- Email: [email protected]
Mitrofanoff continent catheterizable conduits: Top down or bottom up?
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 2008 Available online 10 December 2008
KEYWORDS Bladder exstrophy; Urinary bladder calculi; Bladder catheterization
Abstract Objective: During augmentation and Mitrofanoff procedures, conduits are usually implanted into the posterior bladder wall. Anatomical considerations may necessitate an anterior conduit. To compare the relative drainage efficiency in patients with posterior and anterior 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 underwent augmentation and Mitrofanoff between 1991 and 2003. Patients with 3 years or greater follow-up were included. Fifty-four patients fit this criterion, with a conduit implanted anteriorly (33) or posteriorly (21). We compared rates of bladder stone formation and UTI. Stomal revisions and the status of the bladder neck were also noted. Results: Stone formation and UTI rates were higher in the anterior conduits, although only UTI showed a statistically significant difference. Patient demographics were similar between the two groups, including age and sex. The rates of stomal complications and the bladder neck status were also similar. Conclusions: Patients with anterior conduits had an increased risk of UTI and bladder stone formation compared to those with posterior conduits, although this was not significant in the case of bladder stone rate. This may indicate sub-optimal bladder drainage and should be addressed with careful preoperative counseling and close follow-up. ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction
* Correspondence to: Yegappan Lakshmanan, Children’s Hospital of Michigan, Department of Pediatric Urology, 3901 Beaubien Boulevard, Detroit, MI 48201, USA. Tel.: þ1 313 745 5588; fax: þ1 313 993 8738. E-mail address: [email protected] (Y. Lakshmanan).
The Mitrofanoff principle has revolutionized urinary tract reconstruction in both the adult and pediatric patient. First described in 1980 [1], it has been used in a wide variety of bladder diseases including spina bifida, pelvic malignancy, neuropathic bladder and the exstrophyeepispadias complex. The Mitrofanoff principle involves using the appendix or tapered enteric segment to drain the bladder
1477-5131/$34 ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2008.11.003
Mitrofanoff continent catheterizable conduits via a cutaneous stoma. The conduit is typically sewn into the posterior wall of the bladder. Since then, others have described modifications of this technique to fit unique patient populations and situations. Keating et al. [2] was the first to report a series describing a ‘seromuscular trough’ technique which can be used in cases where adequate backing is not available to create the flap valve continence mechanism in the native bladder. It involves implanting the conduit into a seromuscular trough anteriorly along the augmented portion of bladder. This technique was later dubbed a ‘serosal hammock’. Another anteriorly placed modification includes implantation into the tenia of the colonic segment used for augmentation. Complications of enterocystoplasty are well-known and have been described previously. They are mainly related to poor emptying [3] and include UTI, bladder stone formation, stomal problems, metabolic complications and renal damage. The ability to easily catheterize and efficiently drain the bladder with each attempt can decrease the rate of the aforementioned complications. We hypothesized that anteriorly placed conduits are less efficient at bladder drainage due to the effects of gravity and their position at the top of the augmented bladder. We examined patients with the exstrophyeepispadias complex who underwent bladder augmentation and Mitrofanoff procedure at our institution and compared the drainage efficiency between the anterior and posterior conduits using UTI and bladder stone formation as indicators of poor bladder emptying.
