The Bladder Flap at Cesarean Section: A Randomized Controlled Trial
Condition: Cesarean Section
Study type: Interventional

Summary: 
      Cesarean section is now the most common major surgical procedure performed on women world
      wide. In the United States, approximately 1 in 4 deliveries is by this method. With the
      increasing numbers of cesarean sections, there is the need to utilized evidence based
      techniques to optimize outcomes and minimize complications.Creation of the bladder flap is an
      integral step of the standard cesarean section. The bladder flap is made by superficially
      incising and dissecting the peritoneal lining to separate the urinary bladder from the lower
      uterine segment. Started in the pre-antibiotic era, the rationale for the bladder flap was to
      enable the surgeon gain access to the lower uterine segment while minimizing injury to the
      bladder. Its subsequent closure was supposed to protect the peritoneal cavity from
      intrauterine infection. Since then, closure of the bladder flap has been demonstrated to be
      unnecessary and has been abandoned. The bladder flap however, continues to be performed
      without evidence of benefit.

      Evidence on the role of the bladder flap in cesarean section is very limited. In emergent
      cesarean sections where rapid delivery is the goal, the bladder flap is commonly omitted. A
      simplified method of cesarean section (Pelosi-type) including omission of the bladder among
      other modifications has been shown to be safe and cost saving. The single randomized trial on
      omission of the bladder flap as the only modification suggests short term benefits including
      shorter operating times, reduced blood loss and decreased postoperative analgesic
      requirements. This study has been criticized for evaluating only short term outcomes and
      including only primary cesarean sections. The paucity of evidence for or against this
      commonly utilized technique in cesarean section is the rationale for this study.

      The goal of this study is to employ a well designed randomized controlled clinical trial to
      evaluate the effects of omitting the bladder flap creation at cesarean section. We
      hypothesize that omission of the bladder flap in both primary and repeat cesarean sections
      will be associated with shorter operating time without a significant increase in
      intraoperative and postoperative complications.
    

Detailed description: 
      BACKGROUND

      Cesarean section is the most common major surgical procedure in women world wide. In the
      United States almost 25% of deliveries are by cesarean section and the rate continues to rise
      [1]. In performing this procedure, it is imperative that evidence based techniques are
      utilized to optimize outcomes and minimize complications. Recently, the case has been made
      for simplifying the procedure by eliminating unnecessary and potentially harmful steps [2].

      Rationale for the Bladder Flap Challenged: While the creation of the bladder flap has long
      been an integral part of the standard cesarean section, there is no evidence of benefit.
      Creation of the bladder flap at cesarean section dates back to the pre-antibiotic era of the
      19th century. One rationale was to enable the surgeon gain access to the lower uterine
      segment while minimizing injury to the bladder [3]. While some older case reports suggested
      inadequate bladder flap reflection as a risk factor for bladder injury, it has not been
      collaborated [4]. On the contrary, several studies have identified difficulty encountered
      while developing the bladder flap as a risk factor for bladder injury at cesarean section [5,
      6]. Although uncommon, creation of the bladder flap may also be associated with complications
      such as bladder flap hematoma and dysuria, sometimes requiring re-operation to drain the
      collection or release the bladder flap [7-11]. It has also been suggested that disruption of
      the autonomic innervations by creation of the bladder flap results in an increased incidence
      of urinary retention. In the long term, creation of the bladder flap may result in thick
      adhesions in the lower uterine segment that may lead to difficult subsequent cesarean
      delivery and bladder perforation [3].

      Another rationale for the creation and subsequent closure of the bladder flap was to protect
      the peritoneal cavity from intrauterine infection. With the use of antibiotics, closure of
      the bladder flap has been demonstrated to be unnecessary and associated with increased
      morbidity including febrile morbidity, adhesions and upward dislocation of the urinary
      bladder [12, 13]. This evidence resulted in abandonment of closure of the bladder flap at
      cesarean section. Yet its creation has remained part of standard practice.

      Limited Data on Role of Bladder Flap: Data on the role of the bladder flap in cesarean
      section is very limited. A simplified method of cesarean section (Pelosi-type) involving
      omission of the bladder among other modifications has been shown to be safe and cost saving
      [2]. Only one published study evaluated omission of the bladder flap as the only modification
      [14]. This single randomized trial compared omission of the bladder flap in 53 patients to
      the standard technique of cesarean section in 49 patients. The results showed significant
      short term benefits of omitting the bladder flap including a reduction in operating time,
      blood loss, postoperative pain and microhematuria.

      The value of this European study is limited by the exclusion of repeat cesarean sections,
      lack of medium and long-term outcome measures such as adhesions as well as homogeneity of the
      study population. It has also been argued that the time saved from omitting the bladder flap
      (an average of 5 minutes) is not clinically significant [15]. On the other hand, 5 minutes
      saved for each of the 1 million cesarean sections performed annually in the United States
      will result in 1 million minutes (16667 hours, 694 days) of operating room time saved. Of
      note, this study was not designed to evaluate the effect of omitting the bladder flap on
      major bladder injuries. As the authors rightly argued, the low incidence of major bladder
      injuries at cesarean section (0.14-0.31%) means that a very large samples size (>40,000)
      would be required to demonstrate a difference [5, 16]. Such a study may never be done. The
      study was also limited to primary cesarean sections. The absence of data on omission of the
      bladder flap at repeat cesarean sections is particularly noteworthy. It is in these cases
      that adhesions in the lower uterine segment make creation of the bladder flap difficult and
      time consuming, with the potential for complications.

      The only other report on the effects of omitting the bladder flap at cesarean section is a
      West African case series of 142 patients [17]. That data is of little value, given the
      absence of a comparison group and the unique study setting.

      Evidence needed for Practice: From the above, it appears that the wide spread use of the
      bladder flap at cesarean section is based more on anecdotal evidence and clinical impression
      than scientific evidence [3]. At present, it remains to be established if there is any
      advantage in dissecting the bladder from the lower uterine segment during cesarean section.
      The paucity of evidence for this commonly utilized technique in cesarean section calls for a
      well designed randomized trial to provide the much needed evidence to inform clinic practice.
      With the increasing numbers of cesarean deliveries, eliminating unnecessary and potentially
      harmful steps will reduce morbidity, improve outcomes and save costs.

      RESEARCH OBJECTIVES

      The goal of this study is to employ a well designed randomized controlled clinical trial to
      evaluate the effects of omitting the bladder flap creation at cesarean section. We
      hypothesize that omission of the bladder flap in both primary and repeat cesarean sections
      will be associated with shorter operating time without a significant increase in
      intraoperative and postoperative complications. Specifically, we propose:

      Aim 1: To evaluate short term effects of omitting the bladder flap including duration of
      surgery, blood loss, hematuria and immediate postoperative pain;

      Aim 2: To evaluate medium term effects of omitting the bladder flap such as persistent
      hematuria, dysuria, and ongoing requirement for pain control and

      Aim 3: To evaluate long term effects of omitting the bladder flap including adhesions and
      duration of a subsequent cesarean section.

      STUDY DESIGN AND METHODS

      Study Design: This will be a randomized controlled trial comparing the effects of omission of
      the bladder flap to the standard cesarean section technique. Enrolled patients will be
      stratified into primary and repeat cesarean sections and then randomized by a computer based
      program into 'bladder flap' and 'no bladder flap' groups.

      Recruitment: All eligible patients who are scheduled for cesarean sections from the Barnes
      Jewish and Center for Advanced Medicine OB/GYN clinics will be approached for consent to
      participate in the study. Patients will be given study information and the consent form to
      review at home. For unscheduled patients, consent will be sought once the decision has been
      made to perform a cesarean section. This will be limited to non-emergent indications, where
      consent can be obtained without interfering with patient care.

