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Supernumerary Kidney
OD2 2-534 '7 /83/ l 204-064 9$02. 00 / ~) rfHE JOD:R,NAL OF iJROLOG'!
Vol. Printed
Copyright© 1983 by The \fililli2n1s & \l/ilkins Co.
Octooer U.S.A.
SUPERNUJ\1ERARY GABRIEL N'GUESSAN
AND
F. DOUGLAS STEPHENS
From the Division of Urology, Children's Memorial Hospital, Chicago, Illinois
ABSTRACT
We studied 58 case reports of patients with supernumerary kidneys to determine the morphology, vagaries and embryogenesis of this rare and poorly documented anomaly. The supernumerary kidney usually was located caudal to the ipsilateral kidney when subserved by a bifid ureter and cranially when the ureters were separate. The Weigert-Meyer law for duplex fused kidneys was obeyed by the supernumerary ureter in most fully documented cases of double ureters. Pathologic conditions of the upper urinary tract occurred in more than 50 per cent of the patients with a bifid system, who were prone to have hydronephrosis and calculous disease, and with a double system, who were prone to have complications resulting from supernumerary ureteral ectopia. Double tails to the nephrogenic cords, each induced by a branch of a bifid bud or 1 of 2 separate buds as opposed to tandem inductions of a single metanephros, were regarded as the probable embryogenesis. Fusion of portions of kidneys with bifid or double ureters is a common and well documented duplex type of anomaly. Supernumerary kidneys are separate from the ipsilateral kidney and are subserved by a branch of a bifid ureter or a separate (double) ureter. These kidneys are documented poorly and extremely rare. Geisinger aptly defined a supernumerary kidney as "the 'free' accessory organ, which is a distinct, encapsulated, large or small parenchymatous mass topographically related to the usual kidney by a loose, cellular attachment at most and often by no attachment whatsoever" .1 We herein describe in detail a necropsy specimen of the urinary tract with a supernumerary kidney. Data from case reports concerning the location and morphology of supernumerary kidney, and the orientation of the kidney, ureter and ureteral orifice to that of the ipsilateral kidney and ureter are reviewed. The natural history and mode of embryogenesis are compared to those of fused kidneys. MATERIALS AND METHODS
A specimen of a supernumerary from a newborn with cloacal exstrophy was available for study. The kidneys, ureters, cloaca! structures and vessels were dissected and hissv,.v,.,,u., examinations were made. reviewed a total of 58 cases, specimen. Of these cases 29 were """'"~'"""' and the remainder bilateral supernumerary stances the details were scanty but sufficient tracted to make some firm nn,ru·,c:" CASE REPORT
A 12-day-old male with a of 1,975 gm. and crown-rump length of 31 cm., died of a supernumerary kidney, exomphalos, cloacal exstrophy, and multiple other malformations and deformities. An autopsy specimen consisted of 2 left kidneys, 1 right kidney, cloaca! exstrophy with small segments of ileum and large intestine, and the aorta and inferior vena cava (fig. 1). The testes were not present in the specimen but the nuclear chromatin pattern was male. The left ipsilateral kidney was bulky, low and placed transAccepted for publication February 11, 1983. Supported in part by grants from the Government and National University of the Ivory Coast, West Africa, and the Lucy and Edwin Kretschmer Fund of The Northwestern University Medical School, Chicago, Illinois.
649
versely with the hilus facing left. The kidney measured 5.5 X 1.5 x 1.8 cm. and was grooved deeply the common iliac artery posteriorly. The pelvis was intrarenal. The ureter was normal in caliber and issued from the hilus, traversing the wall of the exstrophic bladder. The aorta had 2 arteries that entered the cortex posteriorly and the hilus posterolaterally. The renal vein emerged from the "'""'",..."".m" in a groove on the anterior surface. Histologically, the kidney was normal in structure, did not exhibit infection and had a radial glomerular count 19 of 6. The supernumerary kidney was small (2 x 0.6 x 0.6 cm.) and reniform but lay transversely in the left loin with the hilus directed caudally. The ureter was 1.5 to 2.0 cm. in diameter and highly tortuous, coursed anterior to and grooved the upper pole of the ipsilateral kidney, and entered the back of the exstrophied bladder contiguous with the ipsilatera! ureter. The supernumerary kidney was hypoplastic and the radial count of glomeruli was 3 to 4. The medulla contained large caliber collecting ducts, some of which were necrosed within small abscesses. Cortical vessels showed perivascular collections of white cells. The contralateral right kidney was disk-shaped, flattened anteroposterior!y and small (3.0 L5 cm.). The kidney lay in the right loin at a level slightly caudal to the supemumerary kidney. The was intrarenal and the hilus was anteromem,,r<,,,r,i·,-" tortuous ureter measured :;;l.5 dial. The cm, in diameter and ho,uar s,cl the wall of the bladder. The and Ieft parts c.z,.,~c,v,J,u<,u bladder were 0
a
extended from cecum a vvide cm. in v~·c~,,,v·~ most of this central alimentary segrnent. The terminal and 2 and slightly tortuous vermiform appendices entered the sac the cecum. There was no hindgut apart from the cecum. The perineum was smooth and the anus 'Nas absent. On each side of the perineum was a small buried penis that lay contiguous with the caudal margins of the spiit trigone. The scrota were wide, flat and lacking testes. Vertebral anomalies associated with the myelomeningocele and multiple hemivertebrae were reported by the radiologist. RESULTS
The supernumerary kidney generally was distinguished from the ipsilateral kidney by its small size and/or abnormal position. The kidney was either a component of a bifid ureteral system or a completely duplicated system. Of 59 kidneys (58
650
N'GUESSAN AND STEPHENS
®
FIG. 1. Left supernumerary kidney. A, anterior view of upper tracts shows transversely oriented supernumerary kidney (long arrow) and megaureter crossing caudally located left kidney (black arrow) with normal caliber ureter (open arrow) and small right kidney with megaureter. B, posterior view of supernumerary kidney (black arrow), left and right kidneys with megaureters, and aorta and left common iliac artery (open arrow). Cloaca! exstrophic bladder and central cecal stoma are flipped over to show perineum, and right and left phallus (white arrows).
patients) 21 were associated with bifid ureters and 19 with double ureters. Of the latter 19 kidneys the ureteral orificekidney correlations were shown clearly in 12, while the correlations were not available in 7. It was not known whether the ureters were bifid or completely separate in 18 patients. There were 25 male and 27 female patients, while the sex was not stated in 6. The supernumerary kidney lay on the right side in 19 patients and the left side in 37, while the side was not stated in 2. Average patient age at the time the supernumerary kidney was discovered was 36 years (25 years for patients with double ureters, 36 years for those with bifid ureters and 33 years for those in the undetermined group). Six patients were ~20 years old, while the age was not recorded in 15. Morphology of the supernumerary and ipsilateral kidneys. The supernumerary kidney was cranial to the ipsilateral kidney in 19 patients, caudal in 32, posterior in 3 and not known in 5. In 2 instances 1 bifid and 1 double supernumerary ureteral systems were associated with structurally normal horseshoe kidney malformations. The separate supernumerary kidney in each instance was cranial to the smaller left component of the horseshoe kidney. The ureters formed a Y junction in 1 patient12 and were completely separate in 1 case in which the supernumerary ureter issued caudally on the trigone. 11 Of the 59 supernumerary kidneys 17 (29 per cent) were small, 10 (17 per cent) had no pathological condition and no information was given in 14 (24 per cent). The remaining 18 kidneys (31 per cent) exhibited some form of pathologic condition: 7 had hydronephrosis, 3 had carcinoma, 1 had papillary cyst adenoma, 4 had pyonephrosis or pyelonephritis, 2 had cysts and 1 had marked lobulation. Of 13 ipsilateral kidneys 2 had hydronephrosis, 3 had carcinoma, 2 had pyonephrosis, 4 had calculi and 2 were horseshoe kidneys, while of the contralateral kidneys 3 had hydronephrosis and 2 were horseshoe kidneys (1 also had hydronephrosis). Of the 58 patients pathological conditions of the supernumerary and ipsilateral kidneys occurred in 6 with bifid ureters, 2 with carcinomas and 2 with hydronephroses. In 2 patients the supernumerary kidney was small and the ipsilateral kidney had calculous disease. Of the patients with double ureters 2 had similar pathologic lesions in the supernumerary and ipsilateral kidneys: 1 had carcinomas and 1 had pyonephroses. Bifid supernumerary combinations. When the urinary systems of the supernumerary and ipsilateral kidneys were confluent the supernumerary kidney was cranial in 5 patients,
caudal in 15 and behind in 1. The supernumerary kidney was smaller than the ipsilateral kidney in 5 patients and the size was not stated in 10. The 6 supernumerary systems with pathological conditions are excluded. The confluence of the ureters took several forms. The ureters converged to form a Y junction in 15 of 21 bifid combinations. In 2 cases the ureter from the caudal supernumerary kidney coursed cranially, forming an inverted Y junction. 20 • 21 In the case reported by Linberg the ipsilateral ureter joined the anterior pelvis of the supernumerary kidney on the pelvic brim and emerged caudally as the common stem ureter for both kidneys. 22 Browne and Glashan described a triple junction at the pelvic brim of the ipsilateral ureter with the supernumerary kidney pelvis, which had its own ureter coursing distally, and also the exiting caudal portion of the ipsilateral ureter. 6 Pinter and associates 13 described a specimen in which 2 cranially located supernumerary rudimentary hydronephrotic kidneys were joined by their ureters to a large hydronephrotic pelvis from which a dilated ureter emerged that became atretic more caudally (fig. 2)_1. 2, 5-7, 10, 12, 13, 20-29 Of the 21 bifid systems reported the supernumerary kidney was small in 5, hydronephrotic in 4 and carcinomatous in 2. The ipsilateral kidney was small in 3 cases, hydronephrotic in 2 and carcinomatous in 2, while calculous disease was present in 3 and 1 was a horseshoe kidney, Of the 21 supernumerary and ipsilateral kidneys (including small kidneys) pathologic conditions occurred in 1 kidney in 52 per cent and in both kidneys in 29 per cent. Supernumerary and ipsilateral kidneys with double ureters. Of the 19 patients in this group the position and correlation of the kidneys and both ureteral orifices were determined accurately in 12, while in 7 the supernumerary and ipsilateral orifices opened on the trigone but the correlation of orifice position with the corresponding kidney and ureter was lacking. The supernumerary kidney was cranial to the ipsilateral kidney in 11 patients, caudal in 7 and unknown in 1. The kidneys were small in 6 patients, hydronephrotic in 2, carcinomatous in 1, infected in 3, cystic in 1, normal in 2 and not described in 4, Pathological conditions of the supernumerary kidney (including small kidneys) occurred in 13 of the 19 patients (68 per cent). Of the 19 ipsilateral kidneys in this group 1 was small, 1 was pyonephrotic, 1 was carcinomatous and 1 was a horseshoe kidney. Excluding the horseshoe kidney, 3 ipsilateral kidneys
651
SUPERNUMERARY KIDNEY
arrangement provides a link in embryogenesis between supernumerary and duplex fused kidneys. COMPARISON OF SUPERNUMERARY AND DUPLEX SYSTEMS
rt ,-,
A
l:
B
C
(
ol
FIG. 2. Bifid ureters with common stem. All kidney positions are relative only and are depicted on left side for ease of interpretation. Dashed lines indicate that detail was not defined. Supernumerary kidneys may be caudal, behind and cranial to ipsilateral kidney. A, supernumerarv ureter beside (or inverted Y with) ipsilateral ureter.1· 2· 5• 7• 10, 20, i,, 23-2• B, supernumerary ureter posterior to ureteropelvic junction.2 C, course of supernumerary ureter is not known.29 D, supernumerary and duplex kidneys with supernumerary and upper pole ureters forming Y junction.1 Common stem joins ipsilateral ureter or remains separate. E to G, extraordinary junctions of supernumerary systems with ipsilateral ureter. 6· 13· 22 H, supernumerary ureter and ureter from separate horseshoe kidney form Y junction. Note that contralateral ureter runs posterior to isthmus. 12
