Study of the Preservation of the Left Colic Artery on Rectum Cancer Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of the Preservation of the Left Colic Artery on Rectum Cancer Surgery (NCT01979029), a randomized na study. The primary outcome is The Blood Pressure of the Arterial Arcade.

2. Clinical Question

The clinical question has both a physiological and a surgical component. The blood-pressure endpoint concerns arterial flow conditions associated with the anastomosis, while the intervention descriptions distinguish preservation of the left colic artery from high ligation of the inferior mesenteric artery. The registry summary also mentions the harvest of No. 253 lymph nodes as a concern in comparing surgical methods. The posted primary endpoint, however, is arterial arcade blood pressure; the record does not identify lymph-node harvest as a primary endpoint.

The comparison is between two assigned surgical approaches, not between surgery and no surgery. The registry record identifies rectum cancer as the condition and describes radical resection as the setting. It does not report additional eligibility criteria, disease stage, or participant characteristics. The results therefore address the recorded comparison in this trial’s enrolled participants; the record alone does not establish how well they apply to other patient groups or surgical settings.

3. Trial Design

The registry record describes a randomized, single-masked, parallel-group study. It reports enrollment of 57 and lists two procedure arms: high ligation of the inferior mesenteric artery and preservation of the left colic artery. The latter arm’s description also specifies resection of the No. 253 lymph node. The arm summaries report 29 participants for high ligation and 28 for left colic artery preservation. These are the posted arm sizes; no additional participant flow information is reported in the registry record.

The trial is marked completed. Its start is recorded as 2013-02 and its primary completion as 2014-09. The phase is listed as NA. The sponsor is listed as Jian Suo. These registry entries describe the record, but do not supply further information about conduct or oversight.

Single masking means the record identifies masking of one party or group, but does not say who was masked. The method used to generate the random allocation sequence, allocation concealment, and procedures for maintaining masking are not reported in the registry record. The record also does not report a protocol, a detailed schedule of assessments, or the trial’s original sample-size justification. The listed enrollment should not be interpreted as evidence about the intended power or design assumptions.

The primary measure is continuous: arterial arcade blood pressure in mmHg, reported as a mean and standard deviation at the stated timeframe, after ligating the inferior mesenteric artery or superior rectal artery. The record lists one secondary outcome, distal colon length, measured after digestive tract reconstruction. There are no reported analyses listed for the secondary outcome. Beyond these outcomes, the registry record does not describe a broader analysis plan, prespecified covariate adjustment, or an intention-to-treat population.

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.

Before assignment: 69 patients initially considered for the study, 11 were excluded because they didn't meet the including criteria. The remaining 58 patients were informed with regard to the study, but they remained blinded to the type of operative technique they would receive. Ultimately, one patient declined to participate in the study.

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 The Blood Pressure of the Arterial Arcade, measured over after ligating the inferior mesentric artery or superior rectal artery.

The primary endpoint is the blood pressure of the arterial arcade, measured in mmHg after ligating the inferior mesenteric artery or superior rectal artery. The registry record specifies a mean and standard deviation as its summary statistics. The posted arm means are 42.31 for high ligation of the inferior mesenteric artery and 48.5 for left colic artery preservation. The posted comparison gives a mean difference of 6.19 for preservation relative to high ligation.

As a general statistical and clinical concept, a pressure measurement can serve as a physiological indicator related to arterial blood supply. In this trial, the endpoint is relevant to the stated interest in blood supply around the anastomosis. It is nevertheless a measured physiological outcome, not itself a direct report of every aspect of healing, complications, or longer-term patient outcomes. The registry record does not report validation of this measure as a surrogate for those outcomes.

The timeframe specifies when the measurement was taken in relation to ligation, but further measurement procedures, equipment, and assessor details are not reported in the registry record. The result should therefore be read as a comparison of the recorded blood-pressure summaries under the trial’s two surgical approaches, rather than as a complete account of all possible consequences of either procedure.

7. Results Posted in the Registry

• Left Colic Artery Preserved: mean 48.50 versus 42.31 on control; difference 6.19 (95% CI 5.05 to 7.33), standardized effect d = 2.84; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Distal Colon Length

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Left Colic Artery Preserved: mean 21.29 versus 20.03 on control; difference 1.26 (95% CI -0.91 to 3.43), standardized effect d = 0.30; z-test p = 0.256.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Left Colic Artery Preserved and the control. The interval gives the range of effects that remain compatible with the data.

The registry record lists distal colon length as the secondary outcome. It is an anatomical measure taken after digestive tract reconstruction, distinct from the primary physiological measure of arterial arcade blood pressure. The posted results for this secondary outcome do not provide a statistically clear difference between the approaches, in contrast with the primary comparison’s interval and unadjusted p-value. The secondary result therefore does not offer the same strength of evidence for a between-arm difference.

The outcomes address related but non-identical questions. Blood pressure concerns a physiological measure associated with arterial supply, whereas distal colon length describes a feature of reconstruction. A pattern in one outcome does not necessarily imply a matching pattern in the other. The secondary measure neither confirms nor refutes the primary result; it provides a separate piece of information about the surgical comparison.

Unadjusted secondary findings generally carry less weight when the record does not establish a prespecified testing hierarchy or multiplicity adjustment. As a general statistical concern, examining multiple outcomes can increase the opportunity for apparently notable findings to arise by chance. The registry record does not report a multiplicity procedure, a detailed analysis plan, or any reported secondary analyses beyond the posted summary comparison. Interpretation should therefore remain cautious and should not elevate a secondary result to the same evidential status as a prespecified primary endpoint without supporting documentation.

The posted secondary information also does not resolve questions about completeness of follow-up, measurement procedures, or the population analyzed. Those details are not reported in the registry record. The secondary outcome can be considered alongside the primary result, but it does not broaden the primary endpoint into a general assessment of surgical outcomes.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Distal Colon Length

9. Statistical Interpretation

10. Statistical Methods Explained

The primary endpoint is continuous, and the registry record summarizes each arm with a mean and standard deviation. A mean represents the arithmetic center of the recorded measurements. A standard deviation describes how dispersed measurements are around that mean. These quantities answer different questions: the means describe the arm-level values, while the standard deviations describe within-arm variability. Neither one alone describes the uncertainty in the between-arm contrast.

What does the mean difference represent?

The comparison is expressed as the mean in the left colic artery preserved arm minus the mean in the high ligation arm. The posted estimate is 6.19 mmHg. A positive estimate in this contrast means the preserved-arm mean is higher. The arm means are 48.5 and 42.31, respectively. The estimate is a contrast between group summaries; it is not an individual participant’s change, and the record does not report paired measurements before and after surgery.

As a general concept, a mean difference keeps the original measurement scale, so the estimate remains interpretable in mmHg. A standardized effect instead expresses the difference relative to a measure of variability. The posted standardized difference is 2.837, using the reported pooled standard deviation of 2.182. This can help describe the size of a contrast in variability units, but it does not replace the original-scale result or establish whether the difference is clinically important.

How should the confidence interval be read?

A confidence interval gives a range of values compatible with the observed data under the statistical procedure used. The interval for the primary mean difference extends from 5.051 to 7.329. It communicates uncertainty around the estimated contrast; it does not mean that a specified proportion of individual measurements fall within that interval. It also does not account automatically for bias, incomplete outcome data, or other limitations in trial conduct.

For a difference, zero represents no difference between arm means. The posted primary interval lies above zero. This supports the reported direction of the comparison under the method used, while the interval’s width conveys the remaining statistical uncertainty. A confidence interval is not a guarantee that the true effect lies within its endpoints, and it is not a direct measure of clinical relevance.

What does the p-value contribute?

The posted unadjusted p-value is <0.001. As a general explanation, a p-value measures how unusual data at least as extreme as those observed would be if a specified null model held. It does not measure the size of an effect, the probability that the null model is correct, or the probability that chance alone caused the observed result. The p-value needs to be considered alongside the estimate, interval, design, and quality of measurement.

“Unadjusted” matters because the registry record does not report an adjustment for multiple outcomes or comparisons. If many outcomes or analyses are examined, the chance of finding at least one apparently notable result can increase. Whether that concern applies in a particular way depends on the analysis plan and the full set of analyses, which are not reported in the registry record. The posted p-value should therefore be understood as an unadjusted result, not as evidence that multiplicity was addressed.

Why do variability and measurement matter?

