title: MRI Findings of Inverted Urothelial Papilloma of the Bladder.
abstract: OBJECTIVE
  The objective of this study was to characterize MRI findings of inverted urothelial papilloma of the bladder.
  
  
  METHODS
  Data pertaining to 16 patients with 18 pathologically proven inverted urothelial papillomas of the bladder who had undergone MRI were retrospectively collected from seven institutions. The shape and surface characteristics of the tumors were evaluated using T2-weighted MR images. In addition, the signal intensity of inverted urothelial papillomas was visually assessed on T1-weighted, T2-weighted, and DW images and on early and delayed phase contrast-enhanced images.
  
  
  RESULTS
  The shape of the 18 inverted urothelial papillomas of the bladder was classified as polypoid with a stalk for 16 tumors (89%) and polypoid without a stalk for two tumors (11%). All stalks were surrounded by urine in the bladder. A total of 15 of the tumor surfaces (83%) were nonpapillary and three (17%) were papillary. All 12 of the inverted urothelial papillomas for which evaluable T1-weighted images were available were isointense with the bladder wall. The lesions had a slightly higher signal intensity than the bladder wall in 15 of the patients (83%) and showed isointensity with the bladder wall in three patients (17%). A total of three patients (17%) had tiny hyperintense foci noted on T2-weighted images. All 16 of the inverted urothelial papillomas examined by DWI had very high signal intensity. All 13 of the lesions for which early phase images were obtained using dynamic contrast-enhanced MRI showed strong enhancement. When compared with early phase images, delayed phase images of the same 13 lesions showed that enhancement was stronger in two lesions (15%), similar in six lesions (46%), and weaker in five lesions (38%).
  
  
  CONCLUSIONS
  On MRI, the typical appearance of inverted urothelial papillomas of the bladder is a polypoid shape with a nonpapillary surface and a thin short stalk surrounded by urine. Cystic foci are also occasionally seen within the tumor.
authors.affiliation: 1 Department of Radiology, Nagoya City University Graduate School of Medical Sciences and Medical School, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takeuchi
authors.affiliation: 2 Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Kohei
authors.initials: K
authors.lastname: Sasaguri
authors.affiliation: 3 Department of Nephro-Urology, Nagoya City University Graduate School of Medical Sciences and Medical School, Nagoya, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Naiki
authors.affiliation: 4 Department of Radiology, Japanese Red Cross Society Himeji Hospital, Himeji, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Mitsumori
authors.affiliation: 5 Department of Radiology, Kajiicho Medical Imaging Center, Kyoto, Japan.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Ito
authors.affiliation: 6 Department of Radiology, Nara Medical University, Nara, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Takahama
authors.affiliation: 7 Department of Radiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Yamada
authors.affiliation: 6 Department of Radiology, Nara Medical University, Nara, Japan.
authors.forename: Nagaaki
authors.initials: N
authors.lastname: Marugami
authors.affiliation: 8 Department of Radiology, Osaka Medical College, Osaka, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsuboyama
authors.affiliation: 9 Department of Diagnostic and Interventional Radiology, Fukuyama City Hospital, Hiroshima, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okumura
authors.affiliation: 10 Department of Radiology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Yoshimitstu
authors.initials: Y
authors.lastname: Ohgiya
authors.affiliation: 3 Department of Nephro-Urology, Nagoya City University Graduate School of Medical Sciences and Medical School, Nagoya, Japan.
authors.forename: Noriyasu
authors.initials: N
authors.lastname: Kawai
authors.affiliation: 3 Department of Nephro-Urology, Nagoya City University Graduate School of Medical Sciences and Medical School, Nagoya, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Kohri
authors.affiliation: 1 Department of Radiology, Nagoya City University Graduate School of Medical Sciences and Medical School, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shibamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003558:Cystoscopy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018308:Papilloma, Inverted / Q000175:diagnosis* / Q000473:pathology; D012189:Retrospective Studies; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis* / Q000473:pathology
keywords: MRI; diagnostic imaging; inverted papilloma; urinary bladder neoplasms