Muscle ultrasound and its application to point-of-care ultrasonography: a narrative review

A look inside the gut as a clue to nutritional status

PURPOSE OF REVIEW

Malabsorption and malnutrition are common gastrointestinal manifestations clinicians face, requiring diagnostic workup for effective diagnosis and management of the underlying cause. This review discusses recent advances in diagnostic approaches to malabsorption and maldigestion of macronutrients - lipids, proteins, and carbohydrates. We highlight underrecognized causes, available testing modalities, and ongoing diagnostic unmet needs.

RECENT FINDINGS

Innovations in the diagnostic landscape are enhancing our understanding of malabsorption syndromes. Stool collection and handling is uncomfortable and commonly avoided. The objective quantification of stool lipids, bile acids, and gut enzymes is therefore underused in the diagnosis and management of common disorders such as exocrine pancreatic insufficiency, bile acid diarrhea, protein-losing enteropathy, and more. We review the recent advancements in spot quantification of stool fat and bile acid content, endoscopic imaging techniques such as endocytoscopy, confocal laser endomicroscopy, and optical coherence tomography and the future place in clinical practice.

SUMMARY

Malabsorption and maldigestion represent significant challenges in clinical nutrition and gastroenterology. Through the integration of advanced diagnostic techniques, clinicians will be better equipped to tailor therapy and monitor treatment response, ultimately improving patient health outcomes. This review underscores the critical role of innovative diagnostic tools in accurately detecting and effectively managing gastrointestinal disorders linked to nutritional status.

Ultrasound Evaluation of Sarcopenia in Patients with Hepatocellular Carcinoma: A Faster and Easier Way to Detect Patients at Risk

The condition of sarcopenia, defined as a progressive loss of musculoskeletal mass and muscular strength, is very common in patients with hepatocellular carcinoma (HCC) and presents a remarkable association with its prognosis. Thus, the early identification of sarcopenic patients represents one of the potential new approaches in the global assessment of HCC, and there is increasing interest regarding the potential therapeutic implications of this condition. The gold standard for the quantification of muscle mass is magnetic resonance imaging (MRI) or computed tomography (CT), but these techniques are not always feasible because of the high-cost equipment needed. A new possibility in sarcopenia identification could be muscle ultrasound examination. The measurement of specific parameters such as the muscle thickness, muscular fascicles length or pennation angle has shown a good correlation with CT or MRI values and a good diagnostic accuracy in the detection of sarcopenia. Recently, these results were also confirmed specifically in patients with chronic liver disease. This review summarizes the role of imaging for the diagnosis of sarcopenia in patients with HCC, focusing on the advantages and disadvantages of the diagnostic techniques currently validated for this aim and the future perspectives for the identification of this condition.

Validation of bioimpedance phase angle in lower extremity of male patients with chronic spinal cord injury

[Purpose] This study aimed to evaluate the relationship between lower extremity phase angle and muscle thickness/echo intensity in males with chronic spinal cord injury. It also compared bioelectrical impedance analysis measurements to investigate skeletal muscle degeneration between individuals with spinal cord injury and healthy controls. [Participants and Methods] This cross-sectional study included 12 male patients with chronic spinal cord injury and 14 healthy male controls. We used bioelectrical impedance analysis and ultrasonography to measure the lower extremity phase angle and muscle thickness/echo intensity of the rectus femoris muscle, respectively. We also compared the bioelectrical impedance analysis measurements between individuals with spinal cord injury and healthy controls. [Results] Lower extremity phase angle was strongly correlated with muscle thickness and echo intensity of the rectus femoris muscle in individuals with spinal cord injury. All measures differed significantly between individuals with spinal cord injury and healthy controls. [Conclusion] These findings suggest that lower extremity phase angle is a valuable skeletal muscle indicator in spinal cord injury. Furthermore, bioelectrical impedance analysis revealed degeneration of the lower extremity skeletal muscles in individuals with chronic spinal cord injury.

Variability in Cross-Sectional Muscle Atrophy: Insights From the Central Rectus Femoris

BACKGROUND AND PURPOSE

This study aimed to evaluate the non-uniformity of cross-sectional areas in atrophic muscles using the central aponeurosis (CA) as a marker for the central region of the rectus femoris (RF).

METHODS

We enrolled 51 consecutively admitted patients (102 limbs) with aortic valve stenosis who were scheduled for elective surgical or catheter-based aortic valve replacement and were expected to have low physical activity-induced muscle atrophy. We obtained short-axis images of the mid-thigh using an ultrasonic diagnostic imaging system (with a 5-cm-wide probe) and measured the deviation of the central region of the rectus femoris from the body surface. Muscle thickness was measured using conventional morphological measurements on the body surface ("On Surface") and landmarks within the ultrasonographic image ("In Images").

