A man in his early 40s presented with acute right flank pain, vomiting and dysuria. Ultrasonography demonstrated an obstructing right upper ureteric calculus with a contralateral renal calculus. CT urography revealed fine, serpiginous contrast-opacified tubular channels extending from the right renal pelvis into the retroperitoneum without evidence of urinoma. Delayed excretory phase imaging demonstrated convergence towards the para-aortic region, consistent with pyelolymphatic backflow rather than collecting system rupture. The imaging pattern reflected markedly elevated intrarenal pressure and prompted urgent decompression. The patient underwent bilateral ureteric stenting followed by definitive endourological management with complete symptomatic resolution. Early recognition of this radiological entity prevents misdiagnosis and guides appropriate pressure-relieving intervention.

Clostridium septicum is an aerotolerant anaerobe classically linked to occult colorectal malignancy and hematologic disease, and a rare but frequently fatal cause of nontraumatic infective aortitis; it also causes gas gangrene, osteomyelitis and spondylodiscitis. Survival depends on radical surgical debridement, as antibiotics alone are almost uniformly fatal. We describe a 71-year-old man with untreated chronic myelomonocytic leukemia (CMML) who presented with back pain, vomiting and rigors. Computed tomography showed perforated appendicitis with extraluminal air together with mediastinitis and aortitis of the aortic arch and the aorta at the diaphragmatic hiatus. Inflammatory markers were markedly elevated and vasculitis serologies negative. The appendix was managed nonoperatively as he remained hemodynamically stable. Despite broad-spectrum antibiotics, repeat angiography on day 5 showed new aneurysmal dilatation of the arch to 5.1 cm, prompting emergent left carotid-subclavian bypass and thoracic endovascular aortic repair. On day 8, thoracotomy revealed necrotic aortic wall with an exposed endograft, which was debrided and covered with a pedicled latissimus dorsi flap; tissue cultures grew C. septicum. Colonoscopy twelve months earlier had shown only polyps and diverticulosis. He completed six weeks of intravenous ampicillin-sulbactam, was transitioned to lifelong oral suppression for retained prosthetic material, and was discharged on day 57 to long-term acute care, ventilator-dependent. This case shows that C. septicum aortitis may arise from a perforated appendix rather than a colorectal neoplasm, that nonoperative appendicitis management may give inadequate source control in an immunocompromised host, and that survival is attainable with a staged hybrid endovascular-and-open strategy.