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A Dangerous Entrapment: Pelvic Aneurysms Causing Hydronephrosis

Abdominal computed tomography scan in the axial plane with contrast injection demonstrating entrapment of the right ureter (arrow) between right (6.1 cm) and left (13 cm) iliac artery aneurysms with peripheral calcifications.

A 75-year-old patient with end-stage kidney disease on chronic hemodialysis was admitted with fever (38.5°C) and rigor. He was a heavy smoker and had long-standing diabetes and hypertension with abdominal aortic aneurysm (repaired 16 years prior with aortobifemoral graft) and peripheral artery disease with left above-knee amputation. Soon after admission, his blood pressure dropped and he required pressor support and meropenem/vancomycin coverage. Blood tests suggested sepsis with disseminated intravascular coagulation (neutropenia, thrombocytopenia), and cultures grew Citrobacter koseri without source of infection on examination, x-ray study, or echocardiography.

Computed tomography imaging with contrast revealed right hydroureteronephrosis owing to pelvic compression by a 13-cm aneurysm of the iliac artery shifting the urinary bladder to the right (Figures 1 and 2). The hydronephrotic sac appeared infected (Figure 2) and was aspirated, yielding pus positive for gram-negative bacilli identified as C. koseri. A right nephrostomy tube was inserted. The patient stabilized.

Our patient presented with sepsis and septic shock caused by C. koseri. Members of the Citrobacter genus are anaerobic gram-negative bacilli that belong to the Enterobacteriaceae family and may colonize the gastrointestinal tract. Albeit rare, Citrobacter has been linked to several types of infections, notably urinary tract infections, bloodstream infections, and abscess formation, mostly in immunocompromised or debilitated hosts.1Our patient’s susceptibility was owing to his advanced age, chronic hemodialysis, and frequent hospital visits.

The patient’s severe sepsis was secondary to an abscess in a barely functioning kidney, secondary to ipsilateral hydronephrosis and ureteronephrosis owing to external compression in the pelvis between 2 large iliac artery aneurysms (Figure 1), in a patient with extensive atherosclerotic vascular disease associated with age, heavy smoking, diabetes, dyslipidemia, and hypertension.

Aneurysmal compression causing an obstructive uropathy is an extremely rare occurrence reported in a few case descriptions. Both abdominal aortic aneurysm and iliac artery aneurysm have been associated with ureteral obstruction.2, 3 The latter may be caused by perianeurysmal inflammatory reaction (‘inflammatory’ aneurysms) or ‘simple’ compression by the enlarging mass. Treatment is directed toward the aneurysm, but here it was governed by the unusual abscess (Figure 2) in the hydronephrotic sac.

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-Ami Schattner, MD, Ina Dubin, MD, Yair Glick, MD

This article originally appeared in the November issue of The American Journal of Medicine.

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