The Effectiveness of Huangkui Lianchang Decoction Enema Solution Compared with Mesalazine Enema for Mild-to-Moderate Active Distal Ulcerative Colitis: Study Protocol of a Multicenter, Prospective, Randomized Controlled Trial

Introduction

UC is a chronic, non-specific inflammatory bowel disease characterized by persistent or recurrent symptoms such as diarrhea, mucus-bloody stools, abdominal pain, and tenesmus.¹ Severe and debilitating pain is a common symptom of inflammatory bowel disease (IBD). Abdominal pain typically results from inflammatory mediators in the colonic mucosa stimulating hypersensitive nerve endings during the pathological process of UC. In addition to abdominal pain, some pain arises from extraintestinal manifestations of UC.² Although current treatment strategies primarily involve Western medications and biologics, these therapies are often limited by the development of drug resistance, adverse effects, high costs, and inconsistent therapeutic effectiveness. Not all patients benefit equally, and access remains a challenge, particularly in low-resource settings. Moreover, the development of treatments tailored to the genetic and clinical characteristics of the Chinese population represents a critical challenge in the field of traditional Chinese medicine (TCM).^3,4 Standard medical management of UC typically includes 5-aminosalicylic acid (5-ASA), corticosteroids, and immunosuppressants. However, these agents are associated with limitations, including poor long-term symptom control, high recurrence rates, multiple adverse effects, and a tendency to induce resistance over time.

The distal colon—including the rectum and left-sided colon—is the most frequently affected site in UC, with studies reporting involvement in up to 77% of cases. Therefore, identifying effective treatments for distal UC is essential to prevent disease progression and improve patient outcomes.⁵ Enemas and suppositories, which allow direct drug delivery to the inflamed mucosa, are considered first-line therapies for distal UC. TCM enemas have been extensively used in clinical practice due to their longstanding history and notable advantages, such as rapid symptom relief (eg resolution of abdominal pain), sustained therapeutic effects, and low cost. However, despite the availability of various TCM enema formulations, high-quality clinical evidence remains limited. Reported remission rates generally range between 70% and 85%^6–8 but treatment precision and formula-syndrome specificity remain suboptimal. As such, the development of a standardized and clinically validated TCM enema formulation represents a significant unmet need in the management of distal UC.

TCM offers unique therapeutic advantages in the management of UC. In TCM theory, UC is classified under syndromes such as “dysentery” “chronic dysentery” and “resting dysentery”. The HKE was developed to treat rectal- and left-sided UC. This formulation has demonstrated favorable clinical effectiveness by promoting mucosal healing and alleviating symptoms such as mucus-bloody stools. It is particularly suited for patients with mild to moderate active UC presenting with mucus-bloody stools. The therapeutic rationale and clinical use of HKE are aligned with the Chinese national clinical practice guideline on diagnosis and management of ulcerative colitis (2023),⁹ issued by the Chinese Society of Integrated Traditional and Western Medicine, the Chinese Association of Traditional Chinese Medicine, and the Chinese Medical Association. These guidelines recognize “damp-heat stagnation in the intestines” and “spleen deficiency with dampness stagnation” as key TCM syndromes associated with UC.

Preliminary clinical studies report an overall efficacy rate of 74.20% (77/101) for HKE in treating UC.¹⁰ Compared to Mesalazine alone, combination therapy with HKE significantly improves core symptoms such as diarrhea, bloody stools, abdominal pain, and tenesmus. It also leads to reductions in Mayo scores, TCM syndrome scores, and fecal calprotectin levels. HKE has demonstrated advantages in rapid symptom control, sustained effectiveness, and mucosal healing, and it has been well received by patients. This research has been granted a national invention patent and is supported by the National Administration of Traditional Chinese Medicine’s Evidence-Based Medicine Capacity Building Project (Grant No. K2023BZ02). The study protocol is registered with the National Medical Research Registration and Filing Information System (Registration No.: MR-32-24-042586). These recognitions further support the clinical relevance and potential of HKE in the integrated treatment of UC.

