A ureteral stricture is a narrowing of the ureter that results in a functional obstruction. It may be the result of a variety of benign and malignant causes, which may be classified as intrinsic or extrinsic processes. The clinical presentation of patients with ureteral strictures depends on the cause of the stricture and the severity and duration of the associated obstruction. In acute ureteral obstruction, pain is a common symptom. Chronic ureteral obstruction is most commonly asymptomatic unless urosepsis or renal failure supervenes. Both acute and chronic ureteral obstruction may manifest as hematuria.
Normal Anatomy
The ureter is a muscular tube that courses in the retroperitoneum connecting the collecting system of the kidney to the bladder. In an adult, the ureteral length varies from 28 to 34 cm. In the abdomen, the ureter is located along the medial aspect of the psoas muscles and passes anterior to the common or external iliac artery. The ureter travels in the lateral pelvic wall before coursing medially toward the bladder. In the female pelvis, the ureter travels beneath the broad ligament, lateral to the cervix and under the uterine artery. In the male, the ureter passes under the vas deferens. The ureters join the bladder and travel submucosally within the bladder wall for 2 to 3 cm before opening into the bladder at the ureteral orifices. The diagonal course of the intramural segment of the ureter helps prevent urinary reflux. This intramural segment of ureter at the ureterovesical junction is a site of normal narrowing and should not be mistaken for a pathologic narrowing. Physiologic narrowing along the course of the ureter also occurs at the ureteropelvic junction (UPJ) and where the ureter passes anterior to the iliac vessels.
The ureter is composed of two muscle layers, an inner longitudinal layer and an outer circular layer. In the wall of the distal ureter, near its insertion into the bladder, a third muscle layer is continuous with the detrusor muscle of the bladder. The mucosa of the ureter is a transitional epithelium. The ureter is surrounded by an outer fibrous layer, the adventitia, which is continuous with the renal capsule and the adventitia of the bladder. The wall of the ureter is usually less than 1 mm thick.
The abdominal portions of the ureters receive their blood supply from a ureteral branch of the renal artery and from branches arising from the aorta, retroperitoneal vessels, gonadal vessels, and iliac vessels. In the abdomen, the arterial branches supplying the ureter are located medial to the ureter, whereas in the pelvis the ureteral arteries arise lateral to the ureter from the iliac, gluteal, obturator, rectal, and vesical arteries. The supplying artery and draining veins travel in the connective tissue surrounding the ureter called the mesoureter. In most patients, an anastomosing plexus forms within the adventitia along the course of the ureter.
The veins and lymphatics follow the arterial supply, also forming an anastomosing plexus along the ureter. The veins of the ureter drain into the renal vein, gonadal vein, lumbar veins, iliac veins, and vesical veins. The lymphatics of the proximal ureter drain into the renal lymphatics, and those of the midureter drain into periaortic and common iliac lymph nodes. The lymphatics of the distal ureter drain into iliac and presacral lymph nodes and join with the lymphatics of the bladder.
The innervation of the ureter consists of sympathetic nerves from the aortic plexus and superior and inferior hypogastric plexus that course with the arterial supply to the connective tissue around the ureter. Pelvic splanchnic nerves from the sacral roots provide parasympathetic innervation to pelvic viscera.
Imaging
The appearance of strictures of the ureter depends on the cause. Intrinsic processes may obstruct the lumen, incite inflammation and edema in the wall of the ureter, or infiltrate the wall of the ureter. Extrinsic processes may cause narrowing of the ureter by compression, encasement, or infiltration. Strictures may be focal or multifocal.
Filling defects in the ureter may be intraluminal, mucosal, or submucosal. Intraluminal filling defects are often completely surrounded by contrast material. Mucosal and submucosal filling defects are intimately associated with the wall of the ureter and can be differentiated by evaluation of the relationship of the lesion to the adjacent ureteral wall, with mucosal lesions typically demonstrating acute angles and submucosal lesions demonstrating obtuse angles.