(16 per cent) had pathological conditions. The contralateral kidneys were hydronephrotic in 2 patients, horseshoe shaped and hydronephrotic in 1, and duplex in 1. Double ureters and the Weigert-Meyer principle. Although this law pertains to duplex (fused) kidneys and their ureters it was found that of the 12 double ureters with known ureteral orifice-kidney correlations 9 obeyed the law, including 8 with supernumerary kidneys cranial and 1 caudal to the ipsilateral kidney (fig. 3). 3 • 11 · 16• 17 • 30- 34 In 2 patients the ureter of the caudal supernumerary kidney did not follow the rule and issued on the trigone below the ipsilateral ureter. In our postmortem specimen the ureters coapted in the wall of the split left half of the trigone of the cloacal exstrophic bladder. Of the 9 cases that obeyed the law the orifice of the supernumerary kidney lay on the trigone in the bladder in 5 and on the urethrovaginal bridge or vagina in 4. The position of the ipsilateral ureteral orifice was trigonal in all 9 cases. In 1 patient with a vaginal supernumerary orifice the contralateral kidney was of the conventional duplex type, obeying the law and with the 2 ureteral orifices on the trigone. Supernumerary kidneys with bi/id or double ureters (indeterminate findings). In these 18 patients the supernumerary and ipsilateral kidneys had 2 ureters, neither of which was traced far enough to determine whether they joined together or remained independent. Of the supernumerary kidneys 10 were caudal, 3 cranial and 2 behind or beside the ipsilateral kidney. The location of 4 kidneys was not known. There were 4 male and 11 female patients, while the sex was not stated in 3. The supernumerary kidney was on the right side in 7 patients and on the left side in 11, while the side was not known in 1. The supernumerary kidney was small in 6 cases, equal in size to the normal left kidney in 1, pathological in 4, normal in 1 and not recorded in 7. In 1 patient the ureter of the supernumerary kidney formed a Y junction with a ureter from an upper pole of a fused duplex kidney. 1 The stem of the Y was separate from the pelvis and adjoining ureter of the lower portion of the duplex kidney (fig. 2). Neither ureter was traced to its destination caudally. This
The anatomic differences between the upper tracts of supernumerary and duplex systems are shown in the table. The supernumerary kidney and ureter of the 21 patients with bifid systems lay posterior to the ipsilateral ureter in 6 and in front in 1,5 while no clear statement was given in the remaining 14. Of the 19 patients with double systems the supernumerary kidney or juxtaposed ureter lay behind the ipsilateral kidney in 3 and in front in 214 (including our study), while no information was available concerning the remaining 14. In patients with duplex, double or bifid systems the ureter from the cranial portion passed anterior to the ureteropelvic junction of the caudal portion. 35 In 15 patients the bifid supernumerary ureters formed a Y junction with the ipsilateral ureter similar to bifid duplex ureters. However, in 2 patients the supernumerary ureters coursed cranially from the caudally located supernumerary kidney to meet in a reverse Y junction, 1 having short infundibular connections with the passing ipsilateral ureter and 1 having a 3-way junction. Finally, 2 patients had horseshoe kidneys in association with separate supernumerary kidneys,
A
E
G
FIG. 3. Kidneys with complete separation of ureters. All kidney
positions are relative only and are depicted on left side for ease of interpretation. Dashed lines indicate that detail was not defined. A, cranial location of supernumerary kidney and ureteral relationshw to ureteropelvic junction of ipsilateral kidney are not known. 3· 30· B, cranial location of supernumerary kidney and ureter was posterior.16· 32· 33 Ureteral orifice positions are caudal to ipsilateral ureteral orifice. C, supernumerary kidney and ureteral orifice are caudal to ipsilateral system. 17 D, supernumerary kidney is caudal and ureteral orifice is cranial to ipsilateral system. 34 E, supernumerary kidney of present case is cranial. Ureter grooved anterior surface of ipsilateral kidney and intramural ureter coapted ipsilateral orifice. F, supernumerary kidney is cranial and ureteral orifice is caudal to ureter of left horseshoe kidney. 11 G, supernumerary kidney is cranial and its ureter is anterior to ureteropelvic junction of ipsilateral kidney with orifice caudal to ipsilateral orifice.1•
-652
N'GUESSAN AND STEPHENS
Parenchyma and calices Capsules Shape* Size* Y junction of bifid systems Calices Vascular supply
Comparison of anatomy of supernumerary and duplex upper urinary tracts Upper Pole of Duplex Kidney Supernumerary Kidney Attached Detached Attached Separate Polar Reniform Smaller Smaller or occasionally equal to or larger y Y, Y reversed or Y with 1 short arm Upper pole major (or minor) calix only and Extra in supernumerary kidney and full set in ipsilateral kidney missing major (or minor) calix in remainder of duplex kidney Separate· Separate Relationship of supernumerary kidney to ipsilateral kidney
In sagittal plane: Cranial Level Caudal Unknown Totals In coronal plane: Bifid Double * When kidney is nonpathologic.
Total No.
Bifid
Double
Indeterminate
19 3 32 5
5 1 15 0
11
3 2 10 4
59 Total No.
21 Posterior
21 19
3 3
whereas those with bifid duplex horseshoe kidneys had parenchymal continuity, although with separate collecting systems_ EMBRYOGENESIS OF SUPERNUMERARY KIDNEYS
The differences between the rare supernumerary kidneys and ureters, and the common fused duplex systems suggest that there may be a fundamental difference in embryogenesis. 1 In fused duplex bifid kidneys with bifid ureters 1 bud bifurcates and each branch penetrates independently a composite metanephric mass of mesenchyme. When 2 buds arise separately from the wolffian duct and penetrate the same metanephric mass 2 independent renal urinary collecting systems form but the parenchymas remain fused. However, the wider apart or the more ectopic the location of the ureteral bud the more likely the renal parenchyma will exhibit hypoplasia or dysplasia. However, the renal parenchymas remain fused. The intrarenal collecting systems of each ureter are integral although separate components of 1 entire kidney. In supernumerary kidneys with bifid ureters 1 bud bifurcates and each branch penetrates independently a metanephric mass, which develops into separate reniform kidneys: 1 usually is the larger ipsilateral kidney, and 1 is the smaller and usually caudally located supernumerary kidney. When separate buds arise from the wolffian duct in close proximity to each other or wide apart the independent supernumerary kidneys usually are cranial and close to the ipsilateral kidney. In other words, the location of the origin of the buds from the wolffian duct does not determine whether the kidneys were fused or separate. However, when the 2 buds arise separately the ureteral orifice of the cranially located supernumerary kidney usually lies caudal to the orifice of the caudally located kidney, indicating that the budding sites are similar to those of the duplex fused kidneys. Therefore, it seems that the difference lies not in the origin of the bud but in the form or topography of the nephrogenic cord. When all of the anatomical relationships of the supernumerary kidney, pelvis and ureter are combined to those of the ipsilateral kidney and ureter the embryogenesis conforms rationally to a theory that invokes separate and twin metanephroi, 1 lying behind the other, rather than a single metanephros divided longitudinally (figs. 2 and 3). The caudal end of the nephrogenic cord may divide into 2 metanephric tails, which separate entirely when the natural involution of the nephrogenic connection with the mesonephros is complete and when induced to form separate renoblasts by either separate or bifid ureteral buds. Alternatively, a single bud may roam up or down across 1 tail to get to the other, inducing a juxtaureteral kidney at the crossing (fig. 2, E), 22 or 1 branch of a bifid bud may induce a duplex segment in 1 tail and the other branch may
0 7 1
All cranial
19
19
Anterior
Unknown
1 2
17 14
Ureteropelvic junction anterior Ureteropelvic junction anterior
divide, inducing 1 pole of the duplex kidney and a supernumerary kidney (fig. 2, D). 1 One bud may induce a renoblast in 1 tail and the other bud may impact into that pelvis but continue beyond to induce an ipsilateral kidney in the other tail (fig. 2, F).s
Another explanation for complete separation of the supernumerary from the ipsilateral kidney may be fragmentation of a metanephros. Fragmentation possibly may occur from linear infarction with the separated viable fragments being induced by separate or bifid ureteral buds. Geisinger proposed that the gap may be caused by a wide break in the vascularization between 2 independently ,vascularized and developing parts of the metanephros. 1 CLINICAL SIGNIFICANCE
Supernumerary kidneys with leaking ectopic orifices, pathologic changes and accompanying symptoms, or stasis and infection or calculous formations in bifid ureters should be removed. However, if the condition is found incidentally without any untoward symptoms or pathological condition what should be the management? If the unsuspected condition is found at the time of an operation, the kidney is small or abnormal in appearance and the renal function of the ipsilateral and contralateral kidneys is satisfactory the supernumerary kidney and its ureter should be excised. However, if the discovery is made incidentally during examination of a patient elective excision of a small and abnormal kidney is indicated and if the kidney is healthy longterm careful observation with regular followup is advisable in view of the risks of infection, calculous disease and neoplastic transformation. REFERENCES 1. Geisinger, J. F.: Supernumerary kidney. J. Urol., 38: 331, 1937. 2. Kretschmer, H. L.: Supernumerary kidney, report of a case with review of the literature. Surg., Gynec. & Obst., 49: 818, 1929. 3. Antony, J.: Complete duplication of female urethra with vaginal atresia and supernumerary kidney. J. Urol., 118: 877, 1977. 4. Assayer: cited by Campbell. 7 5. Bacon, S. K.: Large hydronephrosis of a true supernumerary kidney. J. Urol., 57: 459, 1947. 6. Browne, M. K. and Glashan, R. W.: Multiple pathology in a unilateral supernumerary kidney. Brit. J. Surg., 58: 73, 1971. 7. Campbell, M. F.: Anomalies of the kidney. In: Urology, 3rd ed. Edited by M. F. Campbell and J. H. Harrison. Philadelphia: W. B. Saunders Co., vol. 2, chapt. 36, p. 1422, 1970. 8. Carlson, H. E.: Supernumerary kidney: a summary of fifty-one reported cases. J. Urol., 64: 224, 1950. 9. Exley, M. and Hotchkiss, W. S.: Supernumerary kidney with clear cell carcinoma. J. Urol., 51: 569, 1944. 10. Fourie, T.: A free supernumerary kidney. A case report. S. Afr. Med. J., 60: 251, 1981.
SUPERNUMERARY KIDNEY 11. Hanley, H. G.: Horseshoe and supernumerary kidney; triple kidney with horseshoe component. Brit. J. Surg., 30: 165, 1942. 12. Hicks, C. C., Boehm, G. A. W., Sybers, R. G., Stone, H. H. and O'Brien, D. P., III: Traumatic rupture of horseshoe kidney with partial ureteral duplication associated with supernumerary kidney. Urology, 8: 149, 1976. 13. Pinter, A. B., Schafer, J. and Varro,J.: Two supernumerary kidneys with ureteral atresia. J. Urol., 127: 119, 1982. 14. Rubin, J. S.: Supernumerary kidney with aberrant ureter terminating externally. J. Urol., 60: 405, 1948. 15. Sasidharan, K., Babu, A. S., Rao, M. M. and Bhat, H. S.: Free supernumerary kidney. Brit. J. Urol., 48: 388, 1976. 16. Shane, J. H.: Supernumerary kidney with vaginal ureteral orifice. J. Urol., 47: 344, 1942. 17. Tada, Y., Kokado, Y., Hashinaka, Y., Kadowaki, T., Takasugi, Y., Shin, T. and Tsukaguchi, I.: Free supernumerary kidney: a case report and review. J. Urol., 126: 231, 1981. 18. Wulfekuhler, W. F. and Dube, V. E.: Free supernumerary kidney: report of a case. J. Urol., 106: 802, 1971. 19. Schwarz, R. D., Stephens, F. D. and Cussen, L. J.: The pathogenesis of renal dysplasia. I. Quantification of hypoplasia and dysplasia. Invest. Urol., 19: 94, 1981. 20. Dixon, A. F.: Supernumerary kidney; the occurrence of three kidneys in an adult male subject. J. Anat. Phys., 45: 117, 1910. Cited by Geisinger. 1 21. Thielman, cited by Neckarsulmer, K.: Ueber Beinieren. Berl. Klin. Wchnschr., 51: 1641, 1914. Cited by Geisinger. 1 22. Linberg, B. E.: Zur Frage der Nierenanomalien. Ztschr. f. Urol. Chir., 15: 315, 1924. Cited by Geisinger. 1
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23. Maximovitch, A. S.: Case of accessory kidney. Ztschr. f. Urol., 21: 801, 1927. Cited by Geisinger. 1 24. Saccone, A. and Hendler, H. B.: Supernumerary kidney: report of a case and a review of the literature. J. Urol., 31: 711, 1934. Cited by Geisinger.' 25. Isaja, A.: Rene soprannumerario constato duranti la vita. Ann. de! r. 1st di chi!., Chir. di Roma, 4: 369, 1921. Cited by Geisinger.' 26. McArthur, L. L.: Some renal anomalies. St. Paul Med. J., 10: 440, 1908. Cited by Geisinger. 1 27. Supernumerary kidney. London Med. Gaz., 2: 127, 1838. Cited by Kretschmer. 2 28. Von Hansemann. Ueberzachlige Nieren. Berl. Klin. Wchnschr., p. 81, January, 1897. Cited by Geisinger.' 29. Debierre, cited by Cobb, F. and Giddings, H. G.: Supernumerary kidney, subject of cystadenoma. Ann. Surg., 53: 367, 1911. 30. Clifford, A. B.: Two cases of abnormal kidney. U. S. Naval Med. Bull., 2: 37, 1908. Cited by Geisinger. 1 31. Mills, W. M.: A case of supernumerary kidney. J. Anat. Physiol., 46: 313, 1911. 32. Samuels, A., Kern, H. and Sachs, L.: Supernumerary kidney with ureter opening into vagina. Surg., Gynec. & Obst., 35: 599, 1922. Cited by Geisinger. 1 33. Israel, I.: Diagnose und Operation einer ueberzaehligen Niere. Berl. Klin. Wchnschr., 55: 1081, 1918. Cited by Geisinger. 1 34. Fischer, K. and Rosenloecher, K.: Ueber einem Fall von dritter Niere met selbstaendigem Harnleiter. Ztschr. f. Urol. Chir., 17: 61, 1925. Cited by Geisinger. 1 35. Stephens, F. D.: Anatomical vagaries of double ureters. Aust. New Zeal. J. Surg., 28: 27, 1958.
Vol. Printed
Copyright© 1983 by The \fililli2n1s & \l/ilkins Co.
Octooer U.S.A.
SUPERNUJ\1ERARY GABRIEL N'GUESSAN
AND
F. DOUGLAS STEPHENS
From the Division of Urology, Children's Memorial Hospital, Chicago, Illinois
ABSTRACT
We studied 58 case reports of patients with supernumerary kidneys to determine the morphology, vagaries and embryogenesis of this rare and poorly documented anomaly. The supernumerary kidney usually was located caudal to the ipsilateral kidney when subserved by a bifid ureter and cranially when the ureters were separate. The Weigert-Meyer law for duplex fused kidneys was obeyed by the supernumerary ureter in most fully documented cases of double ureters. Pathologic conditions of the upper urinary tract occurred in more than 50 per cent of the patients with a bifid system, who were prone to have hydronephrosis and calculous disease, and with a double system, who were prone to have complications resulting from supernumerary ureteral ectopia. Double tails to the nephrogenic cords, each induced by a branch of a bifid bud or 1 of 2 separate buds as opposed to tandem inductions of a single metanephros, were regarded as the probable embryogenesis. Fusion of portions of kidneys with bifid or double ureters is a common and well documented duplex type of anomaly. Supernumerary kidneys are separate from the ipsilateral kidney and are subserved by a branch of a bifid ureter or a separate (double) ureter. These kidneys are documented poorly and extremely rare. Geisinger aptly defined a supernumerary kidney as "the 'free' accessory organ, which is a distinct, encapsulated, large or small parenchymatous mass topographically related to the usual kidney by a loose, cellular attachment at most and often by no attachment whatsoever" .1 We herein describe in detail a necropsy specimen of the urinary tract with a supernumerary kidney. Data from case reports concerning the location and morphology of supernumerary kidney, and the orientation of the kidney, ureter and ureteral orifice to that of the ipsilateral kidney and ureter are reviewed. The natural history and mode of embryogenesis are compared to those of fused kidneys. MATERIALS AND METHODS
A specimen of a supernumerary from a newborn with cloacal exstrophy was available for study. The kidneys, ureters, cloaca! structures and vessels were dissected and hissv,.v,.,,u., examinations were made. reviewed a total of 58 cases, specimen. Of these cases 29 were """'"~'"""' and the remainder bilateral supernumerary stances the details were scanty but sufficient tracted to make some firm nn,ru·,c:" CASE REPORT
A 12-day-old male with a of 1,975 gm. and crown-rump length of 31 cm., died of a supernumerary kidney, exomphalos, cloacal exstrophy, and multiple other malformations and deformities. An autopsy specimen consisted of 2 left kidneys, 1 right kidney, cloaca! exstrophy with small segments of ileum and large intestine, and the aorta and inferior vena cava (fig. 1). The testes were not present in the specimen but the nuclear chromatin pattern was male. The left ipsilateral kidney was bulky, low and placed transAccepted for publication February 11, 1983. Supported in part by grants from the Government and National University of the Ivory Coast, West Africa, and the Lucy and Edwin Kretschmer Fund of The Northwestern University Medical School, Chicago, Illinois.
649
versely with the hilus facing left. The kidney measured 5.5 X 1.5 x 1.8 cm. and was grooved deeply the common iliac artery posteriorly. The pelvis was intrarenal. The ureter was normal in caliber and issued from the hilus, traversing the wall of the exstrophic bladder. The aorta had 2 arteries that entered the cortex posteriorly and the hilus posterolaterally. The renal vein emerged from the "'""'",..."".m" in a groove on the anterior surface. Histologically, the kidney was normal in structure, did not exhibit infection and had a radial glomerular count 19 of 6. The supernumerary kidney was small (2 x 0.6 x 0.6 cm.) and reniform but lay transversely in the left loin with the hilus directed caudally. The ureter was 1.5 to 2.0 cm. in diameter and highly tortuous, coursed anterior to and grooved the upper pole of the ipsilateral kidney, and entered the back of the exstrophied bladder contiguous with the ipsilatera! ureter. The supernumerary kidney was hypoplastic and the radial count of glomeruli was 3 to 4. The medulla contained large caliber collecting ducts, some of which were necrosed within small abscesses. Cortical vessels showed perivascular collections of white cells. The contralateral right kidney was disk-shaped, flattened anteroposterior!y and small (3.0 L5 cm.). The kidney lay in the right loin at a level slightly caudal to the supemumerary kidney. The was intrarenal and the hilus was anteromem,,r<,,,r,i·,-" tortuous ureter measured :;;l.5 dial. The cm, in diameter and ho,uar s,cl the wall of the bladder. The and Ieft parts c.z,.,~c,v,J,u<,u bladder were 0
a
extended from cecum a vvide cm. in v~·c~,,,v·~ most of this central alimentary segrnent. The terminal and 2 and slightly tortuous vermiform appendices entered the sac the cecum. There was no hindgut apart from the cecum. The perineum was smooth and the anus 'Nas absent. On each side of the perineum was a small buried penis that lay contiguous with the caudal margins of the spiit trigone. The scrota were wide, flat and lacking testes. Vertebral anomalies associated with the myelomeningocele and multiple hemivertebrae were reported by the radiologist. RESULTS
The supernumerary kidney generally was distinguished from the ipsilateral kidney by its small size and/or abnormal position. The kidney was either a component of a bifid ureteral system or a completely duplicated system. Of 59 kidneys (58
650
N'GUESSAN AND STEPHENS
®
FIG. 1. Left supernumerary kidney. A, anterior view of upper tracts shows transversely oriented supernumerary kidney (long arrow) and megaureter crossing caudally located left kidney (black arrow) with normal caliber ureter (open arrow) and small right kidney with megaureter. B, posterior view of supernumerary kidney (black arrow), left and right kidneys with megaureters, and aorta and left common iliac artery (open arrow). Cloaca! exstrophic bladder and central cecal stoma are flipped over to show perineum, and right and left phallus (white arrows).
patients) 21 were associated with bifid ureters and 19 with double ureters. Of the latter 19 kidneys the ureteral orificekidney correlations were shown clearly in 12, while the correlations were not available in 7. It was not known whether the ureters were bifid or completely separate in 18 patients. There were 25 male and 27 female patients, while the sex was not stated in 6. The supernumerary kidney lay on the right side in 19 patients and the left side in 37, while the side was not stated in 2. Average patient age at the time the supernumerary kidney was discovered was 36 years (25 years for patients with double ureters, 36 years for those with bifid ureters and 33 years for those in the undetermined group). Six patients were ~20 years old, while the age was not recorded in 15. Morphology of the supernumerary and ipsilateral kidneys. The supernumerary kidney was cranial to the ipsilateral kidney in 19 patients, caudal in 32, posterior in 3 and not known in 5. In 2 instances 1 bifid and 1 double supernumerary ureteral systems were associated with structurally normal horseshoe kidney malformations. The separate supernumerary kidney in each instance was cranial to the smaller left component of the horseshoe kidney. The ureters formed a Y junction in 1 patient12 and were completely separate in 1 case in which the supernumerary ureter issued caudally on the trigone. 11 Of the 59 supernumerary kidneys 17 (29 per cent) were small, 10 (17 per cent) had no pathological condition and no information was given in 14 (24 per cent). The remaining 18 kidneys (31 per cent) exhibited some form of pathologic condition: 7 had hydronephrosis, 3 had carcinoma, 1 had papillary cyst adenoma, 4 had pyonephrosis or pyelonephritis, 2 had cysts and 1 had marked lobulation. Of 13 ipsilateral kidneys 2 had hydronephrosis, 3 had carcinoma, 2 had pyonephrosis, 4 had calculi and 2 were horseshoe kidneys, while of the contralateral kidneys 3 had hydronephrosis and 2 were horseshoe kidneys (1 also had hydronephrosis). Of the 58 patients pathological conditions of the supernumerary and ipsilateral kidneys occurred in 6 with bifid ureters, 2 with carcinomas and 2 with hydronephroses. In 2 patients the supernumerary kidney was small and the ipsilateral kidney had calculous disease. Of the patients with double ureters 2 had similar pathologic lesions in the supernumerary and ipsilateral kidneys: 1 had carcinomas and 1 had pyonephroses. Bifid supernumerary combinations. When the urinary systems of the supernumerary and ipsilateral kidneys were confluent the supernumerary kidney was cranial in 5 patients,
caudal in 15 and behind in 1. The supernumerary kidney was smaller than the ipsilateral kidney in 5 patients and the size was not stated in 10. The 6 supernumerary systems with pathological conditions are excluded. The confluence of the ureters took several forms. The ureters converged to form a Y junction in 15 of 21 bifid combinations. In 2 cases the ureter from the caudal supernumerary kidney coursed cranially, forming an inverted Y junction. 20 • 21 In the case reported by Linberg the ipsilateral ureter joined the anterior pelvis of the supernumerary kidney on the pelvic brim and emerged caudally as the common stem ureter for both kidneys. 22 Browne and Glashan described a triple junction at the pelvic brim of the ipsilateral ureter with the supernumerary kidney pelvis, which had its own ureter coursing distally, and also the exiting caudal portion of the ipsilateral ureter. 6 Pinter and associates 13 described a specimen in which 2 cranially located supernumerary rudimentary hydronephrotic kidneys were joined by their ureters to a large hydronephrotic pelvis from which a dilated ureter emerged that became atretic more caudally (fig. 2)_1. 2, 5-7, 10, 12, 13, 20-29 Of the 21 bifid systems reported the supernumerary kidney was small in 5, hydronephrotic in 4 and carcinomatous in 2. The ipsilateral kidney was small in 3 cases, hydronephrotic in 2 and carcinomatous in 2, while calculous disease was present in 3 and 1 was a horseshoe kidney, Of the 21 supernumerary and ipsilateral kidneys (including small kidneys) pathologic conditions occurred in 1 kidney in 52 per cent and in both kidneys in 29 per cent. Supernumerary and ipsilateral kidneys with double ureters. Of the 19 patients in this group the position and correlation of the kidneys and both ureteral orifices were determined accurately in 12, while in 7 the supernumerary and ipsilateral orifices opened on the trigone but the correlation of orifice position with the corresponding kidney and ureter was lacking. The supernumerary kidney was cranial to the ipsilateral kidney in 11 patients, caudal in 7 and unknown in 1. The kidneys were small in 6 patients, hydronephrotic in 2, carcinomatous in 1, infected in 3, cystic in 1, normal in 2 and not described in 4, Pathological conditions of the supernumerary kidney (including small kidneys) occurred in 13 of the 19 patients (68 per cent). Of the 19 ipsilateral kidneys in this group 1 was small, 1 was pyonephrotic, 1 was carcinomatous and 1 was a horseshoe kidney. Excluding the horseshoe kidney, 3 ipsilateral kidneys
651
SUPERNUMERARY KIDNEY
arrangement provides a link in embryogenesis between supernumerary and duplex fused kidneys. COMPARISON OF SUPERNUMERARY AND DUPLEX SYSTEMS
rt ,-,
A
l:
B
C
(
ol
FIG. 2. Bifid ureters with common stem. All kidney positions are relative only and are depicted on left side for ease of interpretation. Dashed lines indicate that detail was not defined. Supernumerary kidneys may be caudal, behind and cranial to ipsilateral kidney. A, supernumerarv ureter beside (or inverted Y with) ipsilateral ureter.1· 2· 5• 7• 10, 20, i,, 23-2• B, supernumerary ureter posterior to ureteropelvic junction.2 C, course of supernumerary ureter is not known.29 D, supernumerary and duplex kidneys with supernumerary and upper pole ureters forming Y junction.1 Common stem joins ipsilateral ureter or remains separate. E to G, extraordinary junctions of supernumerary systems with ipsilateral ureter. 6· 13· 22 H, supernumerary ureter and ureter from separate horseshoe kidney form Y junction. Note that contralateral ureter runs posterior to isthmus. 12
(16 per cent) had pathological conditions. The contralateral kidneys were hydronephrotic in 2 patients, horseshoe shaped and hydronephrotic in 1, and duplex in 1. Double ureters and the Weigert-Meyer principle. Although this law pertains to duplex (fused) kidneys and their ureters it was found that of the 12 double ureters with known ureteral orifice-kidney correlations 9 obeyed the law, including 8 with supernumerary kidneys cranial and 1 caudal to the ipsilateral kidney (fig. 3). 3 • 11 · 16• 17 • 30- 34 In 2 patients the ureter of the caudal supernumerary kidney did not follow the rule and issued on the trigone below the ipsilateral ureter. In our postmortem specimen the ureters coapted in the wall of the split left half of the trigone of the cloacal exstrophic bladder. Of the 9 cases that obeyed the law the orifice of the supernumerary kidney lay on the trigone in the bladder in 5 and on the urethrovaginal bridge or vagina in 4. The position of the ipsilateral ureteral orifice was trigonal in all 9 cases. In 1 patient with a vaginal supernumerary orifice the contralateral kidney was of the conventional duplex type, obeying the law and with the 2 ureteral orifices on the trigone. Supernumerary kidneys with bi/id or double ureters (indeterminate findings). In these 18 patients the supernumerary and ipsilateral kidneys had 2 ureters, neither of which was traced far enough to determine whether they joined together or remained independent. Of the supernumerary kidneys 10 were caudal, 3 cranial and 2 behind or beside the ipsilateral kidney. The location of 4 kidneys was not known. There were 4 male and 11 female patients, while the sex was not stated in 3. The supernumerary kidney was on the right side in 7 patients and on the left side in 11, while the side was not known in 1. The supernumerary kidney was small in 6 cases, equal in size to the normal left kidney in 1, pathological in 4, normal in 1 and not recorded in 7. In 1 patient the ureter of the supernumerary kidney formed a Y junction with a ureter from an upper pole of a fused duplex kidney. 1 The stem of the Y was separate from the pelvis and adjoining ureter of the lower portion of the duplex kidney (fig. 2). Neither ureter was traced to its destination caudally. This
The anatomic differences between the upper tracts of supernumerary and duplex systems are shown in the table. The supernumerary kidney and ureter of the 21 patients with bifid systems lay posterior to the ipsilateral ureter in 6 and in front in 1,5 while no clear statement was given in the remaining 14. Of the 19 patients with double systems the supernumerary kidney or juxtaposed ureter lay behind the ipsilateral kidney in 3 and in front in 214 (including our study), while no information was available concerning the remaining 14. In patients with duplex, double or bifid systems the ureter from the cranial portion passed anterior to the ureteropelvic junction of the caudal portion. 35 In 15 patients the bifid supernumerary ureters formed a Y junction with the ipsilateral ureter similar to bifid duplex ureters. However, in 2 patients the supernumerary ureters coursed cranially from the caudally located supernumerary kidney to meet in a reverse Y junction, 1 having short infundibular connections with the passing ipsilateral ureter and 1 having a 3-way junction. Finally, 2 patients had horseshoe kidneys in association with separate supernumerary kidneys,
A
E
G
FIG. 3. Kidneys with complete separation of ureters. All kidney
positions are relative only and are depicted on left side for ease of interpretation. Dashed lines indicate that detail was not defined. A, cranial location of supernumerary kidney and ureteral relationshw to ureteropelvic junction of ipsilateral kidney are not known. 3· 30· B, cranial location of supernumerary kidney and ureter was posterior.16· 32· 33 Ureteral orifice positions are caudal to ipsilateral ureteral orifice. C, supernumerary kidney and ureteral orifice are caudal to ipsilateral system. 17 D, supernumerary kidney is caudal and ureteral orifice is cranial to ipsilateral system. 34 E, supernumerary kidney of present case is cranial. Ureter grooved anterior surface of ipsilateral kidney and intramural ureter coapted ipsilateral orifice. F, supernumerary kidney is cranial and ureteral orifice is caudal to ureter of left horseshoe kidney. 11 G, supernumerary kidney is cranial and its ureter is anterior to ureteropelvic junction of ipsilateral kidney with orifice caudal to ipsilateral orifice.1•
-652
N'GUESSAN AND STEPHENS
Parenchyma and calices Capsules Shape* Size* Y junction of bifid systems Calices Vascular supply
Comparison of anatomy of supernumerary and duplex upper urinary tracts Upper Pole of Duplex Kidney Supernumerary Kidney Attached Detached Attached Separate Polar Reniform Smaller Smaller or occasionally equal to or larger y Y, Y reversed or Y with 1 short arm Upper pole major (or minor) calix only and Extra in supernumerary kidney and full set in ipsilateral kidney missing major (or minor) calix in remainder of duplex kidney Separate· Separate Relationship of supernumerary kidney to ipsilateral kidney
In sagittal plane: Cranial Level Caudal Unknown Totals In coronal plane: Bifid Double * When kidney is nonpathologic.
Total No.
Bifid
Double
Indeterminate
19 3 32 5
5 1 15 0
11
3 2 10 4
59 Total No.
21 Posterior
21 19
3 3
whereas those with bifid duplex horseshoe kidneys had parenchymal continuity, although with separate collecting systems_ EMBRYOGENESIS OF SUPERNUMERARY KIDNEYS
The differences between the rare supernumerary kidneys and ureters, and the common fused duplex systems suggest that there may be a fundamental difference in embryogenesis. 1 In fused duplex bifid kidneys with bifid ureters 1 bud bifurcates and each branch penetrates independently a composite metanephric mass of mesenchyme. When 2 buds arise separately from the wolffian duct and penetrate the same metanephric mass 2 independent renal urinary collecting systems form but the parenchymas remain fused. However, the wider apart or the more ectopic the location of the ureteral bud the more likely the renal parenchyma will exhibit hypoplasia or dysplasia. However, the renal parenchymas remain fused. The intrarenal collecting systems of each ureter are integral although separate components of 1 entire kidney. In supernumerary kidneys with bifid ureters 1 bud bifurcates and each branch penetrates independently a metanephric mass, which develops into separate reniform kidneys: 1 usually is the larger ipsilateral kidney, and 1 is the smaller and usually caudally located supernumerary kidney. When separate buds arise from the wolffian duct in close proximity to each other or wide apart the independent supernumerary kidneys usually are cranial and close to the ipsilateral kidney. In other words, the location of the origin of the buds from the wolffian duct does not determine whether the kidneys were fused or separate. However, when the 2 buds arise separately the ureteral orifice of the cranially located supernumerary kidney usually lies caudal to the orifice of the caudally located kidney, indicating that the budding sites are similar to those of the duplex fused kidneys. Therefore, it seems that the difference lies not in the origin of the bud but in the form or topography of the nephrogenic cord. When all of the anatomical relationships of the supernumerary kidney, pelvis and ureter are combined to those of the ipsilateral kidney and ureter the embryogenesis conforms rationally to a theory that invokes separate and twin metanephroi, 1 lying behind the other, rather than a single metanephros divided longitudinally (figs. 2 and 3). The caudal end of the nephrogenic cord may divide into 2 metanephric tails, which separate entirely when the natural involution of the nephrogenic connection with the mesonephros is complete and when induced to form separate renoblasts by either separate or bifid ureteral buds. Alternatively, a single bud may roam up or down across 1 tail to get to the other, inducing a juxtaureteral kidney at the crossing (fig. 2, E), 22 or 1 branch of a bifid bud may induce a duplex segment in 1 tail and the other branch may
0 7 1
All cranial
19
19
Anterior
Unknown
1 2
17 14
Ureteropelvic junction anterior Ureteropelvic junction anterior
divide, inducing 1 pole of the duplex kidney and a supernumerary kidney (fig. 2, D). 1 One bud may induce a renoblast in 1 tail and the other bud may impact into that pelvis but continue beyond to induce an ipsilateral kidney in the other tail (fig. 2, F).s
Another explanation for complete separation of the supernumerary from the ipsilateral kidney may be fragmentation of a metanephros. Fragmentation possibly may occur from linear infarction with the separated viable fragments being induced by separate or bifid ureteral buds. Geisinger proposed that the gap may be caused by a wide break in the vascularization between 2 independently ,vascularized and developing parts of the metanephros. 1 CLINICAL SIGNIFICANCE
Supernumerary kidneys with leaking ectopic orifices, pathologic changes and accompanying symptoms, or stasis and infection or calculous formations in bifid ureters should be removed. However, if the condition is found incidentally without any untoward symptoms or pathological condition what should be the management? If the unsuspected condition is found at the time of an operation, the kidney is small or abnormal in appearance and the renal function of the ipsilateral and contralateral kidneys is satisfactory the supernumerary kidney and its ureter should be excised. However, if the discovery is made incidentally during examination of a patient elective excision of a small and abnormal kidney is indicated and if the kidney is healthy longterm careful observation with regular followup is advisable in view of the risks of infection, calculous disease and neoplastic transformation. REFERENCES 1. Geisinger, J. F.: Supernumerary kidney. J. Urol., 38: 331, 1937. 2. Kretschmer, H. L.: Supernumerary kidney, report of a case with review of the literature. Surg., Gynec. & Obst., 49: 818, 1929. 3. Antony, J.: Complete duplication of female urethra with vaginal atresia and supernumerary kidney. J. Urol., 118: 877, 1977. 4. Assayer: cited by Campbell. 7 5. Bacon, S. K.: Large hydronephrosis of a true supernumerary kidney. J. Urol., 57: 459, 1947. 6. Browne, M. K. and Glashan, R. W.: Multiple pathology in a unilateral supernumerary kidney. Brit. J. Surg., 58: 73, 1971. 7. Campbell, M. F.: Anomalies of the kidney. In: Urology, 3rd ed. Edited by M. F. Campbell and J. H. Harrison. Philadelphia: W. B. Saunders Co., vol. 2, chapt. 36, p. 1422, 1970. 8. Carlson, H. E.: Supernumerary kidney: a summary of fifty-one reported cases. J. Urol., 64: 224, 1950. 9. Exley, M. and Hotchkiss, W. S.: Supernumerary kidney with clear cell carcinoma. J. Urol., 51: 569, 1944. 10. Fourie, T.: A free supernumerary kidney. A case report. S. Afr. Med. J., 60: 251, 1981.
SUPERNUMERARY KIDNEY 11. Hanley, H. G.: Horseshoe and supernumerary kidney; triple kidney with horseshoe component. Brit. J. Surg., 30: 165, 1942. 12. Hicks, C. C., Boehm, G. A. W., Sybers, R. G., Stone, H. H. and O'Brien, D. P., III: Traumatic rupture of horseshoe kidney with partial ureteral duplication associated with supernumerary kidney. Urology, 8: 149, 1976. 13. Pinter, A. B., Schafer, J. and Varro,J.: Two supernumerary kidneys with ureteral atresia. J. Urol., 127: 119, 1982. 14. Rubin, J. S.: Supernumerary kidney with aberrant ureter terminating externally. J. Urol., 60: 405, 1948. 15. Sasidharan, K., Babu, A. S., Rao, M. M. and Bhat, H. S.: Free supernumerary kidney. Brit. J. Urol., 48: 388, 1976. 16. Shane, J. H.: Supernumerary kidney with vaginal ureteral orifice. J. Urol., 47: 344, 1942. 17. Tada, Y., Kokado, Y., Hashinaka, Y., Kadowaki, T., Takasugi, Y., Shin, T. and Tsukaguchi, I.: Free supernumerary kidney: a case report and review. J. Urol., 126: 231, 1981. 18. Wulfekuhler, W. F. and Dube, V. E.: Free supernumerary kidney: report of a case. J. Urol., 106: 802, 1971. 19. Schwarz, R. D., Stephens, F. D. and Cussen, L. J.: The pathogenesis of renal dysplasia. I. Quantification of hypoplasia and dysplasia. Invest. Urol., 19: 94, 1981. 20. Dixon, A. F.: Supernumerary kidney; the occurrence of three kidneys in an adult male subject. J. Anat. Phys., 45: 117, 1910. Cited by Geisinger. 1 21. Thielman, cited by Neckarsulmer, K.: Ueber Beinieren. Berl. Klin. Wchnschr., 51: 1641, 1914. Cited by Geisinger. 1 22. Linberg, B. E.: Zur Frage der Nierenanomalien. Ztschr. f. Urol. Chir., 15: 315, 1924. Cited by Geisinger. 1
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23. Maximovitch, A. S.: Case of accessory kidney. Ztschr. f. Urol., 21: 801, 1927. Cited by Geisinger. 1 24. Saccone, A. and Hendler, H. B.: Supernumerary kidney: report of a case and a review of the literature. J. Urol., 31: 711, 1934. Cited by Geisinger.' 25. Isaja, A.: Rene soprannumerario constato duranti la vita. Ann. de! r. 1st di chi!., Chir. di Roma, 4: 369, 1921. Cited by Geisinger.' 26. McArthur, L. L.: Some renal anomalies. St. Paul Med. J., 10: 440, 1908. Cited by Geisinger. 1 27. Supernumerary kidney. London Med. Gaz., 2: 127, 1838. Cited by Kretschmer. 2 28. Von Hansemann. Ueberzachlige Nieren. Berl. Klin. Wchnschr., p. 81, January, 1897. Cited by Geisinger.' 29. Debierre, cited by Cobb, F. and Giddings, H. G.: Supernumerary kidney, subject of cystadenoma. Ann. Surg., 53: 367, 1911. 30. Clifford, A. B.: Two cases of abnormal kidney. U. S. Naval Med. Bull., 2: 37, 1908. Cited by Geisinger. 1 31. Mills, W. M.: A case of supernumerary kidney. J. Anat. Physiol., 46: 313, 1911. 32. Samuels, A., Kern, H. and Sachs, L.: Supernumerary kidney with ureter opening into vagina. Surg., Gynec. & Obst., 35: 599, 1922. Cited by Geisinger. 1 33. Israel, I.: Diagnose und Operation einer ueberzaehligen Niere. Berl. Klin. Wchnschr., 55: 1081, 1918. Cited by Geisinger. 1 34. Fischer, K. and Rosenloecher, K.: Ueber einem Fall von dritter Niere met selbstaendigem Harnleiter. Ztschr. f. Urol. Chir., 17: 61, 1925. Cited by Geisinger. 1 35. Stephens, F. D.: Anatomical vagaries of double ureters. Aust. New Zeal. J. Surg., 28: 27, 1958.