Patients/methods An Institutional Review Board approved retrospective chart review identified exstrophy patients who underwent surgery for augmentation and Mitrofanoff conduits between 1991 and 2003. Only patients with 3 years or greater continuous follow-up at our institution were included. Fifty-four patients fit this criterion, with a conduit implanted anteriorly (33) or posteriorly (21). We compared rates of bladder stone formation and UTI between these groups. In addition, stomal revisions and the status of the bladder neck were noted. Indications for surgery were those patients who had poorly growing bladders with small capacity, poor sphincteric function and refractory incontinence. Patients with spina bifida and cloacal exstrophy were excluded as their coexistent anatomical problems and decreased mobility put them at a higher baseline risk for stone formation. The stoma is placed at the neo-umbilicus. The postoperative
Table 1
123 bladder irrigation protocol at our institution begins on postoperative day 5 with 60 cc normal saline daily. This volume is increased by 60 cc every week until 240 cc is reached. Patients are monitored with renal and bladder ultrasound, pre- and post-void, every 3 months for the first year, and every 6 months thereafter. Bladder stones were diagnosed by ultrasound, CT scan or during cystoscopy, and were usually treated with percutaneous lithotripsy. UTI was diagnosed by patient complaints of foul smelling urine, fever, chills and nausea, with positive urine culture. Stomal complications were defined as patient complaints of difficulty or pain with catheterizing, inability to catheterize, and those requiring stomal revision either for stenosis at the skin level or deeper in the channel. When needed, bladder neck closure was performed at the time of bladder augmentation. P values for continuous variables were calculated using the Student t-test, and the Chi-square test was used for non-continuous variables. Statistical significance was considered 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 statistically significant difference. Except for two that were complicated UTIs requiring hospitalization, the majority of these infections were treated with oral antibiotics. Bladder stone rate was also higher in the anterior conduit group (48.4%), although this was not statistically significant (Table 1). Other patient demographics, including gender and patient age at the time of surgery, were similar between the two groups. Further, stomal complications and bladder neck status (open vs closed) were not statistically different between the groups. Most stomal complications were at the skin level and were resolved with minor revisions (Table 2). In the group with anteriorly placed conduits, 12 had small bowel augments while 21 had colonic augments. In the posterior group, 20 of 21 had small bowel augments. In the anterior group, of the 16 patients with stones, 10 had large bowel and six had small bowel augments. In the posterior group, of the six patients with stones, one had a large bowel augment and five had small bowel augments. For UTI rates, of the 12 patients that had UTIs in the anterior group, four had small bowel augments and eight had large bowel augments. In the posterior group, of the two patients with UTIs, both had small bowel augments.
Patient demographics and complication rates.
Total number Mean age (range) Male/female Bladder stones UTI Stomal complications Bladder neck: closed/open N/S Z not significant.
Anterior
Posterior
P Value
33 9.1 years (5e17) 24 (72.7%)/9 (27.2%) 16 (48.4%) 12 (36.3%) 14 (42.2%) 26 (78.8%)/7 (21.2%)
21 10 years (3e38) 14 (66.7%)/7 (33.3%) 6 (28.5%) 2 (9.5%) 10 (47.6%) 13 (61.9%)/8 (38.1%)
N/S N/S P Z 0.2 P < 0.01 N/S N/S
124 Table 2
J. Berkowitz et al. Complication details.
Stomal complications Patients needing multiple procedures for stomal complications Patients with stomal complications at skin level Average time to stomal complication Bladder stones Patients requiring multiple surgeries for treatment of stones
Anterior (33)
Posterior (21)
14 3/14 (21.4%)
10 4/10 (40%)
12/14 (85.7%) 3.8 years
9/10 (90%) 3.1 years
16 6 4/16 (25%) 0/6 (0%)
Discussion In the early 1980s, Mitrofanoff described the use of the appendix to create a catheterizable channel to empty the bladder. Later, this technique was applied to patients requiring bladder substitution or augmentation and has since become a mainstay for the reconstructive urologist. The surgery involves a low midline abdominal incision and mobilization of the terminal ileum, followed by a circumferential incision around the appendix including a cuff of cecum. The distal appendiceal tip is then opened and irrigated with bibiotic solution. With the bladder bi-valved, a 3-cm tunnel is measured along the posterior wall. The appendix is then placed in the tunnel and finally sewn into place. Because of body habitus, prior surgery or difficulty reaching the bladder, other urologists have modified this technique by attaching the appendix to serosa of small bowel (serosal hammock) or to colonic tenia. To make a serosal hammock, two parallel incisions are made through the serosa of augmented small bowel. The appendix is laid between them and then buried by sewing the lateral margins together, creating a ‘trough’. With large bowel augments, a similar technique is employed, implanting the appendix into a tenia. Once completed, the conduit can be seen in its position along the top of the augmented portion of the bladder (Fig. 1). To our knowledge, this is the first
Figure 1 Bladder augmentation with an anteriorly placed appendix at the top of the bladder.
