{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,21]],"date-time":"2025-12-21T13:46:35Z","timestamp":1766324795291,"version":"3.48.0"},"reference-count":23,"publisher":"BMJ","issue":"12","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2025,11,21]]},"published-print":{"date-parts":[[2025,12]]},"abstract":"<jats:p>Crossed fused renal ectopia (CFRE) is an uncommon and congenital anomaly in which both kidneys are fused and located on one side of the body, often going undetected due to its asymptomatic nature. When symptomatic, it can present unique challenges in the management of nephrolithiasis due to altered anatomy and impaired drainage. We report a rare case of a young adult male with a large renal calculus in a left-to-right crossed-fused ectopic kidney\u2014an anatomical variant seldom encountered in clinical practice. The patient was successfully treated with retrograde intrarenal surgery (RIRS) using a flexible ureteroscope and Holmium: YAG laser. This minimally invasive approach resulted in complete stone clearance, a rapid recovery and no recurrence at follow-up. Intrarenal surgery using flexible scopes can be considered a first-line approach for stone management in patients with CFRE, offering excellent outcomes with minimal morbidity. To our knowledge, this is the first documented case from Pakistan demonstrating the successful use of RIRS in a CFRE patient.<\/jats:p>","DOI":"10.1136\/bcr-2025-267708","type":"journal-article","created":{"date-parts":[[2025,12,21]],"date-time":"2025-12-21T13:45:18Z","timestamp":1766324718000},"page":"e267708","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Crossed fused renal ectopia complicated by a renal stone: endoscopic management with retrograde intrarenal surgery"],"prefix":"10.1136","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-7652-788X","authenticated-orcid":false,"given":"Areeba","family":"Ahmed","sequence":"first","affiliation":[{"name":"Department of Surgery, The Aga Khan University Hospital, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shamila","family":"Ladak","sequence":"additional","affiliation":[{"name":"Department of Surgery, The Aga Khan University Hospital, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7129-5665","authenticated-orcid":false,"given":"Imran Khan","family":"Jalbani","sequence":"additional","affiliation":[{"name":"Department of Surgery, The Aga Khan University Hospital, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2025,12,21]]},"reference":[{"key":"2025122105451305000_18.12.e267708.1","doi-asserted-by":"crossref","first-page":"424","DOI":"10.3390\/healthcare11030424","article-title":"Epidemiology of Kidney Stones","volume":"11","author":"Stamatelou","year":"2023","journal-title":"Healthcare (Basel)"},{"key":"2025122105451305000_18.12.e267708.2","article-title":"Risk Factors of Kidney Stones in Khyber Pakhtunkhwa, Pakistan: A Descriptive Cross-Sectional Study","volume":"16","author":"Waqas","year":"2024","journal-title":"Cureus"},{"key":"2025122105451305000_18.12.e267708.3","article-title":"Perception of Dietary Influences on Renal Stone Formation Among the General Population","volume":"14","author":"Bashir","year":"2022","journal-title":"Cureus"},{"key":"2025122105451305000_18.12.e267708.4","doi-asserted-by":"crossref","first-page":"2","DOI":"10.53778\/pjkd82259","article-title":"Stepping Stones In Prevention of Kidney Stone Disease In Pakistan","volume":"8","author":"Hussain","year":"2024","journal-title":"Pak J Kidney Dis"},{"key":"2025122105451305000_18.12.e267708.5","doi-asserted-by":"crossref","first-page":"232","DOI":"10.1002\/iju5.12295","article-title":"Retrograde ureteroscopic lithotripsy in cross-fused renal ectopia","volume":"4","author":"Somiya","year":"2021","journal-title":"IJU Case Rep"},{"key":"2025122105451305000_18.12.e267708.6","doi-asserted-by":"crossref","first-page":"E752","DOI":"10.5489\/cuaj.2050","article-title":"Management of ureteral obstruction in crossed fused renal ectopia: A case report","volume":"8","author":"Bhojwani","year":"2014","journal-title":"Can Urol