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Vol. 68, No. 2
Ureteral Duplication with Obstruction WALTER I. DELPH, M.D., CARLETON E. PATRICK, M.D., IRVIN SCHLOSSBERG, M.D., Departments of Urology and Radiology, Montefiore Hospital and Medical Center, Bronx, New York
DUPLICATION of the upper renal collecting systems is the most frequent congenital anomaly of that system. Its origin is in utero, but many cases go undiscovered until autopsy, if uncomplicated or asymptomatic. By definition the anomaly is duplication of the renal pelvis and/or ureter. This may occur in a variety of degrees but more generally subdivided into complete versus incomplete. Complete duplication implies double collecting systems with termination in the urinary bladder or other organs as separate orifices. Incomplete duplication implies a degree of uniting of the systems and termination in the bladder as a single orifice.1'2 The incidence of ureteral duplication has been presented in a variety of statistics. Nation, in a series of 16,000 autopsies found the incidence to be 7: 1000.3 Campbell found it to occur more frequently in a larger series of 51,880 (281 adults, 61 infants and children) at a rate of 1:161.2 Clinically, the entity is much more common in the female than the male (ranging from three to four times more frequent). This increase is thought to be related to the associated increased incidence of ureteral ectopia in the female. This will be discussed in further detail. Autopsied incidence, however, approaches equality within the two sexes. There is also a greater incidence on a familiar basis though no clear cut evidence exists for a single gene inheritance. 3 The incidence in first degree relatives of children with duplication was found to be 18 times the incidence in the general population in the series of Whitaker and Dank.4 The clinical significance of ureteral duplication lies in its frequent association with other pathology of the urogenital system. It is
these relationships which lead to the diagnosis and produce symptomatology. Renal agenesis, hypoplasia, ectopia, ureteropelvic obstruction, polycystic disease, malrotation, ectopic orifices, megaureter, vesicoureteral reflux and ureterocele are commonly found to occur in conjunction with duplication. 5 Perrin and Chrenka6 and Newman et al.7 and Johnston 8 have noted the high incidence of dysplastic elements associated with the entity which may lead to severe complications in reconstructive surgery. This likewise will be discussed in further detail. EMBRYOLOGY
The origin of duplication has been traced back to the 38 somite stage of the embryo (5.5 mm D.H. xiv: 29 days).9 It is at this stage of development that the nephric (Wolffian) duct of the mesonephros has differentiated into a "marked deformity" -the 'knee', which is later to become the ureteric bud. The normal ureteric bud migrates cephalad to meet the caudal most portion of the nephrogenic blastema. This blastema is the cap of the metanephros which will subsequently mature into the adult kidney. Once fused, it bifurcates to become the collecting system of the matanephros. The timing and path of ascent is critical to further renal development. If fusion is retarded or strayed, further maturation may be grossly retarded or even terminated. Duplication of the ureter occurs at one of two periods in this development. A popular theory of complete duplication states that not one, but two ureteric buds are formed giving rise to two distinct ureters and two pelvises. This is a normal and frequent occurrence in lower animals such as birds but is abnormal in man.9 Incomplete duplication
126
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION
occurs as the single ureteric bud ascends to the metanephros but bifurcates prior to fusion with the nephrogenic blastema. If bifurcation occurs just prior to fusion, two renal pelvises will form. If bifurcation occurs earlier only one bud may reach the metanephros and the other ends as a blind ureteric diverticulum. At the vesical end of development, the normal incorporation of the ureter to the bladder wall is one of absorption. The common nephric duct contracts into the genital sinus by means of rotation and migration. If there are two ureteric buds, the lower one tends to reach the bladder wall first lending to a very constant positioning of the upper bud to a medial and distal location. This is to be found so constantly as first seen by Weigert and Meyer, that their names are associated with it as the Weigert-Meyer law.
CLINICAL OBSERVATIONS
Though many complicating sequalae are associated with ureteral duplication, most can be categorized within the surroundings of ureterovesical reflux or obstruction. Both of these are likewise related to the ureters developmental history. Ureterovesical Reflux. Ureterovesical reflux is the most common physiologic complication associated with ureteral duplication. It most frequently involves the ureter draining the lower renal segment. The ureter involved is usually in its normal anatomic location. The most popular theory for the phenomenon effecting the upper orifice is stated by Johnston10 and Culp11 in finding a shortened transvesical distance transversed by the ureter with a subsequent perpendicular rather than oblique passage through the muscularis of the bladder wall. This leads to a less competent ureterovesical function leading to frank incompetence and resulting reflux. Obstruction. Obstruction of the duplicated ureter is the next most commonly associated physiologic complication. It can be found with or without infection but is usually found in conjunction with recurrent urinary tract infection. Unlike the complication of uretero-
MARCH, 1976
vesical reflux, obstruction involves the ureter draining and superior renal segment. Its etiology is likewise developmental. It had been stated earlier that the orifice of the superior renal unit is more commonly found at an ectopic position. This is due to its later migration and closer association with the degenerating Wolffian duct. Its orifice can therefore be found along the line of any structure of Wolffian origin. In males since the Wolffian duct leads to only rudimentary structures and degenerates earlier, an ectopic orifice is limited in its occurrence. In the female, however, this orifice may be found as far down as the vagina or Gartner's ducts, far distal to the external urethral sphincter lending to distressing incontinence and subsequent symptomatology. This is the theory behind the higher clinical incidence in the female. Ureterocele is frequently associated with obstructed duplication. It is more common to involve the ectopic orifice of the ureter from the superior renal segment. A very high correlation of dysplastic elements are associated with this complicating factor of duplication and must be anticipated so as to avoid over vigorous reconstruction which may be "futile .6 DIAGNOSIS
Excretory urography is the most consistently positive diagnostic aid in investigation for ureteral duplication. A full urological workup is required including cystoscopy, cystogram and frequently retrograde pyelography. Full cooperation with radiology is essential to investigate any renal axis deviation which may be the only sign of an obstructed superior segment. The upper renal segment is more commonly involved in pathologic changes.8 The only finding that may be present is a laterally displaced upper calyx of a normal lower collecting system. This must be differentiated from a retroperitoneal tumor or adrenal mass.11 The longitudinal axis of the pyelogram may be shifted to a more perpendicular position and the renal shadow may be displaced laterally. In an obstructed duplicated
Vol. 68, No. 2
Ureteral Duplication
segment Culp mentioned a "parenchymal cap" which may be found during retrograde pyelography.9 A "polar notch sign" has most recently been introduced in the literature by Pfister."2 This is defined a "hemispherical concaved defect in the upper pole renal parenchyma". It is indicative of an obstructed ureteral duplication at the extreme upper pole of the kidney. The kidney is usually of normal length. Tomography and echogram are also diagnostic aids in differentiating this entity from a tumor.
ior pole of the left kidney was identified and separated from the grossly normal appearing lower renal segment. The hydroureter was dissected as far as possible into the pelvis with the distal remnant intubated with a No. 12 red rubber catheter and brought out as a ureterostomy through a separate stab incision. The remaining renal segment was fixed to the retroperitoneum. The distal ureter was investigated for its distal orifice but unsuccessfully. The two ureters were separate throughout their entire length. Post-operatively the patient's
"oa ....
CASE PRESENTATION
A 28 year old white female was admitted to Montefiore Hospital and Medical Center with a chief complaint of left flank pain and urgency upon urination. The patient was febrile to 1010 with a positive urine culture of > 100,000 E. coli. Due to the recurrent nature of her disease a full urologic and radiologic workup was undertaken. A cystogram with retrograde pyelogram demonstrated bilaterally competent ureterovesical junctions. Cystoscopy visualized two normally situated ureteral orifices with no ureterocele or ectopic orifices. A prior intravenous pyelogram showed a lateral shift of the left renal axis with suggestion of a superior pole mass (Fig. 1 left.) Both echogram and tomographic cuts from the pyelogram gave evidence of a cystic mass in the left kidney (Fig. 1 right). Arteriography was then performed and demonstrated a single renal artery with no
127
Fig. 2. Arteriogram of the left kidney illustrating an avascular single renal artery, left. Antegrade pyelogram following cyst puncture. Taken in upright position illustrating obstructed duplicated segment, right.
mass with
course was unremarkable with removal of the ureterostomy on the tenth post-operative day. Subsequently the patient has had an uneventful course with no further urinary tract infections and evidence of good urinary function by follow up intravenous pyelograms.
DISCUSSION
Fig. Intravenous pyelogram of the left kidney illustrating Ipolar notch sign"'of Pfister and axial deviation (left). Tomographic cut from nephrogram phase of intravenous pyelogram, .
night.
mass (Fig. 2 left). As is our normal routine with an avascular mass, cyst puncture with antegrade pyelography was performed. Upright films were taken to visualize an obstructed duplicated collecting system (Fig. 2, right). This was aspirated and delayed film showed no further run off of the cyst. The patient was scheduled for surgery and at surgery a widely dilated ureter and grossly hydronephrotic super-
vascularity of the
Renal development is thought to be vulnerable to anomalies because of a multiplicity of reasons. Aside from requiring a delicate coordination of growth from both proximal and distal areas, all development must occur according to a very exacting time schedule. The area in which renal development occurs is excessively complex and limited in space. A requirement of ascent and descent or organ structures is called upon within this area. The area has been called the "umbilical crotch" by Boyden.. It .iS within this area that the two umbilical arteries take their origin from the aorta and that not only ascent of the ureteral bud to the metanephros occurs, but also a 900 rotation of the anatomy must occur.
128
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION
The upper renal segment in the syndrome of duplex kidney is more commonly involved in pathology.2'14 Obstruction by stricture, ureterocele, or ectopic ureteral orifices with subsequent hydronephrosis and hydroureter becomes clinically significant. Surgery is indicated in such cases with close attention to all the possible anomalies so frequently associated with the entity. Radiographic documentation is imperative preoperatively to rule out tumor or simple cyst. Renal arteriography is essential to rule out multiple arterial supply which has been reported in as many as 50% of cases.5 The investigator in duplicated systems must also bear in mind the close association with the anomaly of dysplasia of renal elements.6 Dysplastic elements may be present which can make operative reconstruction "futile". Perrin6 and Culp"1 advise limited extent of ureterectomy for this reason. Adequate drainage and ureterostomy is advised. Cyst puncture was performed in the case cited which lead to a definitive diagnosis. We highly recommend this procedure when associated with the "polar notch signs" to delineate the obstructed duplicated ureter by antegrade pyelography. Proper positioning in the upright position is mandatory. Delayed films are advised to assure adequate aspiration. SUMMARY
The natural history of ureteral duplication is discussed with special attention to embryology and diagnosis. A case of obstructed duplicated ureter is presented with attention to a new diagnostic aid: the "polar notch sign" (Pfister). ACKNOWLEDGMENTS The authors would like to extend sincere appreciation to Carl Patrick, M.D., Department of Urology, and Ms. Gloria Vasquez, Department of Plastic Surgery.
MARCH, 1976
LITERATURE CITED
1. EMMETT, J. and D. Witten, Anomalies of the Genitourinary Tract in Emmett, J. and Witten, D. eds: Clinical Urography, Philadelphia Volume 3, edition 3, p. 1435. 2. CAMPBELL, M. F. and J. H. HARRISON. eds: Urology, Philadelphia, W. B. Saunders Co., 3rd edit., 1970. p. 1489. 3. NATION, E. F. Duplication of the Kidney and Ureter: A Statistical Study of 230 New Cases. Jour. Urol., 51:456, 1944. 4. WHITAKER and DANKS. A Study of the Inheritance of Duplication of the Kidneys and Ureters. Jour. Urol., 95:176, 1966. 5. WATERHOUSE, R. K. and R. E. HACKETT. Congenital Anomalies of the Kidney, Ureter and Bladder in Karafin, L. and Kendall, A. R. eds: Urology, Hagerstown, Maryland, Harper and Row: Urology, Volume 1. p. 35. 6. PERRIN and CHRENKA. Renal Duplication and Dysplasia. Urology, 4:660-664, 1974. 7. NEWMAN, L. N. and W. H. MCALISTER, and J. KISSANE. Segmental Renal Dysplasia Associated with Ectopic Ureteroceles in Childhood. Urology, 3:23, 1974. 8. JOHNSTON, J. H. Problems in the Diagnosis and Management of Ectopic Ureters and Ureteroceles in Johnston, J. H. and Scholtmeiger, R. eds. Pediatric Urology. Amsterdam, Excerpta Medica, 1972. p. 57. 9. MEHTA, H. J. Development of the Ureter in Bergman. ed: The Ureter. Harper and Row, New York. 1967. pp. 1-21. 10. JOHNSTON and HEAL. Reflux in Completely Duplicated Ureters in Children: Management and Technique. Jour. Urol., 105:881-887, 1971. 11. CULP, D. A. Heminephro-Uretectomy: Comparison of One-Stage and Two-Stage Operations. Jour. Urol., 83:369. 1960. 12. PFISTER, R. C. and W. H. HENDREN. Roentgenographic Presentation of American Roentgen Ray Society. 1974. 13. BOYDEN, E. A. Congenital Absence of the Kidney. Anatomy Rec., 52:325, 1932. 14. PERLMUTTER, A. D, and R. P. TIMOTHY, Ureteral Duplication: Clinical Findings and Therapy in 96 Children: Jour. Urol., 105:445-451, 1971.
Give to the NMA Scholarship Fund!
Vol. 68, No. 2
Ureteral Duplication with Obstruction WALTER I. DELPH, M.D., CARLETON E. PATRICK, M.D., IRVIN SCHLOSSBERG, M.D., Departments of Urology and Radiology, Montefiore Hospital and Medical Center, Bronx, New York
DUPLICATION of the upper renal collecting systems is the most frequent congenital anomaly of that system. Its origin is in utero, but many cases go undiscovered until autopsy, if uncomplicated or asymptomatic. By definition the anomaly is duplication of the renal pelvis and/or ureter. This may occur in a variety of degrees but more generally subdivided into complete versus incomplete. Complete duplication implies double collecting systems with termination in the urinary bladder or other organs as separate orifices. Incomplete duplication implies a degree of uniting of the systems and termination in the bladder as a single orifice.1'2 The incidence of ureteral duplication has been presented in a variety of statistics. Nation, in a series of 16,000 autopsies found the incidence to be 7: 1000.3 Campbell found it to occur more frequently in a larger series of 51,880 (281 adults, 61 infants and children) at a rate of 1:161.2 Clinically, the entity is much more common in the female than the male (ranging from three to four times more frequent). This increase is thought to be related to the associated increased incidence of ureteral ectopia in the female. This will be discussed in further detail. Autopsied incidence, however, approaches equality within the two sexes. There is also a greater incidence on a familiar basis though no clear cut evidence exists for a single gene inheritance. 3 The incidence in first degree relatives of children with duplication was found to be 18 times the incidence in the general population in the series of Whitaker and Dank.4 The clinical significance of ureteral duplication lies in its frequent association with other pathology of the urogenital system. It is
these relationships which lead to the diagnosis and produce symptomatology. Renal agenesis, hypoplasia, ectopia, ureteropelvic obstruction, polycystic disease, malrotation, ectopic orifices, megaureter, vesicoureteral reflux and ureterocele are commonly found to occur in conjunction with duplication. 5 Perrin and Chrenka6 and Newman et al.7 and Johnston 8 have noted the high incidence of dysplastic elements associated with the entity which may lead to severe complications in reconstructive surgery. This likewise will be discussed in further detail. EMBRYOLOGY
The origin of duplication has been traced back to the 38 somite stage of the embryo (5.5 mm D.H. xiv: 29 days).9 It is at this stage of development that the nephric (Wolffian) duct of the mesonephros has differentiated into a "marked deformity" -the 'knee', which is later to become the ureteric bud. The normal ureteric bud migrates cephalad to meet the caudal most portion of the nephrogenic blastema. This blastema is the cap of the metanephros which will subsequently mature into the adult kidney. Once fused, it bifurcates to become the collecting system of the matanephros. The timing and path of ascent is critical to further renal development. If fusion is retarded or strayed, further maturation may be grossly retarded or even terminated. Duplication of the ureter occurs at one of two periods in this development. A popular theory of complete duplication states that not one, but two ureteric buds are formed giving rise to two distinct ureters and two pelvises. This is a normal and frequent occurrence in lower animals such as birds but is abnormal in man.9 Incomplete duplication
126
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION
occurs as the single ureteric bud ascends to the metanephros but bifurcates prior to fusion with the nephrogenic blastema. If bifurcation occurs just prior to fusion, two renal pelvises will form. If bifurcation occurs earlier only one bud may reach the metanephros and the other ends as a blind ureteric diverticulum. At the vesical end of development, the normal incorporation of the ureter to the bladder wall is one of absorption. The common nephric duct contracts into the genital sinus by means of rotation and migration. If there are two ureteric buds, the lower one tends to reach the bladder wall first lending to a very constant positioning of the upper bud to a medial and distal location. This is to be found so constantly as first seen by Weigert and Meyer, that their names are associated with it as the Weigert-Meyer law.
CLINICAL OBSERVATIONS
Though many complicating sequalae are associated with ureteral duplication, most can be categorized within the surroundings of ureterovesical reflux or obstruction. Both of these are likewise related to the ureters developmental history. Ureterovesical Reflux. Ureterovesical reflux is the most common physiologic complication associated with ureteral duplication. It most frequently involves the ureter draining the lower renal segment. The ureter involved is usually in its normal anatomic location. The most popular theory for the phenomenon effecting the upper orifice is stated by Johnston10 and Culp11 in finding a shortened transvesical distance transversed by the ureter with a subsequent perpendicular rather than oblique passage through the muscularis of the bladder wall. This leads to a less competent ureterovesical function leading to frank incompetence and resulting reflux. Obstruction. Obstruction of the duplicated ureter is the next most commonly associated physiologic complication. It can be found with or without infection but is usually found in conjunction with recurrent urinary tract infection. Unlike the complication of uretero-
MARCH, 1976
vesical reflux, obstruction involves the ureter draining and superior renal segment. Its etiology is likewise developmental. It had been stated earlier that the orifice of the superior renal unit is more commonly found at an ectopic position. This is due to its later migration and closer association with the degenerating Wolffian duct. Its orifice can therefore be found along the line of any structure of Wolffian origin. In males since the Wolffian duct leads to only rudimentary structures and degenerates earlier, an ectopic orifice is limited in its occurrence. In the female, however, this orifice may be found as far down as the vagina or Gartner's ducts, far distal to the external urethral sphincter lending to distressing incontinence and subsequent symptomatology. This is the theory behind the higher clinical incidence in the female. Ureterocele is frequently associated with obstructed duplication. It is more common to involve the ectopic orifice of the ureter from the superior renal segment. A very high correlation of dysplastic elements are associated with this complicating factor of duplication and must be anticipated so as to avoid over vigorous reconstruction which may be "futile .6 DIAGNOSIS
Excretory urography is the most consistently positive diagnostic aid in investigation for ureteral duplication. A full urological workup is required including cystoscopy, cystogram and frequently retrograde pyelography. Full cooperation with radiology is essential to investigate any renal axis deviation which may be the only sign of an obstructed superior segment. The upper renal segment is more commonly involved in pathologic changes.8 The only finding that may be present is a laterally displaced upper calyx of a normal lower collecting system. This must be differentiated from a retroperitoneal tumor or adrenal mass.11 The longitudinal axis of the pyelogram may be shifted to a more perpendicular position and the renal shadow may be displaced laterally. In an obstructed duplicated
Vol. 68, No. 2
Ureteral Duplication
segment Culp mentioned a "parenchymal cap" which may be found during retrograde pyelography.9 A "polar notch sign" has most recently been introduced in the literature by Pfister."2 This is defined a "hemispherical concaved defect in the upper pole renal parenchyma". It is indicative of an obstructed ureteral duplication at the extreme upper pole of the kidney. The kidney is usually of normal length. Tomography and echogram are also diagnostic aids in differentiating this entity from a tumor.
ior pole of the left kidney was identified and separated from the grossly normal appearing lower renal segment. The hydroureter was dissected as far as possible into the pelvis with the distal remnant intubated with a No. 12 red rubber catheter and brought out as a ureterostomy through a separate stab incision. The remaining renal segment was fixed to the retroperitoneum. The distal ureter was investigated for its distal orifice but unsuccessfully. The two ureters were separate throughout their entire length. Post-operatively the patient's
"oa ....
CASE PRESENTATION
A 28 year old white female was admitted to Montefiore Hospital and Medical Center with a chief complaint of left flank pain and urgency upon urination. The patient was febrile to 1010 with a positive urine culture of > 100,000 E. coli. Due to the recurrent nature of her disease a full urologic and radiologic workup was undertaken. A cystogram with retrograde pyelogram demonstrated bilaterally competent ureterovesical junctions. Cystoscopy visualized two normally situated ureteral orifices with no ureterocele or ectopic orifices. A prior intravenous pyelogram showed a lateral shift of the left renal axis with suggestion of a superior pole mass (Fig. 1 left.) Both echogram and tomographic cuts from the pyelogram gave evidence of a cystic mass in the left kidney (Fig. 1 right). Arteriography was then performed and demonstrated a single renal artery with no
127
Fig. 2. Arteriogram of the left kidney illustrating an avascular single renal artery, left. Antegrade pyelogram following cyst puncture. Taken in upright position illustrating obstructed duplicated segment, right.
mass with
course was unremarkable with removal of the ureterostomy on the tenth post-operative day. Subsequently the patient has had an uneventful course with no further urinary tract infections and evidence of good urinary function by follow up intravenous pyelograms.
DISCUSSION
Fig. Intravenous pyelogram of the left kidney illustrating Ipolar notch sign"'of Pfister and axial deviation (left). Tomographic cut from nephrogram phase of intravenous pyelogram, .
night.
mass (Fig. 2 left). As is our normal routine with an avascular mass, cyst puncture with antegrade pyelography was performed. Upright films were taken to visualize an obstructed duplicated collecting system (Fig. 2, right). This was aspirated and delayed film showed no further run off of the cyst. The patient was scheduled for surgery and at surgery a widely dilated ureter and grossly hydronephrotic super-
vascularity of the
Renal development is thought to be vulnerable to anomalies because of a multiplicity of reasons. Aside from requiring a delicate coordination of growth from both proximal and distal areas, all development must occur according to a very exacting time schedule. The area in which renal development occurs is excessively complex and limited in space. A requirement of ascent and descent or organ structures is called upon within this area. The area has been called the "umbilical crotch" by Boyden.. It .iS within this area that the two umbilical arteries take their origin from the aorta and that not only ascent of the ureteral bud to the metanephros occurs, but also a 900 rotation of the anatomy must occur.
128
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION
The upper renal segment in the syndrome of duplex kidney is more commonly involved in pathology.2'14 Obstruction by stricture, ureterocele, or ectopic ureteral orifices with subsequent hydronephrosis and hydroureter becomes clinically significant. Surgery is indicated in such cases with close attention to all the possible anomalies so frequently associated with the entity. Radiographic documentation is imperative preoperatively to rule out tumor or simple cyst. Renal arteriography is essential to rule out multiple arterial supply which has been reported in as many as 50% of cases.5 The investigator in duplicated systems must also bear in mind the close association with the anomaly of dysplasia of renal elements.6 Dysplastic elements may be present which can make operative reconstruction "futile". Perrin6 and Culp"1 advise limited extent of ureterectomy for this reason. Adequate drainage and ureterostomy is advised. Cyst puncture was performed in the case cited which lead to a definitive diagnosis. We highly recommend this procedure when associated with the "polar notch signs" to delineate the obstructed duplicated ureter by antegrade pyelography. Proper positioning in the upright position is mandatory. Delayed films are advised to assure adequate aspiration. SUMMARY
The natural history of ureteral duplication is discussed with special attention to embryology and diagnosis. A case of obstructed duplicated ureter is presented with attention to a new diagnostic aid: the "polar notch sign" (Pfister). ACKNOWLEDGMENTS The authors would like to extend sincere appreciation to Carl Patrick, M.D., Department of Urology, and Ms. Gloria Vasquez, Department of Plastic Surgery.
MARCH, 1976
LITERATURE CITED
1. EMMETT, J. and D. Witten, Anomalies of the Genitourinary Tract in Emmett, J. and Witten, D. eds: Clinical Urography, Philadelphia Volume 3, edition 3, p. 1435. 2. CAMPBELL, M. F. and J. H. HARRISON. eds: Urology, Philadelphia, W. B. Saunders Co., 3rd edit., 1970. p. 1489. 3. NATION, E. F. Duplication of the Kidney and Ureter: A Statistical Study of 230 New Cases. Jour. Urol., 51:456, 1944. 4. WHITAKER and DANKS. A Study of the Inheritance of Duplication of the Kidneys and Ureters. Jour. Urol., 95:176, 1966. 5. WATERHOUSE, R. K. and R. E. HACKETT. Congenital Anomalies of the Kidney, Ureter and Bladder in Karafin, L. and Kendall, A. R. eds: Urology, Hagerstown, Maryland, Harper and Row: Urology, Volume 1. p. 35. 6. PERRIN and CHRENKA. Renal Duplication and Dysplasia. Urology, 4:660-664, 1974. 7. NEWMAN, L. N. and W. H. MCALISTER, and J. KISSANE. Segmental Renal Dysplasia Associated with Ectopic Ureteroceles in Childhood. Urology, 3:23, 1974. 8. JOHNSTON, J. H. Problems in the Diagnosis and Management of Ectopic Ureters and Ureteroceles in Johnston, J. H. and Scholtmeiger, R. eds. Pediatric Urology. Amsterdam, Excerpta Medica, 1972. p. 57. 9. MEHTA, H. J. Development of the Ureter in Bergman. ed: The Ureter. Harper and Row, New York. 1967. pp. 1-21. 10. JOHNSTON and HEAL. Reflux in Completely Duplicated Ureters in Children: Management and Technique. Jour. Urol., 105:881-887, 1971. 11. CULP, D. A. Heminephro-Uretectomy: Comparison of One-Stage and Two-Stage Operations. Jour. Urol., 83:369. 1960. 12. PFISTER, R. C. and W. H. HENDREN. Roentgenographic Presentation of American Roentgen Ray Society. 1974. 13. BOYDEN, E. A. Congenital Absence of the Kidney. Anatomy Rec., 52:325, 1932. 14. PERLMUTTER, A. D, and R. P. TIMOTHY, Ureteral Duplication: Clinical Findings and Therapy in 96 Children: Jour. Urol., 105:445-451, 1971.
Give to the NMA Scholarship Fund!