study that characterizes the different techniques into ‘anteriorly’ and ‘posteriorly’ placed conduits, and compares the complication rates. In our cohort, we had a large number of anterior conduits, as these patients all had bladder exstrophy with multiple prior surgeries, making posterior placement difficult at times. This could represent a potential selection bias as those who had multiple prior surgeries and therefore received anteriorly placed conduits are at baseline higher risk for complications. The anterior group did have several more patients who had a history of failed reconstructions and multiple revisions. However, these patients did not necessarily go on to develop UTI and stones. Further, we attempted to control for this by examining the bladder neck status and stomal complication rate and found no statistically significant difference between the two groups. In fact, the posterior group had slightly more incidence of stomal issues (The anterior group did have more bladder neck closures.) Patients requiring bladder augmentation and catheterizable stoma are at risk for electrolyte abnormalities, UTI, bladder stones and stoma problems. Some of the increased risk of stone formation is assumed to be due to foreign bodies such as sutures or staples [4], and UTI, which may lead to struvite stone formation [5]. Others hypothesize that mucus acts as a nidus for calcium, facilitating bacterial growth and acting as a heterogeneous nucleator [6]. Regardless of the contribution of mucus to bacterial growth and stone formation, inefficient catheterization can lead to elevated residual urine volume in the augmented bladder. We hypothesize that anteriorly placed conduits are in fact less efficient at drainage, as evidenced by the trend towards higher UTI rates. This percentage is within the range of other published data on bladder augments. Bertschy et al. [7] reported on 28 children who had undergone bladder augmentation, and the UTI rate was 42%. Clark et al. [3] reported an infection rate ranging from 19% to 63%, depending on degree of patient compliance with the catheterizing regimen. We are currently monitoring pre- and post-catheterization residual urine volume by ultrasound at each follow-up visit to ensure that patients are completely emptying each time. In our study, anterior conduits tended to have a higher bladder stone rate, although this was not statistically significant. In the anterior conduit group, a rate of 48.4% was noted, which is higher than in other published series. Duckett and Lotfi [8] in their report on the Children’s Hospital of Philadelphia experience noted a 32% bladder stone rate. In a prior study at our institution the stone rate was 26%, but included several patients with shorter followup [9]. In another study, one third of patients with augment had recurrent stones, and all who went on to develop stones had a history of recurrent UTI [10]. Again, these previous studies did not group patients by position of the conduit. Stomal problems may also lead to UTI and stones as the patient may not catheterize as often if there is pain or difficulty during catheterization. We examined the stomal complication rate in our patients, and there was no significant difference between the two groups. All of the patients with stomal complications needed operative revision in both groups. The vast majority of both groups only needed revision at skin level due to scar tissue (85.7% anterior group and 90% posterior group.) Several needed
Mitrofanoff continent catheterizable conduits more than one revision, with one patient requiring four revisions (Table 2). The stomal complication rates of 42.2% and 47.6% for the anteriorly and posteriorly placed conduits respectively are within the reported ranges. One study quoted a range of 10e56% risk of stomal problems depending on degree of patient compliance [3]. Another factor that may contribute to UTI and stone formation is the bladder neck status, as those who had a bladder neck closure are unable to drain the dependent urine at the trigone via the urethra. Patients with the bladder exstrophyeepispadias complex often require bladder neck closure at the time of augmentation if there is significant urine leak or incontinence from an attenuated or fixed bladder neck, especially after previously failed attempts at continence procedures. Those with the bladder neck left open may drain small amounts of dependent urine via urethra and may have less risk of UTI and stone formation. We examined this in our study and there was no statistically significant difference in the number of bladder neck closures between the two groups. One study confirmed that among all types of bladder reconstruction the risk of stone formation is greatest in patients who require bladder augment, stoma placement and bladder neck procedure [11]. It is notable that 62%e79% of the patients in our study had bladder neck closure at the time of their augments, indicating a high-risk population. A potential for reporting bias exists in our study, as patients with asymptomatic bladder stones may be under diagnosed. However, the range of follow-up was 3e13 years, with a median of 7 years, so most had long enough follow-up to detect such stones. Further, in reviewing the data for our study, patients were found to form stones well before the second postoperative year. Lastly, one study quotes a mean interval to stone formation in augmented bladders of 24 months [12]. A geographic bias exists as patients may have presented to their local urologist for treatment of UTI and stones and not reported these problems to the urologists at our institution. As well, patient non-compliance with catheterization is difficult to assess, especially in a pediatric population, and may contribute to UTI and stone rate despite efficient bladder drainage. The type of intestinal segment used for augmentation could play a role in the differences seen. However, in at least one study, stones have been found to develop with similar frequency in all types of bowel except stomach [11].
Conclusion By highlighting the increased risks of stone formation and UTI in this patient population, this knowledge may be used
125 in preoperative counseling, postoperative care, as well as lifelong vigilance including daily irrigations and frequent bladder emptying. This may go a long way towards reducing the morbidity associated with bladder augmentation surgery, including hospitalization due to complicated UTIs as well as minimizing the invasive procedures needed to eradicate bladder stones.
Conflict of interest statement All authors report no conflict of interest in performing this research. There is no involvement of study sponsors in this work. This work was approved by our institution’s I.R.B. (Institutional Review Board).
References [1] Mitrofanoff P. Cystostomie continente trans-appendiculaire dans le traitement des vessies neurologiques. Chir Pediatr 1980;21:297. [2] Keating MA, Kropp BP, Adams MC, Patil UB, Rink RC. Seromuscular trough modification in construction of continent urinary stomas. J Urol 1993;150:734e6. [3] Clark T, Pope JC, Adams MC, Wells N, Brock JW. Factors that influence outcomes of the Mitrofanoff and Malone antegrade continence enema reconstructive procedures in children. J Urol 2002;168:1537e40. [4] McDougal WS. Metabolic complications of urinary intestinal diversion. J Urol 1992;147:1199e208. [5] Mathoera RB, Kok DJ, Nijman RJM. Bladder calculi in augmentation cystoplasty in children. Urology 2000;56: 482e7. [6] Khoury AE, Salomon M, Doche R, Soboh F, Ackerley C, Jayanthi R, et al. Stone formation after augmentation cystoplasty: the role of intestinal mucus. J Urol 1997;158: 1133e7. [7] Bertschy C, Bawab F, Liard A, Valioulis I, Mitrofanoff P. Enterocystoplasty complications in children: a study of 30 cases. Eur J Pediatr Surg 2000;10:30e4. [8] Duckett JW, Lotfi A. Appendicovesicostomy (and variations) in bladder reconstruction. J Urol 1993;149:567e9. [9] Surer I, Ferrer FA, Baker LA, Gearhart JP. Continent urinary diversion and the exstrophyeepispadias complex. J Urol 2003; 169:1102e5. [10] DeFoor W, Minevich E, Reddy P, Sekhon D, Polsky E, Wacksman J, et al. Bladder calculi after augmentation cystoplasty: risk factors and prevention strategies. J Urol 2004; 172:1964e6. [11] Kronner KM, Casale AJ, Cain MP, Zerin MJ, Keating MA, Rink RC. Bladder calculi in the pediatric augmented bladder. J Urol 1998;160:1096e8. [12] Blyth B, Ewalt DH, Duckett JW, Snyder HM. Lithogenic properties of enterocystoplasty. J Urol 1992;148:575e7.
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 2008 Available online 10 December 2008
KEYWORDS Bladder exstrophy; Urinary bladder calculi; Bladder catheterization
Abstract Objective: During augmentation and Mitrofanoff procedures, conduits are usually implanted into the posterior bladder wall. Anatomical considerations may necessitate an anterior conduit. To compare the relative drainage efficiency in patients with posterior and anterior 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 underwent augmentation and Mitrofanoff between 1991 and 2003. Patients with 3 years or greater follow-up were included. Fifty-four patients fit this criterion, with a conduit implanted anteriorly (33) or posteriorly (21). We compared rates of bladder stone formation and UTI. Stomal revisions and the status of the bladder neck were also noted. Results: Stone formation and UTI rates were higher in the anterior conduits, although only UTI showed a statistically significant difference. Patient demographics were similar between the two groups, including age and sex. The rates of stomal complications and the bladder neck status were also similar. Conclusions: Patients with anterior conduits had an increased risk of UTI and bladder stone formation compared to those with posterior conduits, although this was not significant in the case of bladder stone rate. This may indicate sub-optimal bladder drainage and should be addressed with careful preoperative counseling and close follow-up. ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction
* Correspondence to: Yegappan Lakshmanan, Children’s Hospital of Michigan, Department of Pediatric Urology, 3901 Beaubien Boulevard, Detroit, MI 48201, USA. Tel.: þ1 313 745 5588; fax: þ1 313 993 8738. E-mail address: [email protected] (Y. Lakshmanan).
The Mitrofanoff principle has revolutionized urinary tract reconstruction in both the adult and pediatric patient. First described in 1980 [1], it has been used in a wide variety of bladder diseases including spina bifida, pelvic malignancy, neuropathic bladder and the exstrophyeepispadias complex. The Mitrofanoff principle involves using the appendix or tapered enteric segment to drain the bladder
1477-5131/$34 ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2008.11.003
Mitrofanoff continent catheterizable conduits via a cutaneous stoma. The conduit is typically sewn into the posterior wall of the bladder. Since then, others have described modifications of this technique to fit unique patient populations and situations. Keating et al. [2] was the first to report a series describing a ‘seromuscular trough’ technique which can be used in cases where adequate backing is not available to create the flap valve continence mechanism in the native bladder. It involves implanting the conduit into a seromuscular trough anteriorly along the augmented portion of bladder. This technique was later dubbed a ‘serosal hammock’. Another anteriorly placed modification includes implantation into the tenia of the colonic segment used for augmentation. Complications of enterocystoplasty are well-known and have been described previously. They are mainly related to poor emptying [3] and include UTI, bladder stone formation, stomal problems, metabolic complications and renal damage. The ability to easily catheterize and efficiently drain the bladder with each attempt can decrease the rate of the aforementioned complications. We hypothesized that anteriorly placed conduits are less efficient at bladder drainage due to the effects of gravity and their position at the top of the augmented bladder. We examined patients with the exstrophyeepispadias complex who underwent bladder augmentation and Mitrofanoff procedure at our institution and compared the drainage efficiency between the anterior and posterior conduits using UTI and bladder stone formation as indicators of poor bladder emptying.