Assoc J"},{"key":"2025122105451305000_18.12.e267708.7","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1186\/s12301-020-00084-z","article-title":"Crossed complete fused left to right renal ectopia with solitary left ureter: A rare \u2018Case Report\u2019","volume":"26","author":"Kumawat","year":"2020","journal-title":"Afr J Urol"},{"key":"2025122105451305000_18.12.e267708.8","doi-asserted-by":"crossref","first-page":"352","DOI":"10.1186\/s13256-024-04689-8","article-title":"An uncommon encounter: crossed fused renal ectopia with singular ureter: a case report","volume":"18","author":"Dahal","year":"2024","journal-title":"J Med Case Rep"},{"key":"2025122105451305000_18.12.e267708.9","article-title":"The Rarest of the Rare: Crossed Fused Renal Ectopia of the Superior Ectopia Type","volume":"2015","author":"Akdogan","year":"2015","journal-title":"Case Rep Nephrol"},{"key":"2025122105451305000_18.12.e267708.10","doi-asserted-by":"crossref","DOI":"10.1038\/sj.ki.5002418","article-title":"Crossed fused ectopia of the kidneys","volume":"73","author":"Patel","year":"2008","journal-title":"Kidney Int"},{"key":"2025122105451305000_18.12.e267708.11","doi-asserted-by":"crossref","first-page":"200","DOI":"10.15171\/jrip.2016.42","article-title":"Cross-fused renal ectopia associated with vesicoureteral reflux; 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Anatomy, abdomen and pelvis: kidney nerves. In: Statpearls. Treasure Island (FL): StatPearls Publishing, 2025."},{"key":"2025122105451305000_18.12.e267708.18","first-page":"371","article-title":"Management of upper urinary tract calculi in crossed fused renal ectopic anomaly","volume":"15","author":"Huang","year":"2018","journal-title":"Exp Ther Med"},{"key":"2025122105451305000_18.12.e267708.19","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1089\/cren.2019.0181","article-title":"Efficacy of the Endoscopic Combined Intrarenal Surgery for the Treatment of a Staghorn Calculus in Crossed Fused Renal Ectopia","volume":"6","author":"G\u00f3mez-Regalado","year":"2020","journal-title":"J Endourol Case Rep"},{"key":"2025122105451305000_18.12.e267708.20","doi-asserted-by":"crossref","first-page":"548","DOI":"10.3390\/jpm12040532","article-title":"Endoscopic Combined Intrarenal Surgery Versus Percutaneous Nephrolithotomy for Complex Renal Stones: A Systematic Review and Meta-Analysis","volume":"12","author":"Liu","year":"2022","journal-title":"J Pers Med"},{"key":"2025122105451305000_18.12.e267708.21","first-page":"e2557","article-title":"Case report: Crossed fused renal ectopia with stones: A surgical challenge overcome by robotic surgery","volume":"19","author":"Chai","year":"2023","journal-title":"Int J Med Robot"},{"key":"2025122105451305000_18.12.e267708.22","doi-asserted-by":"crossref","first-page":"485","DOI":"10.21037\/tau-2024-740","article-title":"Radiation-free RIRS and setting a new standard: redefining safety and efficacy in stone surgery","volume":"14","author":"Akram","year":"2025","journal-title":"Transl Androl Urol"},{"key":"2025122105451305000_18.12.e267708.23","doi-asserted-by":"crossref","first-page":"1022","DOI":"10.3390\/jcm13041114","article-title":"Urological Guidelines for Kidney Stones: Overview and Comprehensive Update","volume":"13","author":"Akram","year":"2024","journal-title":"J Clin Med"}],"container-title":["BMJ Case Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bcr-2025-267708","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,21]],"date-time":"2025-12-21T13:45:22Z","timestamp":1766324722000},"score":1,"resource":{"primary":{"URL":"https:\/\/casereports.bmj.com\/lookup\/doi\/10.1136\/bcr-2025-267708"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,12]]},"references-count":23,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2025,12,21]]},"published-print":{"date-parts":[[2025,12]]}},"alternative-id":["10.1136\/bcr-2025-267708"],"URL":"https:\/\/doi.org\/10.1136\/bcr-2025-267708","relation":{},"ISSN":["1757-790X"],"issn-type":[{"value":"1757-790X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,12]]}}}