Transvaginal sonography in the assessment of distal ureteral calculi

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1 Ultrasound Obstet Gynecol 2005; 26: Published online in Wiley InterScience ( DOI: /uog.2610 Transvaginal sonography in the assessment of distal ureteral calculi J.-M. YANG*, S.-H. YANG and W.-C. HUANG *Division of Urogynecology, Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Schools of Medicine and Health and Nutrition, Taipei Medical University and Department of Obstetrics and Gynecology, Cathay General Hospital, Taipei, Taiwan, ROC KEYWORDS: distal ureteral calculi; Doppler flow imaging; ureter; ureter jet phenomenon; ureter papilla ABSTRACT INTRODUCTION Objectives To explore the morphological and functional findings of transvaginal sonography (TVS) in the diagnosis and management of distal ureteral calculi. Methods We retrospectively reviewed the imaging studies in seven cases of distal ureteral calculi (study group) and 20 cases of female volunteers without urinary tract infection (control group). All 27 patients had undergone TVS for assessment of the lower urinary tract. The variables measured on ultrasound included the presence or absence of distal ureteral calculi, the size and location of a calculus if present, the presence or absence of the ureter jet phenomenon, morphological changes of the ureteral papilla and adjoining tissue, and the height of the ureteral papilla, as well as vascular changes seen on Doppler imaging. Results In the controls, 80% of the ureteral papillae were triangular and 20% trapezoidal. The average (± SD) height of the ureteral papillae was 3.5 ± 0.7 mm on the right and 3.6 ± 0.9 mm on the left. There was no statistically significant difference between the heights of the right and left papillae (P = 0.619). In the study group, echogenic stones were identified in all seven patients and a hypoechogenic tubular structure connected to the involved papilla was identified in 6/7 patients. The average height of the involved papilla was 6.7 ± 1.6 mm. Ureteric jets were visible in all patients in both the study and control groups. Conclusion In patients with distal ureteral calculi, TVS provides a rapid, non-invasive and repeatable means of assessing the morphology and function of the distal ureter. Copyright 2005 ISUOG. Published by John Wiley & Sons, Ltd. Around 85% of ureteric stones are located in the distal ureter 1. Calculi in this location often cause pain that radiates to the labia majora in females. Menstrual pain, pelvic inflammatory disease, and ruptured or twisted ovarian tumors may mimic the symptoms of distal ureteral stones, and the full differential diagnosis of the acute abdomen should be considered 2. Sonography provides a rapid, non-invasive and repeatable examination in the evaluation of lower abdominal pain in women. The use of sonography to detect distal ureteral calculi appears promising and may have the potential for replacing conventional radiography and excretory urography for this purpose 3 5. It has been suggested that stones measuring less than 4 mm in diameter have a high chance of spontaneous passage, while the optimum treatment of larger stones is surgical intervention 6. Impaction of a ureteral stone, leading to hydroureter or hydronephrosis or both, requires drainage to prevent significant morbidity and possible mortality 2. Therefore, imaging studies must assess these anatomical details. Renal or ureteral function may be examined non-invasively by detection of the ureter jet phenomenon by color or power Doppler flow imaging 3,7,8. The purpose of the present study was to evaluate the use of transvaginal sonography (TVS) to examine morphology and function in cases of distal ureteral calculi. METHODS We retrospectively reviewed imaging files compiled from January 1992 to June 2004 and identified seven women with distal ureteral calculi who had also had anatomical assessment of the lower urinary tract by TVS. Twenty female volunteers who had no urinary tract infection Correspondence to: Dr W.-C. Huang, Department of Obstetrics and Gynecology, Cathay General Hospital, 280 Jen-Ai Road, Section 4, Taipei 106, Taiwan, ROC ( huangwc0413@hotmail.com) Accepted: 15 March 2005 Copyright 2005 ISUOG. Published by John Wiley & Sons, Ltd. ORIGINAL PAPER