Patients/methods An Institutional Review Board approved retrospective chart review identified exstrophy patients who underwent surgery for augmentation and Mitrofanoff conduits between 1991 and 2003. Only patients with 3 years or greater continuous follow-up at our institution were included. Fifty-four patients fit this criterion, with a conduit implanted anteriorly (33) or posteriorly (21). We compared rates of bladder stone formation and UTI between these groups. In addition, stomal revisions and the status of the bladder neck were noted. Indications for surgery were those patients who had poorly growing bladders with small capacity, poor sphincteric function and refractory incontinence. Patients with spina bifida and cloacal exstrophy were excluded as their coexistent anatomical problems and decreased mobility put them at a higher baseline risk for stone formation. The stoma is placed at the neo-umbilicus. The postoperative
Table 1
123 bladder irrigation protocol at our institution begins on postoperative day 5 with 60 cc normal saline daily. This volume is increased by 60 cc every week until 240 cc is reached. Patients are monitored with renal and bladder ultrasound, pre- and post-void, every 3 months for the first year, and every 6 months thereafter. Bladder stones were diagnosed by ultrasound, CT scan or during cystoscopy, and were usually treated with percutaneous lithotripsy. UTI was diagnosed by patient complaints of foul smelling urine, fever, chills and nausea, with positive urine culture. Stomal complications were defined as patient complaints of difficulty or pain with catheterizing, inability to catheterize, and those requiring stomal revision either for stenosis at the skin level or deeper in the channel. When needed, bladder neck closure was performed at the time of bladder augmentation. P values for continuous variables were calculated using the Student t-test, and the Chi-square test was used for non-continuous variables. Statistical significance was considered 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 statistically significant difference. Except for two that were complicated UTIs requiring hospitalization, the majority of these infections were treated with oral antibiotics. Bladder stone rate was also higher in the anterior conduit group (48.4%), although this was not statistically significant (Table 1). Other patient demographics, including gender and patient age at the time of surgery, were similar between the two groups. Further, stomal complications and bladder neck status (open vs closed) were not statistically different between the groups. Most stomal complications were at the skin level and were resolved with minor revisions (Table 2). In the group with anteriorly placed conduits, 12 had small bowel augments while 21 had colonic augments. In the posterior group, 20 of 21 had small bowel augments. In the anterior group, of the 16 patients with stones, 10 had large bowel and six had small bowel augments. In the posterior group, of the six patients with stones, one had a large bowel augment and five had small bowel augments. For UTI rates, of the 12 patients that had UTIs in the anterior group, four had small bowel augments and eight had large bowel augments. In the posterior group, of the two patients with UTIs, both had small bowel augments.
Patient demographics and complication rates.
Total number Mean age (range) Male/female Bladder stones UTI Stomal complications Bladder neck: closed/open N/S Z not significant.
Anterior
Posterior
P Value
33 9.1 years (5e17) 24 (72.7%)/9 (27.2%) 16 (48.4%) 12 (36.3%) 14 (42.2%) 26 (78.8%)/7 (21.2%)
21 10 years (3e38) 14 (66.7%)/7 (33.3%) 6 (28.5%) 2 (9.5%) 10 (47.6%) 13 (61.9%)/8 (38.1%)
N/S N/S P Z 0.2 P < 0.01 N/S N/S
124 Table 2
J. Berkowitz et al. Complication details.
Stomal complications Patients needing multiple procedures for stomal complications Patients with stomal complications at skin level Average time to stomal complication Bladder stones Patients requiring multiple surgeries for treatment of stones
Anterior (33)
Posterior (21)
14 3/14 (21.4%)
10 4/10 (40%)
12/14 (85.7%) 3.8 years
9/10 (90%) 3.1 years
16 6 4/16 (25%) 0/6 (0%)
Discussion In the early 1980s, Mitrofanoff described the use of the appendix to create a catheterizable channel to empty the bladder. Later, this technique was applied to patients requiring bladder substitution or augmentation and has since become a mainstay for the reconstructive urologist. The surgery involves a low midline abdominal incision and mobilization of the terminal ileum, followed by a circumferential incision around the appendix including a cuff of cecum. The distal appendiceal tip is then opened and irrigated with bibiotic solution. With the bladder bi-valved, a 3-cm tunnel is measured along the posterior wall. The appendix is then placed in the tunnel and finally sewn into place. Because of body habitus, prior surgery or difficulty reaching the bladder, other urologists have modified this technique by attaching the appendix to serosa of small bowel (serosal hammock) or to colonic tenia. To make a serosal hammock, two parallel incisions are made through the serosa of augmented small bowel. The appendix is laid between them and then buried by sewing the lateral margins together, creating a ‘trough’. With large bowel augments, a similar technique is employed, implanting the appendix into a tenia. Once completed, the conduit can be seen in its position along the top of the augmented portion of the bladder (Fig. 1). To our knowledge, this is the first
Figure 1 Bladder augmentation with an anteriorly placed appendix at the top of the bladder.
