Discussion
Renal Cell Cancer
Renal cell cancer (RCC) accounts for 3% of cancers in adults and is the most common
kidney cancer.[1] Renal masses are usually characterized by pre- and postcontrast image acquisition
on computed tomography (CT)/magnetic resonance (MR) with postcontrast sequences acquired
at 20 to 70 seconds (corticomedullary phase), 80 to 120 seconds (nephrographic), and
delayed excretory phases.[2] Imaging techniques and tips with regard to pathological types of RCCs are summarized
in [Table 1].[3]
[4]
Table 1
Imaging tips with pathological subtypes of RCCs
|
Pathological types of renal masses
|
Imaging tips
|
|
Clear cell carcinoma—most common RCC
|
Highest peak of enhancement and washout on renal protocol CT, hypervascular on arterial
phase, intracellular fat with loss of signal on T1 out-of-phase images in up to 60%
cases.[2]
|
|
Papillary cell carcinoma (10–15%)
|
Mild enhancement, homogeneous and hypovascular, T2 low signal and loss of signal on
T1 in-phase images due to haemosiderin-laden macrophages on MRI[2]
[3]
|
|
Chromophobe (4–6%)[2]
|
Lower peak enhancement, no washout, best prognosis
|
|
Multilocular cystic neoplasm of low malignant potential
|
Multilocular cystic RCC—no classical appearance, imaging features range from Bosniak
2 to 4 category of cysts.
Multilocular cystic nephroma-perimenopausal women or in boys <5 years, benign, multiloculated
cystic mass[2]
|
|
TCC/urothelial cancer
|
Usually without pseudocapsule and renal contour distortion[2]
|
|
Collecting duct/medullary cancer (1%)
|
Infiltrative growth, medullary location (<1%), often aggressive presentation with
metastases.
Medullary carcinomas almost exclusive with sickle cell disease[2]
|
|
Tubulocystic RCC (introduced in 2004 WHO classification of renal tumors)[2]
|
Low-grade variant of collecting duct and Bellini duct carcinomas, similar to serous
cystadenomas on appearance with microcystic appearance evident on MR
|
Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging; RCC, renal
cell cancer; TCC, transitional cell carcinoma; WHO, World Health Organization.
Incidentally detected small renal masses and T1 stage tumors are being increasingly
detected with the use of cross-sectional imaging techniques. Small masses can be treated
with renal sparing treatments like partial nephrectomy (PN) besides radioablation
or cryotherapy to preserve renal function.[5]
Imaging tips: Nephrographic phase of renal protocol CT is ideal to evaluate small endophytic masses as these lesions
become more conspicuous against a background of homogeneously intensely enhancing
renal parenchyma and hence are easier to differentiate from the renal medulla.[4] Exact location of such small masses, distance from renal hilum, and vascular (presence
of accessory renal arteries) supply ([Fig. 1]) are important preoperative information for urologists which are easily confirmed
on multiplanar reconstructions.
Fig. 1 (A) Axial-enhanced CT images demonstrated a right renal interpolar lesion being considered
for partial nephrectomy, but close to renal hilum. The mass also shows calcification
inside (white arrow), which favors more toward RCC with osteometaplasia. (B) Complex cystic mass in right kidney lower pole with MIP image demonstrating multiple
accessory renal arteries (black arrows).
PN might be unsuitable even for small tumors if there is insufficient volume of postresection
remnant parenchyma to maintain proper organ function, hence documenting kidney size,
presence of cortical scarring, renal vein thrombosis, unfavorable tumor location (e.g.,
adherence to renal vessels), and status of contralateral kidney is an important preoperative
parameter.
Complicated renal cysts/cystic RCCs are categorized as per Bosniak classification on CT and the criteria have also been validated for use on MR imaging (MRI) as well.
The Bosniak category of a cystic lesion might be upgraded on MRI as MRI with superior
contrast resolution is likely to demonstrate more septations and nodularity.
Imaging tips: Few thin septations (<1 mm) observed in a cystic lesion would be a Bosniak 2 cyst
while multiple septations with nodularity a Bosniak 2F cyst.[6] The distinction between perceived and measurable enhancement in septal or wall nodularity is important as the latter group of cystic
lesions would classify as Bosniak 3 cysts. Bosniak 3 lesions have approximately 50%
chances of harboring potential malignancies and might require surgical excision. On
CT, an unequivocal increase in attenuation values by more than 20 HU after administration
of contrast is taken as a criterion for measurable enhancement. However, it is often
difficult to assess enhancement in small intrarenal masses owing to chances of pseudo-enhancement
which may be due to particular reconstruction algorithm and/or incorporated attenuation
correction techniques. MRI with gadolinium enhanced and subtraction imaging is especially
helpful in characterizing smaller complex lesions ([Fig. 2]).[2]
Fig. 2 (A) CT coronal reformatted images show a complex cystic mass (solid white arrow) with an apparently enhancing nodule (dashed arrow) in left kidney upper pole and another hypodense lesion more inferiorly (circle). (B) Contrast-enhanced MR images downstage the complex cyst in left kidney upper pole
(solid white arrow) with thin septation; however, the mural nodule (dashed arrow) turned out to be a separate proteinaceous cyst without any obvious enhancement.
The more inferior hypodense lesion is a solid enhancing mass more clearly demonstrated
(circle). This information was vital to the surgeon who could spare the cyst and perform
partial nephrectomy for the smaller solid lesion. CT, computed tomography; MR, magnetic
resonance.
Majority of Bosniak 2F and almost 50% of Bosniak 3 cysts are benign with very low
potential to metastasize and hence might be considered suitable for surveillance.[5]
[6] Surgical options are reconsidered in case of interval growth or appearance of solid
elements on follow-up imaging.
Multifocal or bilateral RCCs might be associated with hereditary kidney cancer syndromes like Von Hippel–Lindau disease ([Fig. 3]) or Lynch syndrome.
Fig. 3 VHL patient with multiple recurrent tumor and postpartial nephrectomy-related complication.
(A) Axial-enhanced CT shows a left renal mass (arrow) with pancreatic cysts (ellipse). (B) Postpartial nephrectomy noncontrast CT scan shows a hyperdense focus at the resection
site. (C) CT angiogram confirms this to be a small intrarenal pseudoaneurysm (arrow). (D) Postsurveillance CT scan 1 year later depicts a new intrarenal lesion. CT, computed
tomography; VHL, Von Hippel–Lindau disease.
Imaging tips: Patients with hereditary RCC wherever possible should be considered for MR surveillance to reduce burden of radiation exposure from frequent CT scans. Moreover, superior
contrast resolution of MRI allows better assessment of small cystic lesions. Assessment
and documentation of all suspicious lesions with size, interval growth, and other
visceral lesions are crucial for overall management of such patients.[7]
[8]
Multifocal or bilateral tumors might benefit from cryoablation or RFA (radiofrequency
ablation) to avoid repeated surgical interventions although cystic lesions are ideally
not candidates for ablative treatment.[8]
Appropriately timed nephron-sparing approaches are recommended with the exception of hereditary leiomyomatosis and RCC and succinate
dehydrogenase syndromes, for which surveillance is recommended until the largest solid
tumor reaches 3 cm in diameter, to reduce interventions.[8]
RCCs encountered in patients with end-stage kidney disease might also be multicentric
and bilateral. They are generally found in younger patients (mostly male) and tend
to be less aggressive.[9]
Imaging tips: Baseline split renal function should be estimated using renal scintigraphy preoperatively when renal function is
compromised, in patients with a solitary kidney, multiple or bilateral tumors, as
there might be preoperative chances of converting a PN to total nephrectomy in interpolar
tumors.[9]
Indeterminate masses on imaging like focal pyelonephritis or rheumatoid nodule can
be potential mimickers of RCC. Clinical correlation, prior imaging comparison, short
interval follow-up scans, and percutaneous biopsy are important considerations in
evaluating indeterminate renal masses. Renal masses with bulky lymphadenopathy below
the renal hilar level or bilateral perirenal soft tissue masses should raise suspicion
of secondary involvement by lymphoma or metastatic disease.
