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Introducción: La proctitis actínica crónica hemorrágica (PACH) se presenta secundaria a la radioterapia pélvica. La coagulación con argón plasma (APC) es una terapéutica eficaz, segura, de fácil uso y relativo bajo costo. Objetivo: Describir la respuesta terapéutica a corto y largo plazo del APC en pacientes con PACH, así como evaluar la calidad de vida antes y después de la intervención. Material y Métodos: Estudio observacional, prospectivo de serie de casos en 46 pacientes con PACH, atendidos en el Centro Nacional de Cirugía de Mínimo Acceso entre 2017 y 2020. Se emplearon medidas de resumen y comparación de medias (t de Student pareada) para la hemoglobina inicial y final, así como para los puntajes de calidad de vida aplicados antes y después de la intervención. Para determinar el tiempo libre de resangrado se utilizó l Método de Kaplan-Meier. Se estimó una significación menor a 0.05 para un intervalo de confianza de 95 por . Resultados: Se necesitó una media de 3,6 ± 2,394 sesiones de APC. La media de hemoglobina se incrementó 1,9 g/L. La respuesta terapéutica a corto plazo se observó en 100 por ciento de los pacientes y a largo plazo en 91,3 . La media de puntaje para la calidad de vida descendió en 12,065 puntos (p˂ 0,00), La percepción global percibida se incrementó en una media de 7.326 puntos (p˂ 0,00). Conclusiones: El APC tiene buena respuesta terapéutica a corto y largo plazo con pocas sesiones y bajo número de complicaciones, con mejoría de la calidad de vida de los pacientes(AU)
Introduction: Chronic hemorrhagic radiation proctitis (CHRP) appears secondary to pelvic radiotherapy. Argon plasma coagulation (APC) is an effective, safe, easy-to-use, and relatively inexpensive therapy. Objective: To describe the short- and long-term therapeutic response of APC in patients with CHRP, as well as to evaluate the quality of life before and after the intervention. Material and Methods: Observational, prospective case series study of 46 patients with CHRP, treated at the National Center for Minimally Access Surgery between 2017 and 2020. Summary measures and comparison of means (paired Student's t-test) were used for baseline and final hemoglobin, as well as for the quality of life scores applied before and after the intervention. The Kaplan-Meier method was used to determine the recurrence free time. A level of significance less than 0.05 was estimated for a 95 por ciento confidence interval. Results: A mean of 3,6 ± 2,394 APC sessions was required. The mean hemoglobin increased 1,9 g / L. Short-term therapeutic response was observed in 100 % of patients, and long-term in 91,3 por ciento. The mean score for quality of life decreased by 12,065 points (p˂ 0,00). The perceived global perception increased by a mean of 7,326 points (p˂ 0,00). Conclusions: APC has a good therapeutic response in the short and long term with few sessions and a low number of complications, with an improvement in the quality of life of the patients(AU)
Subject(s)
Humans , Male , Female , Middle Aged , Aged , Proctitis/therapy , Quality of Life , Argon Plasma Coagulation , Gastrointestinal Hemorrhage/therapy , Time Factors , Chronic Disease/therapy , Prospective Studies , Treatment OutcomeABSTRACT
Objective: Radiotherapy is one of the standard treatments for pelvic malignant tumors. However, researches associated with intestinal radiation injury and the quality of life (QoL) of patients receiving radiotherapy were lacking in the past. This study aims to analyze the occurrence of radiation-induced rectal injury after adjuvant radiotherapy for pelvic malignant tumors and call for more attention on this issne. Methods: A retrospectively observational study was conducted. Case data of cervical cancer patients from the database of STARS phase 3 randomized clinical trial (NCT00806117) in Sun Yat-sen University Cancer Center were analyzed. A total of 848 cervical cancer patients who received adjuvant radiation following hysterectomy and pelvic lymphadenectomy in Sun Yat-sen University Cancer Center from February 2008 to August 2015 were recruited. The pelvic radiation dosage was 1.8 Gy/day or 2.0 Gy/day, five times every week, and the total dosage was 40-50 Gy. Among 848 patients, 563 patients received radiation six weeks after surgery, of whom 282 received adjuvant radiation alone and 281 received concurrent chemoradiotherapy (weekly cisplatin); other 285 patients received sequential