study that characterizes the different techniques into ‘anteriorly’ and ‘posteriorly’ placed conduits, and compares the complication rates. In our cohort, we had a large number of anterior conduits, as these patients all had bladder exstrophy with multiple prior surgeries, making posterior placement difficult at times. This could represent a potential selection bias as those who had multiple prior surgeries and therefore received anteriorly placed conduits are at baseline higher risk for complications. The anterior group did have several more patients who had a history of failed reconstructions and multiple revisions. However, these patients did not necessarily go on to develop UTI and stones. Further, we attempted to control for this by examining the bladder neck status and stomal complication rate and found no statistically significant difference between the two groups. In fact, the posterior group had slightly more incidence of stomal issues (The anterior group did have more bladder neck closures.) Patients requiring bladder augmentation and catheterizable stoma are at risk for electrolyte abnormalities, UTI, bladder stones and stoma problems. Some of the increased risk of stone formation is assumed to be due to foreign bodies such as sutures or staples [4], and UTI, which may lead to struvite stone formation [5]. Others hypothesize that mucus acts as a nidus for calcium, facilitating bacterial growth and acting as a heterogeneous nucleator [6]. Regardless of the contribution of mucus to bacterial growth and stone formation, inefficient catheterization can lead to elevated residual urine volume in the augmented bladder. We hypothesize that anteriorly placed conduits are in fact less efficient at drainage, as evidenced by the trend towards higher UTI rates. This percentage is within the range of other published data on bladder augments. Bertschy et al. [7] reported on 28 children who had undergone bladder augmentation, and the UTI rate was 42%. Clark et al. [3] reported an infection rate ranging from 19% to 63%, depending on degree of patient compliance with the catheterizing regimen. We are currently monitoring pre- and post-catheterization residual urine volume by ultrasound at each follow-up visit to ensure that patients are completely emptying each time. In our study, anterior conduits tended to have a higher bladder stone rate, although this was not statistically significant. In the anterior conduit group, a rate of 48.4% was noted, which is higher than in other published series. Duckett and Lotfi [8] in their report on the Children’s Hospital of Philadelphia experience noted a 32% bladder stone rate. In a prior study at our institution the stone rate was 26%, but included several patients with shorter followup [9]. In another study, one third of patients with augment had recurrent stones, and all who went on to develop stones had a history of recurrent UTI [10]. Again, these previous studies did not group patients by position of the conduit. Stomal problems may also lead to UTI and stones as the patient may not catheterize as often if there is pain or difficulty during catheterization. We examined the stomal complication rate in our patients, and there was no significant difference between the two groups. All of the patients with stomal complications needed operative revision in both groups. The vast majority of both groups only needed revision at skin level due to scar tissue (85.7% anterior group and 90% posterior group.) Several needed
Mitrofanoff continent catheterizable conduits more than one revision, with one patient requiring four revisions (Table 2). The stomal complication rates of 42.2% and 47.6% for the anteriorly and posteriorly placed conduits respectively are within the reported ranges. One study quoted a range of 10e56% risk of stomal problems depending on degree of patient compliance [3]. Another factor that may contribute to UTI and stone formation is the bladder neck status, as those who had a bladder neck closure are unable to drain the dependent urine at the trigone via the urethra. Patients with the bladder exstrophyeepispadias complex often require bladder neck closure at the time of augmentation if there is significant urine leak or incontinence from an attenuated or fixed bladder