未置放導尿管病人之尿道憩室內出現紫尿袋症候群樣紫色斑塊：罕見病例報告

吳昊勳¹、陳生文^1,2、張彰琦^1,2、程威銘^1,2、邱逸淳^2,3

¹臺北市立聯合醫院忠孝院區外科部泌尿科

²國立陽明交通大學醫學院

³臺北市立聯合醫院陽明院區外科部泌尿科

A Purple Urine Bag Syndrome–Like Lesion in a Urethral Diverticulum Without Indwelling Catheter: A Rare Case Report

Hao-Hsun Wu ¹, Sheng-Wen Chen ^1,2, Chang-Chi Chang ^1,2, Wei-Ming Chen ^1,2, Yi-Chun Chiu ^2,3

¹ Division of Urology, Department of Surgery, Zhongxiao Branch, Taipei City Hospital

² National Yang Ming Chiao Tung University, School of Medicine, Taipei, Taiwan

³ Division of Urology, Department of Surgery, Yangming Branch, Taipei City Hospital

Introduction:

Purple urine bag syndrome (PUBS) is an uncommon but occasionally encountered clinical condition, most often observed in functionally impaired female patients with long-term indwelling urinary catheters and chronic constipation. It is associated with urinary tract infection by Gram-negative bacteria that produce indoxyl sulfatase and/or phosphatase. The characteristic purple discoloration results from indigo and indirubin pigments adhering to the urine bag. In this case report, we describe an unusual presentation in which the patient did not have a long-term indwelling catheter; instead, we identified a purple plaque-like lesion within a urethral diverticulum, closely resembling the appearance typically seen in PUBS.

Case presentation:

An 88-year-old man with a history of prostate cancer, treated by androgen deprivation therapy and radiotherapy for more than 10 years, old stroke with right hemiplegia resulting in a bedridden status, hypertension, and type 2 diabetes mellitus presented with acute urinary retention and fever. Review of his recent medical records revealed multiple prior hospitalizations for urinary tract infections complicated by sepsis. He also had a history of bilateral ureteral strictures with hydronephrosis, for which he had undergone several endoscopic ureterotomy with double-J stent insertions, as well as recurrent penile urethral strictures treated multiple times with optic internal urethrotomy.

During the current admission, urinalysis revealed pyuria (WBC: >100/HPF)and alkaline urine (pH: 7.5). After adequate control of infection, we performed endoscopic evaluation of the lower urinary tract and identified a severe pinhole-like stricture of the penile urethra. Following repeat optic urethrotomy, a sizable urethral diverticulum was noted in the proximal urethra just behind the stricture ring (Figure 1). The floor of the diverticulum was covered by an extensive purple plaque-like lesion (Figure 2). This plaque was debrided and submitted for microbiological culture, which yielded polymicrobial growth of Gram-negative bacilli, including Providencia stuartii, Morganella morganii, and Proteus mirabilis. The patient subsequently received several days of intravenous antibiotic therapy, showed clinical improvement, and was discharged in stable condition.

Discussion:

PUBS is an uncommon but characteristic phenomenon, most often observed in elderly, bedridden female patients with long-term indwelling urinary catheters, constipation, urinary tract infection, and alkaline urine. Although the exact pathogenesis remains debated, most authors attribute the purple discoloration to the accumulation of indigo (blue) and indirubin (red) pigments on the catheter and urine bag. These pigments are generated through the bacterial metabolism of dietary tryptophan: tryptophan is converted to indole in the gut, further metabolized in the liver to indoxyl sulfate, and then excreted into the urine. In the presence of indoxyl sulfatase- and/or phosphatase-producing bacteria—most commonly Gram-negative bacilli such as Providencia, Proteus, Morganella, Klebsiella, E. coli, and Pseudomonas species—urinary indoxyl sulfate is hydrolyzed to indoxyl, which is subsequently oxidized under alkaline conditions to indigo and indirubin, resulting in a purple hue.

Clinically, PUBS is usually benign and asymptomatic, and is only a visual marker of underlying bacteriuria rather than a disease entity per se. Extensive diagnostic work-up is generally unnecessary beyond routine biochemical tests and urine culture. Most cases can be managed conservatively by treating symptomatic urinary tract infection when present, ensuring adequate hydration, improving bowel habits, maintaining good catheter and perineal hygiene, and periodically changing the catheter and urine bag. Preventive strategies and caregiver education are important, as the condition itself rarely leads to bacteremia or severe systemic complications.

Conclusion:

This case illustrates an unusual presentation resembling PUBS in a patient without a long-term indwelling urinary catheter. We hypothesize that previous pelvic radiotherapy for prostate cancer led to urethral fibrosis and stricture, resulting in chronically elevated urethral pressure and subsequent formation of a urethral diverticulum. The diverticulum likely acted as a stagnant reservoir for urine, providing a favorable environment for bacterial colonization and pigment production. The purple plaque-like lesion observed at the diverticular base, from which multiple PUBS-associated organisms were cultured, supports this mechanism.

Moreover, the patient exhibited several well-known risk factors for PUBS, including advanced age, bedridden status, multiple comorbidities, recurrent urinary tract infections, and alkaline urine, further reinforcing our hypothesis. This case broadens the clinical spectrum of PUBS-like manifestations and emphasizes that purple discoloration may occur even in the absence of a urine bag, particularly in conditions that permit chronic urinary stasis and bacterial overgrowth.