chemoradiotherapy (paclitaxel and cisplatin). Acute adverse events, chronic radiation damage of rectum, and QoL were collected and analyed. The digestive tract symptoms and QoL were evaluated based on EORTC QLQ-C30 questionnaires at one week after surgery (M0), during adjuvant therapy period (M1), and at 12 months and 24 months after the completion of treatments (M12 and M24), respectively. Higher scores in the functional catalog and overall quality of life indicated better quality of life, while higher scores in the symptom catalog indicated severe symptoms and worse QoL. Chronic radiation rectal injury was defined as digestive symptoms that were not improved within three months after radiotherapy. Grading standard of acute adverse events and chronic radiation rectal injury was according to the gastrointestinal part of National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0 (NCI-CTCAE Version 4.0). Results: The mean total radiation dosage of 848 patients was (47.8±4.6) Gy. During adjuvant therapy, the common symptoms of acute intestinal dysfunction were nausea (46.0%, 390/848), vomiting (33.8%, 287/848), constipation (16.3%, 138/848) and abdominal pain (10.3%, 87/848). At M12 and M24, the number of 0 QLQ-C30 questionnaires collected was 346 and 250, respectively. QLQ-C30 questionnaires showed that the scores of nausea or vomiting, appetite decrease, diarrhea, constipation, etc. were improved obviously at M12 or M24 compared with those at M0 or during M1 (all P<0.05). As the extension of the follow-up time, the score of the overall QoL of patients gradually increased [M0: 59.7 (0.0-100.0); M1: 63.1 (0.0-100.0); M12: 75.2 (0.0-100.0); M24: 94.1 (20.0-120.0); H=253.800, P<0.001]. Twelve months after the completion of treatments, the incidence of chronic radiation rectal injury was 9.8% (34/346), mainly presenting as abdominal pain, constipation, stool blood, diarrhea, mostly at level 1 to 2 toxicity (33/34, 97.1%). One patient (0.3%) developed frequent diarrhea (>8 times/d), which was level 3 toxicity. Twenty-four months after all treatments, the incidence of chronic radiation rectal injury was 9.6% (24/250), which was not decreased significantly compared to that in the previous period (χ(2)=0.008, P=0.927). The symotoms of one patient with level 3 toxicity was not relieved. Conclusions: The common symptoms of patients with pelvic maligant tumors during postoperative adjuvant radiotherapy include nausea, vomiting, constipation, abdominal pain and diarrhea. These symptoms are alleviated obviously at 12 and 24 months after adjuvant radiotherapy, and the QoL is significantly improved. However, a few patients may develop chronic radiation rectal injury which is not improved for years or even decades, and deserves attention in clinical practice.
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Female , Humans , Pelvic Neoplasms/radiotherapy , Quality of Life , Radiation Injuries , Radiotherapy Dosage , Radiotherapy, Adjuvant , Rectum/surgery , Retrospective StudiesABSTRACT
Objective To preliminarily evaluate the clinical efficacy of endoscopic argon plasma coagulation (APC) combined with sub-mucosal injection of norepinephrine saline in the treatment of radiation proctitis (RP),especially for refractory RP.Methods Clinical data of 22 RP patients were retrospectively analyzed.The severity of RP was evaluated by a modified endoscopy scoring system (A) or Sherman's classification (B).The criteria of successful treatment are the improvement of clinical symptoms or the cessation of bleeding (or only occasional traces of blood on the stools that do not need further treatment).Results All 22 patients were successfully treated.Among them,18 patients (82％) had no bleeding.According to the classification of A,15 patients (68％) had mild proctitis and 7(32％) experienced severe proctitis.Based on B classification,9 patients (41％) were categorized as mild proctitis and 13(59％) as severe proctitis.Using the classification of A,the number of treatment sessions was significantly correlated with the endoscopic grade (or endoscopic total score) (Spearman's r=0.86,P＜0.001).Conclusions Preliminary evidence demonstrates that endoscopic APC combined with sub-mucosal injection of norepinephrine saline is not only effective for mild and moderate RP,but also maintains long-term efficacy for refractory RP.Modified endoscopy scoring system (A) assessment is more suitable for clinical application compared with B assessment.
