A low-calcium diet is recommended to prevent recurrent stones in patients with idiopathic hypercalciuria, yet long-term data on the efficacy of a low-calcium diet are lacking. Recently, the efficacy of a low-calcium diet has been questioned, and greater emphasis has been placed on reducing the intake of animal protein and salt, but again, long-term data are unavailable.

Human gut microbiota is able to influence the host physiology by regulating multiple processes, including nutrient absorption, inflammation, oxidative stress, immune function, and anabolic balance. Aging is associated with reduced microbiota biodiversity, increased inter-individual variability, and over-representation of pathobionts, and these phenomena may have great relevance for skeletal muscle mass and function. For this reason, the presence of a gut-muscle axis regulating the onset and progression of age-related physical frailty and sarcopenia has been recently hypothesized. In this narrative review, we summarize the studies supporting a possible association between gut microbiota-related parameters with measures of muscle mass, muscle function, and physical performance in animal models and humans. Reduced muscle mass has been associated with distinct microbiota composition and reduced fermentative capacity in mice, and the administration of probiotics or butyrate to mouse models of muscle wasting has been associated with improved muscle mass. However, no studies have targeted the human microbiome associated with sarcopenia. Limited evidence from human studies shows an association between microbiota composition, involving key taxa such as Faecalibacterium and Bifidobacterium, and grip strength. Similarly, few studies conducted on patients with parkinsonism showed a trend towards a different microbiota composition in those with reduced gait speed. No studies have assessed the association of fecal microbiota with other measures of physical performance. However, several studies, mainly with a cross-sectional design, suggest an association between microbiota composition and frailty, mostly assessed according to the deficit accumulation model. Namely, frailty was associated with reduced microbiota biodiversity, and lower representation of butyrate-producing bacteria. Therefore, we conclude that the causal link between microbiota and physical fitness is still uncertain due to the lack of targeted studies and the influence of a large number of covariates, including diet, exercise, multimorbidity, and polypharmacy, on both microbiota composition and physical function in older age. However, the relationship between gut microbiota and physical function remains a very promising area of research for the future.

Inadequate nutrition and physical inactivity are the mainstays of primary sarcopenia–physiopathology in older individuals. Gut microbiota composition is strongly dependent on both of these elements, and conversely, can also influence the host physiology by modulating systemic inflammation, anabolism, insulin sensitivity, and energy production. The bacterial metabolism of nutrients theoretically influences skeletal muscle cell functionality through producing mediators that drive all of these systemic effects. In this study, we review the scientific literature supporting the concept of the involvement of gut microbiota in primary sarcopenia physiopathology. First, we examine studies associating fecal microbiota alterations with physical frailty, i.e., the loss of muscle performance and normal muscle mass. Then, we consider studies exploring the effects of exercise on gut microbiota composition. Finally, we examine studies demonstrating the possible effects of mediators produced by gut microbiota on skeletal muscle, and intervention studies considering the effects of prebiotic or probiotic administration on muscle function. Even if there is no evidence of a distinct gut microbiota composition in older sarcopenic patients, we conclude that the literature supports the possible presence of a “gut–muscle axis”, whereby gut microbiota may act as the mediator of the effects of nutrition on muscle cells.

Background: Acute abdominal pain (AAP) accounts for 7–10% of all Emergency Department (ED) visits. Nevertheless, the epidemiology of AAP in the ED is scarcely known. The aim of this study was to investigate the epidemiology and the outcomes of AAP in an adult population admitted to an urban ED. Methods: We made a retrospective analysis of all records of ED visits for AAP during the year 2014. All the patients with repeated ED admissions for AAP within 5 and 30 days were scrutinized. Five thousand three hundred and forty cases of AAP were analyzed. Results: The mean age was 49 years. The most frequent causes were nonspecific abdominal pain (NSAP) (31.46%), and renal colic (31.18%). Biliary colic/cholecystitis, and diverticulitis were more prevalent in patients aged >65 years (13.17% vs. 5.95%, and 7.28% vs. 2.47%, respectively). Appendicitis (i.e., 4.54% vs. 1.47%) and renal colic (34.48% vs. 20.84%) were more frequent in patients aged <65 years. NSAP was the most common cause in both age classes. Renal colic was the most frequent cause of ED admission in men, whereas NSAP was more prevalent in women. Urinary tract infection was higher in women. Overall, 885 patients (16.57%) were hospitalized. Four hundred and eighty-five patients had repeated ED visits throughout the study period. Among these, 302 patients (6.46%) were readmitted within 30 days, whereas 187 patients (3.82%) were readmitted within 5 days. Renal colic was the first cause for ED readmission, followed by NSAP. In 13 cases readmitted to the ED within 5 days, and in 16 cases readmitted between 5–30 days the diagnosis was changed. Conclusions: Our study showed that AAP represented 5.76% of total ED visits. Two conditions (i.e., NSAP and renal colic) represented >60% of all causes. A large use of active clinical observations during ED stay (52% of our patients) lead to a negligible percentage of changing diagnosis at the second visit.

The gut microbiota composition of elderly hospitalized patients with Clostridium difficile infection (CDI) exposed to previous antibiotic treatment is still poorly investigated. The aim of this study was to compare the microbiota composition by means of 16S rRNA microbial profiling among three groups of hospitalized elderly patients (age ≥ 65) under standard diet including 25 CDI-positive (CDI group), 29 CDI-negative exposed to antibiotic treatment (AB+ group) and 30 CDI-negative subjects not on antibiotic treatment (AB− group). The functional properties of the gut microbiomes of CDI-positive vs CDI-negative subjects were also assessed by shotgun metagenomics. A significantly lower microbial diversity was detected in CDI samples, whose microbiomes clustered separately from CDI-negative specimens. CDI was associated with a significant under-representation of gut commensals with putative protective functionalities, including Bacteroides, Alistipes, Lachnospira and Barnesiella, and over-representation of opportunistic pathogens. These findings were confirmed by functional shotgun metagenomics analyses, including an in-depth profiling of the Peptostreptococcaceae family. In CDI-negative patients, antibiotic treatment was associated with significant depletion of few commensals like Alistipes, but not with a reduction in species richness. A better understanding of the correlations between CDI and the microbiota in high-risk elderly subjects may contribute to identify therapeutic targets for CDI.