As a general statistical point, greater variability makes a group contrast less precise when other features are similar, because the observed means are less stable estimates of their underlying group averages. The standard deviations reported for the primary endpoint are 1.85 and 2.48. The record does not provide raw observations or details that would permit an independent assessment of distribution shape, outliers, or measurement reliability. A summary-based comparison cannot reveal those features.

The comparison records standard errors for the two arm means as 0.344 and 0.469. A standard error describes the estimated sampling uncertainty of a statistic, here an arm mean; it is distinct from the standard deviation across participants. The record does not explain the exact inferential procedure used to obtain the comparison. The confidence interval and p-value should thus be read as the posted unadjusted comparison rather than as a reconstruction of an undocumented full analysis plan.

What do the planning calculations mean?

The planning illustration uses two-sided significance level 0.05, equal allocation between the arms, and a normal approximation. It considers effects defined as stated fractions of the observed effect. Under those assumptions, the listed participants per arm for 80% power are 2, 4, and 8 for planning at 100%, 75%, and 50% of the observed effect, respectively. For 90% power, the corresponding listed values are 3, 5, and 11. These are planning illustrations based on the observed effect, not the trial’s original design calculations.

As a general concept, power is the chance that a planned analysis will detect an effect of a specified size under assumptions about the design and data. The planning values depend on those assumptions, including the chosen effect, variability, significance threshold, allocation, and approximation. Smaller effects require more participants to detect with the same power when the other assumptions are held constant. The figures do not tell how much power the completed trial had before results were observed.

General statistical concepts in this explanation describe how to interpret common summaries. They do not fill in the trial’s unreported protocol, allocation methods, handling of missing observations, or analysis decisions. Those details are not reported in the registry record.

11. Confidence Intervals and Precision

The primary mean difference is 6.19 mmHg, with a confidence interval from 5.051 to 7.329. The interval gives a range of plausible values for the contrast under the calculation method used. Its endpoints are both above zero, so the posted estimate is statistically distinguishable from no difference under that method. The interval also indicates that the estimate is not perfectly precise: values across its range remain compatible with the data and procedure.

The interval is more informative about precision than the p-value alone. A p-value of <0.001 indicates incompatibility with a null difference under the specified test, while the interval expresses the estimated contrast in the original units and its uncertainty. Neither statistic addresses possible bias from measurement, incomplete follow-up, or analysis choices not documented in the registry record.

For context, the arm standard deviations are 1.85 and 2.48, and the posted comparison includes standard errors of 0.344 and 0.469 for the arm means. Standard deviations describe participant-level spread; standard errors describe uncertainty in estimated means. They should not be read interchangeably. The registry record does not provide raw data or enough methodological detail to independently check distributional assumptions or the precise interval construction.

Precision is specific to the endpoint and analysis. The confidence interval does not quantify uncertainty about distal colon length, serious adverse events, or other clinical outcomes. It also does not capture uncertainty about how broadly the result generalizes beyond the enrolled trial participants. Those considerations require information not reported in the registry record.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not a total across the study. They are illustrations computed from the observed effect, rather than the trial’s own design justification. The assumptions listed for the illustration are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The trial’s original sample-size assumptions are not reported in the registry record.

For planning at 100% of the observed effect, the listed values are 2 participants per arm for 80% power and 3 participants per arm for 90% power. For planning at 75% of the observed effect, the values are 4 participants per arm for 80% power and 5 participants per arm for 90% power. For planning at 50% of the observed effect, the values are 8 participants per arm for 80% power and 11 participants per arm for 90% power.

In plain terms, 80% power means that a study planned under the stated assumptions would have an 80% chance of detecting the specified effect at the chosen significance level, if that effect and the assumptions were correct. The 90% column describes the analogous planning target with a higher chance of detection. Higher power generally requires more participants when other assumptions remain the same. A smaller effect is harder to distinguish from random variation and therefore requires more participants than a larger effect under otherwise comparable assumptions.

