British Journal of Radiology (2003) 76, 260-263
© 2003 British Institute of Radiology
doi: 10.1259/bjr/98474499
Descending urethral ultrasound of the native and reconstructed urethra in patients with hypospadias
A P Toms, FRCS, FRCR1,
K N Bullock, MD, FRCS2 and
L H Berman, FRCP, FRCR1
Departments of 1 Radiology and 2 Urology, University of Cambridge and Addenbrooke's Hospital NHS Trust, Hills Road, Cambridge CB2 2QQ, UK
Correspondence: Dr AP Toms, Department of Radiology, Box 219, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK
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Abstract
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A retrospective study, over a 7 year period, examining the use of descending urethral ultrasound in corrected and uncorrected hypospadias was performed. 15 examinations were performed on 14 patients; 12 patients had undergone previous surgery for hypospadias, ranging from urethral reconstruction to stricture dilatation. Eight strictures, four irregular urethras, two normal post-operative urethras and one urethral valve were demonstrated. All the clinically significant abnormalities (those which impaired the flow of urine) demonstrated by ultrasound were confirmed with subsequent urethroscopy or contrast urethrography. This small series illustrates the application of descending urethral ultrasound in patients with hypospadias who are difficult to examine with more conventional radiographic techniques.
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Introduction
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There are technical difficulties associated with imaging the urethra in hypospadias. The ventral position of the urethral meatus and the absence of a navicular fossa make it difficult to anchor a urethral catheter or achieve a satisfactory seal during ascending contrast urethrography. Micturating cystourethrography with excretory urography of the upper tracts has been recommended in early reports of symptomatic patients with hypospadias [1]. Hypospadias is associated with urethral strictures, in particular meatal stenosis. In addition, reconstructive surgery in this group of patients increases the incidence of urethral stricture [1]. Descending urethral ultrasound has been described in the demonstration of the anterior urethra [2], including the fossa navicularis [3]. To the authors' knowledge there are no previous accounts of systematic attempts to image the urethra in patients with hypospadias. The purpose of this study was to determine whether descending urethral ultrasound could be used to assess symptomatic patients with hypospadias both pre- and post-operatively.
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Patients and method
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A retrospective study of patients with a diagnosis of hypospadias undergoing descending urethral ultrasound was performed. Patient details and results of urethral ultrasound were collected from an electronic database maintained within the ultrasound department. Subsequent radiological investigations were retrieved from the hospital's computerized radiological information system. Surgical and clinical follow up was retrieved from the patients' hospital notes.
Between 1994 and 2000 descending urethral ultrasound was performed on 274 occasions at our institution. Of the 274 examinations, 15 (5.5%) were performed on 14 patients known to have hypospadias. Two studies were carried out on the same patient 7 years apart. Patients were aged between 4 years and 38 years (mean age 20.6 years). 12 patients had undergone reconstructive surgery between 6 years and 30 years (mean 16 years) previously. Surgery included Duckett, Matthieu, Horton, Asopa-Bianchi and meatal advancement and glansplasty procedures. Subsequent surgical revision or urethral dilation was documented in 10 cases. Two patients had not undergone surgery. All patients presented to the urological surgical teams with symptoms localized to the lower urinary tract. 11 patients presented with difficulty in voiding urine and 3 presented with dysuria.
Clinical follow-up of the patients, ranging from 6 months to 7 years (mean 2.7 years), was undertaken. 9 of the 15 urethral sonograms were correlated with the results of subsequent urethroscopy (n=7) and conventional contrast urethrography (n=3); one patient underwent both investigations. Following six of the urethral sonograms there was no further surgical or radiological investigation. In these cases ultrasound findings were correlated with subsequent clinical progress.
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Technique
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All 15 descending urethral ultrasound scans were performed and interpreted by a single observer (LHB). Studies were performed using a 5–11 MHz linear array probe in coronal and sagittal planes from the ventral surface of the penis on Toshiba SSD 140, SSD 270 and Powervision machines (Toshiba Medical Systems, Sussex, UK). The technique has been described previously [3], but briefly, the patient attends with a full bladder and voids into a receptacle. After initiating micturition the patient compresses his penis by "pinching" gently, approximately 2 cm proximal to the tip. In cases of hypospadias this is performed at any position along the penile shaft proximal to the meatus whereby arrest of urinary flow is achieved. Urine is thus used as the distending fluid. Images of the bulbar and proximal penile urethra are obtained by insonating the ventral surface of the penis. The distal urethra, e.g. the fossa navicularis in normal subjects or the reconstructed urethra in corrected hypospadias, can also be demonstrated by insonating the ventral penis during micturition (Figures 1 and 2
). Patients with uncorrected hypospadias need to be insonated from the dorsal surface to demonstrate the ventrally positioned meatus (Figure 3). In a single case, ascending instillation of saline through a fine bore catheter (6 Fr) was required to distend the urethra. As it is uncomfortable for the patient if the examination is prolonged, the studies were recorded with video. Image interpretation was performed using these dynamic recordings. Static images were obtained using digital frame capture.
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Figure 1. Sagittal urethrosonographic frame capture montage in a patient who has undergone reconstructive surgery for hypospadias. There is mucosal irregularity of the neo-distal urethra (arrow), which did not impede the flow of urine. The corpus spongiosum (S) surrounding the urethra (asterisk) can be seen separate from, and slightly echogenic compared with, the corpus cavernosum (C).
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Figure 2. (a) A tight stricture is demonstrated in the neo-distal urethra on this sagittal montage (arrow). The prostatic urethra (P) is demonstrated proximal to the bulbar urethra (asterisk) in this example. (b) This was confirmed with ascending contrast urethrography (arrow). This oblique radiograph results in some foreshortening of the urethra accounting for the difference compared with the true sagittal ultrasound montage. The tip of the catheter is demonstrated in the very distal neo-urethra (black arrow) and there is free spillage of contrast medium because an adequate seal cannot be obtained with this technique (arrowhead).
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Figure 3. Montage of sagittal frame capture images from the descending urethrosonographic video of a patient with uncorrected hypospadias. The more proximal images are obtained with the penis "pinched", the urethra (asterisk) distended and insonated from the ventral surface. The distal image of the tip of the penis is obtained during micturition insonated from the dorsal surface. The ventral urethral meatus is clearly demonstrated (arrow) with a more proximal irregular narrowing (arrowheads), which did not impede the flow of urine. The thin echogenic line (curved arrow) bordering the anechoic column of urine represents the urethral mucosa.
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Results
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Results are summarized in Table 1. Satisfactory images were obtained in all 15 studies performed on 14 patients with no failed examinations. Urethral strictures were demonstrated in eight studies, in which all patients had undergone previous reconstructive surgery (Figures 1 and 2
). Of these, five strictures occurred at the anastomosis of native and neo-urethra. Three strictures were demonstrated at other sites. Four other studies demonstrated non-stricturing abnormalities of the distal urethra consisting of mucosal irregularity and tortuosity that did not impede the flow of urine (Figure 1). Impaired flow of urine was considered present if the following criteria were met: ballooning of the urethra proximal to the mucosal irregularity during voiding, lack of dilation of the irregular portion of the urethra and poor stream during the micturition component of the examination. In these patients with non-stricturing abnormalities, two had undergone reconstructive surgery and two had had no previous surgery. In one patient a web was demonstrated at the site of a previous urethrotomy (Figure 4). Two patients with reconstructed neo-distal urethras had otherwise normal studies. The patient who was imaged twice was shown to have an irregularity of the distal neo-urethra at the first visit that had progressed to a stricture by the second examination 7 years later.
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Figure 4. Static sagittal B mode images montaged to demonstrate the persistent urethral web (arrow) at the level of the membranous urethra at the proximal margin of the bulbar urethra (asterisk).
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The results of all 15 ultrasound examinations were subsequently confirmed by urethroscopy (n=6), contrast urethrography (n=2), by both these techniques (n=1) or supported by clinical assessment in out-patient clinics (n=6). The site and extent of the eight urethral strictures were confirmed by urethroscopy (n=6), contrast urethrography (n=1) or by both techniques (n=1). One patient identified as having a stricture by ultrasound, and confirmed by contrast urethrography, declined further surgical intervention. At clinical follow-up, obstructive symptoms continued, which the patient was prepared to tolerate.
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Discussion
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The incidence of urethral abnormalities following repair of hypospadias is common and has been reported in 5% to 25% of cases [4, 5]. In our institution, for the past 7 years, descending urethral ultrasound has been the routine method employed to demonstrate the anterior urethra. Prior to the introduction of descending urethral ultrasound, symptomatic patients with hypospadias at our institution underwent further investigation with either conventional contrast urethrography or urethroscopy.
The abnormal anatomy found in hypospadias, both in the reconstructed and the native urethra, can make conventional ascending urethrography difficult or impossible. In addition, conventional contrast medium techniques for imaging the urethra often result in views of the distal portion being obstructed by a clamp [2] or catheter [3]. These problems can be overcome by using micturating contrast urethrography, but this does require catheterization of the bladder for instillation of the contrast medium, whereas descending urethrosonography avoids this intervention. A further advantage of urethrosonography is that it avoids the use of ionizing radiation. This is particularly desirable in this group of patients who are often young and whose gonads would be in the radiation field.
This study has certain limitations. It is a retrospective review of a small cohort of patients without a standardized comparative. Therefore the sensitivity or specificity of this technique in patients with hypospadias can not be determined. The technique of descending urethrosonography has, however, been validated elsewhere [3, 6–9]. This study describes the particular strength of descending urethrosonography in this group of patients with hypospadias where abnormalities commonly occur in the distal urethra.
The technique of urethrosonography requires good patient co-operation to achieve adequate distension of the urethra. Approximately 90% of patients in our practice are able to co-operate sufficiently to perform the study. Elderly patients, those with motor disabilities and patients unable to void with a sufficient flow rate, such as those with severe prostatism, have difficulty and normally undergo ascending contrast studies. Patients with hypospadias, who are mainly young adults, do not present such problems. The two children in the study, aged 4 years and 7 years, each accompanied by a parent, had no difficulty complying with the requirements of the technique.
Pinching the distal urethra shortly after initiating micturition can be uncomfortable if prolonged and leaves a limited window of opportunity to complete the study. Whilst this is a potential difficulty we did not encounter any problems completing the examination. Static images can be obtained of all but the distal urethra during the "pinch" but real time video acquisition ensures rapid imaging of the urethra, thus minimizing any patient discomfort and maximizing the information recorded in the limited window during micturition. A further potential disadvantage of the technique is that it relies on the patient attending the ultrasound department with a full bladder. In only one study was this inadequate and required retrograde instillation of normal saline to distend the urethra. In all the other 14 studies the volume of urine was satisfactory to image the anterior urethra in its entirety.
In conclusion, descending urethral ultrasound is a simple technique for imaging the anterior urethra in patients with hypospadias before or after reconstructive surgery. These subjects are often difficult or impossible to image using the more traditional techniques of contrast urethrography.
Received for publication May 20, 2002.
Revision received August 21, 2002.
Accepted for publication October 14, 2002.
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References
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Abstract
Introduction
