BackgroundThe complexity of gastrointestinal (GI) disorders associated with Parkinson's disease (PD) and the significant interactions between GI medications and the dopaminergic axis necessitates expert management. The integrated care model for disorders of the brain-gut interaction (DBGI) has advantages, however, has not been applied in concurrent DBGI and PD.ObjectiveTo test the hypothesis that our Parkinson's Research and Integrated Support Model (PRISM) will reduce symptom severity and improve the quality of life (QOL) in patients with GI symptoms associated with PD.MethodsPatients with refractory GI symptoms referred to the PRISM clinic were evaluated and treated by the integrated efforts of movement disorder specialists, neurogastroenterologists, dietitians, occupational therapists, speech-swallow therapists, and neuroscientists. Patients underwent a battery of GI symptoms and QOL questionnaires and personalized actionable biomarkers (motility testing and swallowing studies). Inflammatory markers and stool tests were collected. An individualized standard of care treatment was established based on the specific DBGI diagnosis uncovered during the PRISM evaluation.Results44 adult PD patients with GI complaints were evaluated. The most common symptoms included constipation (97%), dysphagia (61%), and gastroesophageal reflux (34%). Actionable biomarkers were highly positive revealing esophageal dysmotility (20/21, 95%), slow-transit constipation (40/42, 90%), intestinal methanogen overgrowth (7/8, 87%), gastroparesis (17/20, 85%), oropharyngeal dysphagia (28/44, 63%), and dyssynergic defecation (27/42, 61%). GI symptom severity and QOL significantly improved (p < 0.05) as measured by all questionnaires.ConclusionsMore severely affected patients with Parkinson's treated with the Fixel PRISM approach showed significant improvements in GI symptom frequency, severity, and QOL.

Chronic constipation is a common gastrointestinal disorder, and management is crucial. Computed tomography (CT) is useful for evaluating rectal fecal mass but limited owing to radiation exposure, cost, and inaccessibility at certain facilities. Ultrasonography (US) avoids these pitfalls, but it is unknown whether it accurately assesses rectal feces. In this study, we evaluated the diagnostic performance of US compared with CT as the gold standard for assessing rectal feces.

We prospectively evaluated rectal fecal mass retention using US performed within 1 h of CT to assess the degree of agreement between methodologies. Rectal stool findings were evaluated on three levels: no stool (R1), presence of stool (R2), and hard stool filling (R3).

The sample included 100 patients (55 men, 45 women), of whom 47 were constipated. The kappa coefficients for rectal content detection were excellent between US and CT (p <0.001). Eighty-two cases (R1: 46 cases; R2: 28 cases; R3: 8 cases) were matched with CT and US findings, and 18 were not. Cases that did not match had low urine or high gas volumes. CT and US findings showed high agreement in constipation (kappa coefficient 0.674, p <0.001) and non-constipation groups (kappa coefficient 0.677, p <0.001). All cases with R3 on CT were found in the constipation group, while more than half of the cases with R1 on CT were in the non-constipation group.

CT and US showed high agreement in evaluating rectal fecal mass retention, indicating that US can substitute CT.

Our aim was to determine the reliability of plain abdominal radiographs for the evaluation of abdominal gas content in patients with functional digestive symptoms.

Abdominal CT scan scout views, mimicking a conventional plain abdominal radiograph, were obtained from 30 patients both during episodes of abdominal distension and basal conditions. Physicians (n = 50) were instructed to rate the estimated volume of gas in the 60 images presented in random sequence using a scale graded from 0 to ≥600 ml.

The gas volumes estimated in the scout views differed from those measured by CT by a median of 90 (95% CI 70-102) ml, and the misestimation was not related to the absolute volume in the image. The accuracy of the observers, measured by their mean misestimation, was not related to their specialty or the training status (misestimation by 96 (95% CI 85-104) ml in staff vs 78 (70-106) ml in residents; p = 0.297). The accuracy was independent of the order of presentation of the images. Gas volume measured by CT in the images obtained during episodes of abdominal distension differed by a median of 39 (95% CI 29-66) ml from those during basal conditions, and this difference was misestimated by a median of 107 (95% CI 94-119) ml. The accuracy of these estimations was not related to the absolute gas volumes (R = -0.352; p < 0.001) or the magnitude of the differences.

Plain abdominal radiographs have limited value for the evaluation of abdominal gas volume in patients with functional gut disorders.

Evaluation of chronic constipation is important, although it is often difficult to satisfactorily treat due to the complex interplay of factors. This study aimed to determine whether the volume of intraluminal contents and lateral diameter of the colon measured from computed tomography (CT) images were correlated with the symptoms of chronic constipation and stool consistency. Consecutive patients who underwent the Constipation Scoring System (CSS), Bristol Stool Form Scale (BSFS) questionnaires and simple abdominal CT were selected retrospectively. The intestinal tract diameter at each site was measured, and the amounts of stool and gas in the intestinal tract were evaluated at five levels. Of the 149 study participants, 54 were males and 95 were females and their mean age was 72.1 years. In the right hemi-colon, CSS5 (Time) correlated significantly with gas volume (p < 0.01). In the left hemi-colon, stool volume correlated significantly with CSS2 (Difficulty), CSS3 (Completeness), CSS5 (Time) and CSS total (p < 0.05). The BSFS negatively correlated with gas volume and diameter in the right hemi-colon and with gas volume in the rectum (p < 0.05). CT findings including stool volume, gas volume and diameter correlated with some constipation symptoms and stool consistency. These findings may be useful in evaluating and treating constipation.

To investigate whether use of an enema prep reduces the false-negative (FN) rate of PI-RADS 1 MRI of the prostate for clinically significant prostate cancer (csPCa).

1108 consecutive patients with a PI-RADS 1 MRI performed 01/2016-09/2021 were retrospectively collected. Patient charts were examined for subsequent systematic prostate biopsy performed within 1 year if positive or anytime thereafter if negative. Patients without biopsy were excluded. Use of an enema prep 1-2 h before MRI, which was implemented in 03/2019, was recorded. FN rate of MRI for detection of csPCa, defined as Gleason score ≥ 7, using systematic biopsy was assessed per patient and compared between those with and without an enema prep. Χ² test and logistic regression were performed.

255 patients (median age 64, IQR 58-69) with median PSA 5.6 (IQR 4.2-8.1), PI-RADS 1 MRI, and subsequent biopsy were included in the analysis. 66 patients (26%) had an enema prep and 189 patients (74%) did not. 7 (11%) patients with and 21 (11%) patients without enema prep had a FN biopsy. There was no significant association between enema prep and FN biopsy (OR 0.95, 95% CI 0.38-2.35, p = 0.91).

Use of an enema prep prior to prostate MRI did not decrease the FN rate of PI-RADS 1 MRI of the prostate for clinically significant prostate cancer.

The prevalence of irritable bowel syndrome (IBS) in the United States is between 7% and 16%, most common in women and young people, with annual direct costs estimated at more than $1 billion dollars in the United States. Traditionally, the diagnosis of IBS has been based on the positive identification of symptoms that correlate with several different syndromes associated with disorders such as IBS diarrhea, IBS constipation, functional diarrhea, functional constipation, chronic functional abdominal pain, or bloating. Several peripheral and central mechanisms initiate gastrointestinal motor and sensory dysfunctions leading to IBS symptoms. Those dysfunctions may require evaluation in patients whose symptoms do not respond to first-line treatments.

Validation studies of consensus symptom-based criteria have identified deficiencies that favor a simpler identification of the predominant symptoms of abdominal pain, bowel dysfunction, and bloating and exclusion of alarm symptoms such as unintentional weight loss, rectal bleeding, or recent change in bowel function. Symptom-based diagnosis of IBS is enhanced with additional history for symptoms of somatoform and psychological disorders and alarm symptoms, physical examination including digital rectal examination, and screening tests to exclude organic disease (by measuring hemoglobin and C-reactive protein concentrations). The initial treatment plan should include patient education, reassurance, and first-line treatments such as fiber and osmotic laxatives for constipation, opioids for diarrhea, antispasmodics for pain and for management of associated psychological disorders. For patients who do not respond to those IBS treatments, testing for specific functional disorders may be required in a minority of patients with IBS. These disorders include rectal evacuation disorder, abnormal colonic transit, and bile acid diarrhea. Their identification is followed by individualized treatment, such as pelvic floor retraining for rectal evacuation disorders, sequestrants for bile acid diarrhea, and secretory agents for constipation, although there is only limited evidence that this individualized management approach is effective.

Advances in the identification of specific dysfunctions as causes of individual symptoms in the "IBS spectrum" leads to the potential to enhance the diagnosis and management of symptoms for the majority of patients for whom first-line therapies of IBS and management of comorbid psychological disorders are insufficient.

Stool burden on abdominal radiographs is not reflective of constipation, perhaps because of variable fecal shadowing or limited inter-rater agreement. These limitations are hypothetically mitigated by computed tomography (CT). This research aimed (i) to evaluate whether bowel movement frequency, stool form, or a diagnosis of functional constipation correlate or associate with stool burden identified on CT, and (ii) to investigate whether physicians use CT in their assessment of a patients' bowel function.

Patients attending for non-emergent abdominal CT imaging were invited to participate by completing a bowel questionnaire. Stool burden identified on imaging was determined and inter-rater reliability was evaluated in a subgroup of patients (n = 20). Descriptive and comparative analyses were performed. An online questionnaire evaluated the use of abdominal imaging in assessing patients' bowel function in a cross-section of ordering physicians.

The patient response rate was 19% (96/516). No clinically useful associations between fecal burden and stool form, bowel motion frequency, gastrointestinal symptoms or a diagnosis of constipation was identified. The physician response rate was 35% (33/94). Opportunistic use of data was more common than deliberate use. However, an abdominal radiograph or CT scan had been requested by 42% and 18% of physicians respectively to assess patient's chronic bowel habit. Approximately 30% of physicians believed evidence supported this practice.

Physicians may use abdominal CT in their assessment of patients' chronic bowel habits. However, objective assessment does not support this practice. Colonic stool burden does not correlate with patient-reported symptoms or a criteria-based diagnosis of constipation.

There is controversy over the utility of symptoms, examination, and tests for diagnosis of rectal evacuation disorders (REDs) or slow-transit constipation (STC). We aimed to ascertain the pooled prevalence, sensitivity, specificity, and likelihood ratios for clinical parameters to determine pretest and post-test probabilities of diagnoses of RED and STC without RED.

We searched the MEDLINE and PUBMED databases since 1999 for studies that used binary data to calculate sensitivity, specificity, and likelihood ratios to determine the diagnostic utility of history, symptoms, and tests for RED and STC. RED and STC were defined based on confirmation by at least 1 objective anorectal test or colonic transit test. Controls had normal test results based on the specific protocol in each study.

We reviewed 100 articles; 63 studies of RED and 61 studies of STC met the inclusion criteria. Among 3364 patients with chronic constipation, objective tests demonstrated RED alone, 27.2%; normal transit constipation alone, 37.2%; STC alone, 19.0%; and RED with STC, 16.6%. To diagnose RED, discriminant features were urinary symptoms (specificity, 100%; likelihood ratio, above 10; 58 patients), less than 2 findings of dyssynergia in a digital rectal exam (sensitivity, 83.2%; negative likelihood ratio, 0.2; 462 patients) and rectoanal pressure gradient below -40 mm Hg with high anal pressure during straining (specificity, 100%; likelihood ratio, above 10; 101 patients). The features most strongly associated with STC alone were call to stool (specificity, 91.5%; likelihood ratio, 10.5; 75 patients) and absence of abdominal distension, fullness, or bloating (sensitivity, 92.9%; negative likelihood ratio, 0.1; 93 patients).

In a systematic review, we found specific symptoms, lack of dyssynergia in a digital rectal exam, and findings on anorectal manometry to be highly informative and critical in evaluation of RED and STC.

Constipation, irritable bowel syndrome, fecal incontinence, abdominal pain, and anorectal pain are problems that affect 40% of the population. They commonly present with overlapping symptoms indicating that their pathophysiology affects multiple segments of the gut as well as brain and gut interactions. Clinically, although some conditions are readily recognized, dyssynergic defecation, fecal incontinence, and anorectal pain are often missed or misdiagnosed. Consequently, the assessment of lower gastrointestinal symptoms in patients with suspected colonic or anorectal motility disorder(s) remains challenging for most clinicians. A detailed history, use of the Bristol stool form scale, prospective stool diaries, ideally through a phone App, digital rectal examination, and judicious use of complementary diagnostic tests are essential. Additionally, it is important to evaluate the impact of these problems on quality of life and psychosocial issues, because they are intricately linked with these disorders. The Rome IV diagnostic questionnaire for functional gastrointestinal disorders can provide additional information often missed during history taking. Here, we discuss a systematic approach for the clinical evaluation of patients with suspected lower gastrointestinal problems, grouped under 4 common diagnostic categories. We describe how to take a detailed history, perform meticulous digital rectal examination, and use validated tools to supplement clinical evaluation, including assessments of quality of life and scoring systems for disease severity and digital Apps. These tools could facilitate a comprehensive plan for clinical management including diagnostic tests, and translate the patients' complaints into definable, diagnostic categories.

