Nuclear medicine tests for acute gastrointestinal conditions

Integration of advanced methods and models to study drug absorption and related processes: An UNGAP perspective

This collection of contributions from the European Network on Understanding Gastrointestinal Absorption-related Processes (UNGAP) community assembly aims to provide information on some of the current and newer methods employed to study the behaviour of medicines. It is the product of interactions in the immediate pre-Covid period when UNGAP members were able to meet and set up workshops and to discuss progress across the disciplines. UNGAP activities are divided into work packages that cover special treatment populations, absorption processes in different regions of the gut, the development of advanced formulations and the integration of food and pharmaceutical scientists in the food-drug interface. This involves both new and established technical approaches in which we have attempted to define best practice and highlight areas where further research is needed. Over the last months we have been able to reflect on some of the key innovative approaches which we were tasked with mapping, including theoretical, in silico, in vitro, in vivo and ex vivo, preclinical and clinical approaches. This is the product of some of us in a snapshot of where UNGAP has travelled and what aspects of innovative technologies are important. It is not a comprehensive review of all methods used in research to study drug dissolution and absorption, but provides an ample panorama of current and advanced methods generally and potentially useful in this area. This collection starts from a consideration of advances in a priori approaches: an understanding of the molecular properties of the compound to predict biological characteristics relevant to absorption. The next four sections discuss a major activity in the UNGAP initiative, the pursuit of more representative conditions to study lumenal dissolution of drug formulations developed independently by academic teams. They are important because they illustrate examples of in vitro simulation systems that have begun to provide a useful understanding of formulation behaviour in the upper GI tract for industry. The Leuven team highlights the importance of the physiology of the digestive tract, as they describe the relevance of gastric and intestinal fluids on the behaviour of drugs along the tract. This provides the introduction to microdosing as an early tool to study drug disposition. Microdosing in oncology is starting to use gamma-emitting tracers, which provides a link through SPECT to the next section on nuclear medicine. The last two papers link the modelling approaches used by the pharmaceutical industry, in silico to Pop-PK linking to Darwich and Aarons, who provide discussion on pharmacometric modelling, completing the loop of molecule to man.

Overview of spontaneous intraabdominal tumor hemorrhage: etiologies, imaging findings, and management

Hemorrhage is a potential complication of benign and malignant tumors and tumor-like conditions in the abdomen. Patients often have non-specific presentations, although they may present critically ill and hemodynamically unstable. Imaging plays an important role not only in the diagnosis of hemorrhage but also in the detection and characterization of an underlying mass. Ultrasound, computed tomography, and magnetic resonance imaging are utilized in evaluating these patients, with each having particular strengths and limitations. Spontaneous tumor hemorrhage is most commonly seen in hepatic and renal lesions, although it can arise from nearly every abdominal organ. In this article, we will review principles of tumor hemorrhage, illustrate common and uncommon imaging features, and highlight different options for management.

Improved outcomes following implementation of an acute gastrointestinal bleeding multidisciplinary protocol

BACKGROUND

Effective multidisciplinary management of gastrointestinal bleeding (GIB) requires effective communication. We instituted a protocol to standardize communication practices with the hypothesis that outcomes would improve following protocol initiation.

METHODS

We performed a retrospective cohort analysis of 442 patients who required procedural management of acute GIB at our institution during a 50-month period spanning 25 months before and 25 months after implementation of a multidisciplinary communication protocol. The protocol stipulates that when a patient with severe GIB is identified, a conference call is coordinated among the gastroenterology, interventional radiology, and acute care surgery teams. A consensus plan is generated and then reassessed following procedural interventions and changes in patients' status. Patients' characteristics, management strategies, and outcomes were compared before and after protocol initiation.

RESULTS

Patient populations before and after protocol initiation were similar in age, comorbidities, outpatient use of antiplatelet/anticoagulant medications, admission vital signs, and admission laboratory values. The median interval between admission and the first procedure was significantly shorter in the protocol group (40 vs 47 hours, p = 0.046). The proportion of patients who received packed red blood cell transfusions decreased following protocol initiation (41% vs 50%, p = 0.018). Median hospital length of stay was significantly shorter in the protocol group (5.0 vs 6.0 days, p = 0.014). Readmissions with GIB were decreased after protocol implementation (8% vs. 15%, p = 0.023).

CONCLUSION

Implementation of a multidisciplinary protocol for management of acute GIB was associated with earlier intervention, fewer packed red blood cell transfusions, shorter hospital length of stay, and fewer readmissions with GIB. Future research should seek to establish causal relationships between communication practices and outcomes.

LEVEL OF EVIDENCE

Therapeutic study, level III.

Small Bowel Imaging: Computed Tomography Enterography, Magnetic Resonance Enterography, Angiography, and Nuclear Medicine

Radiology examinations play a major role in the diagnosis, management, and surveillance of small bowel diseases and are complementary to endoscopic techniques. Computed tomography enterography and magnetic resonance enterography are the cross-sectional imaging studies of choice for many small bowel diseases. Angiography still plays an important role for catheter-directed therapies. With the emergence of hybrid imaging techniques, radionuclide imaging has shown promise for the evaluation of small bowel bleeding and Crohn disease and may play a larger role in the future. This article reviews recent advances in technology, diagnosis, and therapeutic options for selected small bowel disorders.

