## 1 Introduction  
Purple urine bag syndrome (PUBS) is a rare, uncommon condition that occurs in chronic urinary catheterized patients with urinary tract infection [1, 2]. It is characterized by the blue/purple discoloration of a catheter and of a Foley bag over hours to days [2, 3]. The change in color actually occurs within the urine bag, whereas, interestingly, the urine remains unchanged in color [4]. It is considered a benign condition that requires no treatment other than changing the Foley bag, although antibiotics are occasionally used [2]. However, this condition is worrsome to and causes distress among patients, caregivers, and healthcare providers due to the clearly alarming urine and bag color [5]. PUBS is associated in patients with debilitation, renal failure, bacteriuria, alkaline urine, an indwelling urinary catheter, and chronic constipation [1, 2, 6]. The majority of patients suffering from PUBS are catheterized due to significant disability, typically being chair-bound or bed-bound elderly patients [1].  
Raman Spectroscopy (RS), belonging to the family of vibrational spectroscopic techniques, is a powerful spectroscopic modality that relies on the inelastic scattering process of monochromatic light, such as laser light [7]. The Raman spectra exhibit spectral features that are characteristic for molecular structure and conformation, giving a molecular fingerprint of the sample. RS represents an essential methodology in different research fields, such as chemistry, physics, biology, and material sciences [8; 9; 10; 11], and its advanced applications are currently employed in the biomedical field and many applications were reported [12; 13; 14; 15]. As RS is a rapid and nondestructive analysis technique for the detection of biochemical changes at the molecular level and does not require any preparation before the measurement, RS can be used for in vitro and in vivo measurements of analytes in biological fluids in their native liquid state [16; 17].  
RS, for instance, may apply to analyze the urine, a body fluid providing information about the body's metabolism and renal function. Uranalysis, including physical, chemical, and microscopic examinations, is an important laboratory test that is especially helpful in the diagnosis of urinary tract diseases. RS can be useful to detect various metabolites such as urea and uric acid, creatinine, ketone bodies (hydroxybutyrate and acetoacetate), phosphate, and other nitrogen compounds in urine, many of which are intrinsic native fluorophores [18]. Changes in these components reflect the metabolism of the human body and depend on the different kinds of food intake [19], or may be due to pathological conditions. Therefore, this information may be correlated with clinical criteria for the diagnosis of various renal, metabolic, and systemic diseases [16; 20; 21].  
In addition, scanning electron microscopy (SEM) analysis has been performed to morphologically characterize the sample under investigation. The SEM analysis has been coupled with energy dispersive X-ray spectroscopy (EDX) microanalysis to determine the elemental composition of the sample surface. The combination of these techniques has a wide range of applications in various industrial, commercial, and research fields [22; 23]. These practices are applied in the morpho-compositional analysis of urinary stones [24], but their application in the area of microbial detection is rare [25], whereas SEM plays a crucial role in detecting the cause of infection and disease [26].  
We have not found studies concerning the RS and/or SEM or SEM + EDX characterization of urine and urine bags obtained from PUBS subjects in the literature, even if many clinical cases are reported. Therefore, the aim of the study was to physically characterize urine and urine bag samples of a woman affected by multiple pathologic conditions with an apparent discoloration of the urine collected in the urine bags using these techniques.