title: A review of the natural progression of medullary sponge kidney and a novel grading system based on intravenous urography findings.
abstract: OBJECTIVE
  Medullary sponge kidney (MSK) is a developmental abnormality of the medullary pyramids of the kidney, characterised by cystic dilatations of the collecting ducts. We investigated a cohort of patients with MSK to gain further information about its presentation, clinical course and treatment required. We devised a grading system based upon findings at diagnostic intravenous urography (IVU) and established a relationship between severity of IVU findings and severity of disease.
  
  
  METHODS
  The clinical notes and imaging of 29 patients with MSK were analysed. The severity of IVU findings was classified as follows: grade 1 (one calyx, unilateral), grade 2 (one calyx, bilateral), grade 3 (more than one calyx, unilateral) and grade 4 (more than one calyx, bilateral).
  
  
  RESULTS
  The age range at diagnosis was 12-69 (mean 39), mean follow-up period was 12.7 years. Increasing grade of IVU findings correlated with more frequent symptomatic stone episodes (grade 1: 0.09 episodes per patient per year; grade 4: 0.34). Higher grade was also related to the number of hospital admissions (grade 1: 0.182 per patient per year; grade 4: 0.282) and the number of procedures required (either surgery or extracorporeal shock wave lithotripsy; grade 1: 0.0 interventions per patient per year; grade 4: 0.24).
  
  
  CONCLUSIONS
  MSK presents over a wide age range and can cause long periods of intermittent episodes. Patients can be graded using a novel system based on IVU findings, which correlates with severity of disease. Management strategies such as intensity of follow-up can be modified using this grading.
authors.affiliation: Department of Urology, Pinderfields General Hospital, Mid Yorkshire Hospitals NHS Trust, Wakefield, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Forster
authors.forename: J
authors.initials: J
authors.lastname: Taylor
authors.forename: A J
authors.initials: AJ
authors.lastname: Browning
authors.forename: C S
authors.initials: CS
authors.lastname: Biyani
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003287:Contrast Media / Q000008:administration & dosage; D004108:Dilatation, Pathologic; D018450:Disease Progression; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007472:Iohexol / Q000008:administration & dosage / Q000031:analogs & derivatives; D007674:Kidney Diseases / Q000145:classification* / Q000000981:diagnostic imaging*; D007685:Kidney Tubules, Collecting / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012720:Severity of Illness Index
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide