EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY FOR RADIOLUCENT STONES Shailendra Kumar, MD, MS, FACS, and Vedantham Srinivasan, MD, MS, FRCSC Washington, DC, and Chicago,; Illinois

Eleven patients with radiolucent urinary calculi were treated with shock wave lithotripsy. Nine of these patients experienced successful fragmentation of their stones and subsequent spontaneous passage of the calculi fragments. The majority of the stones were composed of uric acid alone or a mixture of uric acid and calcium oxalate. One stone with metabolites of triamterene also fragmented well. Uric acid calculi can be treated successfully with shock wave lithotripsy using adequate visualization by contrast injection. (J Nati Med Assoc. 1992;84:797-799.) Key words * lithotripsy * urinary calculi * renal stones

Extracorporeal shock wave lithotripsy has become an established treatment method for urinary calculi. Since its inception in 1982, extracorporeal shock wave lithotripsy has become one of the primary modalities for treating urinary calculi.' Initially, renal calculi were the primary stones treated but since then ureteral calculi also have been successfully treated with shock wave lithotripsy using a Dornier HM3 lithotriptor. This article reports on 11 patients who had radiolucent or faintly radiopaque calculi between Feburary 1986 and January 1989.

hematuria, and in one case urosepsis were evaluated in the hospital. Urinary calculi were diagnosed by either intravenous pyelography or retrograde pyelogram. There were five men and six women. All of the patients were white except for one black woman, and the patients' ages ranged from 40 to 75. Nine patients had a single calculus, and two patients had multiple calculi. Six had renal pelvic calculi (Figure), four had ureteral calculi, and one patient had both ureteral and renal calculi. Retrograde pyelograms demonstrated the filling defect. Shock wave lithotripsy was performed using a Dornier HM3 lithotriptor with the patient in a waterbath. Ureteral catheter was placed preoperatively to aid. localization in nine of the 11 cases, and two patients had faintly radiopaque calculus that could be seen for lithotripsy. Stent placement for drainage was performed in six of the 11 patients. All stents were placed preoperatively. The number of shocks administered varied from 1800 to 3000 impulses at 18 to 22 kV. All of the patients remained in the hospital for 1 to 3 days. Complications included postoperative pain that lasted more than 2 to 3 days in three out of eight patients. No patient had a significant obstruction that needed subsequent drainage. Stone fragmentation was successful in 10 of the patients.

RESULTS METHODS AND MATERIALS Between February 1986 and January 1989, 11 patients who presented with symptoms of flank pain, From the Division of Urology, Department of Surgery, Howard University, Washington, DC, and the Division of Urology, Department of Surgery, University of Illinois Chicago, Chicago, Illinois. Requests for reprints should be addressed to Dr Shailendra Kumar, Urology Division, DC General Hospital, 19th St and Massachusetts Ave, SE, Washington, DC 20003. JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 84, NO. 9

One stone did not fragment, and the patient underwent open lithotomy. The stone was 2.5 cm in size, faintly radiopaque, and was composed of a mixture of uric acid and calcium oxalate. The remaining 10 patients passed the stone fragments. Sepsis was not present postoperatively in any of the patients. One patient presented preoperatively with sepsis. No residual fragments were present 3 months postprocedure as demonstrated by an intravenous pyelography or an 797


Figure. Radiolucent stone in left renal pelvis as seen on retrograde pyelogram.

ultrasonography (only one patient needed a pyelolithotomy). One patient who stopped taking allopurinol had a recurrence of uric acid calculi in the ureter 11/2 years later. These calculi were passed spontaneously. All but one of the patients are currently taking allopurinol and are tolerating it well. Stone analysis performed on the fragments revealed the following: in six patients, the stones contained only uric acid; in three patients, the stones contained a mixture of uric acid and calcium oxalate monohydrate with uric acid being the predominant portion of the stone; and in one patient, the stone showed metabolites of triamterene. Triamterene with hydrochlorothiazide is commonly administered as an antihypertensive medication, and metabolites of triamterene have been known to cause calculi in the urinary tract. However, to our knowledge, this is the first instance where a large radiolucent calculus in the renal pelvis with obstruction causing urosepsis was observed. Nevertheless, this stone fragmented quite well, and the stone analysis showed essentially triamterene metabolites rather than uric acid. This patient was advised to stop taking triamterene and was placed on another antihypertensive medication.

DISCUSSION Shock wave lithotripsy for upper urinary calculi has been shown to be an effective procedure with successful fragmentation in more than 90% of patients.2 Studies have revealed that residual fragments were present at 3 months in 10.5% of patients and that a stone-free state was achieved in more than 89.5%.3 It also has been well 798

established that uric acid calculi fragment fairly easily.2 If a coating of calcium oxalate monohydrate is present, the stones do not break well because calcium oxalate monohydrate is difficult to fragment with shock wave lithotripsy. Pure calcium oxalate monohydrate stones are quite difficult to fragment successfully. One of the patients in this series had a fairly large calculus with a coating of calcium oxalate monohydrate over uric acid. The stone did not fragment, necessitating pyelolithotomy. All of the other patients in the series had successful fragmentation. Placing them on allopurinol and alkalizing urine and reducing the purine content in the diet have proved to be successful preventive measures in these patients. Nevertheless, patient compliance is necessary, and recurrences have been observed in those patients who did not strictly follow the diet or who did not take their allopurinol. Nine out of 11 patients have been doing well on this regimen, with follow-up ranging from 3 months to 3 years. Visualization of the stone for localization on fluoroscopy during the procedure can easily be performed by inserting an open-ended ureteral catheter preoperatively and infusing contrast material either continuously or intermittently during the procedure. Evidence of successful stone fragmentation occurs when the contrast material goes between the interstices of the stone and fills the pelvocalyceal system. In large calculi, stenting helps in reducing postoperative pain, obstruction, and sepsis. The interval for passing stone fragments has varied from within a few days to 2 or 3 weeks. The most successful stone-free rate has been obtained with radiolucent uric acid calculi as opposed to calcium calculi. Fairly large calculi have been fragmented using shock wave lithotripsy, resulting in decreased postoperative pain as well as financial savings because these patients did not require surgery. With the availability of endo-urological procedures, including ureteroscopy, extraction of lower ureteral calculi has become feasible. However, if the stones in the ureter are large, ultrasonic lithotripsy through the ureteroscope is not always successful. In most instances, shock wave lithotripsy has obviated the need for open ureterolithotomy. During the past 2 years, we have performed only one ureterolithotomy on a patient who was not treated by shock wave lithotripsy. In this case, ureteroscopy and extraction of multiple calculi was performed. One large calculus, however, could not be retrieved with the stone basket, and therefore, a ureterolithotomy was performed. JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 84, NO. 9


2. Chaussy C, Schmiedt E. Shock wave treatment of stones in the upper urinary tract. Urol Clin North Am. 1983; 1 0:743-750. 3. Chaussy C, Schuller J, Schmiedt E, Brandl H, Jocham D, Lieal B. Extracorporeal shock wave lithotripsy (ESWL) for treatment of urolithiasis. Urology. 1984;23:59-66. 4. Gillenwater JY. Extracorporeal shock wave lithotripsy (ESWL) for treatment of urolithiasis. In: Gillenwater JY, Howards SS, eds. Year Book of Urology. Chicago, III: Year Book Medical Publishers Inc; 1985:128.

Contraindications for shock wave lithotripsy include weight >300 lbs, height >6 ft 6 in, or obstruction distal to the stone.4 None of the patients in this series exhibited any of these characteristics. Literature Cited 1. Chaussy C, Schmiedt R, Jocham D, Brendel W, Forssmann B, Walther V. First clinical experience with extracorporeally induced destruction of kidney stones by shock waves. J Urol. 1982;127:417-420.

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Extracorporeal shock wave lithotripsy for radiolucent stones.

Eleven patients with radiolucent urinary calculi were treated with shock wave lithotripsy. Nine of these patients experienced successful fragmentation...
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