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Evaluation of Imaging Abnormalities of Ureter using MDCT Urography |
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Vedaraju Kadaba Shamachar, Vijay Kumar Kenchanahalli Rangaswamy, Chandalingappa Kuri, Boobapathi Raja 1. Professor and HOD, Department of Radio Diagnosis, Bangalore Medical College & Research Institute, Bengaluru, Karnataka, India. 2. Associate Professor, Department of Radio Diagnosis, Bangalore Medical College & Research Institute, Bengaluru, Karnataka, India. 3. Post Graduate Student, Department of Radio Diagnosis, Bangalore Medical College & Research Institute, Bengaluru, Karnataka, India. 4. Post Graduate Student, Department of Radio Diagnosis, Bangalore Medical College & Research Institute, Bengaluru, Karnataka, India. |
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Correspondence Address : Dr. Vedaraju Kadaba Shamachar, # 515 2nd C Main Nagarabhavi 2nd Stage, 11th Block, Bengaluru-560072, India. E-mail: vedarajuks@yahoo.in |
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| ABSTRACT |  | |||||||||||||||||||||||||||||||||||||||||||||||
: Introduction: Computed Tomography (CT) has become the primary imaging modality for assessment of excretory system. It has essentially replaced intravenous urography as the first line imaging modality. The major advantage of CT-urography is not only in its superior visualisation of the urinary tract, but also assessment of adjacent structures and other organs of the abdomen where intravenous urography fails. Aim: The aim of this study is to identify the pattern of pathologies involving the ureter and provide a systematic approach to interpret such abnormalities at CT urography. Materials and Methods: A prospective study was done using data gathered from 100 patients over a period of six months who were referred for contrast enhanced CT examination of the KUB region for suspected urinary abnormalities between age group of 18-70 years. Non-contrast, cortico-medullary, nephrographic and excretory phases were obtained and analyzed for ureteral abnormalities. Findings were recorded and analyzed using descriptive statistics. Results: The mean age group of study subjects was 38.4±14 years. The imaging findings in our study were basically classified into five groups – congenital abnormality, filling defects, ureteral dilatation, narrowing and deviation in course. Ureteral duplication was the most common congenital abnormality found in our study while calculi were the most common cause of filling defects. Ureteral obstruction due to various causes including calculi, clots, malignancy etc., was the predominant etiology of ureteral dilatation while strictures were the commonest etiology of ureteral narrowing. Two cases of deviation in course of the ureter were reported, one due to retroperitoneal fibrosis and the other due to abdominal aortic aneurysm. Conclusion: This study outlines the most common findings in patients referred for contrast enhanced CT scans for KUB and their imaging findings. A systematic approach to interpreting ureteral abnormalities includes assessment for congenital abnormalities, filling defects, dilatation, narrowing, and deviation in course. Because of the prevalence of ureteral abnormalities, it is vital for radiologists to recognise the varied appearance of ureteral disease at CT-urography. | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Keywords : Calculi, Clots, Congenital abnormality, Ureteral dilatation | ||||||||||||||||||||||||||||||||||||||||||||||||
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| DOI and Others : | ||||||||||||||||||||||||||||||||||||||||||||||||
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| INTRODUCTION |
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Computed Tomography (CT) has become the primary imaging modality for assessment of excretory system in the past decade (1),(2),(3),(4). CT-urography has essentially become superior to intravenous urography as the first line imaging modality since it has more accuracy and sensitivity, particularly for evaluation of haematuria.The major advantage of CT-urography is not only in its superior visualisation of the urinary tract, but also assessment of adjacent structures and other organs of the abdomen where intravenous urography fails (5). CT-urography is currently the preferred imaging modality for many clinical scenarios involving the urinary tract particularly for hematuria Keywords: Calculi, Clots, Congenital abnormality, Ureteral dilatation and in the staging and follow-up of urothelial tumors. The purpose of this study is to comprehensively review the role of CT-urography in evaluation of urinary tract obstruction, depiction of complex congenital or postsurgical urinary tract anatomy, and any clinical scenarios where comprehensive evaluation of the urinary tract is needed. | ||||||||||||||||||||||||||||||||||||||||||||||||
