Trendelenburg, Abdominal Insufflation and Time to Completion of Cystoscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trendelenburg, Abdominal Insufflation and Time to Completion of Cystoscopy (NCT05786391), a randomized na study. The primary outcome is Time in Seconds to Complete the Cystourethroscopy.

2. Clinical Question

The clinical question is whether patient position and abdominal insufflation are associated with the time needed to complete cystourethroscopy. The trial compares four combinations: flat position with no insufflation, Trendelenburg position with insufflation, flat position with insufflation, and Trendelenburg position with no insufflation. The registry describes the objective as comparing cystoscopy efficiency across the position and insufflation interventions.

The outcome is procedural duration rather than a measure of diagnostic accuracy or patient outcome. The posted results can describe completion times by arm, but interpretation of differences as evidence about position or insufflation requires a defined comparison and an analysis. Those analysis details are not reported in the registry record.

3. Trial Design

The registry describes a randomized, single-masked, parallel trial. Enrollment is listed as 122. The record marks the study as completed and gives a start date of 2023-04-11 and a primary completion date of 2024-02-05. The sponsor is The University of Texas Health Science Center, Houston. The phase is listed as NA.

Participants were assigned to one of four arm combinations: flat position with no insufflation; Trendelenburg position and insufflation; flat position and insufflation; or Trendelenburg position with no insufflation. The corresponding arm sizes are 31, 30, 30, and 31. The record does not identify which party was masked, describe how masking was maintained, or report the randomization sequence or allocation-concealment procedure. Those features should not be inferred from the label single-masked.

The primary outcome is time in seconds to complete cystourethroscopy. The outcome timeframe runs from the start of cystoscopy to its completion, described as about 4 minutes. The record reports a median and interquartile range for each arm. It does not list secondary outcome measures. Although the trial objective concerns both position and insufflation, the registry record does not specify a statistical model or a planned set of contrasts to separate those effects or assess their combination.

Enrollment and the reported arm sizes describe the trial record, but they do not by themselves establish which participants contributed to the endpoint analysis. The analysis population and handling of missing outcome data are not reported in the registry record. No inferential analysis results are posted, so the randomized design should not be mistaken for evidence that a particular contrast was statistically tested.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Time in Seconds to Complete the Cystourethroscopy, measured over From the start of the cystoscopy to the completion of the cystoscopy (about 4 minutes).

The primary endpoint is time in seconds to satisfactorily complete cystourethroscopy. The timing begins at the start of cystoscopy and ends at completion. Completion is defined by visualizing the bladder dome, ureteral jets, bladder mucosa, and urethra. The registry describes the timeframe as about 4 minutes.

Duration is used as a measure of procedural efficiency: it records how long the examination takes under each assigned combination of position and insufflation. It is distinct from whether the examination identifies a condition correctly, whether all relevant structures are adequately assessed, or whether a patient experiences a clinical benefit. The endpoint description specifies satisfactory completion, but does not provide a separate measure of visualization quality or diagnostic performance.

The registry reports the endpoint as a median with an interquartile range. The median describes the midpoint of the observed times when ordered from shorter to longer; the interquartile range describes the middle portion of their distribution. These summaries are useful when duration data are skewed or include unusually long observations, because they are less affected by extreme values than the mean and standard deviation. This is a general statistical explanation, not a claim about the actual shape of the trial’s duration data.

The posted arm summaries are: 103.0 seconds (65.0–184.0) for flat position with no insufflation; 117.0 seconds (50.0–223.0) for Trendelenburg position and insufflation; 147.0 seconds (71.0–208.0) for flat position and insufflation; and 82.0 seconds (71.0–136.0) for Trendelenburg position with no insufflation. These are descriptive summaries, not estimates of adjusted or unadjusted treatment effects.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a median and interquartile range for the primary endpoint in each randomized arm. These summaries describe the observed times rather than an estimated difference between arms. They are particularly interpretable when the aim is to present a typical duration and the spread of the central observations without assuming that times follow a symmetric distribution.

What does the median tell the reader?

In general, the median is the middle observation after measurements are ordered. It gives a measure of the center that is less sensitive than the mean to very short or very long values. It does not describe every participant’s time, and it does not indicate how much the arms differ in a way that accounts for sampling variability. The median values in this trial should therefore be read as arm-specific summaries, not as causal effects.

How should the interquartile range be read?

In general, the interquartile range runs from the twenty-fifth percentile to the seventy-fifth percentile and contains the middle half of observations. It conveys spread around the median, but it is not a confidence interval for the median. The registry gives the lower and upper values for each arm. Those endpoints do not show the full distribution, reveal whether observations are clustered, or quantify uncertainty in an arm-to-arm contrast.

Why are comparisons more than a visual difference between medians?

A formal comparison requires defining the estimand—the quantity the analysis is intended to estimate—and specifying a method suited to that quantity and the data. A difference between medians, a ratio of times, and a model-based contrast answer different questions. The registry record does not report the planned estimand, statistical model, hypothesis tests, or confidence intervals. No new contrast should be inferred from the descriptive arm values alone.