neck, especially after previously failed attempts at continence procedures. Those with the bladder neck left open may drain small amounts of dependent urine via urethra and may have less risk of UTI and stone formation. We examined this in our study and there was no statistically significant difference in the number of bladder neck closures between the two groups. One study confirmed that among all types of bladder reconstruction the risk of stone formation is greatest in patients who require bladder augment, stoma placement and bladder neck procedure [11]. It is notable that 62%e79% of the patients in our study had bladder neck closure at the time of their augments, indicating a high-risk population. A potential for reporting bias exists in our study, as patients with asymptomatic bladder stones may be under diagnosed. However, the range of follow-up was 3e13 years, with a median of 7 years, so most had long enough follow-up to detect such stones. Further, in reviewing the data for our study, patients were found to form stones well before the second postoperative year. Lastly, one study quotes a mean interval to stone formation in augmented bladders of 24 months [12]. A geographic bias exists as patients may have presented to their local urologist for treatment of UTI and stones and not reported these problems to the urologists at our institution. As well, patient non-compliance with catheterization is difficult to assess, especially in a pediatric population, and may contribute to UTI and stone rate despite efficient bladder drainage. The type of intestinal segment used for augmentation could play a role in the differences seen. However, in at least one study, stones have been found to develop with similar frequency in all types of bowel except stomach [11].
Conclusion By highlighting the increased risks of stone formation and UTI in this patient population, this knowledge may be used
125 in preoperative counseling, postoperative care, as well as lifelong vigilance including daily irrigations and frequent bladder emptying. This may go a long way towards reducing the morbidity associated with bladder augmentation surgery, including hospitalization due to complicated UTIs as well as minimizing the invasive procedures needed to eradicate bladder stones.
Conflict of interest statement All authors report no conflict of interest in performing this research. There is no involvement of study sponsors in this work. This work was approved by our institution’s I.R.B. (Institutional Review Board).
References [1] Mitrofanoff P. Cystostomie continente trans-appendiculaire dans le traitement des vessies neurologiques. Chir Pediatr 1980;21:297. [2] Keating MA, Kropp BP, Adams MC, Patil UB, Rink RC. Seromuscular trough modification in construction of continent urinary stomas. J Urol 1993;150:734e6. [3] Clark T, Pope JC, Adams MC, Wells N, Brock JW. Factors that influence outcomes of the Mitrofanoff and Malone antegrade continence enema reconstructive procedures in children. J Urol 2002;168:1537e40. [4] McDougal WS. Metabolic complications of urinary intestinal diversion. J Urol 1992;147:1199e208. [5] Mathoera RB, Kok DJ, Nijman RJM. Bladder calculi in augmentation cystoplasty in children. Urology 2000;56: 482e7. [6] Khoury AE, Salomon M, Doche R, Soboh F, Ackerley C, Jayanthi R, et al. Stone formation after augmentation cystoplasty: the role of intestinal mucus. J Urol 1997;158: 1133e7. [7] Bertschy C, Bawab F, Liard A, Valioulis I, Mitrofanoff P. Enterocystoplasty complications in children: a study of 30 cases. Eur J Pediatr Surg 2000;10:30e4. [8] Duckett JW, Lotfi A. Appendicovesicostomy (and variations) in bladder reconstruction. J Urol 1993;149:567e9. [9] Surer I, Ferrer FA, Baker LA, Gearhart JP. Continent urinary diversion and the exstrophyeepispadias complex. J Urol 2003; 169:1102e5. [10] DeFoor W, Minevich E, Reddy P, Sekhon D, Polsky E, Wacksman J, et al. Bladder calculi after augmentation cystoplasty: risk factors and prevention strategies. J Urol 2004; 172:1964e6. [11] Kronner KM, Casale AJ, Cain MP, Zerin MJ, Keating MA, Rink RC. Bladder calculi in the pediatric augmented bladder. J Urol 1998;160:1096e8. [12] Blyth B, Ewalt DH, Duckett JW, Snyder HM. Lithogenic properties of enterocystoplasty. J Urol 1992;148:575e7.