RESULTS

Displacements ≥ 1.5 cm were observed in 56 (54.9%) limbs, and displacements ≥ 2.5 cm were observed in 34 (33%) limbs. The displacements were predominantly in the medial direction and ranged from 4 cm to 1.5 cm. Among the cases in which the deviation was ≥2.5 cm, "On Surface" measurements resulted in images in which the vastus lateralis overlapped with the rectus femoris. The thickness of the rectus femoris was significantly lower with "On Surface" measurements than with "In Images" measurements (right, p < 0.001; left, p = 0.007), with a maximum difference of 10.5 mm.

CONCLUSIONS

In conclusion, it was observed that the rectus femoris at the center was often displaced medially, and the muscle thickness was thinner at the edge than at the center, showing a non-uniform morphology.

Ultrasound utilized by registered dietitians for body composition measurement, nutritional assessment, and nutritional management

BACKGROUND AND AIMS

Ultrasound has been used primarily as a tool for body composition measurement in the field of clinical nutrition. Although many recent reports have demonstrated that ultrasound could be a useful tool for nutritional assessment, it is not well incorporated into registered dietitians' (RDs) practice. The aim of this review was to summarize the usefulness of ultrasound in assessing body composition and nutritional status and in nutritional management by RDs.

METHODS

Studies on ultrasonography, nutritionists, body composition, nutritional assessment, and diet therapy was searched using the MEDLINE databases.

RESULTS

After reviewing the articles, we categorized them into the following topics; 1) principles of muscle measurement using the ultrasound, types of muscle that can be measured, 2) indices of muscle and muscle mass and quality as assessed using ultrasound and its relationship to nutritional indicator, 3) diagnosis of the Global Leadership Initiative on Malnutrition (GLIM) criteria malnutrition using ultrasound, 4) practical nutritional management using ultrasound and 5) education and issues for ultrasound implementation. Ultrasound can evaluate low body mass index, unintentional loss of body weight, low skeletal muscle mass index, decreased food intake/assimilation, and disease burden/inflammation, all which are essential items of the phenotypic and etiologic criteria of the GLIM.

CONCLUSION

Ultrasound may be useful for RDs to perform body composition measurement, nutritional assessment, and nutritional management. It will be important to identify the cutoff values for ultrasound-based measurements of muscle mass. In order for RDs to perform a body composition measurement, nutritional assessment, and nutritional management using ultrasound, educational issues need to be addressed.

Inter-Examiner and Intra-Examiner Reliability of Quantitative and Qualitative Ultrasonography Assessment of Peripheral and Respiratory Muscles in Critically Ill Patients

ICU patients are exposed to several factors that can lead to muscle structural and functional changes, and ultrasonography can identify them. Although several studies have analyzed the reliability of muscle ultrasonography assessment, a protocol with more muscle assessments becomes a challenge. The aim of this study was to analyze the inter and intra-examiner reliability of peripheral and respiratory muscle ultrasonography assessment in critically ill patients. The sample size was 10 individuals aged ≥ 18 years who were admitted to the ICU. Practical training of four health professionals from different backgrounds was performed. After training, each examiner acquired three images to assess the thickness and echogenicity of the muscle groups: biceps brachii, forearm flexor group, quadriceps femoris, tibialis anterior and diaphragm. For the reliability analysis, an intraclass correlation coefficient was performed. Six hundred US images were analyzed for muscle thickness and 150 for echogenicity. Excellent intra-examiner reliability for echogenicity (ICC: 0.867-0.973) and inter-examiner reliability for thickness were found in all muscle groups (ICC: 0.778-0.942). For muscle thickness intra-examiner reliability, excellent results were found (ICC: 0.798-0.988), with a "good" correlation in one diaphragm assessment (ICC: 0.718). Excellent inter- and intra-examiner reliability of the thickness assessment and intra-examiner echogenicity of all muscles analyzed were found.

Frailty and the Interactions between Skeletal Muscle, Bone, and Adipose Tissue-Impact on Cardiovascular Disease and Possible Therapeutic Measures

Frailty is a global health problem that impacts clinical practice. It is complex, having a physical and a cognitive component, and it is the result of many contributing factors. Frail patients have oxidative stress and elevated proinflammatory cytokines. Frailty impairs many systems and results in a reduced physiological reserve and increased vulnerability to stress. It is related to aging and to cardiovascular diseases (CVD). There are few studies on the genetic factors of frailty, but epigenetic clocks determine age and frailty. In contrast, there is genetic overlap of frailty with cardiovascular disease and its risk factors. Frailty is not yet considered a risk factor for CVD. It is accompanied by a loss and/or poor functioning of muscle mass, which depends on fiber protein content, resulting from the balance between protein breakdown and synthesis. Bone fragility is also implied, and there is a crosstalk between adipocytes, myocytes, and bone. The identification and assessment of frailty is difficult, without there being a standard instrument to identify or treat it. Measures to prevent its progression include exercises, as well as supplementing the diet with vitamin D and K, calcium, and testosterone. In conclusion, more research is needed to better understand frailty and to avoid complications in CVD.