The trial includes combinations of position and insufflation. General statistical reasoning distinguishes comparisons of individual combinations from analyses that summarize a position effect across insufflation conditions or an insufflation effect across positions. An interaction analysis asks whether the association with one feature differs according to the other feature. Each requires a clearly defined contrast and analysis plan. The registry does not report which, if any, of these analyses was prespecified or conducted.

What does randomization contribute?

In general, random assignment can help balance measured and unmeasured baseline characteristics across groups, on average, when allocation is implemented as intended. It does not guarantee identical groups in a particular trial, remove the need to account for chance variation, or establish that every randomized participant appears in the reported endpoint summaries. The record identifies the design as randomized but does not report sequence generation, concealment details, baseline characteristics, adherence, or analysis-population rules.

Randomization supports causal interpretation when the design, conduct, outcome measurement, and analysis align with the question. Here, the record gives arm-level endpoint summaries but no analysis results. Consequently, randomization should be treated as a design feature, not as a substitute for an estimated contrast and its uncertainty.

Why does the endpoint’s distribution matter?

In general, procedural times can be asymmetric, and unusually long durations can influence averages. Median and interquartile range summaries avoid some sensitivity to extreme observations. A formal analysis still needs to account appropriately for the outcome’s distribution and the target comparison. Over-dispersion matters in general when a model assumes less variability than the data contain: standard errors can then be too small and uncertainty understated. The registry does not report a distributional assessment or model, so there is no basis to say whether over-dispersion was present or how it was handled in this trial.

Different analysis choices can produce different estimands. A model for mean duration does not necessarily estimate the same quantity as a comparison of medians. Adjustments for prognostic factors may also alter an estimate, but the covariates and adjustment strategy are not reported. The arm summaries should not be relabeled as adjusted results.

What can be inferred from the absence of analysis results?

The registry lists no analysis results. Therefore, it does not provide a test of whether the observed arm summaries are compatible with a common underlying distribution, nor does it provide an uncertainty interval for an effect. A p-value, in general, evaluates the compatibility of data with a specified null model; it does not measure the size or clinical importance of an effect. Since no p-value is reported, no significance conclusion can be drawn. A confidence interval, in general, communicates the precision of an estimate under its assumptions; no contrast interval is reported either.

The record’s planning description states that sample-size illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence that the original trial used them. Such illustrations are not observed power, and they do not show that the trial was designed around a particular contrast. The registry does not report the trial’s own sample-size justification. No numeric planning estimate is interpreted because the record does not state one in the trial details.

Overall, the methodological information supports a descriptive reading of the reported medians and interquartile ranges. It does not support reconstructing a statistical analysis, choosing an unreported contrast, or supplying an uncertainty estimate that the registry does not report.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and no secondary outcome measures. It does not report an analysis plan, hypothesis-testing sequence, or method for controlling multiplicity. Because the question involves position and insufflation across several combinations, more than one contrast could be considered. In general, testing multiple contrasts can increase the chance of at least one false-positive result if no multiplicity strategy is used. The registry record does not say which contrasts were planned or how any multiplicity issue was addressed. No claim about an unadjusted or adjusted significance result is possible because no inferential results are reported.

Missing outcome data and the analysis population are also not described. The endpoint’s population field is blank, and the record does not specify whether the analysis included all randomized participants, only participants with observed completion times, or another set. It does not report the amount or pattern of missingness, reasons for missing values, imputation, or sensitivity analyses. These details matter because missingness can affect estimates if the likelihood of an unobserved duration is related to treatment assignment or outcome.

In general, an intention-to-treat analysis retains participants in their randomized groups, while a per-protocol analysis applies additional criteria related to adherence. The registry does not identify either approach. The reported arm sizes should not be treated as confirmation of the endpoint analysis denominators or of complete outcome ascertainment. Without reporting on missing data and analysis populations, the extent to which the descriptive results represent all randomized participants is not known from the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports no serious adverse events in any arm: 0 among 31 participants in flat position with no insufflation; 0 among 30 in Trendelenburg position and insufflation; 0 among 30 in flat position and insufflation; and 0 among 31 in Trendelenburg position with no insufflation. Deaths are reported as 0 in each arm.

Other adverse events are reported as 1 among 31 participants in flat position with no insufflation, 2 among 30 in Trendelenburg position and insufflation, 1 among 30 in flat position and insufflation, and 0 among 31 in Trendelenburg position with no insufflation. These are the registry’s group counts; they are not evidence by themselves that an event was caused by an assigned position or insufflation condition. The record does not provide serious adverse event terms, and it does not identify the other adverse events in the registry record reported for this outcome.

A zero count means that no event in that category was recorded in the listed group for the registry results. It does not prove that the underlying risk is zero, and it does not establish that risks are equivalent between groups. Event counts are limited by the size and follow-up represented in the record. The registry does not report a comparative safety analysis or additional context for interpreting the other adverse events, so these counts should be read descriptively.

