Nephrolithiasis Flashcards
Calcium Stones
Frequency and Causes
- It is the most common 80% (oxalate is more common than phosphate)
- Idiopathic hypercalciuria (most common cause)
- Primary hyperparathyroidism
- Hypocitraturia that will result in decreased urine pH, it can be caused by:
- Metabolic acidosis (removes Ca++ from bones and decrease citrate levels)
- Ethylene glycol (anti-freeze) ingestion
- Vitamin C abuse
- Malabsorption like Crohn’s disease (increase oxalate absorption)
Ammonium magnesium phosphate (Struvite) Stones
Frequency and Causes
- About 15%
- Infection with urease +ve bugs like:
- P. mirabilis
- S. saprophiticus
- Klebsiella
Uric acid Stones
Frequency and Causes
- About 5%
- Decreased urine volume
- Arid climate
- Acidic pH
- Gout
- Xanthine oxidase deficiency
- High purine turnover states like chemotherapy
Cystine Stones
Frequency and Causes
- Very rare
- Hereditary (AR) condition with loss of function of the Cystine-reabsorbing transporter at the PCT causing cystinuria. Also the defect results in poor reabsorption of Ornithine, Lysine, and Arginine (COLA)
Calcium oxalate Stones
Urine crystal shape
Back of envelop or dumbbell
Calcium phosphate Stones
Urine crystal shape
Wedge-shaped prism
Ammonium magnesium phosphate (Struvite) Stones
Urine crystal shape
Coffin lid
Uric acid Stones
Urine crystal shape
Rhomboid or rosettes
Cystine Stones
Urine crystal shape
Hexagonal
Calcium oxalate Stones
X-ray and CT findings
Radiopaque on both
Calcium phosphate Stones
X-ray and CT findings
Radiopaque on both
Ammonium magnesium phosphate (Struvite) Stones
X-ray and CT findings
Radiopaque on both
Uric acid Stones
X-ray and CT findings
- Radiolucent on X-ray
- Can be visualized on CT
Cystine Stones
X-ray and CT findings
Radiopaque on both
Calcium oxalate Stones
pH changes
Decreased pH
Calcium phosphate Stones
pH changes
Increased pH
Ammonium magnesium phosphate (Struvite) Stones
pH changes
Increased pH
Uric acid Stones
pH changes
Decreased pH
Cystine Stones (pH changes)
Decreased pH
Renal Stones
Presentation
- Acute onset of severe, colicky flank pain that may radiate to the testes or vulva
- There may be associated nausea and vomiting
- Patients are unable to get comfortable and shift position frequently
Renal Stones
Diagnosis
- CT scan to detect the stone and any obstruction like hydronephrosis if present
- U/S is preferred over CT scan in pregnant women and children
- Urine analysis may show gross or microscopic hematuria and an altered urine pH
- We can determine the etiology of the stone by doing the following:
- Stone analysis
- Sodium cyanide nitroprusside test is +ve in cystine stones
- Serum Ca++, sodium, uric acid, PTH, magnesium, and phosphate levels
- 24-hour urine volume for Ca++, oxalate, citrate, cystine, pH, uric acid, phosphate and Mg++
Renal Stones
General Treatment
- Acute episode should be managed with hydration and analgesia like Ketorlac (NSAIDs that can be given orally and IV that provides a level of analgesia similar to opiate medications)
- Stones < 5 mm pass spontaneously
- Stones 5-7 mm can be passed with the help of nifedipine + tamsulosin
- Stones between 0.5 and 2 to 3 cm can be managed with lithotripsy (Extracorporeal shock-wave lithotripsy [ESWL])
- Large stones are removed surgically by percutaneous nephrolithotomy or retrograde ureteroscopy
- Stones halfway up the ureters are treated with lithotripsy. Stones halfway down the ureters are removed from below with a basket
- Stent-placement relieves hydronephrosis from stones caught in distal ureters
Calcium oxalate Stones
Specific Treatment
- Hydration
- Thiazides
- Alkalinization of urine with citrate
- Low sodium and protein diet
- Increase Ca++ intake
Calcium phosphate Stones
Specific Treatment
- Hydration
- Thiazides
- Increase Ca++ intake
Ammonium magnesium phosphate (Struvite) Stones
Specific Treatment
- Hydration
- Eradication of the underlying infection
- Surgical removal of the stones
Uric acid Stones
Specific Treatment
- Hydration
- Alkalinization of urine with citrate
- Dietary purine restriction
- Allopurinol
Cystine Stones
Specific Treatment
- Hydration
- Low sodium diet
- Alkalinization of urine with citrate
- Chelating agents like penicillamine if refractory
Causes of Staghorn Stones
- Ammonium magnesium phosphate (struvite) stones
- Cystine stones
Renal Stones
Prognosis
50% of patients with kidney stones will have a recurrence over the next 5 years
Renal Stones
Complications
- Hydronephrosis
- Pyelonephritis