Imaging tips: CT or MRI allows accurate diagnosis of RCC in majority of solid masses, but cannot
reliably distinguish oncocytoma and fat-poor angiomyolipoma from malignant renal neoplasms.[2] Renal tumor biopsy is not routinely indicated preoperatively. However, image-guided percutaneous biopsy can provide a histological diagnosis of radiologically indeterminate renal masses,
and is ideal for candidates before ablative treatments, on active surveillance, and
to select the most suitable treatment strategy in the setting of metastatic disease.[10]
Locally advanced RCCs are T3 and T4 tumors.[1]
[5] Updated TNM (TNM Classification of Malignant Tumors) classification reclassified
RCCs with invasion of renal sinus fat and involvement of branch renal veins as stage T3a. Centrally located small RCCs (<4 cm) with renal sinus fat or calyceal
invasion should be correctly staged as T3 tumor to prevent inadequate treatment which
might otherwise result in local recurrent disease or metastasis.[1]
Tumor thrombosis in renal vein or inferior vena cava (IVC) in RCC patients is a significant adverse prognostic factor.
Imaging tips: Knowledge of IVC involvement by tumor thrombus is essential for preoperative planning. MRI with its higher sensitivity and specificity
is superior to CT for evaluating the exact extent of tumor thrombus in doubtful cases.[11]
[12] Distinguishing tumoral clot extension along the renal vein from direct invasion
of the IVC wall by RCC is important as the later upstages to T3c and requires more
extensive surgery and preoperative planning.[12]
In patients with metastatic disease, appropriate documentation of all tumoral deposits
is critical for successful outcome of surgical debulking or cytoreductive nephrectomy ([Fig. 4]). This includes patients with primary tumor in place and single or oligo-metastatic
resectable disease, for palliative treatment options, and to control hematuria.[13]
Fig. 4 (A) Axial CT in a case of right renal RCC (*) with pancreatic (arrow) and small-bowel mesenteric (circle) metastases. (B) Not a candidate for surgical debulking.
Imaging tips: RCC metastases are often hypervascular, more easily evident on arterial phases, and can be masked on portal venous phases.[14] For RCCs with loco-regional nodal metastasis, a retrocaval node might necessitate preoperative IVC mobilization to achieve successful nodal excision.[15] Radiologists should be aware of pseudo-progression changes on surveillance scans for metastatic RCCs treated with immunotherapeutic agents and
report findings with knowledge of iRECIST criteria. Correct assessment of treatment
response and true progression of disease can only be possible after evaluating interim
and follow-up scans with background clinical information as there can be deceptive
increase in size of tumoral deposits on initial scan owing to immune response.[16]
Recurrent disease and higher percentage of positive surgical margins are more commonly
associated with PN compared with radical nephrectomy and even higher with tumors treated
by thermal ablation, close to 12%.[1] After nephron-sparing, treatment relapses can be seen in the treated kidney, renal
fossa, as venous tumor thrombus, in ipsilateral adrenal gland, and regional lymph
nodes ([Fig. 5]).
Fig. 5 (A) Axial-enhanced CT images show some soft tissue (arrow) at the site of previous partial nephrectomy (PN) with mild thickening along right
peritoneal reflection (circle). (B) On follow-up scan interval growth in size of soft tissue nodule at the site of PN
in consistent with local recurrence.
Imaging tips: Tumor recurrence affecting the regional lymph nodes, peritoneum, parietes at port
site, or ipsilateral adrenal gland should be interpreted as metastatic spread.[17]
Imaging surveillance postsurgery: There is no universally standardized guidelines
for surveillance of RCCs following surgery; however, follow-up criteria usually depend
on Fuhrman's grading system of renal cancers on histology. Higher grade tumors require more stringent follow-up, whereas lower grade cancers
like chromophobe tumors are eligible for low-risk follow-up.[18] Usually a staging CT of the chest and abdomen is performed for high or intermediate
risk cases at 6 months and thereafter annually till 3 years and then every 2 years.
CT is done for follow-up at 1 year and then every 2 yearly in low-risk cases.
Imaging postablation: Residual tumor post-RFA is usually demonstrated as any soft tissue enhancement >10 HU on day 7 scan.
A noncontrast scan should be included, as it is useful to differentiate residual tumors
from blood degradation products. Ideally, complete tumor ablation is achieved if there is nonenhancement at the site of previous tumor with attenuation
<10 HU. Postablative halo at the penumbral repair zone might show some enhancement
due to an inflammatory reaction at variable duration but usually distinguishable from
solid residual tumor on day 7 scan. Further follow-up scans can be subsequently acquired
at 6 monthly intervals following RFA treatment.[1]
[19] RFA-treated tumors demonstrate variable degree of involution, over a time period,
and radiologists should primarily look for enhancing soft tissue to check for recurrences
rather than size reduction.[19]
An imaging algorithm of various renal masses with corresponding management strategies
is summarized in [Fig. 6].
Fig. 6 Imaging algorithm and management strategies in accordance with type of renal mass
on cross-sectional imaging.
Urothelial Cancers
Urothelial cancers are a heterogeneous spectrum of malignant cancers that can have
their origin from any part of the urinary tract from renal pelvis to proximal urethra.
While most urothelial cancers are of bladder origin and only 5 to 10% involve upper
tracts, there is a notable difference in behavior, management, and prognosis between
upper and lower tract cancers.[20] These cancers are notorious for multicentricity and metachronous presentation across
the entire urinary tract.
Upper tract urothelial cancer (UTUC): CT urography (CTU) is the imaging modality of
choice for evaluating and staging upper-tract transitional cell carcinomas (TCCs).
There is a high degree of variation in practice with regard to acquisition of CTUs
across several centers, although split bolus, dual-phase CTU is the standard practice
in most trusts in England. MR urography has no current role in staging UTUC, however,
has its applications for patients allergic to iodinated contrast agents, obstructed
system, and in relatively younger individuals, pregnant patients. Retrograde pyelography
is reserved for patients with renal insufficiency and hence poor excretion on CTU
or to further characterize CTU findings while antegrade nephrotomograms are attempted
in patients with an obstructed collecting system and difficult-to-catheterize ureteric
orifices, pre-existing urinary diversions.[20]
Imaging tips: Triple-phase CTU for higher grade UTUCs by some studies with urothelial phase images
at 60 seconds has added a usefulness technique in detecting flat lesions over combined
nephrographic–excretory phase images acquired in split bolus.[21]
Ureteroscopic biopsy cannot accurately determine depth of upper tract wall invasion,
hence preoperative cross-sectional imaging has a central role in deciding nephroureterectomy
over kidney sparing surgery.[21]
[22]
UTUCs can have a wide spectrum of appearances on CTU ranging from focal filling defects,
wall enhancements, en plaque or papillary lesions, to frankly infiltrative or invasive
tumors.
Honda et al[21] classified ureteric tumors on CTU in mainly six patterns to differentiate T2 or
lower stage tumors from T3 or higher stage groups:
-
Circumferential wall thickening with no spiculation.
-
Circumferential wall thickening with spiculation.
-
Intraluminal mass with smooth external surface and no spiculation.
-
Asymmetric circumferential wall thickening with spiculation.
-
Intraluminal mass with smooth external surface and spiculation.
-
Intraluminal mass with irregular external surface and spiculation.
Patterns 1 to 3 have been associated with T2 or lower stage tumors, whereas patterns
4 to 6 have been associated with T3 or higher stage tumors ([Fig. 7]) with reported sensitivity and specificity for the latter group on preoperative
CTU being 87.5 and 92.9%, respectively.[21]
Fig. 7 (A) Axial and reformatted coronal CT images: UTUC (pattern 1): circumferential smooth
wall urothelial thickening (arrow) with no spiculation. (B) Axial CT images: UTUC (pattern 2): circumferential wall thickening of right distal
ureter (arrow) with spiculation. (C) Axial CT urogram images: UTUC (pattern 3): small intraluminal soft tissue filling
defect in left distal ureter (arrow) with smooth external surface and no spiculation. (D) Axial CT images reveal UTUC (pattern 4): asymmetric nodular wall thickening in left
proximal ureter anteriorly (arrow) with spiculation. (E) Axial CT images: UTUC (pattern 5): intraluminal mass with smooth external surface.
(F) Axial CT images: UTUC (pattern 6): intraluminal mass with irregular external surface
and speculation (arrow) in left proximal ureter. CT, computed tomography; UTUC, upper tract urothelial cancer.
Imaging tips: Knowledge of lesion location, distortion in normal anatomy, thickness of the urinary
wall, and tumor multiplicity in CTU report would highly aid the urologist before ureteropyeloscopy
and biopsy. Mass-like urothelial cancers in renal pelvis need differentiating from
RCCs with secondary infiltration to renal calyces on imaging owing to their completely
different management. While RCC infiltrating into renal pelvis would be a stage 3
tumor requiring nephrectomy, an invasive urothelial cancer of renal pelvic origin
would mandate radical nephroureterectomy (RNU). Distortion of renal contour, more
distinct demarcation between tumor and renal parenchyma, and pseudo-capsule (associated
with expansive growth of RCC compared with infiltrative growth of TCC) might be helpful,
although in doubtful cases one should seek help of MRI or percutaneous biopsy[23]
[24] ([Fig. 8]).
Fig. 8 (A) Axial CT images in a different case: central RCC (arrows), invading renal sinus, T3 tumor is a close differential for mass like TCC. (B) Mass like TCC with ureteric involvement—reniform shape of kidney maintained—important
to differentiate from RCC. CT, computed tomography; RCC, renal cell cancer; TCC, transitional
cell carcinoma.
Hydronephrosis, lymph nodal disease at the time of presentation, tumors >2 cm in size,
and multifocal disease usually determine high-risk upper tract cancers with poor prognosis.[20]
[21] MR diffusion-weighted imaging has a role in detecting higher cellularity and aggressive
tumors and hence predicting prognosis. Some studies have also documented the role
of T1 fat-suppressed post-gadolinium images in differentiating T3 and higher stage
ureteric tumors (irregular or disruptive enhancing rim) from T2 or lower stage tumors
(smooth rim enhancement).[21]
[25]
Majority of high-risk UTUCs are treated with RNU with bladder cuff excision as the
standard treatment. Bladder cuff and distal ureteric excision alongside nephrectomy
is regularly considered beneficial because of high incidence of recurrence in the
distal ureter. However, excision of distal ureter might be precluded in patients with
chronic fibrotic or adhesive disease process in pelvis from prior interventions or
complex surgery. A common site of recurrence in such cases is the distal ureteric
stump.[26]
[27]
There is a role of neoadjuvant chemotherapy for T3 or higher stage UTUC tumors considering
evidence of increased disease-free survival in such group of patients. Hence, accurate
T staging on preoperative CTU is important although CTU is limited in the assessment
of lower than T2-stage tumors.[21]
[26]
Benign conditions which might pose as differentials of UTUC on imaging are inflammatory
strictures and ureteric amyloidosis. There are several extra-luminal pathologies like
retroperitoneal fibrosis, lymphoma or IgG4 disease, and endometriosis, which can involve
ureters extrinsically and can mimic urothelial cancers.
Imaging tips: Benign strictures are usually long segmental. Ureteric amyloidosis demonstrates
T2 low signal on MR images. Radiological clues like extrinsic soft tissue encasing
ureters, bilateral involvement, medialization of ureters might be helpful in classic
presentation of retroperitoneal fibrosis ([Fig. 9]); however, differentiating atypical presentations of such benign entities from malignant
strictures can be challenging at times and correlation with urinary cytology, ureteroscopic,
or laparoscopic biopsy and follow-up imaging should be sought for in doubtful cases.[21]
[25]
Fig. 9 (A) Coronal reformatted CT images show soft tissue lesion involving right distal ureter
(thin arrows) extending to involve right-sided iliac vessels (block arrows). (B) Axial CT images demonstrate soft tissue thickening (circle) encompassing ureters and retroperitoneal vessels. (C) T2W coronal MR images in a different case show left distal ureteric stricture (arrow) with endometriotic deposits (oval) seen on left ovary. (D) T2W axial MR—endometriosis with secondary ureteric stricture confirmed on laparoscopic
biopsy. CT, computed tomography; T2W, T2 weighted.
Recurrent disease: The rate of bladder recurrence after RNU for UTUC is up to 50%, while recurrence
in the contralateral collecting system is 2 to 6%. Bladder recurrence is however not
considered as a distant recurrence.[25]
Imaging surveillance: Follow-up is more frequent and stricter in patients with invasive cancers and who
have undergone kidney-sparing treatment compared with RNU. Surveillance includes cystoscopy,
urinary cytology, and upper tract assessment by CTU. Usually CTU is recommended 6
monthly for the initial 2 years and then annually for another 3 years. For noninvasive
cancers managed with radical surgery, CTU is done annually.[20]
[26]
Urothelial carcinomas of bladder origin (UCBs): Approximately 90 percent of bladder
cancers are of urothelial origin. Cystoscopy and biopsy at presentation are invaluable
for classifying bladder tumors and guiding further management.[20] Imaging depends on biopsy findings and treatment intent.
Tumor Subtypes
Nonmuscle invasive bladder cancers constitute majority of UCBs, are usually multifocal,
low-grade lesions, but with a higher recurrence rate. However, superficial noninvasive
diseases can recur and transform to higher grade muscle invasive bladder cancer (MIBC)
and are often considered precursors to higher grade cancers and might even coexist.
Carcinoma in situ (CIS) is a flat, high-grade, noninvasive, multifocal urothelial
carcinoma which can be missed or misinterpreted as an inflammatory lesion during cystoscopy
if not biopsied.[28]
Radiology has a limited role in superficial disease (Ta/T1 tumors) which is usually
managed by a repeat complete transurethral resection (TURBT [transurethral resection
of a bladder tumor]) 2 to 6 weeks after initial cystoscopic resection and biopsy.
Superficial lesions in bladder if macroscopically evident on cross-sectional imaging
([Fig. 10a]) can present as either polypoidal filling defect, en-plaque lesions, or focal thickening.
Second resection is often required for larger tumors (>1 cm) or high-grade superficial
tumors with residual disease observed in 33 to 51% cases.[29]
[30]
Fig. 10 Bladder tumor imaging subtypes: (A) T2W axial images demonstrate the superficial lesion in bladder, clearly demarcated
from the hypointense mural layer. (B) Axial T2WMR imaging shows muscle invasive tumor with extravesical spread and infiltration
to right obturator internus. (C) Axial T2W MR images demonstrate T2 intermediate signal tumor in bladder diverticulum
(arrow). MR, magnetic resonance; T2W, T2 weighted.
Imaging tips: Patients with proven invasive disease on biopsy and considered fit for radical treatment
are usually staged locally with MRI. The main aim of imaging is to assess muscle invasive
T3 tumor or extravesical tumor spread ([Fig. 10b]). T2 weighted (T2W) sequence on MRI helps to appreciate the hypointense detrusor
muscle line in contrast to T2 intermediate signal tumor. Dynamic contrast enhanced
imaging exploits differential enhancement of early-enhancing bladder tumors from late-enhancing
mural layer (enhances late at 60 seconds) in assessing mural invasion. CT is limited
in T-staging of bladder tumors and primarily limited to exclude overt extravesical
disease, and nodal or distant metastatic lesions.[31]
[32]
Baseline CTU to assess ureteric involvement prior to cystectomy offered as a routine
investigation for bladder cancer diagnosed on cystoscopy is of questionable significance.
It is usually reserved for high-risk tumors (grade 3, multifocal superficial tumors
with >3 cm in size, CIS, recurrent or MIBC) because incidence of upper tract involvement
in bladder cancer is significantly low (1.8%) but increases to 7.5% for tumors close
to trigone.[33]
[34] Ureteroscopy is considered in cases suspicion of ureteric involvement on imaging.
Invasive diseases limited to bladder or with minimal extravesical spread are managed
by radical cystectomy or radiotherapy. However, radical cystectomy is also considered
for high grade, recurrent, BCG (bacillus Calmette-Guérin) refractory or large superficial
tumors, unusual urothelial histology, and also for CIS.[35]
Tumors in bladder diverticulae have a reported incidence of 2 to 10%.[28] Diverticulae are considered as risk factors to develop tumor due to urinary stasis.