A Novel Timesaving Method for Hepatobiliary Imaging for Suspected Acute Cholecystitis

OBJECTIVE

To optimize resource utilization of cholescintigraphy for suspected acute cholecystitis with a time-saving method without a loss in diagnostic accuracy.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective study. Hepatobiliary imaging data for 81 patients with suspected acute cholecystitis were recalled for modification into 2 summed static images, using only the first and last 5 minutes of the dynamic images, thereby eliminating the middle 50 minutes of imaging data. Two nuclear medicine physicians interpreted the summed images to assess visualization, and those interpretations were compared to the original reports based on using all 60 minutes of dynamic imaging. A third nuclear medicine physician mediated rare inter-reader interpretive disagreements. Comparison of interpretations of time-saving and conventional methods and also inter-observer variability was achieved using the Cohen κ coefficient analysis.

RESULTS

Interpretations rendered using the time-saving method showed near-perfect agreement with those based on the full dynamic imaging protocol (Cohen κ coefficient = 0.92 for both readers). Furthermore, nuclear medicine physician readers agreed with each other (Cohen κ coefficient = 0.95 between the 2 readers), indicating minimal inter-observer variability using this novel optimized technique.

CONCLUSION

In the setting of suspected acute cholecystitis, imaging resource utilization may be improved, via reduced gamma camera and technologist time, using a novel time-saving method without sacrificing diagnostic accuracy. Multicenter larger trials, however, will be necessary to establish reproducibility.

Splenic infarction as a pitfall on labeled red blood cell imaging

Patient with a history of overt gastrointestinal bleeding, diabetes mellitus, hypertension, polycythemia vera, and choledocojejunostomy was hospitalized because of hematemesis and melena. An area of Technetium-99m labeled red blood cells accumulation at the splenic flexure similar to an overt bleeding area, was observed on gastrointestinal bleeding scintigraphy (GIBS). In case of underlying malignancy, abdominal computed tomography was performed and demonstrated the infarction area placed laterally in spleen, appearing as a cold region on sctintigraphic image, separating the inferomedial and upper part of splenic uptake. Splenic variants and pathologies can complicate interpretation of GIBS.

Revisiting morphine-augmented hepatobiliary imaging for diagnosing acute cholecystitis: the potential pitfall of high false positive rate

Purpose

The aim of this retrospective study was to investigate the efficacy of morphine-augmented hepatobiliary imaging (MAHBI) for diagnosing acute cholecystitis (AC).

Methods

Sixty-eight patients (Male:Female = 36:32, age = 54 ± 17 years) referred for diagnosis of AC by 30-min post-morphine MAHBI after the standard 1-h imaging were recruited. Non-visualization of gallbladder on 30-min post-morphine images by visual analysis was considered positive. Final diagnosis of pathological examination for all patients was used as the gold standard.

Results

There was significant correlation of AC and MAHBI (p < 0.05). There were 45 true positive (TP), 19 false positive (FP), 4 true negative (TN), and no false negative (FN) cases using gallbladder visualization by 30-min post-morphine as the criteria, with a high false positive rate of 83%. The sensitivity, specificity, accuracy, positive and negative predictive values of MAHBI in detecting AC were 100%, 17%, 72%, 70%, and 100%, respectively.

Conclusions

MAHBI is sensitive but may not specific for diagnosing AC due to the potential pitfall of high false positive rate. Correlation with other clinical findings is recommended for optimal patient management.

Factors influencing the yield of mesenteric angiography in lower gastrointestinal bleed

AIM: To assess if certain triaging rules could be established to optimize the yield of mesenteric angiography.

METHODS: Medical records of 101 patients were retrospectively reviewed and parameters relating to age, gender, pulse rate, blood pressure, serum hemoglobin, intensive care unit (ICU) admission, and the number of packed red blood cells (PRBC) transfused in the 12 and 24 h prior to the angiography were tabulated in two groups with positive and negative angiography results.

RESULTS: We found no correlation between gender, pulse rate, blood pressure or serum hemoglobin and positivity of the mesenteric angiogram. But patients with positive angiogram were found to be on average 7 years older (73.2 years vs 65.9 years old) (P = 0.02). Angiogram was positive in 39.3 % (11/28) of patients admitted in ICU vs 23.2% (17/73) who were admitted elsewhere in the hospital (P = 0.03). In the 12 and 24 h prior to angiography, patients with a positive angiogram received a mean of 2.7 ± 2.3 and 3.3 ± 2.6 units of PRBC s respectively, while patients with a negative angiogram had a mean of 1.6 ± 1.9 (P = 0.02) and 2.1 ± 2.6 units (P = 0.04) received respectively in the same period.

CONCLUSION: Older age, ICU admission, having received at least 4 units PRBC over 12 h or 5 units over 24 h prior to angiogram are leading indicators for a positive study.

Role of interventional radiology in the management of acute gastrointestinal bleeding

Acute gastrointestinal bleeding (GIB) can lead to significant morbidity and mortality without appropriate treatment. There are numerous causes of acute GIB including but not limited to infection, vascular anomalies, inflammatory diseases, trauma, and malignancy. The diagnostic and therapeutic approach of GIB depends on its location, severity, and etiology. The role of interventional radiology becomes vital in patients whose GIB remains resistant to medical and endoscopic treatment. Radiology offers diagnostic imaging studies and endovascular therapeutic interventions that can be performed promptly and effectively with successful outcomes. Computed tomography angiography and nuclear scintigraphy can localize the source of bleeding and provide essential information for the interventional radiologist to guide therapeutic management with endovascular angiography and transcatheter embolization. This review article provides insight into the essential role of Interventional Radiology in the management of acute GIB.