      Procedures: Before entering the operating room, the surgeon will open a sealed envelope
      containing the randomization number and the patient's allocation. The technique for cesarean
      section will be similar in each group, except for the omission or creation of the bladder
      flap. In the 'no bladder flap' group, a low-transverse uterine incision will be performed
      about 1cm above the vesicouterine peritoneal fold, without dissection and formation of a
      bladder flap [14]. Patients will undergo the procedure based on their allocation unless
      intraoperative findings as determined by the surgeon make the alternative procedure medically
      indicated. Demographic (e.g. age, race, socioeconomic status), obstetric (e.g. parity,
      gestational age, indication for cesarean section, cervical dilation at time of cesarean
      section, presence of chorioamnionitis, surgical complications) and neonatal (e.g. birth
      weight, Apgar score, cord pH) data will be abstracted from the patients chart.

      Follow up Study: We plan a follow up to this study aimed at evaluating long term effects of
      omitting the bladder flap. All enrolled patients who subsequently undergo a repeat cesarean
      section in our facility within 5 years will be assessed for the duration of the subsequent
      surgery and the amount of intraperitoneal adhesions. A previously published adhesion score
      system which includes location and degree of adhesions will be used [18]. The surgeon in the
      repeat cesarean section will be blinded to the initial allocation of the patient.

      Data Analysis: Analysis of the primary outcome and most other analyses will be performed
      separately within the primary and the repeat cesarean section groups as well as in the
      combined study population. Analyses will be based on intent to treat. Surgical time and
      secondary outcome such as blood loss will be compared across groups using unpaired t-tests.
      However, if blood loss is identified to be a skewed variable, it is possible that we will use
      Wilcoxon's test or alternatively, use the t-test following a log transformation of the data.
      If a significant variation is noted in individual surgeons' operating times, further analysis
      will adjust for this using the surgeon's operating time index, defined as operating time /
      mean surgeon's operating time. These analyses will be supplemented with multiple regression
      analyses that adjust for covariates that include the age of the mother, gestational age,
      indication for the cesarean section, and cervical dilation at the time of the surgery that
      are identified to be potential confounding variables. Secondary outcomes such as hematuria
      and whether pain medication is still required at 2-4 weeks will be analyzed using chi square
      tests, with logistic regression being employed to assess significance after adjusting for the
      relevant covariates listed above. A final set of linear and logistic regression analyses will
      include both primary and repeat cesarean sections and will evaluate the interaction between
      the use of the bladder flap and whether the surgery type is primary or repeat to see if the
      impact of the bladder flap is different in one subgroup as compared to the other. Analyses
      will be performed using Stata version 10 (Stata Corp., College Station, TX).

      Sample size considerations: Since the goal of this study is to evaluate the impact of the
      bladder flap separately in primary and repeat cesarean section patients, we provide separate
      power computations for these two groups. Based on a mean duration of 45 minutes(SD
      10minutes)for primary cesareans and an anticipated saving of 5 minutes from omitting the
      bladder flap, our target sample size will be 64 primary cesarean sections per group, to yield
      a statistical power of 0.8 for a two-sided test at the 0.05 level of significance. For the
      repeat cesarean sections we anticipate a larger time saving due to the impact of scar tissue.
      However, to be conservative, we assume a 5 minute time saving in this group as well. We
      incorporate an interim efficacy analysis into this group and, using the Obrien-Fleming
      stopping rule to adjust for type I error, we base our power computations on a nominal p-value
      of 0.047. With this nominal pvalue, the sample size requirement is 65 per group for a power
      of 0.8 to detect a 5-minute operative time difference for a two-sided test at the 0.05 level
      of significance. Thus, a total of 258 patients will be recruited (64 x 2 + 65 x 2).
    

Intervention name(s): Omission of Bladder Flap Creation
Intervention type(s): Procedure
Intervention description(s): Omission of bladder flap creation by making uterine incision 1 cm above the vesico-uterine reflection without incision and dissection of the bladder peritoneum.
Other intervention name(s): No Flap
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Cesarean Section; Bladder Flap; Operating time