EXTRACORPOREAL SHOCK-WAVE LITHOTRIPSY IN HORSESHOE KIDNEYS D. R. LOCKE, M.D. R. C. NEWMAN, M.D. G. S. STEINBOCK, M.D. B. FINLAYSON, M.D., PH.D. * From the Division of Urology, Department of Surgery, University of Florida, Gainesville, Florida

ABSTRACT-Using the Dornier HM-3 lithotriptor, 10 patients (11 renal units) with calculi in horseshoe kidneys were treated with extracorporeal shock-wave lithotripsy (ESWL) and ancillary procedures. Six renal units (55 %) underwent pre-ESWL manipulation consisting of a Double] stent, ureteral catheter, or percutaneous nephrostomy. The "blast path" was employed to treat five renal units which could not be positioned at F2 • Good initial stone fragmentation was obtained in eight renal units (73 %). There were two episodes of post-ESWL obstruction requiring intervention; both occurred in the same patient. A total of seven post-ESWL procedures were performed on two renal units. After all procedures, eight renal units (73 %) were rendered stone-free, six (55 %) with ESWL alone. The average follow-up interval was twelve months (range 1-28 months). ESWL can be used effectively to treat some patients with calculi in horseshoe kidneys. The ectopic location of these renal units may make it difficult to position calculi at F2 , thus necessitating treatment on the blast path or placement of the patient in prone position. Multiple ancillary procedures may be necessary.

Horseshoe kidney occurs in 0.25 percent of the population, or about 1 in 400 births. I - 3 Males are more frequently involved than females with a ratio of two to one. 4 Most clinical problems associated with this anomaly arise from hydronephrosis and renal calculi. 5 The incidence of lithiasis in horseshoe kidneys has been reported to be 21 percent to 60 percent. 6 It has been suggested that urinary stasis, secondary to abnormal position of the renal isthmus and ureteropelvic junction, predisposes to hydronephrosis and formation of calculi. Both open surgicaF and percutaneous techniques 8 .9 have been employed to treat calculi in horseshoe kidneys. Extracorporeal shock-wave lithotripsy (ESWL) has been successfully used in many


'Deceased. July 22, 1988.



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centers to treat renal and upper ureteral calculi in normal kidneys.lo.l! Classically, the calculus is positioned at F 2 • This is possible and preferable when the stone lies no more than 13 cm from the patient's back. However, concretions in horseshoe kidneys may lie more anteriorly than normal; in such circumstances the "blast path" technique may be employed. 12 . 13 Our experience using classic and blast path positioning methods is described. Material and Methods During a two-year period, 10 patients (11 renal units) with stone-bearing horseshoe kidneys were treated with extracorporeal shock-wave lithotripsy. Pretreatment evaluation included complete blood count, serum electrolytes, 407

blood urea nitrogen, creatinine, platelets, prothrombin time, partial thromboplastin time, metabolic profile, liver function tests, urinalysis, urine culture, chest x-ray film, electrocardiogram, and intravenous pyelogram (IVP). The calculi were measured and stone burden was calculated using the following formula: (D = diameter:): Stone Burden (SB) = (maximum D + minimum D) (total # of stones) 2 All patients received peri operative antibiotics consisting of cefazolin or ampicillin. The Dornier H.M-3 lithotriptor was used in each case. In each case an attempt \vas made to focus the stone(s) at F 2 . When this was not possible, calculi were positioned on the ESWL blast path. A plain film of the kidneys, ureters, and bladder was done immediately prior to and within twenty-four hours after treatment to assess the degree of stone fragmentation. A renal ultrasound or an abbreviated IVP and repeat blood studies were obtained on post-treatment day 1. On two occasions, ureteral catheters were placed just prior to ESWL. Double J ureteral stents were placed two and seven days prior to ESWL in 2 other cases. Due to a large stone burden, a retrograde percutaneous nephrostomy, without debulking, was performed in 1 patient. Ureteral catheters and stents were generally removed immediately after treatment. Results There were 9 males and 1 female, ranging in age from twenty-six to sixty-six years (average 49). Seven of those treated had long histories of documented recurrent stone disease associated with frequent urinary tract infections. A Ts paraplegic with neurogenic bladder was managed with an indwelling Foley catheter and suppressive antibiotics. Three patients had undergone multiple open surgeries. In 1 patient the lower right half of one horseshoe kidney had been removed. In.5 cases, calculi were on the right side and 6 on the left. Stones were unilateral in 9 patients. The remaining patient had a right renal and left upper ureteral calculus. The patients treated had one (6/10), two (2/10), or multiple (2/10) calculi. Stone size ranged from 4 mm to 37.,,) mm in greatest diameter (average 13.4 mm).

