Imaging Inflammation and Infection in the Gastrointestinal Tract

Radiosynthesis and Bioevaluation of 99mTc-Labeled Isocyanide Ubiquicidin 29-41 Derivatives as Potential Agents for Bacterial Infection Imaging

To develop a novel 99mTc-labeled ubiquicidin 29-41 derivative for bacterial infection single-photon emission computed tomography (SPECT) imaging with improved target-to-nontarget ratio and lower nontarget organ uptake, a series of isocyanide ubiquicidin 29-41 derivatives (CNnUBI 29-41, n = 5-9) with different carbon linkers were designed, synthesized and radiolabeled with the [99mTc]Tc(I)+ core, [99mTc][Tc(I)(CO)3(H2O)3]+ core and [99mTc][Tc(V)N]2+ core. All the complexes are hydrophilic, maintain good stability and specifically bind Staphylococcus aureus in vitro. The biodistribution in mice with bacterial infection and sterile inflammation demonstrated that [99mTc]Tc-CN5UBI 29-41 was able to distinguish bacterial infection from sterile inflammation, which had an improved abscess uptake and a greater target-to-nontarget ratio. SPECT imaging study of [99mTc]Tc-CN5UBI 29-41 in bacterial infection mice showed that there was a clear accumulation in the infection site, suggesting that this radiotracer could be a potential radiotracer for bacterial infection imaging.

Infection or Inflammation: Are Uncomplicated Acute Appendicitis, Acute Cholecystitis, and Acute Diverticulitis Infectious Diseases?

Background: It is recognized increasingly that common surgical infections of the peritoneal cavity may be treated with antibiotic agents alone, or source control surgery with short-course antimicrobial therapy. By extension, testable hypotheses have emerged that such infections may not actually be infectious diseases, but rather represent inflammation that can be treated successfully with neither surgery nor antibiotic agents. The aim of this review is to examine extant data to determine which of uncomplicated acute appendicitis (uAA), uncomplicated acute calculous cholecystitis (uACC), or uncomplicated mild acute diverticulitis (umAD) might be amenable to management using supportive therapy alone, consistent with the principles of antimicrobial stewardship. Methods: Review of pertinent English-language literature and expert opinion. Results: Only two small trials have examined whether uAA can be managed with observation and supportive therapy alone, one of which is underpowered and was stopped prematurely because of challenging patient recruitment. Data are insufficient to determine the safety and efficacy of non-antibiotic therapy of uAA. Uncomplicated acute calculous cholecystitis is not primarily an infectious disease; infection is a secondary phenomenon. Even when bactibilia is present, there is no high-quality evidence to suggest that mild disease should be treated with antibiotic agents. There is evidence to indicate that antibiotic prophylaxis is indicated for urgent/emergency cholecystectomy for uACC, but not in the post-operative period. Uncomplicated mild acute diverticulitis, generally Hinchey 1a or 1b in current nomenclature, does not benefit from antimicrobial agents based on multiple clinical studies. The implication is that umAD is inflammatory and not an infectious disease. Non-antimicrobial management is reasonable. Conclusions: Among the considered disease entities, the evidence is strongest that umAD is not an infectious disease and can be treated without antibiotic agents, intermediate regarding uACC, and lacking for uAA. A plausible hypothesis is that these inflammatory conditions are related to disruption of the normal microbiome, resulting in dysbiosis, which is defined as an imbalance of the natural microflora, especially of the gut, that is believed to contribute to a range of conditions of ill health. As for restorative pre- or probiotic therapy to reconstitute the microbiome, no recommendation can be made in terms of treatment, but it is not recommended for prevention of primary or recurrent disease.