These values are planning illustrations, not observed power. Because the calculation starts from an effect observed in this trial, the figures should not be treated as an independent justification for the completed study’s enrollment or as a guarantee of future results. The registry record does not report the original design calculation or its intended target effect.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 6.190; pooled standard deviation σ = 2.182.
2. n = 2 × (1.96 + 0.842)² × 2.182² / 6.190² = 2.0, rounded up to 2 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 6.19                      # observed difference in means
sigma <- 2.18212073659798                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1979029)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 2 (80% power), 3 (90% power)
 75% of observed effect: n per arm = 4 (80% power), 5 (90% power)
 50% of observed effect: n per arm = 8 (80% power), 11 (90% power)
power.t.test: 3.3 
Simulated power at n = 2 per arm: 0.360 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record identifies a primary endpoint and one secondary outcome, but it does not report a multiplicity adjustment, a testing hierarchy, or a prespecified strategy for interpreting multiple outcomes. The primary comparison is presented with an unadjusted p-value. The secondary comparison is also unadjusted in the posted summary. Without a stated plan, it is not possible to determine whether the analyses were intended to be confirmatory, exploratory, or interpreted under some other framework.

As a general statistical explanation, multiplicity arises when several hypotheses or outcomes are examined. Even if each test uses the same significance threshold, repeated testing can increase the chance of at least one apparently positive result when no underlying differences exist. Adjustment procedures or a prespecified order of testing can help control that issue, but no such method is reported in the registry record. This uncertainty is most relevant to interpreting secondary findings and any unreported analyses; it does not change the numerical primary estimate or its posted unadjusted interval.

Missing-data handling is also not reported in the registry record. The record gives arm sizes and outcome summaries, but does not state whether every randomized participant contributed a primary measurement, whether any measurements were unavailable, or how missing observations were treated. It does not report sensitivity analyses for missing data. As a result, the summaries cannot be assumed to represent a particular missing-data strategy.

The analysis population is not described. The registry record does not say whether the comparison followed an intention-to-treat principle, included participants according to the procedure received, or used another analysis set. Randomization supports a comparison of assigned groups when analyzed appropriately, but the available record does not establish how assignment, crossover, protocol deviations, or exclusions were handled.

Other statistical-plan details, including covariate adjustment and interim analyses, are not reported in the registry record. Their absence from the record does not establish that a method was or was not used. It means the posted summaries cannot be assessed against a fully documented analysis plan.

15. Safety Results

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

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: anastomotic leakage (10.3%).

The serious adverse event summaries list 3 affected participants among 29 at risk in the high ligation of the inferior mesenteric artery arm, and 1 affected participant among 28 at risk in the left colic artery preserved arm. No other serious adverse events are listed in either arm. The registry record lists anastomotic leakage as a serious adverse event term and gives 10.3%; it does not provide enough detail to connect that term to a specific arm count with certainty.

These are descriptive registry counts. They do not by themselves establish that the difference between arms reflects a causal safety effect, and the record does not report a formal comparison of serious adverse events. The number of events is limited, so small changes in counts could materially alter a comparison. The record also does not report the definitions, severity grading, ascertainment methods, or follow-up window for adverse events.

Deaths are not reported in the registry record. The absence of a listed death count should not be interpreted as confirmation that no deaths occurred. Serious adverse event summaries are only one component of the available outcome information and should not be treated as a complete safety assessment.

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

The posted data show a higher mean arterial arcade blood pressure in the left colic artery preserved arm than in the high ligation arm, with an estimated mean difference of 6.19 mmHg and a confidence interval from 5.051 to 7.329. The unadjusted p-value is <0.001. These results describe the trial’s primary measured endpoint and the precision of its estimated between-arm contrast.

They do not establish that either surgical approach is preferable overall. The primary measure is a physiological endpoint, and the registry record does not report validation showing that this measurement predicts all relevant clinical outcomes. The result cannot be extended automatically to healing, complications, longer-term outcomes, or other aspects of rectal cancer surgery. The posted serious adverse event information is descriptive and is not a formal comparative safety analysis.

Randomization is a useful design feature for comparing assigned approaches, but the record does not report enough detail to assess allocation concealment, who was masked, missing outcome data, or the analysis population. The participant characteristics and eligibility criteria are also not reported in the registry record. These omissions limit assessment of bias and of how broadly the results may apply.