All serum creatinines were within normal limits. In the immediate preoperative period I patient with T 5 paraplegia, neurogenic bladder and indwelling Foley catheter was found t~ have a positive urine culture (lOO,OOO collmL Pseudomonas aeruginosa); all others were cui. ture-negative. No one showed significant hydro. nephrosis or obstruction on pretreatment IVp. Eleven treatments were performed under general endotracheal anesthesia with high fre. quency jet ventilation. 14.15 The position of some calculi did change with respiration. An epi. dural was used in 1 patient while intravenous diazepam and morphine sedation alone were employed in the Ts paraplegic. The blast path was employed to treat four reo nal and one proximal ureteral calculi which could not be positioned at F 2 • The stones were positioned from 2 to 8 cm (in video space) distal to F2 along the path of the blast. Thus, in real space terms the stones were 1 to 4 cm anterior to F 2 • Shocks per kidney per treatment ranged from 800 to 3,000 (average 2,207) at 18 to 26 kY. Total shocks per kidney ranged from 800 to 6,000 (average 3,090). The number of shocks per electrode ranged from 400 to 1,600 (average 1,188).16 The mean energy delivered was 31,.576 ± 9.809 x 1011 (Table I) when calculated as proposed by Whelan, et aZ. 17 There were 14 ESWL treatments performed on 10 patients (11 renal units). A single treatment was performed in 7 patients, 1 with bilateral stones, while 3 of the 10 had required two treatments. Hospitalization ranged from two to eight days (average 3 . .5 days). Average followup was twelve months (range 1 to 30 mas), A kidney-bladder-ureter film (KUB) was used to classify fragmentation as good (2-3 mm), fair (4-10 mm), or poor (> 10 mm) (Table l). In the patients with good stone fragmentations. there was no evidence of obstruction amo~g eight renal units determined by posttreatment renal ultrasonography or abbreviated lVP. Two renal units with fair inidal stone fragmentation underwent repeat ESVVL at. fo~ and one-half and eight months for resldu fragments. A plain film after the second tr~at; ment revealed good fragmentation in 1 patlel1 and minimal change in the other. Neither den): onstrated obstruction as evidenced by renal u trasonography. tial Patient .5 had a large stone burden (par t t e'l staghorn calculus) and underwent pre r ' \' stoHl, ment retrograde percutaneous nep hrO







3 4 5 6


ESWL Energy (x 101l)t

14 12 22 63

8.82 7.06 5.33 12.30 14.80 34.60 11.10 29.00 14.60 8.0 3.2 13.526 ± 9.809

28 20 25 20 18

R 9 IDa lOb Means


3l.27 ± 30.02 =

Summary oj ESIYL horseshoe kidney treatment

Stone Burden (SB) •




Blast Path

+ + + + +

Stone Fragment.:j: Good Good Good Good Good Poor/Good Good Fair/Fair Fair/Good Good Good

Residual Fragments -All Procedures-ESWL Alone-Size Size (mm) (mm) No. No.

0 0 0 4 Mult. Mult. 4 2 0 0 0

0 0 0 2,2,2,3 2-3 2-3 3,3,3,3 9,9 0 0 0

0 0 0 4 0 0 4 2 2 0 0

0 0 0 2,2,2,3 0 0 3,3,3,3 9,9 0 0 0

Final SB

0 0 0 10 0 0 12 18 0 0 0

maximum diameter + minimum diameter x number of stones. 2

tESWL energy is proportional to number of shocks times voltage squared. tGood = (2-3 mm): fair = (4-10 mm); poor = (> 10 mm.)




Number of ancillary procedures associated with ESWL treatment of calculi in horseshoe kidneys

----Pre-ESWL Ureteral Double Catheter J Stent


2 3 4 5 6 7 8 9 lOa lOb

0 0 0 1 1 0 1 0 0 0 0

0 0 0 0 0 0 0 1 0 1 1


ESWL Treat.

Double J Stent

0 0 0 0 1 0 0 0 0 0 0

1 1 1 1 1 2 1 2 2 1 1

0 0 0 0 0 1 0 0 0 0 0

Post-ESWL------Open Ureteral Surg. PNL Catheter PCN

0 0 0 0 0 1 0 0 0 0 0

0 0 0 0 0 1 0 0 0 0 0

0 0 0 0 1 2 0 0 0 0 0

0 0 0 0 0 1 0 0 0 0 0


1 1 1 2 4 7 2 3 2 2 2

(peN). Good initial stone fragmentation was noted, however two months post-ESWL multiple residual renal pelvis fragments remained and the referring physician elected to extract the stones percutaneously. All fragments were retrieved. No obstruction was noted on followup antegrade nephrostogram. The nephrostomy tube was subsequently removed without sequela. In retrospect, considering the large stone burden, this patient would have benefited from a pre-ESWL debulking procedureY In one renal unit with poor initial stone fragmentation complete ureteral obstruction developed immediately after ESWL (patient 6). ADouble J stent was placed and the patient underwent repeat ESWL three days later. The stent was removed immediately after treatIllent. A follow-up film (KUB) revealed good stone fragmentation. Five days later complete

obstruction developed on the patient's treated side for which a left percutaneous nephrostomy tube was placed. The referring physician subsequently performed two percutaneous nephrolithotomies (PNL) and an open pyelolithotomy. The patient is now stone-free. Six renal units were rendered stone-free with ESWL alone. An additional two renal units were rendered stone-free with percutaneous nephrolithotomy or percutaneous nephrolithotomy and open surgery. After all procedures, three renal units had residual fragments ranging from 2 to 9 mm in greatest diameter (Table I). Follow-up data were obtained an average of twelve months after ESWL (range 1-28 months). There was not a significant change in the pre- and post-ESWL laboratory data. Blood pressures remained stable. In 1 patient transient





MAY 1990










1. ESWL monitors are depicted with F2 as designated. Blast path may be localized by drawing (l line 25 degrees ojj horizontal axis (0 = 25 degrees).


fever developed to 38.10 C twenty-four hours post-treatment. The urine culture was negative. Another patient experienced considerable pain after two separate ES\VL treatments; obstruction was noted after both treatments, and intervention was required. Comment After all procedures, eight renal units (73 % ) were rendered stone-free, six (55 0/0) with ESWL alone. Five renal units (45 % ) had residual fragments ranging from 2-9 mm in greatest diameter after ESWL alone. An additional 2 patients were rendered stone-free with percutaneous nephrolithotomy or percutaneous nephrolithotomy and open surgery yielding a residual fragment rate of 27 percent after all procedures (Table II). (The decision to perform post-ESWL percutaneous nephrolithotomy and open stone removal was made by the referring physician. ) In fourteen ESWL treatments there were two (14 0/0) episodes of obstruction, both of which occurred in the same renal unit. The difficulty with stone fragment passage and subsequent obstruction in this patient may have been related to ventral ureteral displacement over the renal isthmus. Due to the difficulty with stone positioning, the blast path was utilized in five renal units. Four renal units (80 % ) treated on the blast path distal to F2 were rendered stone-free after all procedures, three renal units (60 0/0) with

ESWL alone. Only one renal unit (20%) treated using this technique required postESWL manipulation. When performing ESWL, it is generally possible to position the calculus at the second geometric focus F 2 . The distance between FI (site of electrode discharge) and F2 is fixed at 23 cm as determined by the geometry of the semiellipsoid. However, if the patient is of sufficient thickness or the calculus placed far enough anteriorly, as in the horseshoe kidney, it may ~ot be possible to position the calculus at F2 (Fig. 1). The blast path can be employed to treat some stones up to 10 cm away from Fz .(as measured on the video monitors). When usm~ this technique, increasing the kilovoltage setting will enhance the probability of stone fr~c­ ture ..17 ~e~kinslg and associates at the Uni\'cr~~til of Vug1l1Ia have addressed the problem \\ It stone-focusincr bv placina the patient OIl the b c I' gantry in theb prone position. The tec h' mqU . somewhat more cumbersome but can be effcc' tive. There were a total of thirteen ancillary pro' cedures. Seven pre-ES\VL procedures were Pl:~"1 formed on six renal units. Of the renal tll: I . which underwent pre-ES\VL manipulatll)J\ bstruc"I none h a d eVI'dence a f post-treatmen t o· tion. Five of these renal units were ren~~~~':. stone-free with ESWL alone. Six post-£. 'Ii proce d ures were per f orme d on two ren a1. tIJli·"[(Table I). Two renal units had a total of SIX [los. f the sl.\ ESWL procedures performed. Five OJ . .




.' 1111·:1\"'

\'()U.\[E XXX\'. :--1 \

..duTes (83 %) were perfor med on the same .


'llal unIt. . Considering all pre- and post-lI. thotrIp sy ma. ulation, an averag e of 2.5 proced ures were 1 1I rIned per renal unit yieldin g a stone- free pi r,o)f 73 percen t. In those cases with residu al riltl ( h . dl h" nlcn ts ' t e patIen t an or p YSIClan e1ecte d rrtg . '[ t , llllrsu e furthe r treatm ent. The blast path liP.. ( Iumts used in five 0 f e1even 0 f t h ' e rena \I·!.~tcd \\iith ESWL alone three of the five rewa . noll units (GO %) were render ed stone-free. R~. Ilal calculi were extrac ted percut aneous ly m .,111 . 1 other patient trea~~ d usmg t h e ,bl ast pa~ h . When treating calculi m horseshoe kIdneys wlth ESWL one must be prepar ed to use the blast path or the prone positio n due to the ventra l 'Ind caudad locatio n of the stone. If the opera;or anticipates using the prone position, prelTl'atment simula tion should be of value. In this slllall group of patien ts, satisfa ctory results Wl're achieved with the stone positio ned on the hlast path. The gantry need not be modifi ed to usc this techniq ue. As is the case with calcul i in norma lly positioned kidneys, patien ts with a large stone burden (e.g., pts. 4 and 5) in horseshoe kidneys are most likely to benefi t from pre- or post-ES'V'L manipulation. While multip le proced ures may be necessary, debulk ing prior to lithotr ipsy should increase the likelih ood of a successful result with ESWL. fI


Gainesville, Florida 32601 (DR. NEWM AN) Referen ces I. CIl'IIn JF: Analvsis of 51 patients with horseshoe kidney N ~:ngll M"d 2(il: 684'(1959). '

2. Nation EF: Horsesho e kidney, a study of thirty-tw o autopsy and nine surgical cases, J t; rol 53: 762 (1945). 3. Perlmutt er AD, Retik AB, and Bauer SB: Anomalies of the upper urinary tract, in Walsh PC, Gittes Rr~ Perlmutt er AD, and Stamey TA (Eds): Campbe ll's Urology, Philadelp hia, WB Saunders Co, 1986, p 1665. 4. KolIn Gp, Boatman DL, Schmidt JD, and Flocks RH: Horseshoe kidney: a review of 105 patients, J Urol 107: 203 (1972). 5. Pitts WR, and Muecke EC: Horseshoe kidneys: a 40 year experience, J Urol 113: 743 (1975). 6. Evans WP, and Resnick MI: Horseshoe kidney and urolithiasis, J Urol125 : 620 (1981). 7. Proca E: Anterior transperi toneal approach for stone removal in horseshoe kidney (its advantag e for bilateral stones), Br J Ural 53: 201 (1981) . 9. Peartree RJ, Ruotolo RA, Khuri FJ, and \'

Extracorporeal shock-wave lithotripsy in horseshoe kidneys.

Using the Dornier HM-3 lithotriptor, 10 patients (11 renal units) with calculi in horseshoe kidneys were treated with extracorporeal shock-wave lithot...
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