2 Distal ureteral calculi 659 were recruited from the gynecological clinics to serve as control subjects. The average age of the study and control groups was 44 ± 16 years and 45 ± 13 years, respectively. Three (42%) of the seven women in the study group and eight (40%) of the 20 controls were postmenopausal. All of the patients in the study group had acute pain, lasting for 6 hours to 3 days. Only one had an abnormal urinalysis. Plain abdominal films showed a radiopaque object in the lower pelvis in the four patients in whom this investigation was done. Bilateral ultrasound imaging of the kidneys showed mild unilateral hydronephrosis in two women and no renal calculus identified in any of the seven patients. Ureteral calculi passed spontaneously in all seven women within 3 10 days after the first sonographic examination. Follow-up sonography did not reveal any other stones in the distal ureter. The lower urinary tract was assessed by TVS using a Toshiba SSA-260A or Power Vision 6000 (Toshiba Medical Systems, Tokyo, Japan) or Voluson 730 (GE Medical Systems, Zipf, Austria) scanner and a MHz endovaginal probe with the patient lying supine with a comfortably full bladder. After the endovaginal probe was placed in the proximal vagina, the sonographic beam was initially directed to the posterio-inferior aspect of the urinary bladder. The transducer was then directed slightly to the right or left parasagittal plane, looking for two tiny nodules, the ureteral papillae, which are located above the bladder mucosa at the junction of the trigone and bladder. Ureteral peristalsis helps in visualizing them (Figure 1). The site of the ureteral orifice can be identified by urinary flow from the ureteral papilla (ureteric jet) on color or power Doppler imaging (Figure 1b). The variables measured on ultrasound included the presence or absence of distal ureteral calculi, the size and location of any calculi, the presence or absence of a ureteric jet, and morphological changes of the ureteral papilla and adjoining tissue, as well as vascular changes on color or power Doppler or both. The papilla height was measured from the top to the base of the ureteral papilla on each side (Figure 1c). Color or power Doppler flow imaging studies were performed using a low pulse repetition frequency (500 Hz) to optimize the detection of weak Doppler signals. The band-pass filter was set at its lowest setting (50 Hz). Statistical analysis was performed using SPSS 12.0 for Windows (SPSS, Inc., Chicago, IL, USA). For parametric comparison, a paired t-test or Mann Whitney U-test (two-tailed) was used for intra- or intergroup comparison. A value of P < 0.05 was considered significant. (c) Papilla height Orifice Ureter jet RESULTS Sonographic findings in the controls Trigone Against the echogenic overlying bladder mucosa, the ureteral papilla was seen protruding from the bladder wall as a hypoechogenic structure. It was triangular in 80% (16/20) (Figure 1a) and trapezoidal in 20% (4/20) of cases (Figure 1b). The average (± SD) height of the Figure 1 Transvaginal sonography displaying the ureteral papilla shaped as a triangle (a) and as a trapezoid (b). (a) The lumen (black arrow) of the intravesical ureter is clearly visible within the ureteral papilla (white arrow). (b) Power Doppler imaging displaying a ureteric jet. (c) Schematic diagram displaying the papilla height as measured from the top to the base of the papilla.

3 660 Yang et al. papilla was 3.5 ± 0.7 (median, 3.6; range, ) mm on the right and 3.6 ± 0.9 (median, 3.8; range, ) mm on the left. There was no statistically significant difference between the papilla height of the right and left ureters (P = 0.619, paired t-test). The ureteric jet was clearly visible from both ureters on Doppler flow imaging. Sonographic findings in the study group The ultrasonographic features of distal ureteral stones, including four on the right and three on the left, are shown in Table 1. The maximum longitudinal diameter of the seven stones was 8.1 mm and the maximum transverse diameter was 4.5 mm. Five stones were located at the base of the ureteral papilla, while two were near the top of the papilla. All of the involved papillae were expanded with a dome-shaped configuration and had localized hypervascularity (Figure 2) except for Case 6. The involved papillae, with an average (± SD) papilla height of 6.7 ± 1.6 (median, 6.5) mm, were significantly higher than the contralateral uninvolved papillae in the study group (P < 0.001, paired t-test) and the papillae on the matching side in the controls (P = and for the right and left papillae, respectively; Mann Whitney U-test). The ureteric jet was visible in all cases, but it was weak and of short duration in Case 7, where the stone was located near the ureteric orifice. Again with the exception of Case 6, the extra- and intravesical ureter was visible as a hypoechogenic tubular structure connected to the involved papilla in each patient (Figure 3). Realtime imaging revealed the following sequence of the ureter jet phenomenon: accumulation of urine in the intravesical ureter by peristalsis (Figure 