An infiltrative process usually causes an abrupt change in caliber of the ureter with an apple core–like appearance of the involved ureter. The narrowed segment of ureter demonstrates circumferential wall thickening and mucosal irregularity. This appearance is classically produced by neoplastic infiltration, but benign causes, such as irradiation, stone disease, and iatrogenic injury, can cause a similar appearance.
Encasement of the ureter often results in a gradual tapered contour and smooth mucosal surface. Alternatively, encasement of the ureter may result in a focal abrupt transition with a dilated proximal ureter and a narrow or normal-caliber ureter distally. This appearance on intravenous pyelography has been referred to as the “bullet and bodkin” sign, which can be seen with both benign and malignant conditions.
Many of these processes cause focal ureteral abnormalities; however, occasionally a multifocal process occurs. Multifocal involvement is more commonly seen with transitional cell carcinoma (TCC), tuberculosis (TB), metastases, and lymphadenopathy than with other causes of strictures.
Although certain features of the pattern of ureteral narrowing may indicate a benign or malignant cause, there is significant overlap in these characteristics and a definitive diagnosis is not always possible. Often, other associated imaging findings can help narrow the differential diagnosis, such as the location of the stricture, focal or multifocal involvement, deviation of the ureter, and involvement of the kidney, bladder, or other organ systems.
Radiography
Conventional abdominal radiography does not have a major role in imaging ureteral pathology. Excretory urography (EUG), although now largely replaced by computed tomography (CT) urography, is still performed in some centers as part of the initial evaluation of the upper urinary tract in patients with hematuria. EUG is a noninvasive test that was once the study of choice for evaluating the renal collecting system and ureters. Changes in the course and caliber of the ureters as well as filling defects and strictures are well demonstrated on EUG. Disadvantages of this modality include limited utility in patients with impaired renal function and poor soft tissue contrast.
In patients who do not excrete intravenously administered contrast agent in the urine owing to abnormal renal function, direct injection of a contrast medium into the renal collecting system or ureter can be performed with antegrade or retrograde pyelography. This allows evaluation of the collecting system and ureters and the opportunity for interventions such as stent placement. Retrograde urography requires cystoscopy for direct visualization of the ureteral orifice.
Computed Tomography
CT is the major imaging modality for evaluating the ureters. CT allows identification of certain characteristics and secondary findings that help to narrow the differential diagnosis of the cause of the ureteral stricture. In addition to identifying the site of narrowing and the extent of urothelial involvement, CT allows visualization of adjacent structures, which can help differentiate whether the stricture is due to an extrinsic or intrinsic process.
Magnetic Resonance Imaging
Magnetic resonance (MR) urography is not yet commonly used in the evaluation of ureteral disease and is primarily used as a problem-solving tool. The high T2 signal intensity of urine is advantageous in noncontrast images, particularly when the collecting system is dilated. Other techniques, such as intravenous hydration, diuretics, and gadolinium can enhance evaluation of the nondilated collecting system. However, image quality depends on patient cooperation and image acquisition often requires monitoring by a radiologist. Other limitations include motion artifacts from respiration and ureteral peristalsis, small field of view because of coil size, incomplete ureteral distention, and artifacts from adjacent bowel, particularly in 3.0-tesla MRI.
Given the absence of ionizing radiation, MR urography is useful in the evaluation of pediatric patients, particularly in the setting of congenital anomalies, in pregnant women with dilated collecting systems, and in those who cannot receive iodinated contrast media.
However, MRI is insensitive to the presence of calcification, and the sensitivity of MR urography for the detection of urothelial neoplasms has not yet been determined. When compared with CT, MRI offers better contrast resolution but CT has higher spatial resolution. Another consideration in patients with renal insufficiency is the risk for nephrogenic systemic fibrosis secondary to gadolinium versus contrast-induced nephropathy from iodinated contrast media.