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Objective@#To preliminarily evaluate the clinical efficacy of endoscopic argon plasma coagulation (APC) combined with sub-mucosal injection of norepinephrine saline in the treatment of radiation proctitis (RP), especially for refractory RP.@*Methods@#Clinical data of 22 RP patients were retrospectively analyzed. The severity of RP was evaluated by a modified endoscopy scoring system (A) or Sherman′s classification (B). The criteria of successful treatment are the improvement of clinical symptoms or the cessation of bleeding (or only occasional traces of blood on the stools that do not need further treatment).@*Results@#All 22 patients were successfully treated. Among them, 18 patients (82%) had no bleeding. According to the classification of A, 15 patients (68%) had mild proctitis and 7(32%) experienced severe proctitis. Based on B classification, 9 patients (41%) were categorized as mild proctitis and 13(59%) as severe proctitis. Using the classification of A, the number of treatment sessions was significantly correlated with the endoscopic grade (or endoscopic total score)(Spearman’s r=0.86, P<0.001).@*Conclusions@#Preliminary evidence demonstrates that endoscopic APC combined with sub-mucosal injection of norepinephrine saline is not only effective for mild and moderate RP, but also maintains long-term efficacy for refractory RP. Modified endoscopy scoring system (A) assessment is more suitable for clinical application compared with B assessment.
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We report a case of a 57-year-old woman with radiation proctitis (RP) treated by shiunko (SK) enema with promising outcomes. The patient underwent interstitial brachytherapy for anterior vaginal vault recurrence of uterine cancer. Nine months after the treatment, she had anal pain and was diagnosed with RP by clinical course and colonoscopy. The rectal ulcer was so severe that a surgeon proposed permanent stoma formation as one option, given eventual risk of rectovaginal fistula. The patient rejected stoma formation and opted for Kampo medicine. Though she took keishibukuryogankayokuinin for blood stasis at first, her anal pain and rectal bleeding gradually worsened. Thereafter, she mainly used SK enema, kyukikyogaito and magnesium oxide. Anal pain and rectal bleeding decreased after applying SK to the rectal wall per rectum. Magnetic resonance imaging (MRI) and colonoscopy findings of the rectal ulcer also improved. SK effectively reduced anal pain and rectal bleeding as well as stimulated tissue repair in our patient, and therefore SK is worth considering in the treatment of RP.
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Context: Radiotherapy is a very effective treatment modality for pelvic malignancies such as carcinoma of the cervix. However, it is quite common for chronic radiation proctitis (CRP) to manifest after radical radiotherapy. CRP is a source of significant morbidity, and there is a lack of effective treatment modalities. There also exists a general lack of guidelines on management of CRP. Aims: To assess the benefit from 4% formalin application for the treatment of Grade >2 CRP among patients previously treated with radical radiotherapy for cervical carcinoma. Settings and Design: This retrospective descriptive study involved 29 eligible patients who were treated from November 2010 - November 2015 for CRP with 4% formalin application. Materials and Methods: Of the 1864 patients of carcinoma cervix treated during the said patients, 29 patients fulfilled the eligibility criteria. Eligible patients were invited telephonically for follow-up and were assessed for response and complications of the procedure. Results: The treatment of hemorrhagic radiation proctitis with local formalin instillation is effective, well tolerated and safe procedure. The procedure is inexpensive, technically simple and can be done on an outpatient basis. 62% patients had complete freedom from rectal bleed, while 34.5% patients had partial benefit. Only one patient required diversion colostomy for persistent bleeding.
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Objective: To discuss the efficacy of Jiawei Changfengyin with retention enema therapy for acute radiation proctitis and investigate its influence on regulating levels of helper T cell(Th)1/Th2. Method: One hundred and twenty-eight patients were randomly divided into control group and observation group by random number table. Patients in control group (64 cases) got montmorillonite powder (3.0 g), dexamethasone (10 mg) and normal saline (100 mL), with retention enema therapy. Patients in observation group (64 cases) got Jiawei Changfengyin(Changfengyin+Xileisan+pearl powder), with retention enema therapy. Both groups of patients received enema once every night, and the treatment course was 4 weeks in both groups. Before and after treatment, scores of main symptoms, proctoscopy, routine examination of stool+occult blood, and KPS scores of quality of life were graded. Levels of Th1 cell factors[interleukin(IL)-1β, IL-8 and interferon-γ(IFN-γ)], Th2 cell factors (IL-4 and IL-10) were detected. Result: The total effective rate for comprehensive clinical efficacy was 95.31% in observation group, higher than 82.81% in control group (χ2=5.132, PPZ=2.764, PPPβ, IL-8 and IFN-γ in observation group were lower than those in control group, while levels of IL-4 and IL-10 were higher than those in control group (PConclusion: Jiawei Changfengyin can relieve symptoms of acute radiation proctitis, promote healing of rectal mucosa, improve quality of life, and regulate Th1/Th2 cytokines, with good repairing effect for intestinal mucosa.
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Objective@#To evaluate the efficacy of ginsenoside Rg3(GRg3) in the treatment of acute radiation proctitis in rat models.@*Methods@#On the 7th day after 21.5 Gy irradiation, 100 rats were divided into the control group (normal saline, n=20), GRg3 group (gavage of 20 mg/kg, 40 mg/kg and 80 mg/kg GRg3, n=20 for each dose) and Smecta mixture enema group (n=20). After 2 weeks, all rats were anesthetized with chloral hydrate (3 ml/kg) and approximately 5 ml of blood sample was collected from the abdominal aorta prior to sacrifice. The rectal tissues were taken and prepared for detection of Bax and NF-κB contents and HE staining to observe the pathological changes of the rectal tissues. After the blood samples were centrifuged, the supernatants were collected for ELISA to detect the serum levels of IL-2, IL-6, TNF-α and MPO in each group.@*Results@#In the GRg3 group, the serum inflammatory cytokines, serum MPO concentration and the concentration of Bax and NF-κB in the intestinal tissues of rats were decreased along with the increasing dose of GRg3. These parameters in the high-dose GRg3 group were significantly lower than those in the saline group (all P<0.05), whereas did not significantly differ from those in the Smecta mixture enema group (all P>0.05), suggesting that GRg3 exerted good therapeutic effect on acute radiation proctitis in rat models.@*Conclusions@#GRg3 can significantly reduce the concentration of inflammatory cytokines, Bax and NF-κB in the intestinal tissues of rat models with acute radiation proctitis, which is more efficacious than the normal saline. GRg3 can be used to treat acute radiation proctitis in rat models.
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BACKGROUND@#To investigate the effectiveness of topical application of 4% formaldehyde as a minimally invasive treatment of rectal bleeding due to chronic radiation proctitis (CRP) under direct vision of electronic colonoscope.@*METHODS@#The clinical data of 13 CRP patients complicated with ≥ grade II bleeding admitted to our hospital between January 2003 and December 2018 were retrospectively analyzed. Under the guidance of electronic colonoscope, 4% formaldehyde combined with 5-aminosalicylic acid (5-ASA) suppositories was topically applied. Patients were followed up for two months after treatment, and the therapeutic effectiveness was observed and analyzed.@*RESULTS@#The rectal bleeding due to CRP was markedly reduced after topical application of 4% formaldehyde under colonoscope in all 13 patients. The bleeding stopped after one treatment session in 11 patients and after the second session in 2 patients. 5-ASA was also applied along with the use of 4% formaldehyde. The therapeutic effectiveness was satisfactory during the 1- and 2-month follow-up period.@*CONCLUSION@#Topical application of 4% formaldehyde under the direct vision of colonoscope as a minimally invasive treatment for CRB-induced bleeding is a simple, effective, affordable, and repeatable technique without obvious complications, which deserves further exploration and promotion.
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In recent years, the incidence rate of prostate cancer has been gradually elevated year by year in China. External radiotherapy yields similar clinical efficacy to surgery in the treatment of localized prostate cancer. Because the rectum is close to the prostate, the radiotherapy targeting for prostate cancer constantly causes radiation-related proctitis. Recently, multiple researchers have attempted to inject polyethylene glycol hydrogel into the rectal prostate space to separate the rectum from the prostate, thereby reducing the radiation dose coverage for the rectum and minimizing the risk of radiation-related proctitis. In this article, the application basis, radiation stability, injection technology, dosimetry and clinical efficacy of polyethylene glycol hydrogel injection were summarized.
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Objective: To observe and analyze the clinical efficacy of Biafine combined with routine drugs in retention enema treatment for radiation proctitis of cervical cancer. Methods: 80 patients with cervical cancer who have complications of acute radiation proctitis after radiotherapy were divided into observation group(Biafine combined with routine drugs in retention enema treatment, 40 cases)and control group(routine drugs in retention enema treatment, 40 cases). The curative effects of two methods for radiation proctitis of cervical cancer were compared and researched. Results: The effective rate of observation group for curing radiation proctitis was 95% , and it was 75% in control group. The difference of effective rate between the two groups was significant(x2=7.333, P<0.05). Conclusion: It is significant that Biafine is applied to combine with routine drugs in retention enema treatment for radiation proctitis.
