Fibroepithelial Polyps Causing Ureteropelvic Junction Obstruction in Children

0022-5347/03/1695-1834/0 THE JOURNAL OF UROLOGY® Copyright © 2003 by AMERICAN UROLOGICAL ASSOCIATION

Vol. 169, 1834 –1836, May 2003 Printed in U.S.A.

DOI: 10.1097/01.ju.0000061966.21966.94

FIBROEPITHELIAL POLYPS CAUSING URETEROPELVIC JUNCTION OBSTRUCTION IN CHILDREN GREGORY S. ADEY, SARA O. VARGAS, ALAN B. RETIK, JOSEPH G. BORER, JAMES MANDELL, W. HARDY HENDREN, ROBERT L. LEBOWITZ AND STUART B. BAUER From the Departments of Urology, Radiology and Pathology, Children’s Hospital Boston and Harvard Medical School, Boston, Massachusetts

ABSTRACT

Purpose: Fibroepithelial polyps are benign mucosal projections that can be found throughout the urinary system. We review our experience with fibroepithelial polyps of the ureteropelvic junction in children to define more clearly this entity and its outcome following treatment. Methods: We reviewed the records of all children with fibroepithelial polyps causing ureteropelvic junction obstruction treated at our institution between December 1967 and February 2002. Results: Nine patients 6 weeks to 9 years old had 11 ureteropelvic junction obstructions secondary to fibroepithelial polyps, representing a 0.5% incidence of all ureteropelvic junction obstructions seen during that period. The majority of the patients were male (89%) and had obstruction on the left side (78%). Only 22% of the patients had a diagnosis of obstructing polyps suggested preoperatively. All patients underwent dismembered pyeloplasty but 1 required subsequent nephrectomy due to progressive loss of renal function. All lesions were characterized microscopically by polypoid projections of fibrous tissue covered by epithelium and demonstrating varying degrees of inflammation. No recurrences were seen during a mean followup of 44 months. Conclusions: Fibroepithelial polyps are rare lesions that cause ureteropelvic junction obstruction in children, primarily in males and on the left side. Filling defects were diagnosed preoperatively in 22% of the patients in this series. Excision and dismembered pyeloplasty were curative, and recurrences were not observed. The etiology of this disease remains obscure. KEY WORDS: neoplasms, fibroepithelial; polyps; ureteral obstruction; pediatrics

Fibroepithelial polyps of the urinary tract are benign mucosal projections composed of fibrous stroma lined by surface epithelium.1 They may involve the renal pelvis, ureter, bladder or urethra. Fibroepithelial polyps of the upper urinary tract are uncommon in children, with only 7 reported cases involving ureteropelvic junction obstruction.2–7 We review our experience with fibroepithelial polyps of the ureteropelvic junction to define more clearly this entity and its outcome following treatment. METHODS

We identified all children at our institution who were intraoperatively found to have fibroepithelial polyps causing ureteropelvic junction obstruction during the period December 1967 to February 2002. We retrospectively reviewed clinical, imaging, pathological and followup data. Histological features seen on hematoxylin and eosin stained sections were reviewed by 1 pathologist. RESULTS

During this 35-year study period 1,710 pyeloplasties were performed at our tertiary care pediatric hospital. Fibroepithelial polyps were identified as the cause of ureteropelvic junction obstruction in 9 patients, or 0.5% of all children undergoing pyeloplasty (see table). Patients included 8 males (89%) and 1 female (11%), and age ranged from 6 weeks to 9 years (mean 64 months, median 65 months). Seven of the 9 patients presented with intermittent abdominal pain, 1 infant had a palpable abdominal mass and 1 patient was found to have ureteropelvic junction obstruction during radiological assessment for gross hematuria. Two males had bilateral Accepted for publication December 13, 2002.

ureteropelvic junction obstruction caused by fibroepithelial polyps, and the remaining patients had unilateral fibroepithelial polyps (5 on the left and 2 on the right side). In only 2 patients (22%) was the diagnosis of polyps suggested preoperatively, of whom 1 had a filling defect at the ureteropelvic junction on excretory urography and the other had a similar observation on antegrade nephrostography (fig. 1). Preoperative evaluation included renal ultrasound in all 9 patients. In addition, 6 patients underwent excretory urography, 1 underwent antegrade nephrostography and 2 underwent nuclear medicine renal excretion studies. Preoperative ultrasonography showed mild to moderate hydronephrosis in 4 patients (44%) and severe hydronephrosis in 5 (56%). The 2 polyps detected preoperatively in this series occurred in 1974 and 1990. Eleven Anderson-Hynes dismembered pyeloplasties were performed. Gross examination in all cases revealed projections of tan-gray, irregularly folded mucosa (fig. 2 and table). On pathological examination the polyps ranged in size from 0.1 to 3.0 cm. Microscopic examination demonstrated each mucosal surface to have up to several sessile or pedunculated polypoid projections (fig. 3, A). All specimens displayed stromal cores composed of loose fibrous tissue with sparse vascularity and prominent stromal edema (fig. 3, B). Occasional mast cells were observed but inflammation was otherwise minimal. The epithelium overlying the polyps was transitional, often with squamous metaplasia, and showed focal attenuation. There was no evidence of ulceration. Mean followup was 44 months (range 1 to 135), including 2 cases that have been followed for more than 10 years. Stable mild hydronephrosis was found in 3 kidneys (27%), whereas no hydronephrosis was noted in the remaining 7 renal units (64%). No patient had development of an additional benign or malignant neoplasm anywhere else in the urinary tract.

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FIBROEPITHELIAL POLYPS CAUSING URETEROPELVIC JUNCTION OBSTRUCTION Clinical data Pt. No.— Age —Sex

Presentation

1—6 wks.—F

Lt. flank mass at birth

Lt.

2—3 3—4 4—4 5—5

yrs.—M yrs.—M yrs.—M yrs.—M

Abdominal Abdominal Abdominal Abdominal

Rt. Bilat. Rt. Bilat.

6—6 7—6 8—7 9—9

yrs.—M yrs.—M yrs.—M yrs.—M

Abdominal pain Gross hematuria Abdominal pain Abdominal pain

pain pain pain pain

Laterality

Lt. Lt. Lt. Lt.

Early in this series (1967) 1 patient required nephrectomy of the affected kidney for poor function 2 years after the original pyeloplasty. This patient underwent reoperative pyeloplasty for persistent obstruction 4 months after the initial surgery. She continued to have recurrent urinary tract infections after the second procedure. An Hg-197 scan performed 18 months following the second pyeloplasty revealed little or no function within the affected kidney. No qualitative study of renal function had been performed before the first operation. DISCUSSION

Fibroepithelial polyps are an infrequent cause of upper urinary tract obstruction in adults, and they are even rarer in children. Involvement of the ureteropelvic junction is unusual, with only 7 cases previously described in children.2–7 Our review contributes an additional 11 cases of ureteropelvic junction obstruction caused by fibroepithelial polyps, with an incidence of 0.5% during the 35 years evaluated in our study. Average age at presentation with fibroepithelial polyps

FIG. 1. Filling defect (arrow) at left ureteropelvic junction on excretory urogram (patient 8).

Followup Lt. nephrectomy (22 mos. after original pyeloplasty) No hydronephrosis (58 mos.) No hydronephrosis (11 yrs.) No hydronephrosis (25 mos.) Mild lt. hydronephrosis (10 mos.), no rt. hydronephrosis (5 mos.) Mild lt. hydronephrosis (1 mo.) No hydronephrosis (93 mos.) No hydronephrosis (45 mos.) Mild lt. hydronephrosis (2 mos.)

Preop. Filling Defect No Yes No No No No No Yes No

causing ureteropelvic junction obstruction in adults is 40 years, and predominantly males are affected.8 Average age at presentation in our series of children was approximately 5 years, and 89% of these patients were boys. The male preponderance observed in this condition is unexplained. Congenital urethral polyps and fibrous umbilical polyps are other examples of mesenchymal proliferation of the urinary tract with a marked male predilection. While the former condition is thought to represent a developmental anomaly and occurs exclusively in boys,9 the latter is believed to represent an aberrant proliferative response to injury.10 Fibrous umbilical polyp demonstrates a 94% male preponderance.10 Detailed histological descriptions of fibroepithelial polyps in the upper urinary tract are uncommon and usually involve a fibrovascular core covered by transitional epithelium.11 Descriptions of stromal edema, which was prominent in all of our cases, are rare. No previous report mentions the presence of numerous minute polyps or scattered mast cells, which were observed in many of our cases. Rather than representing a new pathological entity, we believe that our series reflects a more thorough description of the entity already known as fibroepithelial polyp. It is most likely that previous reports, presented largely as single cases with minimal pathological detail, simply lacked thorough description. Based on our experience, fibroepithelial polyps causing ureteropelvic junction obstruction present similarly to other types of ureteropelvic junction obstruction not detected prenatally. Seventy-eight percent of the patients in our series experienced intermittent abdominal pain, similar to the presentation of the majority of adults with ureteropelvic junction obstruction caused by fibroepithelial polyps. Ureteropelvic junction obstruction of any cause should be suspected in a child with intermittent abdominal pain of unclear etiology. Differentiating fibroepithelial polyps from other causes of ureteropelvic junction obstruction remains difficult. In only

FIG. 2. Intraoperative photograph of fibroepithelial polyp (arrow) at ureteropelvic junction (patient 6).

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FIBROEPITHELIAL POLYPS CAUSING URETEROPELVIC JUNCTION OBSTRUCTION

FIG. 3. A, polypoid architecture with multiple fibrous projections lined by transitional epithelium (patient 9). H & E, reduced from ⫻4. B, fibrous core shows sparse vascularity, prominent edema and attenuated epithelial lining. H & E, reduced from ⫻40.

22% of our patients was the diagnosis of polyps suggested preoperatively. None of the polyps was visualized with ultrasonography. Seven patients underwent excretory urography, and filling defects were described in just 2. It is noteworthy that these filling defects were observed in the early to mid portion of our series (1974 and 1990). Neither of the 2 patients who underwent nuclear medicine renal scans had evidence of filling defects preoperatively, but it is impossible to know the sensitivity of these modern imaging modalities. At our institution we use ultrasonography and nuclear medicine renal excretion studies for children with suspected ureteropelvic junction obstruction. However, excretory urography probably remains the most sensitive means of diagnosing fibroepithelial polyps preoperatively. The inability to detect a fibroepithelial polyp preoperatively may be related to its size or rarity, or the inadequacy of fully visualizing the ureteropelvic junction area with echography, urography or retrograde pyelography. Perhaps future improvements in ultrasonography, better awareness or more extensive scanning will allow the detection of polyps at the ureteropelvic junction. Traditionally fibroepithelial polyps within the ureter were treated with nephroureterectomy due to concern regarding potential malignant transformation. The majority of cases are now locally resected with primary reanastomosis as they are believed to be benign mesenchymal lesions.12, 13 A growing number of ureteral fibroepithelial polyps in adults are being treated by endoscopic laser ablation. Given the age of the patients and the extensive time span of presentation in our series, ureteroscopic management was not an option. All of the patients in our study were treated with excision of the polyp and an Anderson-Hynes dismembered pyeloplasty. We emphasize the importance of using a dismembered pyeloplasty as polyps could potentially be missed if a spiral flap or Y-V pyeloplasty is performed instead. This approach is particularly important given the small number of fibroepithelial polyps that are diagnosed preoperatively in children. Only 1 patient in our series required nephrectomy for loss of renal function, and none of the patients had recurrence at a mean followup of almost 4 years. In our experience ureteropelvic

junction obstruction caused by fibroepithelial polyps is rare but early diagnosis of obstruction, followed by dismembered pyeloplasty, is curative. REFERENCES

1. Stuppler, S. A. and Kandzari, S. J.: Fibroepithelial polyps of ureter: a benign ureteral tumor. Urology, 5: 553, 1975 2. Thorup, J., Pedersen, P. V. and Clausen, N.: Benign ureteral polyp as a cause of intermittent hydronephrosis in a child. J Urol, 126: 796, 1981 3. Eilenberg, J., Seery, W. and Cole, A.: Multiple fibroepithelial polyps in the pediatric age group: case report. J Urol, 117: 793, 1977 4. Macksood, M. J., Roth, D. R., Chang, C.-H. and Perlmutter, A. D.: Benign fibroepithelial polyps as a cause of intermittent ureteropelvic junction obstruction in a child: a case report and review of the literature. J Urol, 134: 951, 1985 5. Berger, R. M., Lebowitz, J. M. and Carroll, P. A.: Ureteral polyps presenting as ureteropelvic junction obstruction in children. J Urol, 128: 805, 1982 6. Schulman, C. C.: Ureteric polyp as a cause of hydronephrosis in childhood. J Pediatr Surg, 13: 537, 1978 7. Gu¨ p, A.: Benign mesodermal polyp in childhood. J Urol, 114: 619, 1975 8. Williams, P. R., Feggeter, J., Miller, R. A. and Wickham, J. E.: The diagnosis and management of benign fibrous ureteric polyps. Br J Urol, 52: 253, 1980 9. Reuter, V. E.: Urethra. In: Urologic Surgical Pathology. Edited by D. G. Bostwick and J. N. Eble. St. Louis: Mosby-Year Book, pp. 435– 454, 1997 10. Vargas, S. O.: Fibrous umbilical polyp: a distinct fasciitis-like proliferation of early childhood with a marked male predominance. Am J Surg Pathol, 25: 1438, 2001 11. Bennington, J. L. and Beckwith, J. B.: Atlas of Tumor Pathology: Tumors of the Kidney, Renal Pelvis, and Ureter. Washington, D. C.: Armed Forces Institute of Pathology, 2nd series, fasc. 12, pp. 320 –322, 1975 12. Colgan, J. R., III, Skaist, L. and Morrow, J. W.: Benign ureteral tumors in childhood: a case report and a plea for conservative management. J Urol, 109: 308, 1973 13. Young, R. H. and Eble, J. N.: Renal pelvis and ureter. In: Urologic Surgical Pathology. Edited by D. G. Bostwick and J. N. Eble. St. Louis: Mosby-Year Book, chapt. 3, p. 161, 1997