Ultrasonography
Ultrasonography is not generally used to evaluate ureteral stricture but is useful to diagnose urinary obstruction. The ureters sometimes can be imaged at the site of obstruction, particularly in children. For example, a distal ureteral stone may be identified as a shadowing hyperechoic focus at the side of ureteral obstruction, or a retroperitoneal mass may be identified in the setting of retroperitoneal fibrosis. However, overlying bowel often obscures visualization of the midureter. Color Doppler imaging of the bladder may detect jets of urine originating at the ureteral orifices. If this finding is absent, high-grade or complete ureteral obstruction may be present.
Nuclear Medicine
Radionuclide examinations are generally not used for imaging of ureteral disease. Radionuclide studies can help quantify differences in renal function. In the setting of ureteral stricture and obstruction, diuretic renograms can be used to differentiate collecting system dilation from urinary obstruction.
Positron Emission Tomography with Computed Tomography
The role of positron emission tomography (PET) in evaluating urothelial lesions is limited because normal urinary excretion of fluorodeoxyglucose (FDG) limits the evaluation of the ureters, bladder, and adjacent structures. Occasionally, ureteral obstruction may be identified in patients undergoing PET for other processes.
Imaging Algorithm
The imaging algorithm depends on the clinical presentation of the individual patient. Of primary concern is the underlying renal function. Patients with poor renal function may not be well evaluated by EUG and CT urography. If obstructive nephropathy necessitates placement of nephrostomy tubes, antegrade urography can be performed.
When an intrinsic ureteral process is suspected, initial evaluation with ureteroscopy and retrograde ureterography may be helpful because tissue sampling can be obtained at the same time as the imaging. Alternatively, when an extrinsic process is suspected, cross-sectional imaging allows evaluation of tissues adjacent to the genitourinary system.
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“Balloon on a string” sign: Dilation of the renal collecting system and proximal ureter classically seen in UPJ obstruction
- •
“Bullet and bodkin” sign: Encasement of the ureter that causes an abrupt transition at the site of encasement with focal narrowing or normal-caliber ureter and proximal dilation
- •
“Hiked-up” or “purse-string” appearance of the renal pelvis: Results from retraction and stricture formation in patients with TB
- •
“Sawtooth” appearance of the ureter: Occurs in patients with TB involvement of the ureter characterized by luminal irregularity with areas of narrowing and dilation
- •
“Pipe stem” ureter: Occurs later in the course of tuberculous involvement of the ureter with the ureter rigid and straight
- •
“Corkscrew” or “beaded” ureter: Seen after healing and fibrosis in patients with tuberculous involvement of the ureter
- •
“Soft tissue rim” sign: Soft tissue surrounding a ureteral stone from edema within the wall of the ureter at the site of stone impaction ( Figure 67-1 )
Figure 67-1
Noncontrast axial computed tomography image in a patient with flank pain shows soft tissue thickening surrounding a ureteral calculus (arrow), the soft tissue rim sign.
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“Goblet” or “champagne glass” sign: Dilation of the ureter below the site of slowly growing lesions. Although classically seen with TCC, this finding also can be seen with metastases and endometriosis ( Figure 67-2 ).
Figure 67-2
Retrograde urography in a patient with transitional cell carcinoma of the ureter shows dilation of the ureter below the lesion, the goblet sign.
(Courtesy Isabel Yoder, MD.)
- •
Bergman’s sign: Coiling of the catheter within the dilated segment of ureter below the intraluminal lesion during retrograde catheterization
- •
Stipple sign: Foci of contrast agent trapped within the interstices of the projections of papillary transitional carcinoma
- •
Ureteral pseudodiverticulosis: Consists of small (<4 mm) outpouchings in the ureter and is associated with urothelial neoplasms
Imaging
The appearance of strictures of the ureter depends on the cause. Intrinsic processes may obstruct the lumen, incite inflammation and edema in the wall of the ureter, or infiltrate the wall of the ureter. Extrinsic processes may cause narrowing of the ureter by compression, encasement, or infiltration. Strictures may be focal or multifocal.