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Objective To investigate the relationship between acute radiation proctitis and radiation dose,volume as well as radiation time,in the process of intensity-modulated radiation therapy (IMRT) for the cervical cancer patients.Methods A total of 51 patients with locally advanced cervical cancer were enrolled from January 2011 to December 2013.Those patients were then classified into grade 1 to 4 groups,according to the RTOG/EORTCtoxicity grading standard.The exposure dose volume and the average dose of rectum under the standard plan were evaluated with dose-volume histogram (DVH).The ANOVA test was used for analyzing Dmax,D mean,D1 cm3,D2cm3,D40 and V40 values of rectum and the average exposure dose of rectum.Results The average time of acute radiation proctitis with clinical symptoms was (23.06 ± 12.01) d after radiotherapy.Dmaxvalues of rectum in grade 2 group was lower than those in grade 3 and 4 groups (F =5.268,P ＜ 0.05).Moreover,D1 cm3 and D2 cm3 values of rectum in grade 1 and 2 groups were also lower than those in grade 3 and 4 groups (F =4.893,4.406,P ＜ 0.05).There was no statistically significant difference between D40 and V40 values.Conclusions The acute radiation proctitis could be frequently found around 20 days during the IMRT for cervical cancer patients.Mild and moderate acute radiation proctitis are more common,while severe acute radiation proctitis is rare.Minimizing Dmax,D1 cm3 and D2 cm3 values of rectum might reduce the incidence of severe acute radiation proctitis in cervical cancer patients receiving IMRT.
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Radiation proctitis is one of the complications after radiotherapy for pelvic malignancies.Surgery is not necessary for the most of radiation proctitis.However, surgery is unavoidable when rectal obstruction, uncontrollable bleeding, and fistula occur. This article reviews the progress in surgical treatment of radiation proctitis.
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Radiotherapy is an important method of tumor treatment .The incidence of complications caused by radiotherapy is high, which seriously effect patients′quality of life.The current terms of radiation enteritis , radiation proctitis and radiation cystitis can not reflect the changes of physiopathology after radiotherapy .Nowadays , a consensus has been gradually reached that 'pelvic radiation disease'is a more accurate description .This article mainly introduces the definition evolution , significance and current status of pelvic radiation disease to draw the attention of domestic related professionals .A new starting point is opening for the curing of radiotherapy-related complications .
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Objective To explore the optimal method of treatment for radiation proctitis by keeping coloclysis with traditional Chinese medicine (TCM), including administation temperature, infusion time, dosage and catheter depth. Methods The orthogonal experimental design was adopted. Sixty-three patients with radiation proctitis were randomly divided into 9 groups, and they were under enema for 6 weeks according to different test conditions. TCM syndrome score, radiation injury effect and Karnofsky scores were set as evaluation indexes. An orthogonal design and analysis of variance were conducted for optimization. The best technical schemes for traditional Chinese herb in treating radiation proctitis were obtained. Results The obtained optimum methods are:drug temperature of (39±0.5)℃, infusion time of 30 minutes, dosage of 100 mL, catheter depth of 20 cm. Conclusion The optimal scheme of enema for the treatment of radiation proctitis is reasonable and feasible.
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Background: Radiation induced haemorrhagic proctitis is a well recognized complication of pelvic radiotherapy and its treatment is quite challenging. Aim: To evaluate the efficacy of local instillation of 4% formalin in the management of uncontrolled radiation induced haemorrhagic proctitis. Methods: This prospective study included twenty-three patients who underwent formalin instillation. We documented the control of the symptoms, assessed the outcome of the treatment, presence of complications & long term results. Results: All patients were followed for a median of 13 months. In 15 patients, the bleeding stopped after a single treatment and in 6 after a second session. Only two patients required formalin instillation for the third time. During the follow-up period all patients were reviewed systemically with reference to the pretreatment complaints. No recurrent rectal bleeding occurred, bowel frequency was decreased and no further blood transfusion was required. Conclusion: Local instillation of 4% formalin is an effective treatment for uncontrolled radiation induced haemorrhagic proctitis.
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Background: Chronic radiation proctitis is known to be a difficult to treat condition. Argon Plasma Coagulation (APC) though being effective requires prolonged sessions and has limited availability. Formalin, by virtue of its chemical cauterizing effects, has been found to be effective in patients with bleeding radiation cystitis and hemorrhagic proctitis. Our goal was to study the effectiveness of 4% formalin instillation in resistant patients of chronic hemorrhagic radiation proctitis. Methods: 13 patients with chronic radiation proctitis were treated with instillation of 50 ml 4% formalin into the rectum (3 minutes for 3 times). The total mucosal contact time was approximately 10 minutes. Their clinical response, tolerance to treatment and complications were assessed. Patients who did not have complete response were given another session(s) a week later. Results: The mean (SD) age of patients was 48.62±11.66 years. Twelve patients (92%) were female who received radiotherapy for carcinoma cervix and 1(08%) was male with carcinoma prostate. The overall clinical response rate was 100%; eight patients (61.5%) had complete cessation of bleeding while 5 patients (38.5%) had significant cessation of bleeding. Eight patients needed only one session, four needed 2 sessions and one patient needed 3 sessions for the clinical response. Serious complications were not observed . No recurrence of symptoms was seen during follow-up Conclusion: The treatment of hemorrhagic radiation proctitis with local formalin instillation is effective, well tolerated, inexpensive, technically simple and safe procedure.