3a), distension of the intravesical ureteric lumen (Figure 3b) and finally expulsion of urine through the ureteral orifice (Figure 3c). Follow-up sonography within 1 week of spontaneous passage of stones showed that the papilla height of the involved ureter decreased, with progressive restoration of the normal configuration of the ureteral papilla (Figure 4). In some cases, the distal ureter was still visible. DISCUSSION Figure 2 Power Doppler imaging displaying hypervascularity around the calculus (arrow) in the ureteral papilla. We found TVS performed at a high frequency and using the good resolution of an endovaginal probe and Doppler imaging provides a sensitive method for examining the distal ureter containing a stone. In a survey of 132 cases of ureteral calculi, none had multiple calculi on the same side 1. A plain film of the abdomen followed by excretory urography is the traditional approach for patients with suspected ureteral calculi 2. However, the ability to detect stones in the ureter radiographically depends on their composition. Phleboliths or other calcifications may mimic calculi, or stones may be obscured by bowel gas or bony structures. Excretory urography is an invasive procedure using ionizing radiation. It may be inappropriate for patients who are pregnant or who have Table 1 Clinical data, laboratory findings and ultrasonographic results in the study group Ultrasonography Case Age (years) Urinalysis RBC (/HPF) WBC (/HPF) KUB X-ray Expulsion of ureteric stone Calculus Ureteral papilla Extravesical after initial Diameter Papilla ureter sonography (L T) Location height Hyper- Ureteric diameter (day) Side (mm) (mm) Shape vascularity jet (mm) Opaque + 3 Right Base 8.1 Dome Opaque + 3 Right Base 8.7 Dome Opaque + 10 Left Base 6.5 Dome Opaque + 5 Right Base 6.2 Dome NA 7 Left Base 7.8 Dome NA 4 Left Top 4.0 Triangle + ND NA 5 Right Top 5.9 Dome Ureteral papilla height: distance between the top and the base of the ureteral papilla. +, present;, absent; KUB, kidney-ureter-bladder; L, longitudinal diameter; NA, not available; ND, not detectable; opaque, radiopaque object; RBC/HPF, red blood cell per high power field; T, transverse diameter; WBC/HPF, white blood cell per high power field.

4 Distal ureteral calculi 661 Intravesical ureter Distension Calculus Extravesical ureter Figure 3 Transvaginal gray-scale and power Doppler findings and schematic drawing displaying the sequence of the ureteric jet in the presence of a ureteral stone. (a) Accumulation of urine in the intravescial ureter by peristalsis. (b) Distension in the lumen of the intravesical ureter. (c) Ureteric jet. An ovoid, hyperechogenic calculus (solid arrow) is located in the ureteral papilla. The lumen of the intravesical ureter (small arrows) is progressively distended with urine and the extravesical ureter (open arrow) is identifiable as a hypoechogenic tubular structure. The papilla height is 7.8 mm and the diameter of the extravesical ureter is 4.4 mm. renal insufficiency or a history of allergy to contrast media. Moreover, as there may be a delay before a patient undergoes urography, the calculus may be passed in the interval. In a prospective study of 48 patients with distal ureteral stones, 23% of the calculi were not seen on intravenous urography, while ultrasonography detected the stone in every patient 9. Ultrasonography with a transvaginal or transperineal approach has the advantage over the transabdominal approach of not requiring an over-distended bladder 3,4. It also avoids diminished ultrasound penetration caused by obesity and excess intestinal gas. In addition, the transvaginal probe, with a higher frequency and better resolution, is more sensitive at detecting a tiny stone in the distal ureter. However, renal calculi can only be detected by the transabdominal approach. Because 85% of ureteric stones are located in the distal ureter 1 and other pelvic disorders may mimic the symptoms of ureteral calculi, TVS is appropriate as the first test for women with suspected renal colic, with the understanding that pelvic conditions should also be assessed and further imaging may be necessary 1,2,5. The ultrasonographic features of a distal ureteral calculus include identification of a stone within the ureter and demonstration of unilateral dilation of the collecting system 3,4. Under normal circumstances, a non-dilated ureter is not visible 5. It has been stated that a clearly identified ureter, seen as a hypoechogenic tubular structure, is a manifestation of hydroureter 3. By contrast, we believe that visualization of a tubular structure in some cases may simply demonstrate the presence of ureteral edema 5 secondary to inflammation induced by the stones. Three findings support our contention. First, real-time imaging clearly demonstrated that the accumulation of urine and distension of the intravesical ureter did not extend into the extravesical ureter. Second, on follow-up sonography the extravesical ureter was still visible for a short period after spontaneous expulsion of the stone. Third, the ureteral papilla is also deformed by a distal ureteral calculus. The stone may induce regional inflammatory changes resulting in the localized

5 662 Yang et al. acute obstruction and hydroureter, observation may be tried first with expectation of spontaneous passage of the stone and, even though it may take as long as 40 days, it avoids the risks associated with intervention 12.Impacted stones are those that remain unchanged in the same location for at least 2 months 14. TVS is a repeatable and non-invasive way to look for ureteral obstruction, either on initial presentation or on follow-up. Our study confirms that TVS demonstrates both the morphology and function of the distal ureter and ureteral papilla in the presence of distal ureteral calculi. REFERENCES Figure 4 Three days after spontaneous passage of a ureteral stone, follow-up sonography shows restoration of the normal configuration of the involved ureteral papilla (compare with Figure 3 in the same patient, Case 5) with a persistently identifiable distal ureter (open arrow). The papilla height is 5.9 mm and the diameter of the extravesical ureter is 4.4 mm. hypervascularity displayed on Doppler flow imaging. The inflammatory edema appears to enlarge and distort the configuration of the papilla and also extends to the distal ureter, making it visible on ultrasound. Morphologically, these specific ultrasonographic findings will differentiate distal ureter calculi from phleboliths or fecaliths without difficulty 10. However, a stone, such as in Case 6, may not induce any morphological changes. The absence of echogenicity in the ureteral papilla on follow-up scanning and a subjective history of passage of stone supported our diagnosis of distal ureter calculus. In the case of ureteric stones, the goal of any imaging is to detect obstructing calculi. TVS with Doppler flow imaging helped to exclude the possibility of acute obstruction. The appearance of a ureteric jet eliminated the possibility of complete obstruction. Stones that were smaller, more distal or on the right were more likely to pass spontaneously and required little intervention 11,12. However, intervention is necessary in up to 50% of ureteric calculi greater than 5 mm 6,12,13.It has been reported that the average diameter of a calculus determined by ultrasonography is significantly larger than that obtained by plain radiography 9. In the absence of 1. Yaqoob J, Usman MU, Bari V, Munir K, Mosharaf F. Unenhanced helical CT of ureterolithiasis: incidence of secondary urinary tract findings. J Pak Med Assoc 2004; 54: Stoller M, Bolton DM. Urinary stone disease. In Smith s General Urology (15th edn), Tanagho EA, McAninch JW (eds). McGraw-Hill: New York, NY, 2000; Laing FC, Benson CB, DiSalvo DN, Brown DL, Frates MC, Loughlin KR. Distal ureteral calculi: detection with vaginal US. Radiology 1994; 192: Hertzberg BS, Kliewer MA, Paulson EK, Carrol BA. Distal ureteral calculi: detection with transperineal sonography. AJR Am J Roentgenol 1994; 163: Saita H, Matsukawa M, Fukushima H, Ohyama C, Nagata Y. Ultrasound diagnosis of ureteral stones: its usefulness with subsequent excretory urography. JUrol1988; 140: Anagnostou T, Tolley D. Management of ureteric stones. Eur Urol 2004; 45: Matsuda T, Saitoh M. Detection of the urine jet phenomenon using Doppler color flow mapping. Int J Urol 1995; 2: Wiesner W, Wedegaertner U, Stoffel F, Sonnet S, Bongartz G, Steinbrich W. Autonomous pelvi-ureteric peristalsis in renal transplants confirmed by color Doppler mapping of the jet phenomenon. Eur Radiol 2001; 11: Ohnishi K, Watanabe H, Ohe H, Saitoh M. Ultrasound findings in urolithiasis in the lower ureter. Ultrasound Med Biol 1986; 12: Lerner RM, Robens D. Distal ureteral calculi: diagnosis by transrectal sonography. AJR Am J Roentgenol 1986; 147: Hollenbeck BK, Schuster TG, Faerber GJ, Wolf JS Jr. Comparison of outcomes of ureteroscopy for ureteral calculi located above and below the pelvic brim. Urology 2001; 58: Miller OF, Kane CJ. Time to stone passage for observed ureteral calculi: a guide for patient education. J Urol 1999; 162: Boulier JA, Laguna P, Parra RP. Treatment options for distal ureteral stones. Arch Esp Urol 1997; 50: Lotan Y, Gettman MT, Roehrborn CG, Cadeddu JA, Pearle MS. Management of ureteral calculi: a cost comparison and decision making analysis. JUrol2002; 167: