Emphysematous cystitis, also known as 'cystitis emphysematosa,' is a rare complicated urinary tract infection characterized by gas within the bladder wall. Most cases are mild and detected incidentally; however, delayed management can lead to significant morbidity and mortality, particularly when infection extends to the upper urinary tract. With increasing use of cross-sectional imaging, radiologists are encountering this condition more frequently. This pictorial review presents 20 cases of emphysematous cystitis from our institution, illustrating the range of CT imaging patterns and clinical features from representative cases. We identified three distinct patterns of gas distribution: loculated or curvilinear focal collections (40% of cases), single layer of cobblestone/beaded necklace pattern (30% of cases), and circumferential dissection of the bladder wall with multilayered gas (30% of cases). Diabetes is the most common predisposing factor. Other risk factors included neurogenic bladder, long-term urinary catheters, immunosuppression, chemotherapy, recurrent urinary stones, and frequent urologic procedures. The clinical presentation ranges from incidental detection on imaging to symptomatic patients presenting with acute abdomen and dysuria in the emergency department (ED). Treatment primarily consists of antibiotic therapy, with surgical intervention required only in select severe cases. Understanding these CT patterns along with the associated clinical features and risk factors allows radiologists to accurately diagnose emphysematous cystitis and guide timely clinical management.

Immune-related cystitis is an uncommon immune-related adverse event (irAE) linked to immune checkpoint inhibitors (ICIs), and managing cases refractory to corticosteroids remains clinically challenging due to the lack of standardized treatment guidelines. We describe a 56-year-old male with extensive-stage small-cell lung cancer who developed corticosteroid-refractory immune-related cystitis following fourth-line therapy with Tislelizumab combined with irinotecan and anlotinib. The patient presented with frequent urination, urgent urination, and dysuria. Urine cultures were negative, and antibiotic treatment failed to alleviate symptoms, leading to a diagnosis of immune-related cystitis (CTCAE grade 3). Initial treatment with methylprednisolone 80 mg/day provided symptom relief, but symptoms recurred when the dose was tapered. Even after escalating the dose to 40 mg/day, symptoms persisted, confirming corticosteroid refractoriness. Combination therapy with prednisone 30 mg/day and mycophenolate mofetil (MMF) 1 g once daily resulted in symptom resolution within 1 week, with normalization of urine routine findings by 8 weeks. Corticosteroids were successfully tapered off without recurrence. This is the first reported case of successful MMF use for ICI-related cystitis, offering a new therapeutic option for corticosteroid-refractory cases. We also discuss considerations for ICI reinitiation to provide a clinical reference.

Histiocytic sarcomas (HSs) are uncommon malignant neoplasms in cats, typically affecting older animals and not previously associated with feline leukemia virus (FeLV). Here, we describe 2 cases of disseminated HS in young FeLV-positive domestic shorthair cats that clinically and grossly mimicked lymphoma. Case 1, a 1-y-old female cat, was presented with hemiplegia and dysuria and was euthanized because of the clinical suspicion of spinal lymphoma. Case 2, a 4-y-old male cat, had hyporexia, ocular abnormalities, and bilateral renal enlargement and was euthanized because of the clinical suspicion of renal and ocular lymphoma. Both cases tested positive for feline leukemia virus (FeLV) infection with a SNAP test. At autopsy, case 1 had a white, irregular, intradural spinal cord mass at the C6-C7 segment, and case 2 had coalescing, unencapsulated, white nodules that effaced both renal cortices, along with uveal thickening in the left eye with hyphema. Both cases had highly pleomorphic neoplastic round-cell proliferation in neoplastic masses, with strong cytoplasmic labeling for vimentin and IBA1 on immunohistochemistry and no CD20 or CD3 labeling, confirming disseminated HS. The neoplastic cells also had strong cytoplasmic immunolabeling for FeLV, suggesting a possible oncogenic role of FeLV in feline HSs.