With a worldwide prevalence of 15%, chronic constipation is one of the most frequent gastrointestinal diagnoses made in ambulatory medicine clinics, and is a common source cause for referrals to gastroenterologists and colorectal surgeons in the United States. Symptoms vary among patients; straining, incomplete evacuation, and a sense of anorectal blockage are just as important as decreased stool frequency. Chronic constipation is either a primary disorder (such as normal transit, slow transit, or defecatory disorders) or a secondary one (due to medications or, in rare cases, anatomic alterations). Colonic sensorimotor disturbances and pelvic floor dysfunction (such as defecatory disorders) are the most widely recognized pathogenic mechanisms. Guided by efficacy and cost, management of constipation should begin with dietary fiber supplementation and stimulant and/or osmotic laxatives, as appropriate, followed, if necessary, by intestinal secretagogues and/or prokinetic agents. Peripherally acting μ-opiate antagonists are another option for opioid-induced constipation. Anorectal tests to evaluate for defecatory disorders should be performed in patients who do not respond to over-the-counter agents. Colonic transit, followed if necessary with assessment of colonic motility with manometry and/or a barostat, can identify colonic dysmotility. Defecatory disorders often respond to biofeedback therapy. For specific patients, slow-transit constipation may necessitate a colectomy. No studies have compared inexpensive laxatives with newer drugs with different mechanisms. We review the mechanisms, evaluation, and management of chronic constipation. We discuss the importance of meticulous analyses of patient history and physical examination, advantages and disadvantages of diagnostic testing, guidance for individualized treatment, and management of medically refractory patients.

Functional constipation is common in children and adults worldwide. Functional constipation shows similarities in children and adults, but important differences also exist regarding epidemiology, symptomatology, pathophysiology, diagnostic workup and therapeutic management. In children, the approach focuses on the behavioural nature of the disorder and the initial therapeutic steps involve toilet training and laxatives. In adults, management focuses on excluding an underlying cause and differentiating between different subtypes of functional constipation - normal transit, slow transit or an evacuation disorder - which has important therapeutic consequences. Treatment of adult functional constipation involves lifestyle interventions, pelvic floor interventions (in the presence of a rectal evacuation disorder) and pharmacological therapy. When conventional treatments fail, children and adults are considered to have intractable functional constipation, a troublesome and distressing condition. Intractable constipation is managed with a stepwise approach and in rare cases requires surgical interventions such as antegrade continence enemas in children or colectomy procedures for adults. New drugs, including prokinetic and prosecretory agents, and surgical strategies, such as sacral nerve stimulation, have the potential to improve the management of children and adults with intractable functional constipation.

The inner workings of the intestines, in which the body and microbiome intersect to influence gut function and systemic health, remain elusive. Carbon dioxide, hydrogen, methane and hydrogen sulfide, as well as a variety of trace gases, are generated by the chemical interactions and microbiota within the gut. Profiling of these intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. Indeed, different tools for measuring these intestinal gases have been developed, including newly developed gas-sensing capsule technology. Gases can, according to their type, concentration and volume, induce or relieve abdominal symptoms, and might also have physiological, pathogenic and therapeutic effects. Thus, profiling and modulating intestinal gases could be powerful tools for disease prevention and/or therapy. As the interactions between the microbiota, chemical constituents and fermentative substrates of the gut are principally influenced by dietary intake, altering the diet, which, in turn, changes gas profiles, is the main therapeutic approach for gastrointestinal disorders. An improved understanding of the complex interactions within the intestines that generate gases will enhance our ability to prevent, diagnose, treat and monitor many gastrointestinal disorders.

The overall objectives of this review are to summarize actionable biomarkers for organic etiology of lower functional gastrointestinal disorders (FGIDs) that lead to individualized treatment for their FGIDs and to assess the pipeline for novel approaches to the management of constipation, diarrhea, and chronic abdominal pain in lower FGIDs. The new approaches to therapy include ion exchangers/transporters for functional constipation (sodium-glucose cotransporter 1, Na+/H+ exchanger 3, and solute carrier family 26 member 3 inhibitors), bile acid modulators for constipation such as ileal bile acid transporter inhibitors and fibroblast growth factor 19 analog for functional constipation, and bile acid sequestrants or farnesoid X receptor agonists for functional diarrhea. Treatment for chronic abdominal pain remains an unmet need in patients with lower FGIDs, and promising novel approaches include delayed-release linaclotide, nonclassical opioid visceral analgesics, and selective cannabinoid receptor agonists. The role of probiotics, fecal microbial transplantation, and possible future microbiome therapies is discussed.

This study aimed to evaluate the capability of ultrasonography to predict favorable outcomes of various medical therapies in patients with chronic constipation.

We enrolled 223 patients with chronic constipation (75 men, 148 women; mean age 62.9 ± 3.4 years). Transverse diameters of four segments of the colon (ascending [A], transverse [T], descending [D], sigmoid [S]), and the rectum [R]) were measured. The patients' stool and/or gas distribution was evaluated using the constipation index (CI) ([A + T + D + S + R]/5) and the left/right distribution ratio ([D + S]/[A + T]) according to our previous study. Patients were first treated with fiber- or osmosis-based laxatives for 2 weeks. When constipation was not alleviated, stimulant-based laxatives were added, and the patients were followed for another 2 weeks.

Based on their clinical courses, patients were divided into four groups: nonresponders (group A) or responders (group B) to fiber- or osmosis-based laxatives; nonresponders to any medical therapy (group C); and responders to stimulant-based laxatives (group D). The CI was significantly higher in group A than group B (P < 0.05), with the receiver operating characteristic (ROC) curve analysis showing a CI cut-off of 21.2 for predicting favorable outcomes of either fiber- or osmosis-based laxatives (P < 0.05). Left/right distribution ratio was significantly lower in group C than group D (P < 0.05), and the ROC curve analysis showed a left/right cut-off of 0.5 for predicting responders to stimulant-based laxatives (P < 0.05).

These findings could help physicians predict favorable outcomes with laxatives without side effects for this patient population.

Balloon expulsion test (BET) and high-resolution anorectal manometry (HRM) are used in diagnosis of rectal evacuation disorders (REDs); their performance characteristics are suboptimal.

We audited records of 449 consecutive patients with chronic constipation (CC). We documented anal sphincter tone and contraction, puborectalis tenderness, and perineal descent on digital rectal exam (DRE); maximum resting and squeeze pressures, and rectoanal pressure gradient on HRM; weight or time to balloon expulsion; colonic transit, and area of rectal area on radiograph (RASF). We based the diagnosis of RED on ≥2 abnormalities on both DRE and HRM, excluding results of BET, as the performance of BET is being investigated. Results of RED vs non-RED and results obtained using tbBET vs wbBET groups were compared. We used multivariate logistic regressions to identify predictors of RED using different diagnostic modalities.

Among 449 individuals, 276 were included (74 RED and 202 non-RED). Predominant exclusions were for no HRM (n = 79) or use of low resolution anorectal manometry (n = 77). Logistic regression models for abnormal tbBET showed time >60 seconds, RASF and age-predicted RED. For tbBET, the current cutoff of 60 seconds had sensitivity of 39.0% and specificity 93.0% to diagnose RED; on the other hand, applying the cutoff at 22 seconds, the sensitivity was 77.8% and specificity 69.8%.

The clinical diagnosis of RED in patients with CC is achieved with combination of DRE, HRM and an optimized, time-based BET. Prospective studies are necessary to confirm the proposed 22 second cutoff for tbBET.

The evolution of medical devices has led to the introduction of medical devices that include "substances" and which, due to their presentation and sites of application may resemble medicinal products. The difference between substance-based medical devices and medicinal products lies in the proper definition of the principal mechanism of action. The major problem at the moment is the lack of a proper procedure for the demonstration of a mechanism that is "not pharmacological, immunological or metabolic." We aimed to design an experimental set up to demonstrate the difference between the mechanism of action of two substances used commonly for the treatment of constipation, lubiprostone (example of medicinal product) and glycerine (example of medical device). By implementing cellular models and molecular analyses we demonstrate the difference in their mechanism of action. This set up can be considered an example on the possibility to define a paradigm for the case by case study of the mechanism of action of substances and combination of substances in medical devices.

Constipation, a condition characterized by heterogeneous symptoms, is common in Western society. It is associated with reduced physical health, mental health, and social functioning. Because constipation is rarely due to a life-threatening disease (for example, colon cancer), current guidelines recommend empiric therapy. Limited surveys suggest that fewer than half of treated individuals are satisfied with treatment, perhaps because the efficacy of drugs is limited, they are associated with undesirable side effects, or they may not target the underlying pathophysiology. For example, although a substantial proportion of constipated patients have a defecatory disorder that is more appropriately treated with pelvic floor biofeedback therapy than with laxatives, virtually no pharmacological trials formally assessed for anorectal dysfunction. Recent advances in investigational tools have improved our understanding of the physiology and pathophysiology of colonic and defecatory functions. In particular, colonic and anorectal high-resolution manometry are now available. High-resolution anorectal manometry, which is increasingly used in clinical practice, at least in the United States, provides a refined assessment of anorectal pressures and may uncover structural abnormalities. Advances in our understanding of colonic molecular physiology have led to the development of new therapeutic agents (such as secretagogues, pro-kinetics, inhibitors of bile acid transporters and ion exchangers). However, because clinical trials compare these newer agents with placebo, their efficacy relative to traditional laxatives is unknown. This article reviews these physiologic, diagnostic, and therapeutic advances and focuses particularly on newer therapeutic agents.

The first aim of this study was to develop a new ultrasonographic method (US) to evaluate stool and/or gas distribution. The second aim was to apply this method to compare stool and/or gas distribution between healthy subjects and patients with chronic constipation and evaluate whether US parameters could be an alternative to the colonic transit time (CTT).

We enrolled seven healthy volunteers (four men, three women; mean age 29.3 ± 5.2 years) who underwent US and computed tomography (CT) on the same day to evaluate the reproducibility of US results. We then enrolled 268 patients with chronic constipation (94 men, 174 women; mean age 63.3 ± 4.2 years) and 66 age- and sex-matched healthy subjects (controls). The transverse diameters of four segments of the colon [ascending (AC), transverse (TC), descending (DC), and sigmoid (SC)] and the rectum (R) were measured, and their stool and/or gas distribution was evaluated using the constipation index (CI) [AC + TC + DC + SC + R/5] and left/right (L/R) distribution [(DC + SC)/(AC + TC)]. The CTT was assessed using radiopaque markers.

All healthy subjects underwent US and CT successfully, with a sufficiently high reproducibility coefficient for this method and significant correlation between the US and CT parameters. The stool and/or gas distribution evaluated by US showed a significant difference in one of the US parameters between healthy subjects and patients, and the CI was an indirect indicator for the CTT.

These findings may assist physicians evaluate stool and/or gas distribution of patients with chronic constipation, which is an indirect indicator for CTT.

To summarize the advances in diagnostic modalities and management options for defecatory dysfunction and highlight the areas in need of further research.

The diagnostic utility of high-resolution anorectal manometry (ARM), which has emerged as a promising tool for the diagnosis of defecatory dysfunction, appears to be questionable in differentiating disease from normal physiology. There also seems to be discrepancy between results of various tests of anorectal function in the diagnosis of defecatory dysfunction. New revisions in diagnostic criteria for defecatory dysfunction by Rome IV consortium, may enhance its diagnostic yield. Biofeedback remains to be the most effective evidence-based treatment option for patients with defecatory dysfunction. Anorectal pressure profile cannot predict or mediate the success of biofeedback. Biofeedback may improve the symptoms through central effects.

Despite the advances in the ARM and defecography techniques, no one test has been able to be considered as the 'gold standard' for diagnosis of defecatory dysfunction. The mechanism of action of biofeedback in defecatory dysfunction remains poorly understood.

Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry (ARM) and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED.The aim of this study was to obtain cut-off values of RGV, MRGTA, and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on ARM, balloon expulsion test (BET), and colon transit test.

We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA, and RASF, as previously described. We constructed receiver operating characteristics curves based on different values, and we estimated AUC, specificity, and positive predictive value (PPV) to detect RED in patients with constipation.

Receiver operating characteristics of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both P<.001), and 0.623 for RASF (P=.029). At specificity of 90%, RGV of 30 mL had a PPV 77.3%, MRGTA of 10 cm² had a PPV 75.0%, and RFAS of 9 cm² had a PPV of 68.8% for identifying constipated patients with RED.

Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90% specificity for RED, RGV of 20 or 30 mL or MRGTA of 10 cm² on CT has PPV ~75%, and RASF of >9 cm² has PPV of ~69%.