- Email: [email protected]
CONGENITAL MID URETERAL STRICTURES
0022-5347/05/1745-1999/0 THE JOURNAL OF UROLOGY® Copyright © 2005 by AMERICAN UROLOGICAL ASSOCIATION
Vol. 174, 1999 –2002, November 2005 Printed in U.S.A.
DOI: 10.1097/01.ju.0000176462.56473.0c
CONGENITAL MID URETERAL STRICTURES ANDREW H. HWANG,* IRENE M. MCALEER, ELLEN SHAPIRO, OREN F. MILLER,† HENRY F. KROUS AND GEORGE W. KAPLAN From the Division of Urology, Childrens Hospital Los Angeles, Los Angeles, California (AHH), Pediatric Urology of Central Texas, Austin, Texas (IMM), Department of Urology, New York University School of Medicine, New York, New York (ES), and Department of Urology, Naval Medical Center (OFM), and Department of Pathology (HFK) and Division of Urology (GWK), Children’s Hospital and Health Center, San Diego, California
ABSTRACT
Purpose: Congenital mid ureteral stricture is rare. We report 7 cases, and discuss the differences in preoperative evaluation and surgical management compared to other obstructive entities. Materials and Methods: Medical records and imaging studies of 7 children identified with mid ureteral strictures between 1998 and 2002 were reviewed retrospectively. Five newborns presented with prenatal hydronephrosis, and 2 children presented at age 15 years, one in the course of evaluation of blunt trauma, and one due to pain and abdominal mass. Imaging studies included renal ultrasound, voiding cystourethrography, radionuclide renography and computerized tomography. All patients underwent retrograde pyelography. Pathological examination of each specimen was undertaken at the respective institutions. Results: Prenatal hydronephrosis was the most common presentation. There were no urinary tract infections. All patients had significant obstruction on the affected side. No patient had vesicoureteral reflux. After imaging but before surgery the urinary obstruction was believed to be at the ureteropelvic junction in 4 patients and the ureterovesical junction in 2, and secondary to posterior urethral valves in 1. At cystoscopy all of the affected ureters had a normally located and normally configured orifice. Retrograde pyelography led to an accurate diagnosis of mid ureteral narrowing in all patients. Six patients underwent ureteroureterostomy, all of whom had satisfactory outcomes. In 1 of these patients contralateral nephrectomy was performed due to nonfunction of the multicystic dysplastic kidney. The remaining patient underwent nephrectomy for ipsilateral end stage kidney disease and hydronephrosis. In this patient the ureters were stenotic and suggested asymmetry in the thickness of the muscular coat, perhaps secondary to extrinsic compression. Conclusions: Congenital mid ureteral stricture is rare. Renal ultrasound and radionuclide renography alone do not reliably demonstrate the site of obstruction. Retrograde pyelography at the time of surgical correction of presumed ureteral obstruction is an important adjunct for correctly identifying the site of narrowing in the affected ureteral segment, unless the ureter has been imaged with another modality. KEY WORDS: ureteral obstruction; hydronephrosis; pediatrics; congenital, hereditary, and neonatal diseases and abnormalities
With the advent of ultrasonography during pregnancy 0.9% of fetuses are diagnosed with a urinary tract abnormality, primarily hydronephrosis. Postnatal evaluation of newborns with hydronephrosis generally includes urinary tract ultrasonography, radionuclide renography and voiding cystourethrography (VCUG). These studies are obtained to define the physiological significance of any hydronephrosis and to rule out vesicoureteral reflux. Additionally, these studies often suffice to define the location of any obstructing lesions that are present. The majority of congenital obstructing lesions in the ureter are located at either the proximal or the distal end. However, congenital obstructions can occur between the 2 ends as well.
In a consecutive autopsy series of 12,080 children ureteral narrowing was found in 72 children (a prevalence of 1 in 150 autopsies).1 Of these cases 34% were at the ureteropelvic junction (UPJ) and 62% were at the ureterovesical junction (UVJ). Only 3 of the 12,080 children (4% of those with obstruction) had mid ureteral narrowing. In another series of children with prenatal hydronephrosis 2 (5%) were observed to have a lesion that was located between the 2 ends rather than at either end of the ureter.2 During a 5-year period 7 children with physiologically significant, presumably congenital, mid ureteral narrowing were identified and treated. We review our experience with these patients.
Submitted for publication December 1, 2004. The views expressed in this article are those of the authors and do MATERIALS AND METHODS not reflect the official policy or position of the Department of the Seven children with mid ureteral narrowing were identiNavy, Department of Defense or the United States Government. *Correspondence and requests for reprints: Childrens Hospital fied between 1998 and 2002. The medical records and patholLos Angeles, 4650 Sunset Blvd., Mailstop No. 114, Los Angeles, Cal- ogy specimens were reviewed retrospectively with special ifornia 90027 (telephone: 323-669-2334; FAX: 323-906-8034; e-mail: attention to the mode of presentation, preoperative imaging, [email protected]). † Current institution: Urologic Specialists of Oklahoma, Tulsa, intraoperative findings, management and surgical result. Postnatal ultrasound (US) confirmed hydronephrosis in 5 Oklahoma 74136. 1999
2000
CONGENITAL MID URETERAL STRICTURES
patients. VCUG was performed in all 7 patients. Relative renal function and assessment of obstruction were determined by radioisotopic mercaptoacetyltriglycine (MAG3) renography in 6 patients. In addition, a 15-year-old patient with hydronephrosis diagnosed incidentally on computerized tomography (CT) obtained for evaluation of trauma underwent dimercapto-succinic acid renography, which confirmed nonfunction of the involved kidney. All 7 patients underwent retrograde pyelography at the time of surgery (table 1). During retrograde pyelography a 3Fr whistle tip soft ureteral catheter was used to intubate the ipsilateral ureteral orifice and advanced for a distance of 3 to 4 cm. Intravenous grade 68% iodine radiographic contrast medium was injected with a 10 cc syringe and fluoroscopic images were obtained. Excision of the ureteral stricture and primary ureteroureterostomy were performed through a low Gibson extraperitoneal incision. When possible the distance from the ipsilateral ureteral orifice to the area of obstruction was measured grossly at the time of surgical exploration to correlate with findings during the retrograde pyelogram and to determine the optimal surgical approach. The excised surgical specimens were fixed in formalin and examined grossly. The ureters and kidneys when available were subsequently submitted as transverse sections for microscopic evaluation using hematoxylin and eosin staining. Masson trichrome stain was used in 1 case.
demonstrated improved drainage with preservation of renal function. Gross and microscopic findings for each specimen are described in table 2. In general, the excised ureteral segments were funnel-shaped, leading to stenotic zones that were generally 0.1 cm in internal diameter after formalin fixation. The entire ureter in patient 3 exhibited tubular hypoplasia with diffuse narrowing of the lumen. The ureters proximal to the sites of severe stenosis were dilated to 4 to 6 times the diameter of the ureters distal to the stenosis, and the muscular coats were hypertrophied (fig. 3). Microscopic sections at the stenotic sites suggested mild asymmetry in the thickness of the muscularis, which was determined to be the medial side in patient 6. However, slight tangential sectioning could not be excluded as the cause of this finding. Significant acute or chronic inflammation, fibrosis, hemosiderin and vasculopathy were not identified at the sites of ureteral stenosis. Ureteral valves or folds were not identified either grossly or microscopically in any of the patients who underwent surgical repair. The kidney associated with diffuse tubular ureteral hypoplasia (patient 3) exhibited multicystic dysplasia. In patient 7 the kidney was characterized by end stage disease and severe hydronephrosis in association with severe hydroureter proximal to the site of stenosis.
RESULTS
DISCUSSION
Prenatal hydronephrosis was the reason for presentation in 5 of 7 cases. Two additional children presented at age 15 years, 1 in the course of evaluation of blunt trauma and 1 because of pain and abdominal mass. All patients had grade 3 or 4 hydronephrosis according to the Society for Fetal Urology classification. There were no urinary tract infections. All patients had significant ipsilateral obstruction, which was observed on MAG3 scan in 6 and on CT showing severe hydronephrosis of the ipsilateral kidney in 1. No patient had vesicoureteral reflux. Preoperative imaging led to the impression of urinary obstruction at the ureteropelvic junction in 4 patients and the UVJ in 2, and secondary to posterior urethral valves in 1. At cystoscopy all of the affected ureters had a normally positioned and configured orifice. Retrograde pyelography in all 7 patients led to an accurate diagnosis of mid ureteral narrowing (figs. 1 and 2). Six patients underwent excision of the narrowed area with primary ureteroureterostomy of the dilated proximal ureter to the normal caliber distal ureter with satisfactory outcomes. In 1 of these patients (patient 3) contralateral nephrectomy was performed due to nonfunction of the multicystic dysplastic kidney. The remaining patient underwent ipsilateral nephrectomy for end stage kidney disease as a result of chronic obstruction. All 6 patients undergoing repair subsequently underwent a MAG3 renal scan, which
Although congenital narrowing of the ureter at its proximal or distal end is common, congenital mid ureteral obstruction is rare.1 The etiology of mid ureteral narrowing is usually 1 of 2 distinct lesions, either ureteral valves or ureteral strictures. Wall and Wachter proposed criteria for diagnosis of ureteral valves in 1952, which consisted of anatomically demonstrable transverse folds of ureteral mucosa containing bundles of smooth muscle fibers, obstructive disease changes proximal to the valve with a normal ureter distally, and no other evidence of mechanical or functional obstruction.3 Rabinowitz et al modified these standards by stating that a true valve can exist without the presence of smooth muscle in the fold itself, as long as smooth muscle fibers are present at the base of the valve, the urothelium is normal and the other criteria are met.4 A thorough longitudinal or transverse serial sectioning of the fully embedded specimen is required to make the correct diagnosis. Sectioning of our 6 specimens did not show folds that could be considered valves. Congenital ureteral stricture may also be caused by increased, decreased or disorganized arrangement of the ureteral musculature, with or without fibrosis, accompanied by normal urothelium.5 True narrowing of the ureteral lumen is present in strictures but not necessarily in cases of ureteral valves.6 We did not identify disorganization of the muscularis in our patients. However, there was a suggestion of asymme-
TABLE 1. Patient characteristics and evaluation Pt No. — Age — Sex
Side
Presentation
Preoper Imaging Studies
1 — 1 Mo — M
Lt
Prenatal hydronephrosis
US, VCUG, MAG3
2 — 2 Mos — M 3 — 4 Mos — M
Rt Lt
Bilat prenatal hydronephrosis Bilat prenatal hydronephrosis
US, VCUG, MAG3 US, VCUG, MAG3
4 — 6 Mos — M
Rt
Bilat prenatal hydronephrosis
US, VCUG, MAG3
5 — 7 Mos — M 6 — 15 Yrs — F
Lt Rt
US, VCUG, MAG3 US, VCUG, MAG3, CT
7 — 15 Yrs — F
Rt
Bilat prenatal hydronephrosis Rt lower abdominal quadrant pain, abdominal mass Incidental trauma, abdominal pain, nausea, vomiting
CT, dimercapto-succinic acid scan, VCUG
Preop Diagnosis
Associated Anomaly
Lt upper ureteral obstruction Rt UPJO Lt lower ureteral obstruction Rt UPJO, posterior urethral valves Lt UPJO Rt UVJ obstruction
Twin gestation, penoscrotal hypospadias None Rt multicystic dysplastic kidney 22 Ring, 22q13 deletion syndrome None None
Rt UPJO
None
2001
CONGENITAL MID URETERAL STRICTURES
FIG. 1. Patient 2. A, retrograde pyelography reveals right mid ureteral stricture. Distance from ureteral orifice to point of narrowing is approximately 5 cm. B, preoperative renal ultrasound of affected kidney shows hydronephrosis but no hydroureter. C, preoperative MAG3 renography demonstrates delayed drainage of right kidney with apparent site of obstruction at UPJ (image obtained at 45 minutes).
FIG. 2. Patient 5. A, retrograde pyelography reveals left mid ureteral stricture. Distance from ureteral orifice to point of narrowing is approximately 4 cm. B, preoperative renal ultrasound shows severe hydronephrosis but no apparent hydroureter. C, preoperative MAG3 renography demonstrates delayed drainage of left kidney with apparent site of obstruction at UPJ (image obtained at 45 minutes).
TABLE 2. Characteristics of stricture Pt No.
Stricture Location
Distance From Orifice to Dilated Ureter (cm)
Length Excised Segments (cm)
1
Mid ureter
5
1
2
At crossing over common iliac vessels
4–5 (kinked)
1
3
Immediately distal to crossing over common iliac vessels
3–4
4
Near iliac vessels
5.5
5
Near bladder, 2 cm below iliac vessels
4 (kinked)
1 (separate segment), 6.5 (segment in continuity with 53 gm, 8.5 cm kidney) 1.5 and 0.4 (2 strictures) 5.0 and 0.7 (2 segments)
6
Near bladder, 4 cm below iliac vessels
5 (narrow)
0.9
7
At pelvic brim
5 (narrow)
23 (funnel-shaped)
try in the thickness of this tissue in several cases. It is unclear whether this finding was of functional significance. Although congenital, it is unclear what developmental error produces these strictures. In our study the 6 lesions that were excised were found at or near the point where the ureter crosses the common iliac vessels. This location is the third most common area of physiological or pathological narrowing of the ureter, with the others being the ureteropelvic and ureterovesical junctions. This site represents an area of trans-
Pathology Findings Narrowest lumen 0.04 cm, asymmetry of smooth muscle bundles with mild fibrosis Narrowest lumen 0.1 cm, slight muscularis thickness asymmetry, proximal ureteral dilatation and muscularis hypertrophy Narrowest short segment lumen 0.1 cm, slight muscularis thickness asymmetry, diffuse tubular hypoplasia of ureteral segment continuous with kidney, renal multicystic dysplasia Extensive interstitial fibrosis, 0.1 cm lumen Narrowest lumen 0.1 cm, muscularis thickness asymmetry, proximal hydroureter and muscularis hypertrophy Narrowest lumen 0.1 cm, medial ureteral muscularis thinner than lateral wall, proximal ureteral muscular hypertrophy Narrowest lumen 0.1 cm, proximal hydroureter, end stage kidney disease, hydronephrosis
ition, since the source of the ureteral blood supply changes from the abdominal aorta proximally to the iliac and hypogastric arteries distal to the common iliac artery. Therefore, it is possible that mid ureteral strictures result from relative ischemia during development. This hypothesis is supported by the normal development of the trigone and the absence of vesicoureteral reflux. Causes of ischemia in this region include abnormal development of ureteral vasculature, thrombosis of branch arter-
2002
CONGENITAL MID URETERAL STRICTURES
FIG. 3. Patient 1. Histological evaluation reveals asymmetrical muscular hypertrophy with increased collagen deposition between muscle fibers. Masson trichrome, reduced from x100.
ies and extrinsic compression. Cases of mid ureteral strictures occurring at the same level on both sides have been reported. It has been postulated that these strictures are produced by malformation of medial branched arteries. It is also possible that the juxtaposition of these vessels precludes normal development of the ureter at this site. Ureteral strictures in other cases of narrowing in the pelvic ureter have also been attributed to compression of the ureteral vasculature by the vas deferens or the uterine artery.1 In this study gross and microscopic evaluation of these specimens indicated these structures were characterized by nearly normal architecture, aside from being small. The absence of significant fibrosis, hemosiderin and inflammation argues against the stenosis being caused by ischemic injury, infarction or infection. This finding leaves open the possibility of an extrinsic etiology and pathogenesis. The lesions that we describe could easily be mistaken for nonrefluxing obstructive megaureters. However, the discrete narrowing as well as the location well above the intramural ureter supports a lesion different from nonrefluxing obstructive megaureter. All 6 patients were treated with excision of the narrowed area and primary ureteral anastomosis, leaving the distal ureter intact. The fact that hydronephrosis was decreased and drainage postoperatively was significantly improved compared to preoperative studies is further evidence that these mid ureteral lesions were obstructing urine flow. Conventional imaging of the urinary tract in children currently includes ultrasonography, voiding cystourethrography and isotopic renography. These modalities lead to an accurate diagnosis in the vast majority of cases. The common use of prenatal ultrasound has permitted early diagnosis and treatment of obstructive lesions. Ultrasonography depicts hydronephrosis with excellent resolution but may be of limited value in determining the location of distal ureteral obstruction. If the bladder is full during the study, the fact that the dilated ureter does not abut the bladder may be missed. A dilated ureter may also be misin-
terpreted as a loop of bowel on ultrasonography. Lastly, hydroureter could be missed in these cases because the distal most ureter is not dilated next to the bladder and may not be well imaged in the upper flank. In our series 4 of the mid ureteral lesions were misinterpreted as being ureteropelvic junction obstruction (UPJO) due to marked hydronephrosis and the absence of visualization of the distal hydroureter near the bladder. Although renography should theoretically identify a dilated ureter, a poor response to furosemide may not permit visualization. Performing routine retrograde pyelography at the time of reconstruction is controversial. In our experience with pyeloplasties and megaureter repairs we have occasionally uncovered unexpected lesions such as ureteral polyps, retrocaval ureters and mid ureteral strictures. For this reason we recommend routine retrograde pyelography using the same anesthetic but before repair, unless the ureter distal to the point of obstruction is well visualized by other means. Conversely, in a review of pyeloplasties performed in 108 patients between 1986 and 1992 Rushton et al found that routine retrograde pyelography to define the level of obstruction is not necessary for successful repair.7 Gitlin and Kaefer reported a case of prenatal hydronephrosis in which the diagnosis of mid ureteral abnormality was suggested during an ultrasound performed at 32 weeks of gestation.8 In that case retrograde pyelography demonstrated the presence of a mid ureteral stricture associated with an ectopic upper pole ureter. CONCLUSIONS
In 5 of our 7 patients the preoperative diagnosis after imaging but before retrograde pyelography was obstruction at the UPJ or upper ureter. The other 2 patients were thought to have nonrefluxing obstructive megaureter with the site of pathology just above the intramural tunnel. Without retrograde pyelography an inappropriately located high or low incision would have been made, leading to surgery on the wrong segment of the ureter or at least a more difficult exposure. Therefore, retrograde pyelography at the time of surgical correction of presumed ureteral obstruction is an important adjunct for correctly identifying the site of narrowing in the affected ureteral segment, unless the ureter has been imaged with another modality. REFERENCES
1. Campbell, M. F.: Clinical considerations of the anatomy, physiology, embryology, and anomalies of the urogenital tract. In: Pediatric Urology. New York: MacMillan Co., vol. 1, pp. 188, 273, 287–289, 1937 2. Kim, E. K. and Song, T. B.: A study on fetal urinary tract anomaly: antenatal ultrasonographic diagnosis and postnatal follow-up. J Obstet Gynaecol Res, 22: 569, 1996 3. Wall, B. and Wachter, E.: Congenital ureteral valve: its role as a primary obstructive lesion: classification of the literature and report of an authentic case. J Urol, 68: 684, 1952 4. Rabinowitz, R., Kingston, T. E., Wesselhoeft, C. and Caldamone, A. A.: Ureteral valves in children. Urology, 51: 7, 1998 5. Ayyat, F. M. and Adams, G.: Congenital midureteral strictures. Urology, 26: 170, 1985 6. Kosto, B.: Congenital mid-ureteral stricture in a solitary kidney. J Urol, 106: 529, 1971 7. Rushton, H. G., Salem, Y., Belman, A. B. and Majd, M.: Pediatric pyeloplasty: is routine retrograde pyelography necessary? J Urol, 152: 604, 1994 8. Gitlin, J. and Kaefer, M.: Congenital mid ureteral stricture presenting as prenatal hydronephrosis. J Urol, 168: 1154, 2002
Vol. 174, 1999 –2002, November 2005 Printed in U.S.A.
DOI: 10.1097/01.ju.0000176462.56473.0c
CONGENITAL MID URETERAL STRICTURES ANDREW H. HWANG,* IRENE M. MCALEER, ELLEN SHAPIRO, OREN F. MILLER,† HENRY F. KROUS AND GEORGE W. KAPLAN From the Division of Urology, Childrens Hospital Los Angeles, Los Angeles, California (AHH), Pediatric Urology of Central Texas, Austin, Texas (IMM), Department of Urology, New York University School of Medicine, New York, New York (ES), and Department of Urology, Naval Medical Center (OFM), and Department of Pathology (HFK) and Division of Urology (GWK), Children’s Hospital and Health Center, San Diego, California
ABSTRACT
Purpose: Congenital mid ureteral stricture is rare. We report 7 cases, and discuss the differences in preoperative evaluation and surgical management compared to other obstructive entities. Materials and Methods: Medical records and imaging studies of 7 children identified with mid ureteral strictures between 1998 and 2002 were reviewed retrospectively. Five newborns presented with prenatal hydronephrosis, and 2 children presented at age 15 years, one in the course of evaluation of blunt trauma, and one due to pain and abdominal mass. Imaging studies included renal ultrasound, voiding cystourethrography, radionuclide renography and computerized tomography. All patients underwent retrograde pyelography. Pathological examination of each specimen was undertaken at the respective institutions. Results: Prenatal hydronephrosis was the most common presentation. There were no urinary tract infections. All patients had significant obstruction on the affected side. No patient had vesicoureteral reflux. After imaging but before surgery the urinary obstruction was believed to be at the ureteropelvic junction in 4 patients and the ureterovesical junction in 2, and secondary to posterior urethral valves in 1. At cystoscopy all of the affected ureters had a normally located and normally configured orifice. Retrograde pyelography led to an accurate diagnosis of mid ureteral narrowing in all patients. Six patients underwent ureteroureterostomy, all of whom had satisfactory outcomes. In 1 of these patients contralateral nephrectomy was performed due to nonfunction of the multicystic dysplastic kidney. The remaining patient underwent nephrectomy for ipsilateral end stage kidney disease and hydronephrosis. In this patient the ureters were stenotic and suggested asymmetry in the thickness of the muscular coat, perhaps secondary to extrinsic compression. Conclusions: Congenital mid ureteral stricture is rare. Renal ultrasound and radionuclide renography alone do not reliably demonstrate the site of obstruction. Retrograde pyelography at the time of surgical correction of presumed ureteral obstruction is an important adjunct for correctly identifying the site of narrowing in the affected ureteral segment, unless the ureter has been imaged with another modality. KEY WORDS: ureteral obstruction; hydronephrosis; pediatrics; congenital, hereditary, and neonatal diseases and abnormalities
With the advent of ultrasonography during pregnancy 0.9% of fetuses are diagnosed with a urinary tract abnormality, primarily hydronephrosis. Postnatal evaluation of newborns with hydronephrosis generally includes urinary tract ultrasonography, radionuclide renography and voiding cystourethrography (VCUG). These studies are obtained to define the physiological significance of any hydronephrosis and to rule out vesicoureteral reflux. Additionally, these studies often suffice to define the location of any obstructing lesions that are present. The majority of congenital obstructing lesions in the ureter are located at either the proximal or the distal end. However, congenital obstructions can occur between the 2 ends as well.
In a consecutive autopsy series of 12,080 children ureteral narrowing was found in 72 children (a prevalence of 1 in 150 autopsies).1 Of these cases 34% were at the ureteropelvic junction (UPJ) and 62% were at the ureterovesical junction (UVJ). Only 3 of the 12,080 children (4% of those with obstruction) had mid ureteral narrowing. In another series of children with prenatal hydronephrosis 2 (5%) were observed to have a lesion that was located between the 2 ends rather than at either end of the ureter.2 During a 5-year period 7 children with physiologically significant, presumably congenital, mid ureteral narrowing were identified and treated. We review our experience with these patients.
Submitted for publication December 1, 2004. The views expressed in this article are those of the authors and do MATERIALS AND METHODS not reflect the official policy or position of the Department of the Seven children with mid ureteral narrowing were identiNavy, Department of Defense or the United States Government. *Correspondence and requests for reprints: Childrens Hospital fied between 1998 and 2002. The medical records and patholLos Angeles, 4650 Sunset Blvd., Mailstop No. 114, Los Angeles, Cal- ogy specimens were reviewed retrospectively with special ifornia 90027 (telephone: 323-669-2334; FAX: 323-906-8034; e-mail: attention to the mode of presentation, preoperative imaging, [email protected]). † Current institution: Urologic Specialists of Oklahoma, Tulsa, intraoperative findings, management and surgical result. Postnatal ultrasound (US) confirmed hydronephrosis in 5 Oklahoma 74136. 1999
2000
CONGENITAL MID URETERAL STRICTURES
patients. VCUG was performed in all 7 patients. Relative renal function and assessment of obstruction were determined by radioisotopic mercaptoacetyltriglycine (MAG3) renography in 6 patients. In addition, a 15-year-old patient with hydronephrosis diagnosed incidentally on computerized tomography (CT) obtained for evaluation of trauma underwent dimercapto-succinic acid renography, which confirmed nonfunction of the involved kidney. All 7 patients underwent retrograde pyelography at the time of surgery (table 1). During retrograde pyelography a 3Fr whistle tip soft ureteral catheter was used to intubate the ipsilateral ureteral orifice and advanced for a distance of 3 to 4 cm. Intravenous grade 68% iodine radiographic contrast medium was injected with a 10 cc syringe and fluoroscopic images were obtained. Excision of the ureteral stricture and primary ureteroureterostomy were performed through a low Gibson extraperitoneal incision. When possible the distance from the ipsilateral ureteral orifice to the area of obstruction was measured grossly at the time of surgical exploration to correlate with findings during the retrograde pyelogram and to determine the optimal surgical approach. The excised surgical specimens were fixed in formalin and examined grossly. The ureters and kidneys when available were subsequently submitted as transverse sections for microscopic evaluation using hematoxylin and eosin staining. Masson trichrome stain was used in 1 case.
demonstrated improved drainage with preservation of renal function. Gross and microscopic findings for each specimen are described in table 2. In general, the excised ureteral segments were funnel-shaped, leading to stenotic zones that were generally 0.1 cm in internal diameter after formalin fixation. The entire ureter in patient 3 exhibited tubular hypoplasia with diffuse narrowing of the lumen. The ureters proximal to the sites of severe stenosis were dilated to 4 to 6 times the diameter of the ureters distal to the stenosis, and the muscular coats were hypertrophied (fig. 3). Microscopic sections at the stenotic sites suggested mild asymmetry in the thickness of the muscularis, which was determined to be the medial side in patient 6. However, slight tangential sectioning could not be excluded as the cause of this finding. Significant acute or chronic inflammation, fibrosis, hemosiderin and vasculopathy were not identified at the sites of ureteral stenosis. Ureteral valves or folds were not identified either grossly or microscopically in any of the patients who underwent surgical repair. The kidney associated with diffuse tubular ureteral hypoplasia (patient 3) exhibited multicystic dysplasia. In patient 7 the kidney was characterized by end stage disease and severe hydronephrosis in association with severe hydroureter proximal to the site of stenosis.
RESULTS
DISCUSSION
Prenatal hydronephrosis was the reason for presentation in 5 of 7 cases. Two additional children presented at age 15 years, 1 in the course of evaluation of blunt trauma and 1 because of pain and abdominal mass. All patients had grade 3 or 4 hydronephrosis according to the Society for Fetal Urology classification. There were no urinary tract infections. All patients had significant ipsilateral obstruction, which was observed on MAG3 scan in 6 and on CT showing severe hydronephrosis of the ipsilateral kidney in 1. No patient had vesicoureteral reflux. Preoperative imaging led to the impression of urinary obstruction at the ureteropelvic junction in 4 patients and the UVJ in 2, and secondary to posterior urethral valves in 1. At cystoscopy all of the affected ureters had a normally positioned and configured orifice. Retrograde pyelography in all 7 patients led to an accurate diagnosis of mid ureteral narrowing (figs. 1 and 2). Six patients underwent excision of the narrowed area with primary ureteroureterostomy of the dilated proximal ureter to the normal caliber distal ureter with satisfactory outcomes. In 1 of these patients (patient 3) contralateral nephrectomy was performed due to nonfunction of the multicystic dysplastic kidney. The remaining patient underwent ipsilateral nephrectomy for end stage kidney disease as a result of chronic obstruction. All 6 patients undergoing repair subsequently underwent a MAG3 renal scan, which
Although congenital narrowing of the ureter at its proximal or distal end is common, congenital mid ureteral obstruction is rare.1 The etiology of mid ureteral narrowing is usually 1 of 2 distinct lesions, either ureteral valves or ureteral strictures. Wall and Wachter proposed criteria for diagnosis of ureteral valves in 1952, which consisted of anatomically demonstrable transverse folds of ureteral mucosa containing bundles of smooth muscle fibers, obstructive disease changes proximal to the valve with a normal ureter distally, and no other evidence of mechanical or functional obstruction.3 Rabinowitz et al modified these standards by stating that a true valve can exist without the presence of smooth muscle in the fold itself, as long as smooth muscle fibers are present at the base of the valve, the urothelium is normal and the other criteria are met.4 A thorough longitudinal or transverse serial sectioning of the fully embedded specimen is required to make the correct diagnosis. Sectioning of our 6 specimens did not show folds that could be considered valves. Congenital ureteral stricture may also be caused by increased, decreased or disorganized arrangement of the ureteral musculature, with or without fibrosis, accompanied by normal urothelium.5 True narrowing of the ureteral lumen is present in strictures but not necessarily in cases of ureteral valves.6 We did not identify disorganization of the muscularis in our patients. However, there was a suggestion of asymme-
TABLE 1. Patient characteristics and evaluation Pt No. — Age — Sex
Side
Presentation
Preoper Imaging Studies
1 — 1 Mo — M
Lt
Prenatal hydronephrosis
US, VCUG, MAG3
2 — 2 Mos — M 3 — 4 Mos — M
Rt Lt
Bilat prenatal hydronephrosis Bilat prenatal hydronephrosis
US, VCUG, MAG3 US, VCUG, MAG3
4 — 6 Mos — M
Rt
Bilat prenatal hydronephrosis
US, VCUG, MAG3
5 — 7 Mos — M 6 — 15 Yrs — F
Lt Rt
US, VCUG, MAG3 US, VCUG, MAG3, CT
7 — 15 Yrs — F
Rt
Bilat prenatal hydronephrosis Rt lower abdominal quadrant pain, abdominal mass Incidental trauma, abdominal pain, nausea, vomiting
CT, dimercapto-succinic acid scan, VCUG
Preop Diagnosis
Associated Anomaly
Lt upper ureteral obstruction Rt UPJO Lt lower ureteral obstruction Rt UPJO, posterior urethral valves Lt UPJO Rt UVJ obstruction
Twin gestation, penoscrotal hypospadias None Rt multicystic dysplastic kidney 22 Ring, 22q13 deletion syndrome None None
Rt UPJO
None
2001
CONGENITAL MID URETERAL STRICTURES
FIG. 1. Patient 2. A, retrograde pyelography reveals right mid ureteral stricture. Distance from ureteral orifice to point of narrowing is approximately 5 cm. B, preoperative renal ultrasound of affected kidney shows hydronephrosis but no hydroureter. C, preoperative MAG3 renography demonstrates delayed drainage of right kidney with apparent site of obstruction at UPJ (image obtained at 45 minutes).
FIG. 2. Patient 5. A, retrograde pyelography reveals left mid ureteral stricture. Distance from ureteral orifice to point of narrowing is approximately 4 cm. B, preoperative renal ultrasound shows severe hydronephrosis but no apparent hydroureter. C, preoperative MAG3 renography demonstrates delayed drainage of left kidney with apparent site of obstruction at UPJ (image obtained at 45 minutes).
TABLE 2. Characteristics of stricture Pt No.
Stricture Location
Distance From Orifice to Dilated Ureter (cm)
Length Excised Segments (cm)
1
Mid ureter
5
1
2
At crossing over common iliac vessels
4–5 (kinked)
1
3
Immediately distal to crossing over common iliac vessels
3–4
4
Near iliac vessels
5.5
5
Near bladder, 2 cm below iliac vessels
4 (kinked)
1 (separate segment), 6.5 (segment in continuity with 53 gm, 8.5 cm kidney) 1.5 and 0.4 (2 strictures) 5.0 and 0.7 (2 segments)
6
Near bladder, 4 cm below iliac vessels
5 (narrow)
0.9
7
At pelvic brim
5 (narrow)
23 (funnel-shaped)
try in the thickness of this tissue in several cases. It is unclear whether this finding was of functional significance. Although congenital, it is unclear what developmental error produces these strictures. In our study the 6 lesions that were excised were found at or near the point where the ureter crosses the common iliac vessels. This location is the third most common area of physiological or pathological narrowing of the ureter, with the others being the ureteropelvic and ureterovesical junctions. This site represents an area of trans-
Pathology Findings Narrowest lumen 0.04 cm, asymmetry of smooth muscle bundles with mild fibrosis Narrowest lumen 0.1 cm, slight muscularis thickness asymmetry, proximal ureteral dilatation and muscularis hypertrophy Narrowest short segment lumen 0.1 cm, slight muscularis thickness asymmetry, diffuse tubular hypoplasia of ureteral segment continuous with kidney, renal multicystic dysplasia Extensive interstitial fibrosis, 0.1 cm lumen Narrowest lumen 0.1 cm, muscularis thickness asymmetry, proximal hydroureter and muscularis hypertrophy Narrowest lumen 0.1 cm, medial ureteral muscularis thinner than lateral wall, proximal ureteral muscular hypertrophy Narrowest lumen 0.1 cm, proximal hydroureter, end stage kidney disease, hydronephrosis
ition, since the source of the ureteral blood supply changes from the abdominal aorta proximally to the iliac and hypogastric arteries distal to the common iliac artery. Therefore, it is possible that mid ureteral strictures result from relative ischemia during development. This hypothesis is supported by the normal development of the trigone and the absence of vesicoureteral reflux. Causes of ischemia in this region include abnormal development of ureteral vasculature, thrombosis of branch arter-
2002
CONGENITAL MID URETERAL STRICTURES
FIG. 3. Patient 1. Histological evaluation reveals asymmetrical muscular hypertrophy with increased collagen deposition between muscle fibers. Masson trichrome, reduced from x100.
ies and extrinsic compression. Cases of mid ureteral strictures occurring at the same level on both sides have been reported. It has been postulated that these strictures are produced by malformation of medial branched arteries. It is also possible that the juxtaposition of these vessels precludes normal development of the ureter at this site. Ureteral strictures in other cases of narrowing in the pelvic ureter have also been attributed to compression of the ureteral vasculature by the vas deferens or the uterine artery.1 In this study gross and microscopic evaluation of these specimens indicated these structures were characterized by nearly normal architecture, aside from being small. The absence of significant fibrosis, hemosiderin and inflammation argues against the stenosis being caused by ischemic injury, infarction or infection. This finding leaves open the possibility of an extrinsic etiology and pathogenesis. The lesions that we describe could easily be mistaken for nonrefluxing obstructive megaureters. However, the discrete narrowing as well as the location well above the intramural ureter supports a lesion different from nonrefluxing obstructive megaureter. All 6 patients were treated with excision of the narrowed area and primary ureteral anastomosis, leaving the distal ureter intact. The fact that hydronephrosis was decreased and drainage postoperatively was significantly improved compared to preoperative studies is further evidence that these mid ureteral lesions were obstructing urine flow. Conventional imaging of the urinary tract in children currently includes ultrasonography, voiding cystourethrography and isotopic renography. These modalities lead to an accurate diagnosis in the vast majority of cases. The common use of prenatal ultrasound has permitted early diagnosis and treatment of obstructive lesions. Ultrasonography depicts hydronephrosis with excellent resolution but may be of limited value in determining the location of distal ureteral obstruction. If the bladder is full during the study, the fact that the dilated ureter does not abut the bladder may be missed. A dilated ureter may also be misin-
terpreted as a loop of bowel on ultrasonography. Lastly, hydroureter could be missed in these cases because the distal most ureter is not dilated next to the bladder and may not be well imaged in the upper flank. In our series 4 of the mid ureteral lesions were misinterpreted as being ureteropelvic junction obstruction (UPJO) due to marked hydronephrosis and the absence of visualization of the distal hydroureter near the bladder. Although renography should theoretically identify a dilated ureter, a poor response to furosemide may not permit visualization. Performing routine retrograde pyelography at the time of reconstruction is controversial. In our experience with pyeloplasties and megaureter repairs we have occasionally uncovered unexpected lesions such as ureteral polyps, retrocaval ureters and mid ureteral strictures. For this reason we recommend routine retrograde pyelography using the same anesthetic but before repair, unless the ureter distal to the point of obstruction is well visualized by other means. Conversely, in a review of pyeloplasties performed in 108 patients between 1986 and 1992 Rushton et al found that routine retrograde pyelography to define the level of obstruction is not necessary for successful repair.7 Gitlin and Kaefer reported a case of prenatal hydronephrosis in which the diagnosis of mid ureteral abnormality was suggested during an ultrasound performed at 32 weeks of gestation.8 In that case retrograde pyelography demonstrated the presence of a mid ureteral stricture associated with an ectopic upper pole ureter. CONCLUSIONS
In 5 of our 7 patients the preoperative diagnosis after imaging but before retrograde pyelography was obstruction at the UPJ or upper ureter. The other 2 patients were thought to have nonrefluxing obstructive megaureter with the site of pathology just above the intramural tunnel. Without retrograde pyelography an inappropriately located high or low incision would have been made, leading to surgery on the wrong segment of the ureter or at least a more difficult exposure. Therefore, retrograde pyelography at the time of surgical correction of presumed ureteral obstruction is an important adjunct for correctly identifying the site of narrowing in the affected ureteral segment, unless the ureter has been imaged with another modality. REFERENCES
1. Campbell, M. F.: Clinical considerations of the anatomy, physiology, embryology, and anomalies of the urogenital tract. In: Pediatric Urology. New York: MacMillan Co., vol. 1, pp. 188, 273, 287–289, 1937 2. Kim, E. K. and Song, T. B.: A study on fetal urinary tract anomaly: antenatal ultrasonographic diagnosis and postnatal follow-up. J Obstet Gynaecol Res, 22: 569, 1996 3. Wall, B. and Wachter, E.: Congenital ureteral valve: its role as a primary obstructive lesion: classification of the literature and report of an authentic case. J Urol, 68: 684, 1952 4. Rabinowitz, R., Kingston, T. E., Wesselhoeft, C. and Caldamone, A. A.: Ureteral valves in children. Urology, 51: 7, 1998 5. Ayyat, F. M. and Adams, G.: Congenital midureteral strictures. Urology, 26: 170, 1985 6. Kosto, B.: Congenital mid-ureteral stricture in a solitary kidney. J Urol, 106: 529, 1971 7. Rushton, H. G., Salem, Y., Belman, A. B. and Majd, M.: Pediatric pyeloplasty: is routine retrograde pyelography necessary? J Urol, 152: 604, 1994 8. Gitlin, J. and Kaefer, M.: Congenital mid ureteral stricture presenting as prenatal hydronephrosis. J Urol, 168: 1154, 2002