What Are the Common Metabolic Causes of Urolithiasis?

A 21-year-old male came to the emergency room with acute onset of severe back pain and emesis for 3 hours.
He was awoken with the pain which he described as starting in his left costovertebral angle (CVA) and radiating across the flank and toward the pelvis.
The pain was most intense in the CVA and diminished as it radiated. He had one episode of emesis of a small amount of stomach contents that was non-bilious.
He also had a small amount of concentrated urine.
The day previous, he had drunk very little because of being busy with his classes and had worked outside in a hot environment as a landscaper.
The family history was positive for kidney stones in his father x 2 that resolved spontaneously.
The past medical history and review of systems were otherwise negative.
The pertinent physical exam showed a male in moderate distress secondary to pain with an elevated blood pressure. He was slightly diaphoretic but was afebrile.
He had dry mucous membranes and skin turgor.
He had exquisite tenderness in the left CVA that radiated around the left flank and toward the pelvis. He had no abdominal masses and his genitourinary examination was normal.
The laboratory evaluation showed an urinalysis with a specific gravity of > 1.030, 50 red blood cells, no white blood cells, no casts, and some crystals.
A complete blood count and a basic metabolic profile were normal including a blood urea nitrogen, creatine, calcium and phosphorus.
The diagnosis of urolithiasis was made. He was given intravenous morphine for the pain and 2.5 liters of normal saline fluid.
At that point he started to be able to drink fluids but was still nauseated. His blood pressure had also returned to normal.
He was discharged with instructions to drink small amounts of fluid almost continuously to maintain a copious urine output.
Codeine was given for pain control and he was given a sieve to screen his urine.
He was also instructed on the necessity to drink throughout his day especially when he was performing manual labor or in a hot environment to maintain hydration and try to prevent another stone.
The patient’s clinical course two days later showed he went to the student health service at his university with the stone that was later identified as a calcium urate stone.
The urine culture from the emergency room was negative. A repeated urinalysis was normal.
The physician re-emphasized the need to maintain adequate or increased hydration as a way to help prevent future stone formation.
Further metabolic testing was deferred to his primary care physician in his hometown because of medical insurance.

Metabolic causes of urolithiasis are increasing.
The common metabolic causes of urolithiasis in children are below along with their percentages:

  • Hypercalciuria – 30-50%, these are radiopaque on radiographs
  • Hyperoxaluria – 20%, these are radiopaque on radiographs
  • Hyperuricosuria – 2-10%, these are not radiopaque on radiographs
  • Cystinuria – <1%, these are not radiopaque on radiographs
  • Xanthinuria – <1%, these are not radiopaque on radiographs

Patients presenting with urolithiasis should have a metabolic evaluation to help determine the etiology and possible treatments.
Metabolic evaluation may include the following:

  • Serum – electrolytes, creatinine, calcium, phosphorus, uric acid, and alkaline phosphatase.
    Parathyroid hormone in patients with hypercalciuria, hypercalcemia or hypophosphatemia.

  • 24-hour urine collection – creatine, calcium, sodium, urate, oxalate, citrate and cystine.
  • Urine culture

Learning Point
Urolithiasis is uncommon in children compared to adults. Children are only ~2-3% of all cases of urolithiasis and have about 1/50th the rate of hospital admission for urolithiasis compared to adults.
Boys have urolithiasis more commonly than girls. There are also geographical differences. The southeastern area of the United States has a higher incidence.
Globally, areas around the Balkans, Turkey, Pakistan and India have a higher rate of urolithiasis and bladder stones, presumably because of dietary and hydration differences.
In a United Kingdom study in 2003, the underlying causes of urolithiasis were metabolic (44%), infectious (30%) and idiopathic (26%).

Factors that are involved in urolithiasis formation include:

  • Metabolic
    • Urine
      • Concentration
      • Ionic activity
      • Solubility
      • Abnormal metabolites present
      • Elevated concentration of normal metabolites
  • Infectious
    • Klebsiella
    • Proteus
    • Pseudomonas
  • Other
    • Anatomic abnormalities of the urinary tract
    • Foreign bodies – stents, sutures
    • Prematurity – infants < 32 weeks gestation have a higher risk for developing urolithiasis

Questions for Further Discussion
1. What radiological modalities can be used to image urolithiasis?
2. What are the indications for lithotripsy or surgery for urolithiaisis?
3. Where are the most common anatomic places for urolithiasis to lodge?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Kidney Stone.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Nicoletta JA, Lande MB. Medical evaluation and treatment of urolithiasis.
Pediatr Clin North Am. 2006 Jun;53(3):479-91, vii.

Hiorns MP.
Imaging of urinary tract lithiasis: who, when and how?

Pediatr Radiol. 2008 Jun;38 Suppl 3:S497-500

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Interpersonal and Communication Skills
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

    January 19, 2009