Materials and Methods

Design

This trial adopts a prospective, randomized, active-controlled, non-inferiority design. Figure 1 shows the trial flowchart. A total of 172 patients with mild to moderate active distal UC will be randomly assigned in a 1:1 ratio to receive either HKE or Mesalazine enemas. Each trial site provides participants with sufficient medication for an 8-week treatment period, in accordance with the Technical Guidelines for Clinical Trials of Drugs for the Treatment of Ulcerative Colitis (Applicable to Chemical Drugs and Biologics).¹¹ The study consists of a screening period, an 8-week treatment period, and a follow-up period. Colonoscopic evaluations and follow-up of any abnormal laboratory results will be conducted within 28 days after treatment discontinuation. For more details, please refer to Supplemental Material 2 [Investigational Schedule]. The study is guided by the Declaration of Helsinki,¹² the Standard Protocol Items: Recommendations For Interventional Trials (SPIRIT) (Supplemental Material 1 [SPIRIT checklist]).¹³

Figure 1 Trial flowchart.

Study Settings and Participants

Study Sites

This RCT was conducted at eight hospitals, including Jiangsu Province Hospital of Chinese Medicine, Yancheng No.1 People’s Hospital, Changshu No. 2 People’s Hospital, Huai’an First People’s Hospital, Lianyungang Hospital of Traditional Chinese Medicine, the First People’s Hospital of Lianyungang, Changzhou No. 2 People’s Hospital, and Affiliated Hospital of Jiangnan University. The establishment of research centers that combine traditional Chinese medicine and Western medicine will help reduce patients’ subjective bias toward traditional Chinese medicine treatment.

Sample Size Calculation

According to literature reports, the remission rate of mesalazine in the treatment of UC is 64.0%. A preliminary clinical study (n = 101) confirmed that the remission rate of HKE in the treatment of UC is 74.2%.¹⁰ Considering a clinically meaningful threshold of 15%, under the conditions of a=0.025 (one-sided) and a test power of β = 90%, the experimental group and control group were enrolled in a 1:1 ratio. Using SAS 9.4 proc power, a total of 142 cases were required for enrollment. Considering a 20% dropout rate, a total of 172 cases were required for enrollment, resulting in 86 cases per group.

Inclusion and Exclusion Criteria

Inclusion Criteria

(1) Meet UC medical diagnostic criteria:^1,11,14 a. Disease stage: active phase; b. Disease severity is mild to moderate (refer to the modified Truelove and Witts disease severity classification criteria,¹⁵ see Table 1 for details); c. Lesion location is rectal or left-sided colonic type (recommended to use the Montreal classification,¹⁶ see Table 2 for details); d. Modified Mayo score¹⁷ of 3–10 points, and an endoscopic subscore of 2 or higher (modified Mayo score, see Table 3);

Table 1 Modified Truelove and Witts Disease Severity Staging Criteria

Table 2 Montreal Classification of Extent of UC

Table 3 Modified Mayo Scoring System for Assessment of Ulcerative Colitis Activity

(2) Traditional Chinese medicine diagnosis of damp-heat accumulation in the intestines or spleen deficiency with dampness accumulation;

(3) Age between 18 and 65 years;

(4) The patient voluntarily signs an informed consent form.

Exclusion Criteria

1. Patients with infectious colitis such as bacterial dysentery, amoebic dysentery, chronic schistosomiasis, intestinal tuberculosis, as well as Crohn’s disease, ischemic colitis, and radiation colitis;
2. Patients with severe complications such as local stricture, intestinal obstruction, intestinal perforation, toxic megacolon, massive bleeding, colorectal cancer, or rectal cancer;
3. Patients with other primary or secondary infectious diseases, such as cholecystitis or pneumonia;
4. Patients who have undergone enema therapy within the past two weeks;
5. Patients currently receiving treatment with corticosteroids, thiopurine drugs, biologics, or probiotics;
6. Patients with severe cardiovascular, hepatobiliary, pulmonary, renal, or hematological diseases;
7. Patients with allergic constitutions, such as a history of allergy to two or more drugs or foods, or a known allergy to the investigational drug;
8. Patients with suspected or confirmed history of alcohol or drug abuse;
9. Pregnant or breastfeeding women;
10. Patients with disabilities as defined by law (blindness, deafness, mutism, intellectual disabilities, mental disorders, or physical disabilities);
11. Other conditions that, in the investigator’s judgment, may reduce eligibility or complicate enrollment, such as frequent changes in work environment that may lead to loss to follow-up;
12. Patients currently participating in other clinical trials.

Randomization

In this trial, each center used a competitive enrollment method to include study subjects. A professional statistical analyst generated the random sequence for the treatment (trial drug and control drug) received by the 172 subjects using the SAS (Proc Plan) statistical analysis software based on the randomization method of the trial center, ie Listing the treatment allocation corresponding to serial numbers 001 to 172. All randomization codes were distributed to each trial center in segments according to the randomization protocol. Investigators enrolled eligible patients in the order of their visits, and the medication administrator sequentially distributed the corresponding trial medications to patients in ascending order of their assigned codes.

Interventions

According to the “General Principles for Clinical Research on New Traditional Chinese Medicines” issued by the National Medical Products Administration in 2015, a positive control drug should be selected based on recognized effectiveness, safety, and comparability for the target disease. In this study, Salofalk enema solution is chosen as the positive control for the local treatment of distal RCT, in accordance with these regulatory guidelines.

Basic treatment medication: All participants receive standard treatment with Salofalk (mesalazine enteric-coated tablets) at a dosage of 2 g/day, administered orally (specification: 0.5 g × 40 tablets per bottle). In addition to pharmacological treatment, patients are advised to adhere to the following lifestyle recommendations: 1. Maintain regular bowel habits and practice proper perianal hygiene after each bowel movement; 2. Follow a light and easily digestible diet, avoiding high-fiber foods, as well as spicy, greasy foods, tobacco, and alcohol; 3. Maintain a regular daily routine, balance work and rest, engage in moderate physical activity to improve fitness, and manage emotional well-being.

The experimental group received standard treatment and HKE therapy. HKE, 60 mL per dose, once daily at bedtime, administered via enema (specification: 250 mL per bottle). The treatment course will last for 8 weeks unless the subject discontinues the trial prematurely. Patients will undergo follow-up assessments on days 14, 28, 42, 56, and 28 days after discontinuation of treatment. The trial schedule is outlined in Supplemental Material 2 [Investigational Schedule]. All participants receive a detailed video tutorial on the correct enema technique and are provided with single-use, sterile enema kits. At Visit 3 and Visit 5, patients will return any remaining medication for compliance assessment by the investigator. To help patients improve adherence, we will provide operational guidance and address questions at each visit.

The control group received standard treatment and Salofalk (mesalazine enema solution) therapy. Salofalk (mesalazine enema solution), 60 mL/4 g per dose, once daily at bedtime, administered via enema (drug specification: 60 mL: 4 g). Assessment methods were the same as those for the experimental group.

Withdrawal Criteria

1. Participants will be withdrawn from the trial under any of the following conditions:
2. Occurrence of severe adverse reactions;
3. Development of an allergic reaction to the investigational drug during the study;
4. Inability to tolerate the study drug;
5. Non-adherence to the prescribed dosing regimen, defined as receiving more than 120% or less than 80% of the theoretical dose;
6. Lack of cooperation from participants or their family members, inability to complete the study as planned, or unauthorized modification of the medication regimen;
7. Loss to follow-up.

Management of Withdrawal Cases

In the event of withdrawal, investigators are required to make reasonable efforts to contact the participant through home visits, scheduled follow-ups, telephone calls, or written correspondence to determine the reason for withdrawal. The time of the last medication administration should be recorded, and all assessable items should be completed to the extent possible.

For withdrawals due to allergic reactions, adverse events, or lack of effectiveness, appropriate medical management should be provided based on the participant’s condition. All data from withdrawn cases must be retained for documentation and included in the full analysis set. Replacement of withdrawn participants is not required.

Outcome

Data are collected by GCP-trained researchers using standardised data collection forms.

Primary Outcome

Clinical efficacy is assessed using the modified Mayo score system. Clinical remission is defined as a total modified Mayo score of ≤2 points post-treatment, with no individual subscore exceeding 1 point. Clinical response is defined as a ≥30% or ≥3-point reduction in the total modified Mayo score from baseline.

Secondary Outcome

1. Endoscopic efficacy: The endoscopic response rate and endoscopic mucosal healing rate (Ulcerative colitis endoscopic severity index (UCEIS); Table 4)¹⁸ are assessed.
2. Symptom quantification: Detailed in Tables 5 and 6, symptom quantification⁶ and Traditional Chinese Medicine syndrome efficacy assessment are evaluated.
3. Improvement and resolution rates for individual symptom scores⁶ are measured.
4. Changes in CRP, ESR, fecal calprotectin and histological scores for mucosal healing (Table 7)¹⁹ from baseline are analyzed.

Table 4 UCEIS Scoring System

Table 5 Symptom Quantification Scale

Table 6 TCM Syndrome Efficacy Evaluation Standard Table

Table 7 Mucosal Healing Histological Scoring Table

All primary and secondary outcomes will be measured at baseline, 8 weeks after randomisation. The modified Mayo sub-scores for Stool frequency and Rectal bleeding and Symptom quantification scale will be clinically reviewed at 2, 4, 6 weeks after randomisation. While the colonoscopy and related score can be performed at the 8th week or within one month after completing medication.

