CASE REPORT ©Copyright 2026 The Author. Published by Galenos Publishing House on behalf of the Society of Urological Surgery. This is an open access article under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 (CC BY-NC-ND) International License. J Urol Surg Gautam Shubhankar, Vikas Kumar Panwar, Anup Kumar Mandal All India Institute of Medical Sciences (AIIMS), Department of Urology, Uttarakhand, India Abstract Renal infective cystic diseases frequently mimic renal cell carcinoma (RCC) in clinical and imaging settings, leading to diagnostic challenges, especially in patients with chronic kidney disease (CKD). These misdiagnoses can result in unnecessary surgical interventions and extended antibiotic treatments without clear benefits. This report highlights two unique cases, demonstrating the critical role of a structured antibiotic regimen in accurately diagnosing and managing such conditions. The first case involves a 40-year-old woman with CKD presenting with high-grade fever, left flank pain, and oliguria. Imaging revealed two renal lesions suggestive of malignancy. However, following a ten-day course of intravenous antibiotics and a subsequent six-week course of oral antibiotics, her symptoms improved, and a renal biopsy confirmed benign interstitial nephritis. The second case describes a 58-year-old male with a history of multiple comorbidities who presented with high-grade fever and pyuria. Imaging indicated a renal mass with high fluorodeoxyglucose uptake. After a six-week antibiotic treatment, follow-up imaging showed complete resolution of the mass, confirming its benign nature. These cases illustrate the diagnostic complexity of differentiating renal infective cysts from RCC. A six-week course of broad-spectrum antibiotics effectively resolved infective lesions, significantly reducing the need for invasive procedures. The findings underscore the importance of considering infectious etiologies in atypical renal masses and highlight the potential benefits of conservative management strategies in preserving renal function and improving patient outcomes. Keywords: Renal infective cysts, renal cell carcinoma, chronic kidney disease, antibiotic therapy, diagnostic challenges, imaging techniques, patient management, conservative treatment Acute Pyelonephritis - Like Presentations of Infective Renal Cysts Masquerading as Carcinoma: Diagnostic Value of a Six-Week Antibiotic Trial Introduction Renal cell carcinoma (RCC) accounts for approximately 2-3% of all adult malignancies and remains the most common primary renal neoplasm (1). Advances in imaging have led to an increased detection rate of renal masses, many of which are incidental findings. However, certain benign conditions—particularly infective renal lesions—can closely mimic RCC in both clinical presentation and radiological appearance, creating significant diagnostic uncertainty. Infective renal cystic disease encompasses a spectrum of conditions in which localised bacterial infection causes cyst wall thickening, enhancement, and perilesional inflammatory changes. These radiological features overlap considerably with malignant masses, and differentiating between the two is especially challenging in patients with chronic kidney disease (CKD). The use of contrast-enhanced imaging in CKD is often restricted due to the risk of contrast-induced nephropathy or nephrogenic systemic fibrosis, limiting diagnostic options and potentially increasing reliance on less specific modalities (1,2). In some cases, functional imaging such as, F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been employed to aid diagnosis, but its specificity is reduced in the setting of infection or inflammation, which can produce false-positive results (2). Consequently, without careful integration of clinical, laboratory, and imaging data, patients may be subjected to unnecessary invasive procedures, including nephrectomy, with significant implications for renal function and overall morbidity. A conservative diagnostic strategy that incorporates an initial trial of broad-spectrum antibiotics in carefully selected patients, Correspondence: Vikas Kumar Panwar MD, All India Institute of Medical Sciences (AIIMS), Department of Urology, Uttarakhand, India E-mail: vikaspanwar446@gmail.com ORCID-ID: orcid.org/0000-0001-6441-6775 Received: 13.08.2025 Accepted: 03.10.2025 Epub: xxxxxxxxxxxxxxx Cite this article as: Shubhankar G, Panwar VK, Mandal AK. Acute pyelonephritis - like presentations of infective renal cysts masquerading as carcinoma: diagnostic value of a six-week antibiotic trial. J Urol Surg. [Epub Ahead of Print] General Urology Doi: 10.4274/jus.galenos.2025.2025-8-7