Filling defects in the ureter may be intraluminal, mucosal, or submucosal. Intraluminal filling defects are often completely surrounded by contrast material. Mucosal and submucosal filling defects are intimately associated with the wall of the ureter and can be differentiated by evaluation of the relationship of the lesion to the adjacent ureteral wall, with mucosal lesions typically demonstrating acute angles and submucosal lesions demonstrating obtuse angles.
An infiltrative process usually causes an abrupt change in caliber of the ureter with an apple core–like appearance of the involved ureter. The narrowed segment of ureter demonstrates circumferential wall thickening and mucosal irregularity. This appearance is classically produced by neoplastic infiltration, but benign causes, such as irradiation, stone disease, and iatrogenic injury, can cause a similar appearance.
Encasement of the ureter often results in a gradual tapered contour and smooth mucosal surface. Alternatively, encasement of the ureter may result in a focal abrupt transition with a dilated proximal ureter and a narrow or normal-caliber ureter distally. This appearance on intravenous pyelography has been referred to as the “bullet and bodkin” sign, which can be seen with both benign and malignant conditions.
Many of these processes cause focal ureteral abnormalities; however, occasionally a multifocal process occurs. Multifocal involvement is more commonly seen with transitional cell carcinoma (TCC), tuberculosis (TB), metastases, and lymphadenopathy than with other causes of strictures.
Although certain features of the pattern of ureteral narrowing may indicate a benign or malignant cause, there is significant overlap in these characteristics and a definitive diagnosis is not always possible. Often, other associated imaging findings can help narrow the differential diagnosis, such as the location of the stricture, focal or multifocal involvement, deviation of the ureter, and involvement of the kidney, bladder, or other organ systems.
Radiography
Conventional abdominal radiography does not have a major role in imaging ureteral pathology. Excretory urography (EUG), although now largely replaced by computed tomography (CT) urography, is still performed in some centers as part of the initial evaluation of the upper urinary tract in patients with hematuria. EUG is a noninvasive test that was once the study of choice for evaluating the renal collecting system and ureters. Changes in the course and caliber of the ureters as well as filling defects and strictures are well demonstrated on EUG. Disadvantages of this modality include limited utility in patients with impaired renal function and poor soft tissue contrast.
In patients who do not excrete intravenously administered contrast agent in the urine owing to abnormal renal function, direct injection of a contrast medium into the renal collecting system or ureter can be performed with antegrade or retrograde pyelography. This allows evaluation of the collecting system and ureters and the opportunity for interventions such as stent placement. Retrograde urography requires cystoscopy for direct visualization of the ureteral orifice.
Computed Tomography
CT is the major imaging modality for evaluating the ureters. CT allows identification of certain characteristics and secondary findings that help to narrow the differential diagnosis of the cause of the ureteral stricture. In addition to identifying the site of narrowing and the extent of urothelial involvement, CT allows visualization of adjacent structures, which can help differentiate whether the stricture is due to an extrinsic or intrinsic process.
Magnetic Resonance Imaging
Magnetic resonance (MR) urography is not yet commonly used in the evaluation of ureteral disease and is primarily used as a problem-solving tool. The high T2 signal intensity of urine is advantageous in noncontrast images, particularly when the collecting system is dilated. Other techniques, such as intravenous hydration, diuretics, and gadolinium can enhance evaluation of the nondilated collecting system. However, image quality depends on patient cooperation and image acquisition often requires monitoring by a radiologist. Other limitations include motion artifacts from respiration and ureteral peristalsis, small field of view because of coil size, incomplete ureteral distention, and artifacts from adjacent bowel, particularly in 3.0-tesla MRI.
Given the absence of ionizing radiation, MR urography is useful in the evaluation of pediatric patients, particularly in the setting of congenital anomalies, in pregnant women with dilated collecting systems, and in those who cannot receive iodinated contrast media.
However, MRI is insensitive to the presence of calcification, and the sensitivity of MR urography for the detection of urothelial neoplasms has not yet been determined. When compared with CT, MRI offers better contrast resolution but CT has higher spatial resolution. Another consideration in patients with renal insufficiency is the risk for nephrogenic systemic fibrosis secondary to gadolinium versus contrast-induced nephropathy from iodinated contrast media.
Ultrasonography
Ultrasonography is not generally used to evaluate ureteral stricture but is useful to diagnose urinary obstruction. The ureters sometimes can be imaged at the site of obstruction, particularly in children. For example, a distal ureteral stone may be identified as a shadowing hyperechoic focus at the side of ureteral obstruction, or a retroperitoneal mass may be identified in the setting of retroperitoneal fibrosis. However, overlying bowel often obscures visualization of the midureter. Color Doppler imaging of the bladder may detect jets of urine originating at the ureteral orifices. If this finding is absent, high-grade or complete ureteral obstruction may be present.
Nuclear Medicine
Radionuclide examinations are generally not used for imaging of ureteral disease. Radionuclide studies can help quantify differences in renal function. In the setting of ureteral stricture and obstruction, diuretic renograms can be used to differentiate collecting system dilation from urinary obstruction.
Positron Emission Tomography with Computed Tomography
The role of positron emission tomography (PET) in evaluating urothelial lesions is limited because normal urinary excretion of fluorodeoxyglucose (FDG) limits the evaluation of the ureters, bladder, and adjacent structures. Occasionally, ureteral obstruction may be identified in patients undergoing PET for other processes.
Imaging Algorithm
The imaging algorithm depends on the clinical presentation of the individual patient. Of primary concern is the underlying renal function. Patients with poor renal function may not be well evaluated by EUG and CT urography. If obstructive nephropathy necessitates placement of nephrostomy tubes, antegrade urography can be performed.
When an intrinsic ureteral process is suspected, initial evaluation with ureteroscopy and retrograde ureterography may be helpful because tissue sampling can be obtained at the same time as the imaging. Alternatively, when an extrinsic process is suspected, cross-sectional imaging allows evaluation of tissues adjacent to the genitourinary system.
- •
“Balloon on a string” sign: Dilation of the renal collecting system and proximal ureter classically seen in UPJ obstruction
- •
“Bullet and bodkin” sign: Encasement of the ureter that causes an abrupt transition at the site of encasement with focal narrowing or normal-caliber ureter and proximal dilation
- •
“Hiked-up” or “purse-string” appearance of the renal pelvis: Results from retraction and stricture formation in patients with TB
- •
“Sawtooth” appearance of the ureter: Occurs in patients with TB involvement of the ureter characterized by luminal irregularity with areas of narrowing and dilation
- •
“Pipe stem” ureter: Occurs later in the course of tuberculous involvement of the ureter with the ureter rigid and straight
- •
“Corkscrew” or “beaded” ureter: Seen after healing and fibrosis in patients with tuberculous involvement of the ureter
- •
“Soft tissue rim” sign: Soft tissue surrounding a ureteral stone from edema within the wall of the ureter at the site of stone impaction ( Figure 67-1 )
Figure 67-1
Noncontrast axial computed tomography image in a patient with flank pain shows soft tissue thickening surrounding a ureteral calculus (arrow), the soft tissue rim sign.
- •
“Goblet” or “champagne glass” sign: Dilation of the ureter below the site of slowly growing lesions. Although classically seen with TCC, this finding also can be seen with metastases and endometriosis ( Figure 67-2 ).
Figure 67-2
Retrograde urography in a patient with transitional cell carcinoma of the ureter shows dilation of the ureter below the lesion, the goblet sign.
(Courtesy Isabel Yoder, MD.)
- •
Bergman’s sign: Coiling of the catheter within the dilated segment of ureter below the intraluminal lesion during retrograde catheterization
- •
Stipple sign: Foci of contrast agent trapped within the interstices of the projections of papillary transitional carcinoma
- •
Ureteral pseudodiverticulosis: Consists of small (<4 mm) outpouchings in the ureter and is associated with urothelial neoplasms
Treatment
The management of strictures of the ureter depends on the cause of the stricture. Benign strictures are usually successfully managed with balloon dilation and stent placement. Endoureterotomy also has been helpful in management of benign strictures. Stent placement is helpful for both benign and malignant strictures. In some instances, surgery may be the only option. Placement of a percutaneous nephrostomy tube is often used to relieve obstruction and preserve renal function until a definitive intervention can be performed.
Congenital Disorders
Primary Megaureter
Primary megaureter is one of the causes of obstructive uropathy in infants and children. Boys are more commonly affected than girls, and in some patients’ primary megaureter can be bilateral. Associated anomalies in the contralateral kidney include renal agenesis and dysplasia.
When the ureter of a child is dilated to a diameter greater than 7 mm, it is considered a megaureter. A megaureter can be primary or secondary. There are three types of primary megaureter : obstructing, refluxing, and nonobstructing nonrefluxing.
In the obstructing type, an aperistaltic segment of ureter just proximal to the ureterovesical junction causes a functional obstruction with proximal dilation. Refluxing megaureter is due to an absent or short intravesical ureteral insertion or other abnormalities at the ureterovesical junction. The cause of nonobstructing nonrefluxing megaureter, which is the most common cause of primary megaureter in neonates, is unknown; it presents as ureteral dilation beginning just above the bladder.
Clinical Presentation
Primary megaureter is often detected by fetal screening. Other children may present with abdominal pain, urinary tract infections (UTIs), or fevers. Patients may have microscopic hematuria.
Pathophysiology
It has not been determined whether the cause is related to abnormal innervation, abnormal musculature, or abnormal connective tissue of the distal ureter.
Imaging
Imaging begins with ultrasonography of the kidneys and bladder to document the presence of obstruction. In primary obstructed megaureter, ultrasound imaging may demonstrate peristaltic waves in the dilated ureter and a persistently narrowed distal segment. Recently, the use of Doppler ultrasonography has shown potential in monitoring and potentially diagnosing obstruction. In adults, a resistive index greater than 0.7 may indicate obstruction. Although children may have slightly higher values normally, an elevated resistive index is also an indicator of obstruction in children.
Secondary causes of megaureter must be excluded before a diagnosis of primary megaureter can be made. A voiding cystourethrogram is usually performed to exclude reflux as a cause of megaureter.
Once it is determined that there is no vesicoureteral reflux, diuretic renography is performed to determine whether urinary obstruction is present. In an obstructed primary megaureter, the radiotracer will not wash out of the collecting system after diuretic administration. An excretory urogram may demonstrate a tortuous and dilated ureter proximal to the aperistaltic, normal-caliber distal segment ( Figure 67-3 ). The distal ureter is often more dilated than the proximal ureter and collecting system.
The nonrefluxing nonobstructed subtype can be distinguished from obstructed primary megaureter by evaluating the distal ureter. In the nonrefluxing nonobstructed subtype, the distal ureter is also dilated rather than normal in caliber.
Differential Diagnosis
The differential diagnosis of megaureter in a child consists of the various types of primary megaureter as well as secondary causes of megaureter. The list of secondary causes of megaureter is long and includes posterior urethral valves, urethral strictures, bladder abnormalities, and other causes of vesicoureteral reflux.
Treatment
Expectant management of the refluxing or nonobstructed nonrefluxing primary types of megaureter may result in improvement over time. In severe or persistent cases, surgery may be necessary.
Ureteropelvic Junction Obstruction
UPJ obstruction is a common cause of obstruction in newborns and is more common in males. Occasionally, adults can present with UPJ obstruction.
Clinical Presentation
Children with UPJ obstruction may present with intermittent abdominal pain, hematuria, or recurrent UTIs or be asymptomatic. Increasingly, patients are identified by prenatal screening. Adult patients may be asymptomatic or may experience episodes of urinary colic, particularly after ingesting large volumes of fluid or alcohol, known as Dietl’s crisis.
Pathophysiology
There are many causes of UPJ obstruction, and the cause varies depending on patient age and clinical history. UPJ obstruction may be functional or anatomic and is most commonly the result of a congenital smooth muscle abnormality that leads to abnormal peristalsis and focal ureteral narrowing. Congenital causes include ureteral hypoplasia, ureteral valves, abnormal insertion of the ureter into the renal pelvis, and crossing vessels. The obstruction may be due to scarring or may be related to prior surgery. Secondary causes include extrinsic tumors, iatrogenic injury, or extrinsic inflammation.
Imaging
Children with UPJ obstruction are usually evaluated with a voiding cystourethrogram and with diuretic renograms. Contrast-enhanced CT, although associated with a higher radiation dose, is helpful to evaluate structures adjacent to the ureter such as crossing vessels. A classic appearance of UPJ obstruction is the balloon on a string sign produced by dilation of the renal collecting system and proximal ureter ( Figure 67-4 ).
After repair, patients are followed using a combination of renal ultrasonography and diuretic renography.
Differential Diagnosis
The differential diagnosis of UPJ obstruction includes congenital causes such as ureteral hypoplasia, ureteral valves, and crossing vessels, as well as other intrinsic and extrinsic causes of ureteral strictures that happen to occur at the UPJ, such as stone disease, scarring, and urothelial and extrinsic neoplasms.
Treatment
Management of UPJ obstruction depends on the cause of the obstruction. Endoscopic intervention or surgical pyeloplasty can be performed. It is essential to identify extrinsic structures, such as crossing blood vessels that may cause UPJ obstruction and be injured during operative management.
Inflammatory Disorders
Pyeloureteritis Cystica
Pyeloureteritis cystica is a rare disease, first described by Morgagni in 1761. It occurs in the setting of chronic inflammation when degeneration of cells results in the formation of submucosal cysts. The disorder is classically found in patients 50 to 60 years of age. Some studies report that this disorder is more common in women.
Clinical Presentation
Patients are often asymptomatic but may have a history of UTIs, ureterolithiasis, or hematuria. Obstruction is not usually present.
Pathophysiology
Suburothelial cysts form as a result of chronic inflammation. The pathophysiology is unknown. Cyst rupture, chronic inflammation, or associated stone disease may result in hematuria.
Imaging
Pyeloureteritis cystica results in multiple round filling defects 2 to 3 mm in size that produce a scalloped appearance of the ureter. There is usually no associated obstruction. The process generally involves the proximal ureter and is more often unilateral than bilateral. The diagnosis is often made by intravenous pyelography, retrograde pyelography, or ureteroscopy ( Figure 67-5 ).
Differential Diagnosis
Pyeloureteritis cystica can appear similar to other submucosal or extrinsic processes such as malakoplakia, intramural hemorrhage, polyposis, urothelial tumors, and metastasis. However, the filling defects seen with intramural hemorrhage and malignant neoplasms are usually not as uniformly round as those seen with pyeloureteritis cystica.
Treatment
Historically, management included ureteral dilation, rupture of the cysts, and instillation of silver nitrate. Current therapy is targeted at treating the underlying inflammatory process and associated complications, such as ureterolithiasis. With management of the underlying infection, the cysts may resolve, but they often persist for many years. The disease has a benign course, with no malignant potential. Nonetheless, follow-up imaging is often performed to evaluate for resolution of the lesions and possible neoplasms such as papillomas.
Malakoplakia
Malakoplakia is a rare granulomatous disease that usually occurs in immunocompromised patients, especially those with diabetes mellitus. The disease is most often seen in middle-aged women and is associated with chronic UTIs. The bladder is more commonly involved than the ureter.
Clinical Presentation
Patients often have a history of chronic UTIs and may be immunocompromised. Symptoms can mimic TCC and include hematuria, flank pain, and dysuria.
Pathophysiology
Chronic inflammation results in the formation of subepithelial plaques. The plaques contain basophilic inclusions called Michaelis-Gutmann bodies, which represent fragments of incompletely digested bacteria.
