title: Gas-containing renal stones: findings from five consecutive patients.
abstract: OBJECTIVE
  To describe the clinical course, microbiology, and metabolic findings of 5 patients presenting to our institution with gas-containing renal stones.
  
  
  METHODS
  During a 20-month period beginning in 2009, 5 patients were identified by computed tomography scanning to harbor gas-containing renal calculi. Despite similar imaging and referral practice patterns, no such cases had been seen at our institution in the preceding 20 years. The records of these patients were reviewed to better characterize this unique condition.
  
  
  RESULTS
  All 5 subjects were premenopausal women. One patient presented with urosepsis and 4 presented with flank pain. All had urinary tract infections, and Escherichia coli was isolated from a voided urine specimen in 3. Stone culture was positive in 2 and was concordant with the voided specimen in 1. The stones were solitary in 4 and multiple in 1 patient. All the stones were composed of calcium phosphate. Of the 5 patients, 3 had pure calcium phosphate stones and 2 had stones with calcium oxalate monohydrate components. Also, 3 subjects had diabetes mellitus, 3 had hypertension, and 1 had a history of gout. Two subjects underwent 24-hour urine metabolic testing, and abnormalities were identified in both. All patients were rendered stone free: 4 with percutaneous nephrostolithotomy and 1 using robotic pyelolithotomy.
  
  
  CONCLUSIONS
  Gas-containing renal stones are rare but might be increasing in prevalence. The pathophysiology is unknown but is most likely influenced by a combination of metabolic and infectious factors.
authors.affiliation: Department of Urology, Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina 27157, USA.
authors.forename: Ted B
authors.initials: TB
authors.lastname: Manny
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Mufarrij
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Lange
authors.forename: Majid
authors.initials: M
authors.lastname: Mirzazadeh
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Hemal
authors.forename: Dean G
authors.initials: DG
authors.lastname: Assimos
mesh_terms: D000328:Adult; D002130:Calcium Phosphates / Q000032:analysis; D005260:Female; D005740:Gases; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry / Q000209:etiology* / Q000378:metabolism / Q000601:surgery; D008875:Middle Aged; D011247:Pregnancy; D011248:Pregnancy Complications / Q000209:etiology* / Q000378:metabolism / Q000601:surgery; D012189:Retrospective Studies; D014552:Urinary Tract Infections / Q000150:complications / Q000382:microbiology*
chemical_list: D002130:Calcium Phosphates; D005740:Gases; C020243:calcium phosphate