12. What the Result Does, and Does Not, Mean

The posted results establish that the registry contains arm-specific summaries of cystoscopy completion time and adverse events for a randomized, parallel trial. The primary endpoint is clearly described as time from the start to satisfactory completion of cystourethroscopy. Median times range across the reported arm summaries, with accompanying interquartile ranges. The registry also records the serious and other adverse event counts for each group.

Those observations do not establish that one position or insufflation condition makes cystoscopy faster. A difference between observed medians can reflect treatment-related effects, chance variation, or other features of the trial and its measurements. Without a defined contrast and inferential analysis, the record does not quantify the magnitude or precision of a between-arm effect. It also does not establish that the four combinations are equivalent.

The trial’s objective concerns procedural efficiency, but time is only one dimension of an examination. The endpoint definition includes visualization of specified structures, yet the registry does not report a separate visualization-quality outcome or diagnostic accuracy measure. The reported times therefore should not be interpreted as proof that examination quality, patient outcomes, or clinical decisions differ.

The absence of serious adverse events in the listed results is reassuring only as a description of recorded events in the groups; it is not proof of no risk. The small arm-level event counts and absence of a reported comparative safety analysis limit conclusions about relative safety. The record also does not report the population details, missing-data handling, or analysis plan needed to judge the scope of the results fully.

In short, the record documents a completed randomized comparison and descriptive outcome data. It does not report a statistical test, uncertainty interval, or sponsor analysis for the time outcome. The evidence available in the registry therefore supports description of observed times and events, not a definitive causal conclusion about which procedural combination should be preferred.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its research question involves two procedural features—position and abdominal insufflation—while the endpoint is a continuous duration measure. The four reported combinations make clear that the interpretation depends on which contrast is being asked. Comparing two specific combinations is not the same as estimating an average position effect, an average insufflation effect, or whether those features interact. Statistical conclusions depend on defining that target in advance.

Completion time is also a useful example of an outcome for which the center and spread need careful description. The registry reports medians and interquartile ranges rather than means and standard deviations. This choice presents the typical duration and central spread without implying that the values follow a symmetric distribution. It also gives readers a reminder that an arm’s median is not an estimate of the difference between arms and that an interquartile range is not an uncertainty interval for that difference.

The randomized design is relevant, but design labels alone do not complete the statistical argument. A reader also needs the analysis population, missing-data approach, planned contrasts, model, and uncertainty estimates to assess what the data support. These details are not reported in the registry record. The distinction between descriptive results and inferential evidence is therefore especially important for this trial.

The trial also illustrates why safety counts should be interpreted separately from the procedural-time endpoint. Zero recorded serious adverse events is a descriptive finding, not a guarantee of no risk or a formal demonstration of equivalent safety. With no comparative safety analysis reported, the event counts have a limited role in assessing differences between conditions.

For biostatisticians and clinical researchers, the central lesson is that a clearly stated endpoint and randomized allocation still need an explicit estimand and transparent analysis reporting. The arm summaries are informative as observations, but not a replacement for the planned comparison and its precision.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several trial-specific uncertainties. It does not report eligibility criteria or a detailed participant population, so the setting and scope of applicability cannot be assessed from the record. Although the endpoint is described as satisfactory visualization of specified structures, no separate visualization-quality result is reported. The registry also does not provide an analysis population, a missing-data account, or the reasons that any endpoint values might be unavailable.

The single-masked designation is not accompanied by a description of who was masked or how masking was maintained. The record does not describe randomization sequence generation or allocation concealment. These omissions do not show that procedures were inadequate; they mean the registry does not supply enough detail to evaluate them.

No statistical analysis results are posted. In particular, no arm contrast, p-value, confidence interval, adjusted estimate, or statistical model is reported. The intended comparisons among position and insufflation conditions are not specified, and no approach to multiplicity is described. Thus, the descriptive medians cannot be turned into a formal conclusion about the intervention effects using the registry information alone.

The registry reports limited safety details: serious event counts and other adverse event counts, without serious event terms or a comparative safety analysis. The results also do not provide broader context for the other adverse events. Finally, the record does not report the trial’s own sample-size justification. These limitations concern what is documented in the registry record; they should not be taken as proof that the underlying study did not collect or analyze additional information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Trendelenburg, Abdominal Insufflation and Time to Completion of Cystoscopy — NCT05786391.
• Registry record last updated 2025-02-24; status last verified 2025-02.
• Results first posted 2025-02-24.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT05786391 is a completed randomized, single-masked, parallel trial sponsored by The University of Texas Health Science Center, Houston. Enrollment is listed as 122, and the record gives dates of 2023-04-11 for study start and 2024-02-05 for primary completion. The four arms combine flat or Trendelenburg position with use or no use of abdominal insufflation.

The primary endpoint is time in seconds to satisfactorily complete cystourethroscopy. The registry reports a median and interquartile range for each arm. It lists no secondary outcome measures and no analysis results. Serious adverse events and deaths are reported as 0 in each arm; other adverse event counts are also listed by arm.

The record supports descriptive interpretation of the posted outcome summaries. It does not report the statistical contrasts, uncertainty estimates, analysis population, missing-data methods, or multiplicity strategy needed for an inferential conclusion about position or insufflation.