients needing multiple

procedures for stomalcomplications

3/14(21.4%)

4/10 (40%)

Patients with stomalcomplications at skin level

12/14(85.7%)

9/10 (90%)

Average time to stomalcomplication

3.8 years 3.1 years

Bladder stones 16 6Patients requiring multiple

surgeries for treatment ofstones

4/16 (25%) 0/6 (0%)

124 J. Berkowitz et al.

Discussion

In the early 1980s, Mitrofanoff described the use of theappendix to create a catheterizable channel to empty thebladder. Later, this technique was applied to patientsrequiring bladder substitution or augmentation and hassince become a mainstay for the reconstructive urologist.The surgery involves a low midline abdominal incision andmobilization of the terminal ileum, followed by a circum-ferential incision around the appendix including a cuff ofcecum. The distal appendiceal tip is then opened and irri-gated with bibiotic solution. With the bladder bi-valved,a 3-cm tunnel is measured along the posterior wall. Theappendix is then placed in the tunnel and finally sewn intoplace. Because of body habitus, prior surgery or difficultyreaching the bladder, other urologists have modified thistechnique by attaching the appendix to serosa of smallbowel (serosal hammock) or to colonic tenia. To makea serosal hammock, two parallel incisions are made throughthe serosa of augmented small bowel. The appendix is laidbetween them and then buried by sewing the lateralmargins together, creating a ‘trough’. With large bowelaugments, a similar technique is employed, implanting theappendix into a tenia. Once completed, the conduit can beseen in its position along the top of the augmented portionof the bladder (Fig. 1). To our knowledge, this is the first

Figure 1 Bladder augmentation with an anteriorly placedappendix at the top of the bladder.

study that characterizes the different techniques into‘anteriorly’ and ‘posteriorly’ placed conduits, andcompares the complication rates. In our cohort, we hada large number of anterior conduits, as these patients allhad bladder exstrophy with multiple prior surgeries, makingposterior placement difficult at times. This could representa potential selection bias as those who had multiple priorsurgeries and therefore received anteriorly placed conduitsare at baseline higher risk for complications. The anteriorgroup did have several more patients who had a history offailed reconstructions and multiple revisions. However,these patients did not necessarily go on to develop UTI andstones. Further, we attempted to control for this byexamining the bladder neck status and stomal complicationrate and found no statistically significant differencebetween the two groups. In fact, the posterior group hadslightly more incidence of stomal issues (The anterior groupdid have more bladder neck closures.)

Patients requiring bladder augmentation and catheter-izable stoma are at risk for electrolyte abnormalities, UTI,bladder stones and stoma problems. Some of the increasedrisk of stone formation is assumed to be due to foreignbodies such as sutures or staples [4], and UTI, which maylead to struvite stone formation [5]. Others hypothesizethat mucus acts as a nidus for calcium, facilitating bacterialgrowth and acting as a heterogeneous nucleator [6].

Regardless of the contribution of mucus to bacterialgrowth and stone formation, inefficient catheterization canlead to elevated residual urine volume in the augmentedbladder. We hypothesize that anteriorly placed conduitsare in fact less efficient at drainage, as evidenced by thetrend towards higher UTI rates. This percentage is withinthe range of other published data on bladder augments.Bertschy et al. [7] reported on 28 children who hadundergone bladder augmentation, and the UTI rate was42%. Clark et al. [3] reported an infection rate ranging from19% to 63%, depending on degree of patient compliancewith the catheterizing regimen. We are currently moni-toring pre- and post-catheterization residual urine volumeby ultrasound at each follow-up visit to ensure that patientsare completely emptying each time.

In our study, anterior conduits tended to have a higherbladder stone rate, although this was not statisticallysignificant. In the anterior conduit group, a rate of 48.4% wasnoted, which is higher than in other published series.Duckett and Lotfi [8] in their report on the Children’sHospital of Philadelphia experience noted a 32% bladderstone rate. In a prior study at our institution the stone ratewas 26%, but included several patients with shorter follow-up [9]. In another study, one third of patients with augmenthad recurrent stones, and all who went on to develop stoneshad a history of recurrent UTI [10]. Again, these previousstudies did not group patients by position of the conduit.

Stomal problems may also lead to UTI and stones as thepatient may not catheterize as often if there is pain ordifficulty during catheterization. We examined the stomalcomplication rate in our patients, and there was no signif-icant difference between the two groups. All of thepatients with stomal complications needed operative revi-sion in both groups. The vast majority of both groups onlyneeded revision at skin level due to scar tissue (85.7%anterior group and 90% posterior group.) Several needed

Mitrofanoff continent catheterizable conduits 125

more than one revision, with one patient requiring fourrevisions (Table 2). The stomal complication rates of 42.2%and 47.6% for the anteriorly and posteriorly placed conduitsrespectively are within the reported ranges. One studyquoted a range of 10e56% risk of stomal problemsdepending on degree of patient compliance [3].

Another factor that may contribute to UTI and stoneformation is the bladder neck status, as those who hada bladder neck closure are unable to drain the dependenturine at the trigone via the urethra. Patients with thebladder exstrophyeepispadias complex often requirebladder neck closure at the time of augmentation if there issignificant urine leak or incontinence from an attenuated orfixed bladder neck, especially after previously failedattempts at continence procedures. Those with the bladderneck left open may drain small amounts of dependent urinevia urethra and may have less risk of UTI and stoneformation. We examined this in our study and there was nostatistically significant difference in the number of bladderneck closures between the two groups. One studyconfirmed that among all types of bladder reconstructionthe risk of stone formation is greatest in patients whorequire bladder augment, stoma placement and bladderneck procedure [11]. It is notable that 62%e79% of thepatients in our study had bladder neck closure at the timeof their augments, indicating a high-risk population.

A potential for reporting bias exists in our study, as patientswith asymptomatic bladder stones may be under diagnosed.However, the rangeof follow-up was3e13years,witha medianof 7 years, so most had long enough follow-up to detect suchstones. Further, in reviewing the data for our study, patientswere found to form stones well before the second post-operative year. Lastly, one study quotes a mean interval tostone formation in augmented bladders of 24 months [12].

A geographic bias exists as patients may have presentedto their local urologist for treatment of UTI and stones andnot reported these problems to the urologists at our insti-tution. As well, patient non-compliance with catheteriza-tion is difficult to assess, especially in a pediatricpopulation, and may contribute to UTI and stone ratedespite efficient bladder drainage.

The type of intestinal segment used for augmentationcould play a role in the differences seen. However, in atleast one study, stones have been found to develop withsimilar frequency in all types of bowel except stomach [11].

Conclusion

By highlighting the increased risks of stone formation andUTI in this patient population, this knowledge may be used

in preoperative counseling, postoperative care, as well aslifelong vigilance including daily irrigations and frequentbladder emptying. This may go a long way towards reducingthe morbidity associated with bladder augmentationsurgery, including hospitalization due to complicated UTIsas well as minimizing the invasive procedures needed toeradicate bladder stones.

Conflict of interest statement

All authors report no conflict of interest in performing thisresearch. There is no involvement of study sponsors in thiswork. This work was approved by our institution’s I.R.B.(Institutional Review Board).

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