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Common Urological Problems

Urinary Stone Disease Intervention

  • - General Urology - Common Urological Problems - Urinary Stone Disease
  • Jul 25, 2010
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Tags: | citric acid | computed tomography | dissolution agents | fluoroscopic imaging |

A. CONSERVATIVE OBSERVATION
Most ureteral calculi pass and do not require intervention.

Spontaneous passage depends on stone size,  shape,  location,  and associated ureteral edema (which is likely to depend on the length of time that a stone has not progressed). Ureteral calculi 4–5 mm in size have a 40–50% chance of spontaneous passage. In contrast, calculi >6 mm have a <5% chance of spontaneous passage. This does not mean that a 1-cm stone will not pass or that a 1- to 2-mm stone will always pass uneventfully.

The vast majority of stones that pass do so within a 6-week period after the onset of symptoms. Ureteral calculi discovered in the distal ureter at the time of presentation have a 50% chance of spontaneous passage, in contrast to a 25%  and 10%  chance in the mid-  and proximal ureter, respectively.

B. DISSOLUTION AGENTS
The effectiveness of dissolution agents depends on stone surface area, stone type, volume of irrigant, and mode of delivery. Oral alkalinizing agents include sodium or potassium bicarbonate and potassium citrate. Extra care should be employed in patients susceptible to congestive heart failure or renal failure.  Citrate is metabolized to bicarbonate and comes in a variety of preparations.

Polycitra contains potassium and sodium citrate and citric acid. Bicitra contains only sodium citrate and citric acid. Food does not alter the effectiveness of these agents. Alternatively, orange juice alkalinizes urine. Intravenous alkalinization is effective with one-sixth molar sodium lactate.

image Figure 16–15.  A: Scout abdominal radiograph demonstrating large left staghorn renal calculus. B: Nuclear scintigraphic evaluation of renal calculi. Posterior view demonstrating uptake on large left staghorn calculus after furosemide (Lasix) diuresis. Note right kidney with uptake in lower pole. C: Follow-up tomogram confirms calculus (arrow) in right lower pole missed on initial radiograph.

Intrarenal alkalinization may be performed successfully under a low-pressure system (<25 cm water pressure).  This may be achieved through a percutaneous nephrostomy tube or an externalized retrograde catheter.

A manometer,  similar to those used for central venous pressure monitoring,  is cheap,  available,  and practical.

Urinary Stone Disease

Urinary Stone Disease

Agents include sodium bicarbonate, 2–4 ampules in 1 L of normal saline,  producing a urinary pH between 7.5 and 9. Tromethamine-E and tromethamine can produce urinary pHs of 8–10.5 and are especially effective with pH-sensitive calculi as in uric acid and cystine lithiasis.

Cystine calculi can be dissolved with a variety of thiols, including D–penicillamine (0.5%  solution),  N–acetylcysteine (2–5%  solution),  and alpha-mercaptopropionylglycine (Thiola) (5% solution).

Struvite stone dissolution requires acidification and may be achieved successfully with Suby’s G solution and hemiacidrin (Renacidin). Urinary pH may get down to 4.

Hemiacidrin must be used with sterile urine and careful monitoring of serum magnesium levels is required.  The Food and Drug Administration has not approved hemiacidrin for upper-tract irrigations,  and thus appropriate informed consent is required.

C. RELIEF OF OBSTRUCTION
Urinary stone disease may result in significant morbidity and possible mortality in the presence of obstruction,  especially with concurrent infection.  A patient with obstructive urinary calculi with fever and infected urine requires emergent drainage. Retrograde pyelography to define upper-tract anatomy is logically followed by retrograde placement of a double-J ureteral stent.

On occasion such catheters are unable to bypass the offending calculus or may perforate the ureter. In such situations one must be prepared to place a percutaneous nephrostomy tube.

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