Abstract
Congenital ureteral strictures are rare both in human and veterinary medicine. While the diagnosis is generally made after a symptomatic or febrile urinary tract infection, we report here a case in which this condition represented an incidental finding during routine ultrasonography. To the best of the authors' knowledge imaging findings of a double monolateral ureteral stricture have not previously been reported.
Case report
An 8-month-old male Maine Coon cat underwent ultrasonography in order to provide further information about an undescended right testicle retained in the inguinal canal. The cat was of normal size and stature for his age and breed, weighing 5.5 kg, and no signs of previous illness were recorded by the owner. On physical examination general body condition was very good.
Ultrasonographic abdominal evaluation performed with a 7.5–10 MHz electronic linear array transducer revealed an enlarged left kidney with dilation of the renal pelvis (0.71 cm) and corresponding ureter at the ureteropelvic junction (0.52 cm) (Fig. 1). Dimensions of the left and right kidney were 50×29 mm and 41×19 mm, respectively.
Longitudinal ultrasonogram of the left kidney. Pelvic and proximal ureteral dilation can be appreciated.
The hydronephrosis and hydroureter were postulated to be caused by a luminal obstruction, therefore a scan of the retroperitoneal space was performed to rule out the presence of ureterolith or masses in the retroperitoneal space or in the tissues surrounding the ureters. This revealed no pathological findings. Ultrasonography of the urinary bladder and ureterovesical junctions also showed no abnormalities.
Results of complete blood count, serum biochemistry and urinalysis are shown in Table 1 and revealed no significant abnormalities. Urine samples were collected via cystocentesis and culture did not yield any significant aerobic or anaerobic bacterial growth.
Results of laboratory tests
After ruling out a pre-existing renal insufficiency, according to Adin et al. (2003), intravenous urography was performed by injecting a bolus of 8.6 g of iopamidol (Iopamiro 300; Bracco, Milan, Italy) through a catheter in the right cephalic vein.
Ventrodorsal and lateral abdominal radiographs were taken at 0, 5, 10, 20, 35, 45, 55, 120 min after administration of the contrast medium. Fig. 2 shows the left pelvic and proximal ureteral dilation at 10 min after injection. Figs. 3a and 4a and b show the proximal and mid-ureteral strictures at 45 and 120 min, respectively. In both cases dilation of the segment of ureter proximally provided evidence of the partial obstructions. Lateral projection radiograph (Fig. 3b) showed left and right ureters filled with contrast material extending to the ureterovesical junctions. Narrowing of the ureteral lumen, either congenital or acquired, is relatively common in humans (Blyth and Snyder, 1994; Snow, 1994; Gitlin and Kaefer, 2002) and animals (Feeney and Johnston, 2002; Adin et al., 2003; Stieger et al., 2003). Bilateral stenosis is also reported both in human (Namiki et al., 1987) and veterinary medicine (Pullium et al., 2000).
Ventrodorsal radiograph obtained 10 min after injection of contrast medium. The dilated left pelvis and proximal ureter filled with contrast medium are evident (arrow). The urinary bladder was filled with filtered air with the aim of slowing down the ureteral flow.
Ventrodorsal (a) and lateral (b) view at 45 min after injection of contrast medium. (a) Proximal and mid-ureteral strictures are appreciable (arrows). The proximal stricture presents a characteristic aspect of kinking at the ureteropelvic junction. (b) Arrows point to the left and right ureters filled with contrast material extending to the ureterovesical junctions (the small radiopaque spot which is superimposed on L7 in Fig. 2 and on L5 in (a) is an artifact).
Ventrodorsal (a) and lateral (b) view at 120 min after injection of contrast medium. Stasis of contrast medium in the left pelvis and ureter caused by the two strictures is evident.
To the best of the authors' knowledge this is the first time in which an incidental finding of a double monolateral ureteral stricture has been imaged in mammals including the human.
Congenital and acquired ureteral obstructions are reported. The commonest causes of acquired obstructions both in human and small animal medicine are: ureteroliths (Stieger et al., 2003; Adin et al., 2003), infections (Gitlin and Kaefer, 2002; Feeney and Johnston, 2002), tumours of the bladder, ureter and ureteral surrounding structures (Snow, 1994; Reichle et al., 2003; Stieger et al., 2003), fibrosis caused by surgery (Snow, 1994; Adin et al., 2003) and mucus plugs (Snow, 1994; Adin et al., 2003). Reported human causes are: masses in the retroperitoneal space consequent to idiopathic retroperitoneal fibrosis (Namiki et al., 1987) or fibrosis related to idiopathic systemic fibrosis and collagen disease (Namiki et al., 1987).
We believe that the pathologies listed above are unlikely to be the cause of the findings in this case.
History, clinical condition and age of the subject together with diagnostic imaging and haemato-biochemical and urinalysis results allowed each of the hypotheses mentioned above to be ruled out. Furthermore, the reported human cases of idiopathic systemic fibrosis are usually associated with connective tissue diseases such as systemic lupus erythematosus or polyarteritis and arthritis (Namiki et al., 1987). Finally, we believe that a double acquired ureteral stricture is highly unlikely.
Congenital ureteral strictures, whether localised at the ureteropelvic junction or mid-ureteral strictures, are reported to be caused by fibrosis of the ureteral wall itself in man and dogs (Blyth and Snyder, 1994; Namiki et al., 1987; Pullium et al., 2000; Gitlin and Kaefer, 2002). These strictures normally appear as narrowings of the ureteral lumen (Snow, 1994). Excess fibrous tissue at the ureteropelvic junction may be secondary to muscle reduction and may curtail or block downward peristalsis and increase the rigidity of the ureteral wall, causing kinking at the ureteropelvic junction (Pullium et al., 2000). In man, obstructions of the ureteropelvic junction are reported to be more common in males than in females (ratio 2:1) particularly in the neonate, with two-thirds of cases being described on the left side (Blyth and Snyder, 1994).
Further causes of abnormal ureteral flow linked to ectopic ureter (Feeney and Johnston, 2002) were excluded because of the lack of clinical signs, and on the basis of radiological findings (not included in the present paper) which show the ureters ending at the bladder trigone.
In human medicine surgical treatment of this condition is recommended only in individuals presenting with a symptomatic ureteral obstruction such as urosepsis or a history of vomiting and cyclic flank pain. Those detected incidentally at the time of routine ultrasound and in which renal function, assessed by a diuretic urogram after injection of a radioisotope (ie, 99mTc-DTPA), is better than 35%, are followed-up with repeat scans at 6 or 12 month intervals. Surgery is considered only when a clear deterioration in renal function is evident (Blyth and Snyder, 1994).
At the time of writing (5 months after) the cat is in excellent physical condition, therefore no further medical or surgical intervention is currently planned.
As the clinical evolution of the double ureteral stricture and correspondent hydronephrosis cannot be predicted, ultrasonographic re-examination of the kidneys should be performed at regular intervals unless worsening of the condition of the cat suggests a different approach. At the same time serum biochemical analyses, urinalysis and culture should be performed in order to evaluate early appearance of renal failure and/or urinary tract infections.
Footnotes
Acknowledgments
The authors would like to thank Dr. Giacomo Sivori for his excellent technical assistance.