Nephrolithiasis
Nephrolithiasis is kidney stones. Most contain calcium, either calcium oxalate stones or calcium phosphate. Others are comprised of uric acid, magnesium ammonium phosphate (struvite) or cystine. All fundamentally develop when the amount of their components exceeds saturation. Obesity is a major risk factor.
Calcium stones
- Are caused by hypercalciuria, hyperoxaluria, hyperuricosuria or an insufficiency of citrate (hypocitraturia)
- There is a strong genetic component to these elements.
Uric acid stones
- Most patients have reduced urinary pH (as pH lowers, uric acid is less soluble)
- Diarrhea and diet play a large role in acidic urinary pH
- Diet with lots of organ meats, shellfish, fish and meat extract increases the risk.
- Disorders such as gout also increase the risk
Struvate stones
- Constitute the majority of staghorn calculi, which extend beyond a single calyx. Much more common in women due to their increased susceptibility to UTIs
- Form in alkaline urine with ammonium ions - alkaline urine only occurs where urease-producing bacteria are present (e.g. Proteus, Klebsiella, s.epidermidis, mycoplasma spp.)
Cystine stones
- Cystinuria is due to AR mutation of SLC3A1 gene or SLC7A9 gene
- Increased cystine causes insolubility, and precipitate to form
Clinical presentation is typically renal colic (pain) with hematuria). On occasion acute kidney injury will present as well (due to total obstruction). The pain is abrupt and can intensify into severe, excruciating flank pain, often radiating around the groin and back. However, calculi can also be totally asymptomatic, even obstructive types, and nephrolithiasis should be considered in the differential for unexplained kidney disease.
Diagnosis is typically via radiographic evaluation and/or ultrasonography.
Axial non-contrast CT of the abdomen showing a bright, dense calculus in the left ureter (red arrow) beside the lumbar spine.
Image: “Midureterstonehydro” by James Heilman, MD, CC BY-SA 3.0, via Wikimedia Commons.
Treatment
- Medical
- Pain control with NSAIDs (IV ketorolac and ibuprofen orally can be recommended). Ensure adequate hydration as NSAIDs can cause severe kidney damage. Morphine can be given if these are insufficient.
- 70% of stones <5mm will pass without incidence, and even those 5-10mm have a 50% chance of passing. Use alpha-adrenergic receptor blockers (tamsulosin 0.4mg/day oral, or terazosin, or doxazosin) or calcium-channel blockers (nifedipine XL 30mg/day or twice daily) to reduce ureteral spasm and allow more effective passing.
- Non-medical
- Surgical