## 3 Results  
Urine specimens collected both from the renal pelvis and from drainage \"blue\" bags revealed no color alteration, nor differences in coloration. The difference between the average Raman spectrum of the urine sample collected from the renal pelvis and the average Raman spectrum of the sample collected from the drainage urinary bag was calculated to remove the spectral features of urine from the spectrum of a mixture of compounds. The difference spectrum has been baselined. The resulting Raman spectra are shown in Figure 1.  
The profile of the final spectrum (the green line in Figure 1) reveals the presence of indigo and the experimental vibrational peaks with their tentative assignments are detailed in Table 1. In the same table, based on literature, the vibrational peaks of a pilot study [27] are also reported. Typical morphological images obtained using a SEM technique from the control urine bag and the \"blue\" one are displayed in Figure 2, whereas a thick biofilm of the deposited material covers the surface of the \"blue\" bag in the right side of the figure. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Experimental** & **Ref Peaks** & **Intensity** & **Assignment** \\
**Peaks (cm\({}^{-1}\))** & **(cm\({}^{-1}\))** [25] & **Intensity** & **Assignment** \\ \hline
469.2 & 467 & vw & \(\gamma\) C-C & \\ \hline
546.7 & 544 & m & \(\delta\) C=C-CO-C & \\ \hline
600.0 & 598 & vw & \(\delta\) C=O & \(\delta\) C-H & \(\delta\) C-NH-C \\ \hline
639.6 & 635 & w & \(\gamma\) N-H & \\ \hline
676.3 & 674 & vw & \(\delta\) C-C & \\ \hline
759.5 & 758 & vw & \(\delta\) C-H & \(\delta\) N-C-C \\ \hline
867.9 & 868 & vw & \(\gamma\) C-N & \\ \hline
948.9 & 940 & vw & \(\gamma\) C-H & \\ \hline
1008.8 & 1015 & m & \(\delta\) C-H & \\ \hline
1149.1 & 1147 & vw & \(\delta\) C-C & \\ \hline
1226.2 & 1224 & s & \(\delta\) C-H & \(\gamma\) C-N \\ \hline
1248.9 & 1248 & m & \(\delta\) C-H & \(\delta\) C=O \\ \hline
1312.7 & 1310 & s & \(\gamma\) C-C & \\ \hline
1364.6 & 1365 & s & \(\delta\) N-H & \(\delta\) C-H \\ \hline
1461.8 & 1460 & s & \(\gamma\) C-C & \(\delta\) C-H \\ \hline
1486.2 & 1482 & s & \(\gamma\) C-C & \(\delta\) C-H \\ \hline
1575.1 & 1582 & vs & \(\gamma\) C=C & \(\gamma\) C=O \\ \hline
1624.4 & 1625 & s & \(\gamma\) C-C & \(\delta\) C-H \\ \hline
1697.9 & 1701 & w & \(\gamma\) C=C & \(\gamma\) C=O \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental vibrational peaks with their tentative assignments, based on literature. Legend for intensity: vw = very weak; w = weak; m = medium; s = strong; vs = very strong. Figure 1: Average spectrum of the patient urine specimens from the renal pelvis (red line), from the drainage “blue” bag (blue line) and the difference spectrum between them (green line). Yellow arrows point out peaks located at 546 cm\({}^{-1}\), 600 cm\({}^{-1}\), 676 cm\({}^{-1}\), 759 cm\({}^{-1}\), 1226 cm\({}^{-1}\), 1313 cm\({}^{-1}\), 1461 cm\({}^{-1}\), and 1573 cm\({}^{-1}\) in the urine from the renal pelvis spectrum that are not present in the urine from drainage “blue” bag spectrum. The EDX analysis was applied to detect the elemental composition of the bag both before (control) and after the use by the patient (\"blue bags\"). The results of the EDX analysis are reported in Table 2. EDX provides elemental data in both atomic and weight percentages automatically through the built-in software. The major components of the control bag and samples were CI, C and O. In the sample bags Ca and P, and small traces of K, were also detected. In the \"blue bag\" sample, it is possible to notice an increase in the amount of chlorine, oxygen, magnesium and calcium, compared to the control one. In particular, SEM + EDX analysis, performed on urine bags, before and after the presence of urine, showed an increase of \(\sim\)32% of CI, \(\sim\)33% of O, \(\sim\)66% of Ca, \(\sim\)65% of Al and Mg, while C decreased by about 41%. Traces of P, Na, and K were found in the analyzed urine bag.