The secondary outcome is a separate measure and does not carry the same evidential weight as the primary endpoint. The record does not report a multiplicity plan or a detailed analysis plan. The statistical evidence should be interpreted as a result on the posted endpoint, rather than a definitive statement about all effects of the procedures. Clinical importance cannot be determined from the p-value alone, and the registry record does not state a threshold for a clinically meaningful blood-pressure difference.

In short, the results quantify a between-arm difference in the recorded arterial arcade blood pressure. They do not establish the full clinical consequences of preserving the left colic artery, nor do they settle questions that were not measured or reported in the registry record.

17. Why This Trial Matters Statistically

This trial is statistically interesting because it contrasts two surgical approaches using a direct continuous physiological measurement as its primary outcome. The reported mean difference remains in the original unit, mmHg, while the accompanying confidence interval communicates uncertainty in that contrast. Considering the estimate and interval together gives a more informative account than relying on a p-value alone.

The randomized parallel-group design is relevant to interpretation because random allocation can reduce systematic differences between assigned groups. Yet design labels are not a substitute for details about implementation. The record does not describe sequence generation, allocation concealment, the identity of the masked party, or the analysis population. Those omissions make the registry entry a limited basis for judging the risk of bias.

The contrast between a clear primary comparison and a secondary outcome without a statistically clear difference also illustrates why outcomes should not be treated as interchangeable. Blood pressure and distal colon length represent different domains. A trial can show a notable result on one measure without establishing a broad pattern across all outcomes. Without a reported multiplicity plan, unadjusted secondary findings deserve particular restraint.

The planning illustration is another useful statistical lesson. Its participant requirements change with the assumed fraction of the observed effect and the target power. This demonstrates the dependence of planning on effect size, but it does not reconstruct the trial’s original design rationale. The original sample-size assumptions are not reported in the registry record.

Overall, the record supports careful reading of effect estimates, confidence intervals, and the limits of registry reporting. It offers a focused comparison on a physiological endpoint, while leaving important design, analysis, and clinical-interpretation questions unresolved.

18. 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.

Several limitations specific to this trial follow from the information recorded. The registry entry gives a primary outcome summary and a secondary outcome summary, but does not include raw data. That prevents independent inspection of distributions, outliers, unusual values, or participant-level patterns. The measurement equipment, protocol, and assessor procedures for arterial arcade blood pressure are not reported, so measurement reliability cannot be evaluated from the record.

The record does not describe the random sequence generation or allocation concealment. It identifies the study as single-masked but does not specify who was masked or how masking was maintained. These omissions make it difficult to assess protection against selection and measurement bias. Participant eligibility criteria and baseline characteristics are also not reported, limiting assessment of the enrolled population and its comparability across arms.

Participant flow, missing outcome data, protocol deviations, crossovers, and the analysis population are not reported. The record therefore does not establish whether all randomized participants were included in each endpoint analysis or how any unavailable measurements were handled. A detailed statistical analysis plan, multiplicity strategy, covariate adjustment, and interim-analysis information are also not reported in the registry record.

The primary outcome is a physiological measure, and no validation as a surrogate for broader clinical outcomes is reported. The secondary outcome is limited to distal colon length, while serious adverse event information is descriptive and lacks details on ascertainment and follow-up. The record does not provide a complete assessment of longer-term or patient-centered outcomes. These limitations constrain conclusions to the posted summaries and should not be filled by assumptions about procedures that are not documented.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Study of the Preservation of the Left Colic Artery on Rectum Cancer Surgery — NCT01979029.
• Registry record last updated 2016-06-06; status last verified 2016-04.
• Results first posted 2016-06-06.
• 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.

22. Record Summary

NCT01979029 is a completed randomized, single-masked, parallel-group study of surgery for rectum cancer. It compares high ligation of the inferior mesenteric artery with preserving the left colic artery and resecting the No. 253 lymph node. Enrollment is recorded as 57.

The primary outcome is arterial arcade blood pressure in mmHg, reported as a mean and standard deviation after ligating the inferior mesenteric artery or superior rectal artery. The posted mean difference for left colic artery preservation relative to high ligation is 6.19, with a confidence interval from 5.051 to 7.329 and an unadjusted p-value of <0.001. Distal colon length is the listed secondary outcome.

The record does not report the original sample-size assumptions, detailed analysis plan, missing-data procedures, or analysis population. The posted results describe the measured outcomes and should be interpreted within those reporting limits.