What is happening in that urinary catheter bag?

An 86-year-old nursing home woman with an indwelling urinary catheter presented to our emergency department for abdominal pain, nausea, hyporexia after nine days of stubborn constipation despite the use of laxatives, on a background of IV stage Chronic Kidney Disease (CKD), type 2 diabetes, hypothyroidism, and bed rest syndrome with chronic pain treated with fentanyl transdermal patch. Blood tests showed a worsening of renal function (creatinine 5.7 mg/dL, nv 0.6-1; azotemia 177 mg/dL, nv 10-50), and increased C reactive protein value (5 mg/dL, nv < 0.5). Glucose and serum electrolytes were normal. Abdomen X-ray was unremarkable, and PoCUS excluded hydronephrosis and bladder globe. The urine drainage bag was purple with smelly urine.