Safety Observations

1. Incidence of Adverse Events/Serious Adverse Events

The types, severity, and relationship to the investigational drug of all adverse events occurring during the trial will be described in a table.

1. Vital Signs, Physical Examination, Laboratory Tests, 12-Lead Electrocardiogram

Statistical descriptions of changes in vital signs (body temperature, heart rate, respiration, systolic blood pressure, diastolic blood pressure) before and after treatment.

Adverse Events

The investigational drug, HKE, has demonstrated good safety in previous clinical use. In extremely rare cases, patients have experienced gastrointestinal irritation, but no significant adverse reactions have been observed. If patients experience gastrointestinal irritation, it is recommended to dilute the solution with 20 mL of warm water or saline before administration. If the patient cannot tolerate the irritation, the procedure should be discontinued.

For adverse events occurring during the trial, investigators should record the time of occurrence, severity, duration, management measures, and outcome in the case report form, and assess their relationship to the investigational drug.

If a serious adverse event (SAE) occurs during the trial, the investigator must immediately take measures to protect the safety of the subject and promptly report it to the research center. All adverse events should be followed up, with detailed records of the management process and outcomes until the issue is resolved or the condition stabilizes.

We have purchased clinical trial liability insurance for the subjects to protect their legitimate rights and interests.

Monitoring

The sponsor appoints a designated monitor to ensure that the rights and welfare of trial participants are protected throughout the study. The monitor is responsible for verifying that the data recorded in case report forms and final reports are accurate, complete, and consistent with source documents. Additionally, the monitor ensures that the clinical trial is conducted in accordance with the approved protocol, GCP guidelines, and applicable regulatory requirements. Any protocol deviations identified during the trial are promptly reported by the monitor to both the sponsor and the ethics committee.

Data Management

An electronic data capture (EDC) system is utilized in this trial. Case report forms (CRFs) are developed by data managers in accordance with the study protocol and source documentation.

Statistical Analysis

Exclusion Criteria

1. Cases that do not meet the inclusion criteria but meet any exclusion criteria;
2. Cases that do not receive the investigational drug;
3. Cases with no available data after randomization.

Prior to statistical analysis, the statistical analyst and the principal investigator discuss and determine the exclusion of specific cases. Statistical analyses are conducted using SAS version 9.4 or higher. Trial results are presented in summary tables (or figures) and listings.

All statistical tests will be two-sided. A p-value less than 0.05 will be considered statistically significant. Exploratory analyses will not undergo multiple comparison correction. Intergroup comparisons or within-group comparisons of quantitative data will be performed using t-tests or rank-sum tests. If other factors are considered, covariance analysis (or other statistical methods specified in the SAP) will be used. Intergroup comparisons of categorical data were performed using chi-square tests or Fisher’s exact probability method. If other factors were considered, the CMH chi-square test was used. If multiple baseline confounding factors were considered, logistic regression models were used. Time-to-event indicators were analyzed using the Kaplan–Meier method, describing median time, quartile time, and their 95% confidence intervals (95% CI), and survival curves were plotted.

Discussion

TCM enemas for UC have a long history of use in China and remain an important component of UC management. The Chinese Guidelines for the Diagnosis and Treatment of Ulcerative Colitis (2023·Xi’an) recommend oral 5-ASA combined with enema therapy for patients with mild to moderate active left sided UC. Enema medications include 5-ASA, topical glucocorticoid preparations, and TCM formulations.⁹

TCM enemas have a long history of use. The active components of these medicines can exert their effects either by being directly absorbed into intestinal tissues or indirectly through absorption into the bloodstream or adsorption onto the intestinal mucosa. HKE demonstrates favorable clinical efficacy in treating UC.^10,20 International studies have shown that Abelmoschus manihot flower²¹ has anti-inflammatory, antioxidant, antidepressant, anti-fibrotic, vasculogenic, and lipid metabolism-regulating effects; Pteris multifida herb^22,23 has antioxidant, antitumor effects; Euphorbia humifusa herb^24,25 has antibacterial, anti-inflammatory, and antidiarrheal effects. Preliminary studies show that administration of total flavonoids extracted from Abelmoschus manihot flowers effectively suppresses inflammatory mediators associated with inflammatory bowel disease and promotes intestinal mucosal healing.²⁶ In addition, HKE improves dextran sulfate sodium (DSS)-induced colitis in mice through modulation of the NF-κB pathway.²⁷ Although HKE enema therapy is recognized by both Chinese scholars and patients and has been included in the Chinese Medicine Diagnosis and Treatment Guidelines for Ulcerative Colitis (2023), it is classified only as a weak recommendation supported by low-quality evidence.²⁸ At present, high-quality clinical evidence for HKE enema therapy in UC remains insufficient.²⁹ Previous clinical studies on enema therapies have been hampered by methodological issues, including small sample sizes, non-standardized research designs, and a narrow range of outcome measures. Therefore, it is imperative to conduct a standardized, high-quality clinical study to address these shortcomings.