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Objective:To study whether sacral lymph nodes should be included in the target volume delineation for those patients with early (stageⅠB-ⅡA) uterus cervix cancer during postoperative radiotherapy. Methods:Forty-six patients with early uterus cervix cancer were given postoperative three dimensional conformal radiation therapy (3D-CRT) in our department for one month after radical resection. The patients were randomly divided into two groups. The sacral lymph nodes were not included in the target volume delineation in the treatment group. But they were delineated in control group. All the patents had no radiotherapy-related contraindications and signed the consent agreement. The patients were followed up. The local controlling rate and the incidence and degree of radioactive proctitis were compared between the two groups. Results:The local controlling rate of the two groups had no significant difference(t=0.000, P=1.000). The doses received by the 5% and 95% volume of the rectum(V_5, V_95), the average dose, and the minimum dose had significant difference between the two groups(t_(V5)=2.169, P_(V5)=0.041; t_(V95)=4.036, P_(V95)=0.001;t_(mean)=2.236, P_(mean)=0.036; t_(min)=2.265, P_(min=0.034), but the maximum dose received by the rectum had no obvious difference (t_(max)=0.518, P_(max)=0.610). The incidence of radioactive proctitis had significant difference between the two groups(t=2.174, P=0.190). Conclusion:For the early uterus cervix cancer patients who have recurrent risk after radical surgery, sacral lymph nodes should not be included in the delineation of target volume during 3D-CRT in order to decrease the incidence of radioactive proctitis.
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Objective:To investigate the effect and safety of QingreBuyi decoction(QBD) in treating acute radiation proctitis(ARP).Methods:Sixty patients were randomized into the treatment group(QBD plus conventional therapy,n=30) and the control group(conventional therapy,n=30).The changes of syndromes and signs score,D-lactic-acid and diamine oxidase,total effective rate,hepatic/renal function and adverse event were observed.Results:The levels of D-lactic-acid and diamine oxidase in the treatment group were decreased than those in the control group after treatment(P
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PURPOSE: Proctitis is one of acute complications encountered when radiotherapy was applied to the pelvis. Radiation-induced proctitis represents similar microscopic findings that are observed in inflammatory bowel disease (IBD). Nitric oxide (NO) plays an important role in the inflammatory process and many data suggest a close relationship between NO production and gastrointestinal inflammation. This study was aimed to establish the optimal radiation dose for radiation-induced proctitis in rat and to find a relationship between radiation proctitis and NO production. MATERIALS AND METHODS: Female Wistar rats, weighing from 150 to 220 g, received various doses(10-30 Gy) of radiation to the rectum. On the 5th and 10th day after irradiation, rectal specimens were evaluated grossly and microscopically. In addition, the degree of NO production by irradiation dose was evaluated by study with NOS expression and nitrite production in the irradiated rectal tissue. To evaluate relationship between radiation proctitis and NO, we administered aminoguanidine, iNOS inhibitor and L-arginine, substrate of NOS to rats from 2 days before to 7 days after the irradiation. RESULTS: There were obvious gross and histological changes after 17.5 Gy or higher radiation dose but not with 15 Gy or less radiation dose. Twenty Gy or higher dose of radiation caused Grade 4 damage in most of rectal specimens which were more likely to be related to the late complications such as fibrosis, rectal bleeding and rectal obstruction. A single fraction of 17.5 Gy to the rat rectum is considered to be an optimal dose to produce commonly experienced proctitis in the clinic. The result demonstrated that severity of microscopic damage of rectal mucosa from irradiation significantly correlated with iNOS overexpression. However, administration of iNOS inhibitor or substrate of iNOS did not influence the degree of rectal damage. CONCLUSION: A single fraction of 17.5 Gy irradiation to the rat rectum considered to be an optimal dose for radiation induced proctitis model. These results indicated that an excess production of NO contributes to pathogenesis of radiation-induced proctitis in part but was not the direct cause of rectal damage.