title: The occurrence of Wilms tumor in horseshoe kidneys: a report from the National Wilms Tumor Study Group (NWTSG).
abstract: OBJECTIVE
  An increased incidence of Wilms tumor has been noted in patients with a horseshoe kidney. These represent a difficult diagnostic and therapeutic challenge. The charts of all National Wilms Tumor Study Group (NWTSG) patients with Wilms tumor occurring in a horseshoe kidney were reviewed.
  
  
  METHODS
  From 1969 to 1998, 8,617 patients were enrolled in the NWTSG. Forty-one patients were found to have a Wilms tumor arising in a horseshoe kidney for an incidence of 0.48%. Their records were reviewed retrospectively.
  
  
  RESULTS
  Horseshoe kidney was not recognized preoperatively in 13 patients, 10 of whom were evaluated with computed tomography (CT). Four of the 10 also had renal ultrasonography and one an intravenous pyelogram (IVP). Two of the 13 were evaluated with an IVP only, and the last had no preoperative imaging studies performed. Stage at presentation was stage I, 10 pts; stage II, 10; stage III, 12; stage IV, 6; stage V, 3. Primary surgical resection was performed in 26 patients, including 23 nephrectomies and 3 partial nephrectomies. Fifteen children were treated with preoperative chemotherapy after initial biopsy of the tumor. The mean total remaining renal parenchyma after all operations (excluding treatment of relapses) was approximately 75%. Surgical complications occurred in 14.6% of patients, including 2 urine leaks, 2 ureteral obstructions, and 1 ureteral injury. Two patients had transient renal failure.
  
  
  CONCLUSIONS
  The diagnosis of horseshoe kidney often was missed on preoperative imaging. Accurate preoperative diagnosis is important in planning the operative approach and may help to decrease complications related to transection of the urinary collecting system. Although 37% of patients with Wilms tumor arising in a horseshoe kidney were judged inoperable at initial exploration, all were amenable to resection after chemotherapy.
authors.affiliation: Department of Surgery, University of Texas, Houston Medical School, Houston, TX, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Neville
authors.forename: Michael L
authors.initials: ML
authors.lastname: Ritchey
authors.forename: Robert C
authors.initials: RC
authors.lastname: Shamberger
authors.forename: Gerald
authors.initials: G
authors.lastname: Haase
authors.forename: Sharon
authors.initials: S
authors.lastname: Perlman
authors.forename: Teri
authors.initials: T
authors.lastname: Yoshioka
mesh_terms: D001706:Biopsy; D017024:Chemotherapy, Adjuvant; D002675:Child, Preschool; D015897:Comorbidity; D000013:Congenital Abnormalities / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007668:Kidney / Q000002:abnormalities* / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D009367:Neoplasm Staging; D009392:Nephrectomy; D011292:Premedication; D012189:Retrospective Studies; D015996:Survival Rate; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D009396:Wilms Tumor / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy