腎臟與輸尿管壞死性發炎偽裝為上泌尿道上皮癌：病例報告

陳冠甫¹、張延驊^1,2、黃逸修^1,2

1臺北榮民總醫院泌尿部；

2國立陽明交通大學醫學院泌尿學科及書田泌尿科學研究中心
Necrotizing inflammation of the kidney and ureter mimicking

Upper Tract Urothelial Carcinoma - A case report

Kuan-Fu Chen¹, Yen-Hwa Chang^1,2, Eric Yi-Hsiu Huang^1,2
1 Department of Urology, Taipei Veterans General Hospital, Taipei, Taiwan

² Department of Urology, College of Medicine and Shu-Tien Urological Science

Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan

Introduction: Upper tract urothelial carcinoma (UTUC) is a significant consideration in patients presenting with hydronephrosis and ureteral obstruction accompanied by soft tissue lesions on imaging. However, benign inflammatory conditions such as chronic infections, granulomatous disease, or necrotizing inflammation may present with similar radiographic findings, posing a diagnostic challenge. In this case report, we document a patient with soft tissue lesion noted over left kidney and ureter who received radical nephroureterectomy, and the pathological examination revealed necrotizing inflammation.

Case presentation: A 63-year-old woman with no significant past medical history was diagnosed with gastrointestinal stromal tumor (GIST) in September 2024. At diagnosis, contrast-enhanced CT of the abdomen and pelvis revealed a primary GIST lesion along with incidental findings of heterogeneous soft tissue lesions involving the left kidney and ureter, associated with left-sided hydroureter and hydronephrosis.

The patient was started on imatinib for GIST and followed up regularly in the outpatient department. A repeat CT scan in December 2024 demonstrated regression of the GIST, indicating good treatment response. However, persistent heterogeneous soft tissue lesions occupying the left kidney were noted, with associated calcifications. The left hydronephrosis and hydroureter persisted, extending to the distal ureter, where a suspicious soft tissue lesion was identified. Urologists were then consulted for evaluation. Given the concern for upper tract malignancy, diagnostic ureteroscopy was performed on January 9, 2025. Endoscopic evaluation revealed a blind-ending ureter approximately 4 cm from the ureteral orifice, preventing further advancement. Urine cytology showed negative result for malignant cells. However, given the high suspicion of malignancy, radical nephroureterectomy with bladder cuff excision was decided after multidisciplinary discussion.

The patient underwent the operation on January 20, 2025 smoothly. Gross examination of the surgical specimen revealed extensive cheese-like necrotic material filling the entire renal pelvis and ureter. Histopathological analysis demonstrated necrotizing inflammation, with total necrosis of renal pelvis mucosa and ureter mucosa and submucosa, associated with marked fibrosis, granulation tissue, and focal calcification. No evidence of malignancy was noted. The post-operative course was uneventful and the patient was discharged on post-operative day 5. She was subsequently referred back to the medical oncology clinic for continued management of her GIST.

Preoperative diagnosis was particularly challenging. Ureteroscopy failed to provide histological confirmation due to complete luminal obstruction, a scenario not uncommon in advanced UTUC but also seen in severe inflammatory conditions. Differential diagnoses include renal tuberculosis, xanthogranulomatous pyelonephritis, and fungal bezoars, all of which may present with necrotic debris and obstructive uropathy.

Given the inability to exclude malignancy and the presence of a non-functioning obstructed system, radical nephroureterectomy was considered clinically appropriate. This reflects a common real-world dilemma in which definitive diagnosis can only be established postoperatively.

Conclusions: Necrotizing inflammation of the upper urinary tract can closely mimic malignancy both radiologically and endoscopically. Although rare, it should be considered in the differential diagnosis of obstructive upper tract lesions. When diagnostic uncertainty persists, surgical intervention remains justified to ensure both oncologic safety and symptom resolution.