British Journal of U r i h (1992). ~ ~ 70,352-354

0 1992 British Journal of Urology

The Use of Extracorporeal Shock Wave Lithotripsy for Medullary Sponge Kidneys S. A. V. HOLMES, I. EARDLEY, D. A. CORRY, I. NOCKLER and H. N. WHITFIELD Departments of Urology and Radiology, St Bartholomew’s Hospital, London

Summary-A number of patients with medullary sponge kidney recurrently form and pass stones with the risk of developing an obstructive nephropathy. These patients may benefit from extracorporeal shock wave lithotripsy to the medullary collections, a s this appears to reduce the frequency of symptomatic stone passage.

Medullary sponge kidney (MSK) is a relatively common cause of symptomatic stone formation. The condition is a developmental anomaly of the renal medulla characterised by fusiform and cystic dilatation of the collecting tubules confined to the renal pyramids. It may be restricted to a few pyramids or be diffuse, unilateral or bilateral (Harrison and Rose, 1979). The true prevalence of the condition is unknown as patients may be entirely asymptomatic, the diagnosis being made at intravenous urography performed for some other purpose. When present, symptoms are related to the associated nephrolithiasis. Calcium oxalate or phosphate stones form in the dilated ducts and cysts and erosion of these stones into the collecting system leads to the problems related to their presence and passage. Treatment of patients with symptomatic MSK has previously consisted of the control of associated metabolic disorders such as hypercalciuria, the eradication of infection and the surgical management of problematic stones and damagcd kidneys. The aim of this study was to evaluate the potential role of extracorporeal shock wave lithotripsy (ESWL) in the management of these patients.

Based on a Poster Demonstration at the 47th Annual Meeting of the British Associationof Urological Surgeons in Glasgow, June 1991

Patients and Methods

A total of 22 kidneys in 17 patients were diagnosed as having MSK on the characteristic radiological findings after intravenous urography. These patients were all symptomatic with loin pain and/or recurrent passage of stones. The patients had a mean age at the time of treatment of 48 years (range 34-63). The average duration of symptoms was 12 years, with the majority of patients previously receiving treatment with antibiotics, dietary control and surgical removal of obstructing calculi. Two patients had lost the function of one kidney as a result of stones. Treatment was performed initially on a Wolf 2200 (3 patients) and subsequently on a Dornier MPL 9000 (14 patients), which has both X-ray and ultrasound imaging modalities. The patients were assessed radiologically prior to treatment with intravenous urography, and with plain X-ray 2 weeks and 2 months after treatment. They were subsequently reviewed as out-patients. Urine was cultured and renal function and blood pressure were measured at each visit. Patients were also asked about the symptoms of renal colic, the frequency of stone passage and the incidence of urinary infection both before and after treatment. Two patients required the passage of a double pigtail stent prior to treatment because of the presence of obstructing stones. Each kidney received a mean of 1.8 treatments, with an average of 1600 shocks at each session.

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USE OF ESWL FOR MEDULLARY SPONGE KIDNEYS

Treatment was aimed initially at any stones within the collecting system and then at collections of stones within the renal pyramids.

Table Radiological Response of MSK Kidneys to Treatment with ESWL in Terms of Stone Burden

Results All treatments were well tolerated. Nineteen treatments were followed by the visible passage of stone gravel and haematuria and 17 kidneys showed a reduction in the stone burden of the renal medulla, as judged radiologically 2 months after the final treatment. Radiological reduction in stone burden was described as good (>50% reduction in visible stone) (Fig.), moderate (0-50% reduction) and no response (Table). Urine cultures failed to reveal infection either before or after treatment. Urea, creatinine and electrolytes also failed to show any change. One patient developed significant hypertension 2 months after treatment, though this patient had a contralateral non-functioning kidney which was subsequently removed. Follow-up continued for a mean of 16 months. Seven patients noticed a long-term reduction in the frequency of passage of stone particles. These were the patients who had been troubled by recurrent passage of gravel, from stones eroding into the collecting system. Renograms were performed in 3 patients before and 7 days after treatment and no deterioration in renal function was detected.

Response

No.

None Moderate Good

5 11 6

Discussion Although the incidence of MSK in unselected patients undergoing urography is only 0.5% (Myall, 1970), the incidence among patients presenting with stones has been reported to be as high as 21% (Yendt et al., 1981). The condition is congenital, although there is no evidence of a raised familial incidence. Individuals may be entirely asymptomatic and these benign cases are not associated with any loss of renal excretory function. It can, however, lead to the recurrent passage of stones, which increases the likelihood of an obstructive nephropathy. Several factors contribute to the nephrolithiasis and include urinary stasis within the dilated ducts, defective urinary acidification and hypercalciuria. A raised urinary pH has been reported in up to 40% of patients with MSK (Higashihara et al., 1984) and this is known to facilitate precipitation of calcium phosphate. Hy-

Fig. Radiographs of patient with MSK. Urogram taken prior to treatment, and plain X-rays taken after 1 and 2 treatments, showing > 50%reduction in stone burden.

354 percalciuria occurs in a similar number of patients (Harrison and Rose, 1979); unlike patients with idiopathic hypercalciuria, however, 95% of whom are men, it occurs with equal incidence in women with MSK. The aetiology of this hypercalciuria is unclear. Infection can also increase the potential for stone formation if urea splitting organisms are involved, and is always difficult to eradicate once established. Treatment of patients with MSK has centred around limiting these contributions to nephrolithiasis. Higashihara et af.(1988) treated hypercalciuric MSK patients with alkali (sodium bicarbonate) and reported a reduction in urinary calcium excretion and the frequency of passage of stones. ‘Theyconcluded that acidosis led to a depression in renal tubular reabsorption of calcium. It has been suggested that the acidification defect is the primary event in the pathological sequence of stone formation in these patients (Osther et af., 1988). Treatment of relapsing infection may be controlled with long-term suppressive antibiotics, though eradication is more difficult. Patients with MSK localisd to one portion of the kidney, with damage to that part resulting from recurrent infection, have been treated by partial nephrectomy. The main role of surgery has been the removal of obstructing stones within the urinary tract. The advent of ESWL increased the potential for treating stones before they caused obstructive nephropathy. Its use in kidneys affected by MSK has been limited (Nakatsuka et af., 1988). This study suggests that it may have a role in treating calculi that are within the collecting system, reducing the number of calculi that are still within the renal medulla and decreasing the number of episodes of colic. All of the stones were not eradicated but it is believed that those that were close to eroding into the collecting system were susceptible to ESWL, or were knocked out of their cysts or dilated ducts. ESWL to stones within the collecting duct tubules raises the question of whether damage to the tubules ensues. Tubular enzyme levels in the urine were not measured but this may be necessary in a future study. The finding that one of our patients developed significant hypertension 2 months after treatment was clouded by the fact that he had a contralateral non-functioning kidney. Nevertheless, the potential for tubular damage in these patients may be greater than in patients with conventional collecting system calculi and this should be considered when treating patients until further evidence becomes available.

BRITISH JOURNAL OF UROLOGY

This study suggests that there is a role for ESWL in the treatment of patients with MSK. Patients who recurrently form and pass stones are in danger of developing an obstructive nephropathy. These patients may benefit from treatment to these stones before they accumulate and grow in the collecting system and ESWL appears to be able to do this and reduce the frequency of stone passage. It may be that patients should be treated at suitable intervals, such as annually or biannually, to prevent accumulation of collecting system stones and to remove stones that are close to eroding into the calices. Patients and clinicians can not expect to clear MSK kidneys of stones, but a reduction in symptomatic passage and prophylaxis against obstructive nephropathy are realistic goals.

References Harrison,A. R.and Rose, G. A. (1979). Medullary sponge kidney. Urol. Res., I,191-207. Higashihara, E., Nutahara, K. and Niijima, T. (1988). Renal hypercalciuria and metabolic acidosis associated with medullary sponge kidney: effect of alkali therapy. Urol. Res., 16,95100. Higashihara,E., Nutahara, K., Tago, K. et UJ! (1984). Medullary sponge kidney and renal acidification defect. Kidney Znt., 25, 453-459. Myall, G. F. (1970). The incidence of medullary sponge kidney. Clin. Rudiol., 21, 171-174. Nakatsuka, S., Kmoshita, H., Ueda, H. et al. (1988). Combined treatment of medullary sponge kidney by EDTA potassium citrate and extracorporeal shock wave lithotripsy. Eur. Urol., 14,339-342. Osther, P. J., Hansen, A. B. and Rohl, H. F. (1988). Renal acidification defects in medullary sponge kidney. Br. J. Urol., 61,392-394. Yendt, E. R., Jarzylo, S., F d s , W. et UJ! (1981). Medullary sponge kidney (tubular ectasia) in calcium urolithiasis. In Urolithiusis: Clinical and Basic Research, ed. Smith, L. H., Robertson, W. G. and Finlayson, B. Pp. 105-112. New York: Plenum Press.

The Authors S. A. V. Holmes, FRCSE, Registrar, Department of Urology, St Mary’s Hospital, Portsmouth. I. Eardley, MA, MChir, FRCS(Urol), Senior Registrar, Department of Urology, Norfolk and Norwich Hospital, Norwich. D. Corry, DCRR, DMU, Senior Radiographer, Lithotriptor Unit, St Bartholomew’s Hospital. I. Nockler, FRCR, Consultant Radiologist, St Bartholomew’s Hospital. H. N. Whitfield, MA, MChir, FRCS, Consultant Urologist, St Bartholomew’s Hospital. Requests for reprints to: S. A. V. Holmes, Department of Urology, St Mary’s Hospital, Milton Road, Portsmouth PO3 6AD.

The use of extracorporeal shock wave lithotripsy for medullary sponge kidneys.

A number of patients with medullary sponge kidney recurrently form and pass stones with the risk of developing an obstructive nephropathy. These patie...
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