Imaging
Malakoplakia usually causes multiple filling defects in the lower ureter. Circumferential ureteral involvement may cause a ureteral stricture with proximal hydroureter. The lesions are usually multiple and may cause a cobblestone appearance. The ureter may be dilated above the lesion.
Differential Diagnosis
Malakoplakia can be difficult to distinguish from other lesions that produce ureteral strictures and filling defects, including pyeloureteritis cystica and TCC. The diagnosis is established by biopsy.
Treatment
Therapy involves treating the underlying infection, although the disease may recur after therapy.
Infectious Disorders
Tuberculosis
The genitourinary tract is the second most common site of tuberculous involvement. Patients are usually older than 40 years of age when they become symptomatic.
Clinical Presentation
Clinical symptoms include hematuria, dysuria, and suprapubic pain. Confirmation of the diagnosis can be made by urinary culture and by examination of a tissue biopsy specimen.
Pathophysiology
Hematogenous dissemination of Mycobacterium tuberculosis results in renal infection, with subsequent spread to the ureters and bladder by descent in the urine. After the initial acute inflammatory phase of infection, healing results in fibrosis that can lead to ureteral strictures.
Imaging
Ureteral TB usually occurs in the setting of renal and bladder TB. Therefore, it is helpful to be familiar with the appearance of TB involving the kidneys and bladder. The classic appearance of tuberculous involvement of the kidneys is the “putty” kidney. Other findings include calyceal irregularity with a moth-eaten appearance that can coalesce, resulting in cavitation of the renal papilla. If the renal pelvis is involved, retraction and stricture formation may result in a hiked-up or purse-string appearance. Bladder involvement may result in a calcified bladder with small bladder volume known as a “thimble” bladder.
Strictures caused by TB usually involve the distal ureter with long-segment strictures, but occasionally short strictures may develop. The strictures may be multifocal, with an irregular or sawtooth appearance. After healing and fibrosis, the ureter may have a corkscrew or beaded appearance ( Figure 67-6 ). With more long-standing disease, the ureter may become rigid and straight. This appearance is often called a pipe stem ureter. Ureteral calcifications may be seen but are less common than renal calcification. Cross-sectional imaging may show ureteral wall thickening and enhancement.
Differential Diagnosis
Whenever multifocal ureteral strictures are seen, TB should be the main differential diagnosis. Other considerations include metastatic disease and lymphadenopathy.
Treatment
Systemic antituberculous chemotherapy is the mainstay of treatment. Strictures may require stenting or surgical management.
Schistosomiasis
Schistosomiasis is endemic in many parts of the world. It is estimated that 8% of the world population is infected. Schistosoma hematobium is the causative organism of urinary schistosomiasis.
Clinical Presentation
Patients may present with hematuria and dysuria and, later, with hydronephrosis, proteinuria, and renal dysfunction. Affected individuals are predisposed to secondary bacterial UTI and squamous cell carcinoma (SCC) of the urinary tract. Finding schistosome eggs in urine or feces makes the diagnosis. Malignancy secondary to schistosomiasis occurs most commonly in the bladder and rarely in the ureter.
Pathophysiology
The eggs of S. hematobium hatch in fresh water, and the organism grows in the intermediate host, the snail. The larvae enter the skin of humans who come in contact with the water, migrate to the lungs and liver, and, subsequently, when mature, migrate to the pelvis, including the walls of the genitourinary system, where they then deposit eggs. The eggs incite fibrosis and dystrophic calcification, which leads to stricture formation.
Imaging
Schistosomiasis of the ureter is seen in the presence of bladder involvement. Conventional radiography can show calcification of the bladder and ureter ( Figure 67-7 ). In addition to ureteral wall calcification, CT may demonstrate ureteral wall thickening. The distal ureter is most commonly involved. The ureter may be displaced cephalad and medially. Filling defects may be seen early in the course of the disease; however, as the disease progresses, multiple strictures form, resulting in a beaded appearance. If the ureterovesical junction is involved, vesicoureteral reflux can result.
