Urinary Calculus Disease
94 URINARY CALCULUS DISEASE
Bretat B. Abernathy M.D.
1. What are the most common types of urinary stones found in North America?
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* Calcium stones (calcium oxalate, calcium phosphate, or mixed calcium stones): 70%.
* Struvite or magnesium ammonium phosphate stones, often associated with infection: 20%.
* Uric acid stones (radiolucent): 5%
* Cystine stones, often with a genetic association: 5%
2. What are the typical presenting symptoms of a patient with an obstructing stone?
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* Pain, usually colicky in the flank or radiating to the groin; patients are usually agitated and cannot get in a comfortable position
* Hematuria, gross or microscopic
* Nausea and vomiting caused by obstruction and pressure on the renal capsule
3. What studies are best to diagnose stones?
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1. Excretory urogram, or intravenous pyelogram (IVP). Ninety percent of stones are radiopaque and can be seen on a plain radiograph of the kidney, ureter, and bladder (KUB). The IVP serves as a functional study to determine the degree of obstruction, level of obstruction, and presence of a contralateral kidney.
2. Currently, rapid-sequence helical computed tomography (CT) scan has gained popularity. Helical CT can accurately identify both renal and ureteral stones. Its advantages include no need for contrast; speed; and ability to identify calcium, uric acid, and cystine stones. Disadvantages include increased cost compared with IVP and inability to distinguish between radiolucent (uric acid) stones and radiopaque (calcium-containing) stones. A KUB should be obtained if the CT has positive results, to distinguish between radiolucent and radiopaque stones.
3. Ultrasound is particularly advantageous in pregnant women.
4. When should a patient with an obstructing stone be admitted to the hospital?
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* Any sign of infection (e.g., fever, leukocytosis, bacteriuria); infection behind an obstructing stone may result in urosepsis and death
* Intractable vomiting requiring intravenous (IV) fluids
* Pain requiring parenteral analgesics
* Bilateral obstructing stones or obstruction in a solitary kidney
5. What are the treatment options for ureteral calculi?
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* Wait and watch to see if the stone passes; it usually does. Approximately 90% of stones, 3 mm in size in the distal ureter, will pass. Fifty percent of 5-mm stones will pass, and 20% of stones larger than 6 mm will pass.
* Ureteroscopy and stone basketing or intraureteral lithotripsy (stone blasting) with a laser (holmium, pulsed dye) or electrohydraulic lithotripsy (EHL)
* Extracorporeal lithotripsy (ESWL), or shock waves directed at the stone to break it into small pieces that can then pass spontaneously
* Open ureterolithotomy, now rarely used because of the success of the less invasive techniques listed above
KEY POINTS: URINARY CALCULUS DISEASE
1. The most common stones in patients in the United States are calcium stones.
2. Excretory urogram or intravenous pyelogram, rapid-sequence helical CT, and ultrasound are the imaging studies used to diagnose stones.
3. Steinstrasse is a collection of small calculi that pile up together in the ureter and cause obstruction or symptoms.
6. What are the treatment options for renal calculi?
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* Expectant management in asymptomatic noninfectious stones
* ESWL
* Ureteropyeloscopy with lithotripsy using a laser. This has become more popular with smaller, flexible, deflectable ureteroscopes, but it is still a challenging procedure for large stones.
* Percutaneous nephrostolithotomy (particularly for stone burden > 2 cm)
* Combination of ESWL and percutaneous nephrostolithotomy
* Open lithotomy (less common because of the success of less invasive treatment options)
7. What is a steinstrasse?
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Steinstrasse (German for “stone street”) is a collection of small calculi that pile up together in the ureter and cause obstruction or symptoms. This problem may occur after lithotripsy treatment.
8. What is a stent?
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A stent is a small plastic catheter that coils in the renal pelvis, traverses the ureter, and coils in the bladder. Stents are useful to relieve ureteral obstruction temporarily and possibly facilitate stone passage after the stent is removed. Stents often cause some degree of ureteral dilatation after they have been removed.
9. What is a metabolic evaluation? Who needs one?
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A metabolic evaluation involves examining both serum and 24-hour urine specimens for factors that contribute to stone formation. The goals are to identify an abnormality and to treat it medically to prevent further stone formation. Indications for metabolic evaluation include recurrent stones, multiple stones, bilateral stones, stones in children, and non-calcium-containing stones.
10. Can stones be dissolved?
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* Uric acid stones often can be dissolved by alkalinizing the urine and with hydration therapy.
* Cystine, struvite, and apatite stones sometimes can be dissolved.
* Calcium stones cannot be dissolved.
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Abernathy’s Surgical Secrets, Updated Edition (Book w / Student Consult)
Author / s: Harken Alden H., Abernathy Charles, Moore Ernest Eugene
Year: 2004
Pages: 473
Publishers: Elsevier Mosby; 5th Bk & Acc edition
ISBN: 0323034160