| Material and Methods |
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This study was a prospective study done in patients presenting to Victoria Hospital, Bowring and Lady Curzon Hospital and Vani Vilas Hospital attached to Bangalore Medical College and Research Institute, Bengaluru, India, over a period of six months from July 2015 to December 2015. Total 100 patients were studied. Sample size was calculated based on the prevalence of abnormalities with 15% error allowance. All adult patients of age group between 18 to 70 years who were referred for contrast enhanced CT examination of the KUB region for suspected urinary abnormalities were included in the study. Patients with known hypersensitivity to contrast media were excluded. Those with abnormal renal function tests (serum creatinine greater than 2.0 mg/dL) were also excluded from the study. Prior ethical committee approval was obtained. Informed consent was taken from all the patients. The patients underwent CT-scans of Kidney, Ureter and Bladder (KUB) region using a 6-slice Siemens SOMATOM and a 128- slice Philips Ingenuity Core CT scanner. Non-enhanced and contrast enhanced scans were done. Contrast enhanced CT was performed using a three-phase protocol. All patients were administered 400–500 mL of water orally 20-30 minutes before the examination. Unenhanced CT-scans of the abdomen and pelvis were obtained. Corticomedullary phase images were acquired first at 40 seconds and nephrographic phase images beginning 100 seconds after a 30-second injection of iohexol (Omnipaque 300, GE Healthcare) at a dose of 1.5 mL/kg. Eight minutes after the injection of contrast material, excretory phase images were obtained. Tube current used ranged from 110–380 mA with pitch of 1.375 and a collimation of 1.25 mm. Unenhanced, cortico medullary and nephrographic phase images were reconstructed as 3 mm thick sections. The excretory phase scans were reconstructed as 1.25 mm thin sections.Multiplanar reconstruction, maximum intensity projection and volume rendered images were obtained wherever necessary. Images thus acquired were analysed for various pathologies. Statistical Analysis Data was recorded and presented in the form of graphs and charts. Descriptive studies were presented in terms of mean and standard deviation.Qualitative data were presented as frequency multivariate analysis. Other sub stratified analysis will be carried out using appropriate software. | ||||||||||||||||||||||||||||||||||||||||||||||||
| Results |
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All adult patients of age group between 18 to 70 years who were referred for contrast enhanced CT examination of the KUB region for suspected urinary abnormalities were studied. Patients presenting with urinary symptoms like flank pain, oliguria, anuria, haematuria, etc., were included. The mean age of the study subjects was 38.4 years as shown in (Table/Fig 1). Malignancy was more prevalent in older age groups while ureteric calculi were the most common finding in the younger and middle age groups as shown in (Table/Fig 2). The most common presenting symptom in patients for CTurography in our study was abdominal/flank pain (45 cases), followed by haematuria (36 cases) (Table/Fig 3), trauma (3 cases), evaluation of a congenital abnormality (10 cases), oliguria and anuria (4 cases) and suspected genito-urinary tuberculosis (2 cases). The imaging findings in our study were basically classified into five groups – congenital abnormality, filling defects, ureteral dilatation, narrowing and deviation in course. Many filling defects and congenital abnormalities will cause ureteral dilatation. Malignancies can cause filling defects with dilatation and narrowing. Hence, the classification is overlapping and not mutually exclusive as shown in (Table/Fig 4). Congenital Abnormalities: These were classified under ureteral duplication which may be complete or partial, smooth muscle dysfunction which includes PUJ obstruction and primary megaureter, and abnormal termination of a single ureter (no duplication) which includes ectopic ureter, ureteroceles and VUR (Table/Fig 5). Ureteral Filling Defects: The most common cause of ureteral filling defect observed in our study was calculus (Table/Fig 6). Total 31 patients had a calculus in the ureter of which the most common location was the vesico-ureteric junction (20 patients- 70%). Twenty eight out of the 31 patients had obstructive features presenting with proximal ureteric dilatation and hydronephrosis to various extents. The second most common cause was malignancy (8 patients). seven out of the eight patients were proved to be uroepithelial tumors on further histopathology while one was found to be squamous cell carcinoma. Four patients presented with a clot which appeared as a high attenuating non enhancing focus. Two had a history of antecedent trauma while the rest two were on anticoagulants. Infectious etiology was found in five patients out of which four patients had tuberculosis characterised by nodular wall thickening and debris by sloughed papilla. One case of papillary necrosis was reported in our study. Other uncommon causes of ureteral filling defects like hyperplastic lesions (leukoplakia, malacoplakia) were not found in our study. Ureteral Dilatation: The most common cause of ureteral dilatation in our study was ureteral obstruction (Table/Fig 7) due to one or the other causes (54 patients) out of which an obstructing calculus was the predominant imaging finding (28 patients). Out of the 78 patients, 18 of them had bilateral dilated ureter. VUR (five cases) and bladder outlet obstruction (eight cases) were the predominant causes of bilateral dilated ureter. An enlarged prostate (five cases) was the most common finding in bladder outlet obstruction while the rest were malignancy. Ureteral Narrowing: Strictures (Table/Fig 8) were the most common cause of ureteral narrowing which included malignancy (four cases), Infection (three cases), Radiation therapy (two cases) and iatrogenic (one case). Extrinsic compression is also an important cause of Ureteral narrowing – pelvic malignancy (four cases), CA colon, retroperitoneal fibrosis and a giant fibroid (one case each). A normal ureter can appear narrowed at its UPJ, pelvic brim and VUJ, an abrupt turn or kink or due to an incomplete opacification. Deviation in Course: One case of retroperitoneal fibrosis and one case of abdominal aortic aneurysm showed a deviated ureter. | ||||||||||||||||||||||||||||||||||||||||||||||||
| Discussion |
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Findings in pathologic ureteral conditions can be classified as congenital abnormality, filling defect, dilatation, narrowing, or deviation in course. Congenital Abnormalities: Ureteral duplication is the most common congenital anomaly of the urinary tract in our study. Duplications can be unilateral or bilateral, partial or complete (Table/Fig 9). A partial duplication occurs when the initially separate upper and lower pole ureters fuse proximal to the vesico-ureteric junction into a common ureter, which then empties into the urinary bladder. Partial duplications are more common than complete duplications and most often are not clinically significant (6). A complete duplication occurs when the duplicated ureters remain separate throughout their course. The Weigert-Meyer rule states that in a complete duplication, the upper pole ureter terminates inferior and medial to the lower pole ureter (6),(7). The lower pole moiety is prone to reflux due to an abnormal VUJ valve mechanism, while the upper pole moiety generally has an ureterocele or an ectopic insertion (Table/Fig 10),(Table/Fig 11) or normal insertion on the bladder (6). Ureterocele (Table/Fig 12) is a bulbous dilatation into the bladder wall. On imaging, it appears as a rounded filling defect that projects into the lumen of the bladder (8),(9). Smooth muscle dysfunction can occur as either proximally at the Pelvi-Ureteric Junction (PUJ) resulting in a PUJ obstruction or distally at the vesico-ureteric junction resulting in a primary megaureter. The important feature of PUJ obstruction is proximal dilatation of the renal pelvis and calyces with abrupt narrowing. Rest of the ureter appears normal. Primary megaureter refers to a abnormality at the VUJ causing abnormal peristalsis (7),(10). At CT-urography, the abnormal ureteral segment is often normal in caliber with marked proximal dilatation. Filling Defects: Filling defect is one of the commonest manifestations of various pathologies involving the ureter. The most common causes of filling defects are calculi, tumours and clots. Calculi are identified at non enhanced CT as hyper dense foci along the course of the ureter. Any filling defect with which is not hyper dense and is with a soft-tissue attenuation are to be considered malignant until proven otherwise and should be further assessed by ureteroscopy and biopsy. Calculi were the most common cause of ureteral filling defects in our study (Table/Fig 13). Typically, they measure more than 200 HU. Hence, caution is advised while interpreting in an excretory phase image since they may be obscured by excreted contrast. A bone window setting might be but not always useful in such scenarios. Hence, always a nonenhanced CT is the preferred modality for diagnosing ureteral calculi and a contrast phase is essential to look for anomalies or conditions that might predispose and to look for the function and excretion of the kidneys. Calculi are most often located at the normal anatomic sites of ureteral narrowing such as PUJ, pelvic brim, and VUJ. Transitional cell carcinoma is the most common uro-epithelial tumour. The commonest locations are the urinary bladder and second in the renal pelvis. As far as ureter is concerned (Table/Fig 14) it frequently involves the distal ureter (11). A ureteral clot can occur from an intraureteral haemorrhage due to trauma, calculi, underlying malignancy, or anticoagulation. At CT, clots appear as a small rounded filling defect or as a vermiform defect that fills the ureter. It does not enhance. It can be identified on a non-enhanced image as hyper attenuating (>50 HU) both to urine and the surrounding soft tissues, A urine clot interface can also be occasionally identified (12). Follow-up imaging is also useful as it may demonstrate resolution of the clot. Ischaemic filling defects are uncommon. Renal papillary necrosis is the most common causative factor. Papillary necrosis can occur due to analgesic abuse, obstructive uropathy, sickle cell disease, pyelonephritis, renal vein thrombosis, tuberculosis, and diabetes (14). Necrotic papillae can also cause hydroureteronephrosis by embolizing themselves. Hence, it is important to look for signs of papillary necrosis such as caliceal cavities and blunting in any case of ureteral filling defect. In a study of 57 patients with haematuria and unexplained hydronephrosis evaluated with both CT-urography and retrograde pyelography after acquisition of non-diagnostic excretory urograms or US scans, there were 38 intrinsic urothelial lesions including 15 transitional cell carcinomas, 13 urinary stones, five cases of ureteropelvic junction obstruction, three cases of ureteral stricture, and two bladder polypoid lesions (14). While in our study, out of the 78 cases of dilated ureter, calculus was the predominant imaging finding (28 patients). Other causes of ureteral obstruction and proximal dilatation included malignancy (eight patients), clots (three patients), extrinsic compression (seven patients) and strictures (eight patients). Ureteral Dilatation/Narrowing: The normal diameter of ureter is 3 mm or less.Obstruction is the most common, but not only the cause of a dilated ureter. Physiologic narrowing can be identified by the absence of proximal dilatation and by changing nature in different phases and acquisitions. Proximal dilatation can occur due to abrupt turns or kinks throughout its course. A ureteral narrowing is called a stricture when it is a fixed narrowing with associated proximal dilatation (Table/Fig 15). The location (i.e., proximal, mid, or distal ureter) and length of the stricture must be described accurately in the report for proper surgical planning (15),(16). Limitations The study concentrates mainly on the intrinsic ureteral imaging patterns. Many of these pathologies on imaging are due to a cause outside the ureter which includes the proximal and distal excretory system. While contrast enhanced CT-scan of the KUB region provides a lot of information about the whole of the excretory system including masses and abnormalities of the vasculature and kidneys which could lead to potential abnormalities in the ureter, these were not concentrated adequately in the study. Secondly, children less than 18 years of age were not included in the study in whom, the prevalance and patterns might be different than those of adults. | ||||||||||||||||||||||||||||||||||||||||||||||||
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