Will MRI of gastrointestinal function parallel the clinical success of cine cardiac MRI?

Magnetic resonance imaging as a non-invasive tool to assess gastric emptying in mice

BACKGROUND

Methods to study gastric emptying in rodents are time consuming or terminal, preventing repetitive assessment in the same animal. Magnetic resonance imaging (MRI) is a non-invasive technique increasingly used to investigate gastrointestinal function devoid of these shortcomings. Here, we evaluated MRI to measure gastric emptying in control animals and in two different models of gastroparesis.

METHODS

Mice were scanned using a 9.4 Tesla MR scanner. Gastric volume was measured by delineating the stomach lumen area. Control mice were scanned every 30 min after ingestion of a 0.2 g meal and stomach volume was quantified. The ability of MRI to detect delayed gastric emptying was evaluated in models of morphine-induced gastroparesis and streptozotocin-induced diabetes.

KEY RESULTS

Magnetic resonance imaging reproducibly detected increased gastric volume following ingestion of a standard meal and progressively decreased with a half emptying time of 59 ± 5 min. Morphine significantly increased gastric volume measured at t = 120 min (saline: 20 ± 2 vs morphine: 34 ± 5 mm³ ; n = 8-10; p < 0.001) and increased half emptying time using the breath test (saline: 85 ± 22 vs morphine: 161 ± 46 min; n = 10; p < 0.001). In diabetic mice, gastric volume assessed by MRI at t = 60 min (control: 23 ± 2 mm³ ; n = 14 vs diabetic: 26 ± 5 mm³ ; n = 18; p = 0.014) but not at t = 120 min (control: 21 ± 3 mm³ ; n = 13 vs diabetic: 18 ± 5 mm³ ; n = 18; p = 0.115) was significantly increased compared to nondiabetic mice.

CONCLUSIONS AND INFERENCES

Our data indicate that MRI is a reliable and reproducible tool to assess gastric emptying in mice and represents a useful technique to study gastroparesis in disease models or for evaluation of pharmacological compounds.

Cine magnetic resonance urography as a new approach for postoperative evaluation of the reconstructed upper urinary tract: a multicenter study

PURPOSE

To evaluate the feasibility and usefulness of cine magnetic resonance urography (cine MRU) as a novel postoperative examination after upper urinary tract reconstruction surgery.

METHODS

Ninety-six patients underwent cine MRU for postoperative evaluation between August 2015 and August 2020. The morphological observations included regular peristalsis, anastomosis, urine flow signals, and reflux. The quantitative evaluations included luminal diameter, peristaltic amplitude, contraction ratio, peristaltic waves, and ureteric jets. The surgical outcomes were classified as success, gray area, or failure by combining the results of cine MRU, symptoms, and the degree of hydronephrosis.

RESULTS

There was no obvious stenosis of the anastomosis in 83 patients (86.46%). Regular peristalsis of the ureter and signals of urination was observed in 85 (88.54%) and 84 patients (87.50%), respectively. In addition, three patients (3.13%) showed urine reflux. The patients in both the success group and the gray area group showed significantly different creatinine levels (success 86.2 ± 22.3 μmol/L vs. failure 110.7 ± 8.2 μmol/L, P = 0.016; gray area 81.0 ± 20.0 μmol/L vs. failure 110.7 ± 8.2 μmol/L, P = 0.009) and estimated glomerular filtration rate (success: 88.5 ± 23.1 mL/min·1.73 m2, failure: 61.6 ± 14.1 mL/min·1.73 m2, P = 0.014; gray area: 94.7 ± 24.6 mL/min·1.73 m2, failure: 61.6 ± 14.1 mL/min·1.73 m2, P = 0.007) compared to those in the failure group. The ipsilateral split renal function was 33.6 ± 15.0, 24.5 ± 13.4, and 20.1 ± 0.4 mL/min in the success, gray area, and failure groups, respectively (P = 0.354).

CONCLUSION

Cine MRU demonstrates the morphology and function of the reconstructed upper urinary tract. The results of cine MRU can be used to evaluate the surgical effect, providing guidance for further treatment.

Constipation in ulcerative colitis: pathophysiology and practical management

Clinical experience suggests that there is a cohort of patients with refractory colitis who do have faecal stasis that contributes to symptoms. The underlying physiology is poorly understood, partly because until recently the technology to examine segmental colonic motility has not existed. Patients are given little information on how proximal faecal stasis can complicate colitis. Treatment guidelines are scanty and many patients are offered little apart from laxatives and advice on increasing fibre intake, which often makes symptoms worse. This article aims to review the history, pathology and management, and create impetus for future research on this underappreciated condition.

Assessment of fasted and fed gastrointestinal contraction frequencies in healthy subjects using continuously tagged MRI

BACKGROUND

Continuously tagged MRI during free breathing can assess bowel motility at frequencies as low as the slow wave, motility pattern range. This study aimed to evaluate noninvasive gastrointestinal-tagged MRI for small bowel motility assessment and to observe the physiological response to a 300-kcal meal challenge in healthy, overnight-fasted volunteers.

METHODS

After overnight fasting, 16 healthy subjects (7 women, mean age 25.5, range 19-37 years) underwent a free breathing, tagged MRI scan to capture small bowel motility. Each subject underwent a (a) baseline motility scan, (b) food challenge, (c) postchallenge scan, and (d) second postchallenge scan (after 20 minutes). Motility was quantified using a frequency analysis technique for measuring the spectral power of the strain, referred to as motility score. Motility score was assessed in 20 frequency intervals between 1 and 20 contractions per minute (cpm), and the data were analyzed with linear mixed-effect models.

KEY RESULT

The stimulation protocol demonstrated an immediate, food-induced, motility response in the low-frequency range (2-10 cpm), which is consistent with the stomach and small bowel frequency range (3-12 cpm).

CONCLUSIONS AND INFERENCES

This study shows that this MRI tagging technique is able to quantify the fasted-to-fed response to a 300-kcal meal challenge within the specific small bowel motility frequency range in healthy subjects. The food provocation MRI protocol provides a tool to explore the gut's response to a stimulus in specific motility frequency ranges in patients with gastrointestinal dysmotility and functional disorders.

"Development of Fixed Dose Combination Products" Workshop Report: Considerations of Gastrointestinal Physiology and Overall Development Strategy

The gastrointestinal (GI) tract is one of the most popular and used routes of drug product administration due to the convenience for better patient compliance and reduced costs to the patient compared to other routes. However, its complex nature poses a great challenge for formulation scientists when developing more complex dosage forms such as those combining two or more drugs. Fixed dose combination (FDC) products are two or more single active ingredients combined in a single dosage form. This formulation strategy represents a novel formulation which is as safe and effective compared to every mono-product separately. A complex drug product, to be dosed through a complex route, requires judicious considerations for formulation development. Additionally, it represents a challenge from a regulatory perspective at the time of demonstrating bioequivalence (BE) for generic versions of such drug products. This report gives the reader a summary of a 2-day short course that took place on the third and fourth of November at the Annual Association of Pharmaceutical Scientists (AAPS) meeting in 2018 at Washington, D.C. This manuscript will offer a comprehensive view of the most influential aspects of the GI physiology on the absorption of drugs and current techniques to help understand the fate of orally ingested drug products in the complex environment represented by the GI tract. Through case studies on FDC product development and regulatory issues, this manuscript will provide a great opportunity for readers to explore avenues for successfully developing FDC products and their generic versions.

MRI of the Colon in the Pharmaceutical Field: The Future before us

Oral solid drug formulation is the most common route for administration and it is vital to increase knowledge of the gastrointestinal physiological environment to understand dissolution and absorption processes and to develop reliable biorelevant in vitro tools. In particular, colon targeted drug formulations have raised the attention of pharmaceutical scientists because of the great potential of colonic drug delivery. However, the distal bowel is still a relatively understudied part of the gastrointestinal tract. Recently, magnetic resonance imaging (MRI) has been gaining an emerging role in studying the colon. This article provides a comprehensive; contemporary review of the literature on luminal MRI of the colonic environment of the last 15 years with specific focus on colon physiological dimensions; motility; chyme and fluids; transit and luminal flow. The work reviewed provides novel physiological insight that will have a profound impact on our understanding of the colonic environment for drug delivery and absorption and will ultimately help to raise the in vitro/in vivo relevance of computer simulations and bench models.