This trial was consciously designed to respond to several common critiques of clinical research in TCM. First, we employed a standardized, quality-controlled HKE formulation and integrated exploratory biomarker assessments to link clinical outcomes with potential mechanistic insights into host metabolism. Second, recognizing the paramount importance of rigor, we implemented a controlled design with a positive control drug. Third, while TCM emphasizes individualized treatment, this study adopts a “disease-pattern” focused approach using a fixed formula for a well-defined patient population (active mild-to-moderate UC). This is a necessary and valid strategy to establish initial efficacy evidence within a controlled experimental framework. Finally, by adhering to SPIRIT reporting guidelines and providing exhaustive details on the intervention, we ensure transparency and reproducibility. We contend that this multifaceted approach strengthens the validity of our findings and contributes to a more scientifically rigorous evaluation of TCM therapies.

This study has several notable strengths. Our research has a larger sample size than previous clinical studies of HKE, which can reduce random errors and assist statisticians in conducting meaningful subgroup analyses, and increase the statistical power to detect adverse events and rare outcomes. In the evaluation of outcome measures, we employed multiple scoring systems including clinical symptom scores from both traditional Chinese and Western medicine, endoscopic scores, and histological healing scores to objectively and multidimensionally assess the efficacy of HKE. The control group receives active drug therapy, featuring a more rigorous and standardized study design compared to previous clinical studies on Chinese herbal enemas.³⁰ All participants receive appropriate doses of oral mesalazine as baseline therapy, ensuring patient safety during active disease and improving adherence to follow-up assessments. In addition, study sites include both traditional Chinese medicine hospitals and Western medicine hospitals, thereby minimizing selection bias toward specific healthcare settings and enhancing the overall validity of the findings.

This study also has certain limitations. Although a randomized controlled enrollment design is adopted, due to the color difference between HKE and mesalamine enema solution, a blind method cannot be employed. Furthermore, as the trial is conducted exclusively across multiple centers in Jiangsu Province, a traditional center of Chinese medicine with abundant TCM resources, a large patient base, and high cultural acceptance, the generalizability of the findings to other regions of China may be limited.

In summary, this study represents a large-scale, multicenter randomized controlled trial of enema therapy for UC in China. The trial provides a model for generating high-quality evidence to evaluate the efficacy of other Chinese herbal compound enemas in the treatment of UC both domestically and internationally. If standardized clinical studies demonstrate that HKE achieves equivalent or superior clinical efficacy compared to standard Western pharmaceutical treatments for UC, this would provide evidence supporting the efficacy and safety of HKE enemas for treating ulcerative colitis. This study aims to generate high-quality evidence on the treatment of UC with Chinese herbal medicine retention enemas through rigorous clinical investigation. The findings are intended to inform the optimization of therapeutic strategies in clinical guidelines, expand the diagnostic and therapeutic scope of Chinese herbal enema therapy for UC, highlight its distinctive advantages, and provide new insights for advancing enema-based treatment approaches for UC.

Trials Status

This trial was registered at the International Traditional Medicine Clinical Trial Registry (https://itmctr.ccebtcm.org.cn/mgt/project/view/-7877458543771072185) on 11 November 2024 (registered number: ITMCTR2024000702, the protocol version number: V7.0). This study is currently in the recruitment stage. The first patient was randomized on 14 January 2025, and recruitment is expected to be completed by June 2026, and the trial is estimated to end in December 2025.

Conclusion

The outcomes of this research aim to provide evidence supporting the efficacy and safety of HKE enemas for treating ulcerative colitis and generate high-quality evidence on the treatment of UC with Chinese herbal medicine retention enemas through rigorous clinical investigation. The findings are intended to inform the optimization of therapeutic strategies in clinical guidelines.