Molecular Imaging in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are chronic immune-mediated inflammatory diseases affecting the gastrointestinal tract. Classically, two subtypes of IBD are recognized: Ulcerative colitis and Crohn's disease. There is not a single and reliable test for IBD diagnosis but the nuclear medicine techniques like ^99mTc-HMPAO autologous labelled leukocytes scintigraphy (WBCS) and PET/CT plays a role in the management of IBD. Leukocytes can be labelled "in vitro" (using ^99mTc-HMPAO in Europe or ¹¹¹In-oxine in America) or "in vivo" using antigranulocyte monoclonal antibodies. Nuclear medicine techniques are not the first choice to investigate IBD. Ultrasonography and magnetic resonance (radiation free) are probably the first option, and the diagnosis is commonly established by endoscopic biopsies. Nevertheless, WBCS is highly sensitive and accurate and represent a real option when other methods cannot used for whatever reason. In fact, a normal scan discards the presence of active IBD. The test is also useful to measure the extension and severity of the diseases and to evaluate the response to treatment. PET/CT imaging using ¹⁸F-FDG has recently been introduced and studied in both children and adults showing an excellent sensitivity for detecting active intestinal inflammation, but poor specificity in some studies. PET alone appears to be sufficient for the evaluation of ulcerative colitis, but PET/CT provides considerably more information than PET alone in the evaluation of Crohn's disease. Current clinical applications of PET in IBD include its use in the early evaluation of IBD, especially in children who may not tolerate an invasive test such as colonoscopy. Many questions remain to be answered, but PET appears to be a promising tool in the non-invasive evaluation of IBD. On the other hand, PET/MR could become in the near future a powerful tool in the evaluation of IBD patients. In addition, immuno-PET with antibodies targeting innate immune markers is also being investigated to detect colonic inflammation. The development of these technologies in humans could offer a less invasive method than endoscopy for the diagnosis and monitoring of IBD.

Advances in Imaging of Inflammation, Fibrosis, and Cancer in the Gastrointestinal Tract

Gastrointestinal disease is prevalent and broad, manifesting itself in a variety of ways, including inflammation, fibrosis, infection, and cancer. However, historically, diagnostic technologies have exhibited limitations, especially with regard to diagnostic uncertainty. Despite development of newly emerging technologies such as optoacoustic imaging, many recent advancements have focused on improving upon pre-existing modalities such as ultrasound, computed tomography, magnetic resonance imaging, and endoscopy. These advancements include utilization of machine learning models, biomarkers, new technological applications such as diffusion weighted imaging, and new techniques such as transrectal ultrasound. This review discusses assessment of disease processes using imaging strategies for the detection and monitoring of inflammation, fibrosis, and cancer in the context of gastrointestinal disease. Specifically, we include ulcerative colitis, Crohn's disease, diverticulitis, celiac disease, graft vs. host disease, intestinal fibrosis, colorectal stricture, gastric cancer, and colorectal cancer. We address some of the most recent and promising advancements for improvement of gastrointestinal imaging, including unique discussions of such advancements with regard to imaging of fibrosis and differentiation between similar disease processes.

Neutropenic Enterocolitis as a Complication of Autologous Stem Cell Transplant in Patients With Multiple Myeloma: A Case Series

Neutropenic enterocolitis (NE) is a rare but severe complication occurring in neutropenic patients undergoing intensive chemotherapy. Mortality is high, so early diagnosis is required to start urgent medical or surgical treatment. Data analysis of the development of NE after hematopoietic stem cell transplantation remains scarce. The aim of this case series is to discuss five out of 100 patients receiving autologous stem cell transplants (ASCTs) for multiple myeloma complicated with NE between 2016 and 2020 in the hematology department of the Cheikh Khalifa International University Hospital, Casablanca, Morocco. The patients were diagnosed with IgA and IgG multiple myeloma and aged between 58 to 64 years. They received induction therapy with four cycles of a triplet regimen including a proteasome inhibitor, an immunomodulatory drug, and corticosteroids, allowing a complete remission. Intensification was based on ASCT with melphalan at 200 mg/m2. The period of aplasia was marked by the sudden appearance of NE, diagnosed based on clinical, biological, and imaging criteria. Treatment included antibiotherapy and supportive care. We report no complications in our cases, nor the need for surgical care. Therefore, we consider that early diagnosis and treatment allowed a good evolution in our case series. The management of NE must be multidisciplinary associating hematologists, gastroenterologists, radiologists, and biologists. More studies and trials are needed to establish specific diagnostic criteria and better treatment options. 

PET/MRI Improves Management of Children with Cancer

Integrated PET/MRI has shown significant clinical value for staging and restaging of children with cancer by providing functional and anatomic tumor evaluation with a 1-stop imaging test and with up to 80% reduced radiation exposure compared with ¹⁸F-FDG PET/CT. This article reviews clinical applications of ¹⁸F-FDG PET/MRI that are relevant for pediatric oncology, with particular attention to the value of PET/MRI for patient management. Early adopters from 4 different institutions share their insights about specific advantages of PET/MRI technology for the assessment of young children with cancer. We discuss how whole-body PET/MRI can be of value in the evaluation of certain anatomic regions, such as soft tissues and bone marrow, as well as specific PET/MRI interpretation hallmarks in pediatric patients. We highlight how whole-body PET/MRI can improve the clinical management of children with lymphoma, sarcoma, and neurofibromatosis, by reducing the number of radiologic examinations needed (and consequently the radiation exposure), without losing diagnostic accuracy. We examine how PET/MRI can help in differentiating malignant tumors versus infectious or inflammatory diseases. Future research directions toward the use of PET/MRI for treatment evaluation of patients undergoing immunotherapy and assessment of different theranostic agents are also briefly explored. Lessons learned from applications in children might also be extended to evaluations of adult patients.

Magnetic Resonance Imaging for the diagnosis and management of acute colonic diverticulitis: a review of current and future use

Diverticular disease is one of the most common causes of outpatient visits and hospitalisations across Australia, North America and Europe. According to the Gastroenterological Society of Australia (GESA, 2010), approximately 33% of Australians over 45 years of age and 66% over 85 years of age have some form of colonic diverticulosis. Patients with colonic diverticulosis are known to develop subsequent complications such as acute colonic diverticulitis (ACD), and when more than one attack of diverticulitis occurs, there is a 70-90% chance that the individual will experience ongoing problems and recurring infections throughout their lifetime. Medical imaging is fundamental in the diagnosis, treatment and ongoing management of ACD and its complications, with Computed Tomography (CT) identified as the prevailing gold standard in the last few decades. Cross-database searching highlighted a large gap in the literature regarding the effectiveness of Magnetic Resonance Imaging (MRI) as a non-ionising radiation alternative imaging tool for ACD imaging after the mid-2000s, despite ongoing technological advancements in this modality. This narrative review identified 13 key publications (11 primary prospective cohort studies, 1 systematic review and 1 meta-analysis) that evaluate MRI for ACD imaging, of which five were published within the last decade. Several existing MRI protocols are deemed suitable for ACD imaging, and it is recommended they be re-evaluated in larger cohorts. Future studies should consider the rapidly growing technological improvements of MRI, its cost efficiency and its applicability in modern day healthcare settings when addressing ACD management. This is especially important considering the gradual rise in radiation dose among the Australian population attributable to increased CT referrals, alongside increased reporting of ACD cases in younger individuals.

Antimicrobial Dosing in Specific Populations and Novel Clinical Methodologies: Obesity

Obesity and its related comorbidities can negatively influence the outcomes of certain infectious diseases. Specific dosing recommendations are often lacking in the product label for patients with obesity that leads to unclear guidance in practice. Higher rates of therapeutic failure have been reported with some fixed dose antibiotics and pragmatic approaches to dose modification are limited for orally administered agents. For i.v. antimicrobials dosed on weight, alternate body size descriptors (ABSDs) have been used to reduce the risk of overdosing. These ABSDs are mathematical transformations of height and weight that represent fat-free weight and follow the same principles as body surface area (BSA)-based dosing of cancer chemotherapy. However, ABSDs are rarely studied in pivotal phase III studies and so can risk the underdosing of antimicrobials in patients with obesity when incorrectly applied in the real-world setting. Specific case examples are presented to highlight these risks. Although general principles may be considered by clinicians, a universal approach to dose modification in obesity is unlikely. Studies that can better distinguish human body phenotypes may help reduce our reliance on height and weight to define dosing. Simple and complex technologies exist to quantify individual body composition that could improve upon our current approach. Early evidence suggests that body composition parameters repurposed from medical imaging data may improve upon height and weight as covariates of drug clearance and distribution. Clinical trials that can integrate human body phenotyping may help us identify new approaches to optimal dose selection of antimicrobials in patients with obesity.

Ultrasonography in infectious and neoplastic diseases of the bowel and peritoneum

Ultrasonography is not the most cited imaging technique for the evaluation of infectious and neoplastic diseases of the gastrointestinal tract and the peritoneum, but it is often the initial technique used in the initial workup for nonspecific clinical syndromes. Despite its limitations, ultrasonography's strengths enable it to provide meaningful diagnostic information. To discuss the most important ultrasonographic, clinical, and epidemiological findings for infectious disease, we follow a topographical approach: stomach (Anisakis), proximal small bowel (Giardia lamblia, Strongyloides stercoralis, Mycobacterium avium-intracellulare complex, and Cryptosporidium), distal small bowel (Yersinia, Salmonella, and Campylobacter), terminal ileum and cecum (tuberculosis), right colon (Entamoeba histolytica), left colon (Shigella), sigmoid colon and rectum, pancolitis (Clostridium difficile, Cytomegalovirus, and Escherichia coli), and peritoneum. To discuss the ultrasonographic and clinical findings of the most common neoplastic diseases, we follow a nosological approach: polyploid lesions as precursors of tumors, carcinomas, neuroendocrine tumors, hematological tumors, mesenchymal tumors, and metastases. We briefly discuss tumors of the peritoneum and the use of ultrasonography to guide percutaneous biopsy procedures.

Molecular Imaging of Inflammatory Disease

Inflammatory diseases include a wide variety of highly prevalent conditions with high mortality rates in severe cases ranging from cardiovascular disease, to rheumatoid arthritis, to chronic obstructive pulmonary disease, to graft vs. host disease, to a number of gastrointestinal disorders. Many diseases that are not considered inflammatory per se are associated with varying levels of inflammation. Imaging of the immune system and inflammatory response is of interest as it can give insight into disease progression and severity. Clinical imaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI) are traditionally limited to the visualization of anatomical information; then, the presence or absence of an inflammatory state must be inferred from the structural abnormalities. Improvement in available contrast agents has made it possible to obtain functional information as well as anatomical. In vivo imaging of inflammation ultimately facilitates an improved accuracy of diagnostics and monitoring of patients to allow for better patient care. Highly specific molecular imaging of inflammatory biomarkers allows for earlier diagnosis to prevent irreversible damage. Advancements in imaging instruments, targeted tracers, and contrast agents represent a rapidly growing area of preclinical research with the hopes of quick translation to the clinic.

Diverticulosis, Diverticulitis, and Diverticular Bleeding

Diverticulosis is an anatomic change in the colon that is characterized by outpouching of the mucosa and submucosa through the muscularis. Its prevalence increases with age so most of the elderly patients have this condition. Although diverticulosis is common, diverticular disease, in which there are clinical sequelae, is rare. This collective term includes diverticulitis, diverticular hemorrhage and less well-defined entities such as segmental colitis associated with diverticulosis, and symptomatic uncomplicated diverticular disease. Diverticulitis presents as acute lower abdominal pain, and initial management traditionally includes antibiotics, with surgery reserved for complicated disease, although newer evidence questions the optimal role and timing of both interventions.

A gut dysbiotic microbiota-based hypothesis of human-to-human transmission of non-communicable diseases

Non-communicable diseases (NCDs) have replaced communicable diseases as the leading cause of premature death worldwide over the past century. Increasing numbers of studies have reported a link between NCDs and dysbiotic gut microbiota. Some gut microbiota, such as Helicobacter pylori, have been implicated in person-to-person transmission. Based on these reports, we develop a hypothesis regarding dysbiotic microbiota-associated NCDs, and explore how the presence of communicable NCDs could be confirmedexperimentally. We have also reviewed reports on environmental factors, including a high-fat diet, alcohol, smoking, exercise, radiation and air pollution, which have been associated with dysbiotic microbiota, and determined whether any of these parameters were also associated with NCDs. This review discusses the potential mechanism by which dysbiotic microbiota induced by environmental factors are directly or indirectly involved in person-to-person transmission. The hypothetical interplay between the environment, gut microbiota and host can be tested through high-throughput sequencing, animal models, and cell studies, although each of these modalities presents specific challenges. Confirmation of a causative association of dysbiotic microbiota with NCDs would represent a paradigm shift in efforts to prevent and control these diseases, and should stimulate additional studies on the associations among environmental factors, gut microbiota, and NCDs.