Tumor within a narrow-necked diverticulum can be missed on cystoscopy but easily picked
up on MRI ([Fig. 10c]).
Imaging tips: Cancer in bladder diverticulum is usually an invasive T3 disease with increased
risk for extravesical spread as the muscle layer is absent in bladder diverticulae.[28]
Advanced and metastatic tumors: Advanced T4 bladder cancers with involvement of prostate,
vagina, and recto-sigmoid might present with fistulation, and at times are considered
for anterior or complete pelvic exenteration. Extravesical spread of tumor to the
abdominal or pelvic wall represents T4b disease.[31]
[36]
Imaging tips: Radiologists should document clear extensions of advanced bladder masses as tumors
invading to sacrosciatic notches, lumbosacral plexus, or tumor/nodes encasing external
iliac vessels or extending above the level of true pelvis are not candidates for pelvic
exenterations.[35] Sigmoid tumors might as well fistulate in bladder dome and appearances might be
confusing on MRI with regard to the primary origin of tumor. In ambiguous cases, colonoscopy
is recommended before definitive surgery as nonbulky fistulating sigmoid tumors can
be managed by less extensive surgery like partial cystectomy and segmental anterior
resection of sigmoid rather than pelvic exenteration.[36]
[37]
Currently, there is no evidence supporting routine use of positron emission tomography
(PET) in nodal staging of UBC. Nodes above the level of aortic bifurcation are considered
as metastatic diseases, and are generally more commonly seen with tumors close to
the bladder trigone.[38] Multiple regional nodal metastases in true pelvis (N2) and common iliac nodes (N3),
if detected on preoperative MRI, preclude orthotopic reconstruction of neo-bladder.[39]
Local recurrence can take place as soft-tissues at the original surgical site in the
bladder bed or as nodal recurrence in the area of lymph node dissection. UTUCs occur
in 1.8 to 6.0% of cases and represent the most common sites of late recurrence. Distant
disease seen in up to 50% of patients treated with cystectomy for MIBC involves lymph
nodes, lungs, liver, and bones.[40]
Imaging tips: Patients with multifocal disease, MIBC with CIS, or positive ureteral margins are
at higher risk of developing late (>3 years) upper tract disease. Monitoring of the
upper tracts with CTU for a longer period is mandatory in such cases.[40]
Imaging postsurgery: Postinflammatory changes as bladder wall thickening and extravesical
fat stranding can often be seen on a CT/MRI, acquired within short-interval post-TURBT
([Fig. 11]). Radiologists reading such postintervention scans should be cautious as not to
interpret such postbiopsy changes as a T3 disease. A short-interval follow-up scan
might often be helpful to clear dilemma in such cases.[20]
Fig. 11 Post TURBT CT urogram 2 weeks for superficial papillary tumor with preserved muscle
on biopsy. (A) Axial image shows extensive bladder wall thickening, perivesical stranding and a
suspicious right internal iliac lymph node (arrow). (B) On follow-up CTU after 3 months, although bladder inflammatory changes resolve,
right internal iliac node (arrow) persists. (C) The node (arrow) demonstrates stable appearances with no significant uptake on a follow-up PET CT
and no other evidence of disease elsewhere, hence considered a reactive node. CT,
computed tomography; CTU, computed tomography urography; PET, positron emission tomography;
TURBT, transurethral resection of a bladder tumor.
Ureteroileal anastomotic junction should be evaluated carefully for recurrent lesions
in cases with urinary diversion and ileal conduit ([Fig. 12a, b]). Patients with a history of recurrent urinary stent exchange following urinary
diversion might show inflammatory thickening of upper tracts and a follow-up scan
or ureteroscopic biopsy might avoid misinterpreting such inflammatory thickening as
a recurrent disease.[40]
[41]
Fig. 12 (A) Postradical cystectomy coronal CTU images in a different patient: recurrent soft
tissue (arrow) seen at ureteroileal anastomosis on postcystectomy surveillance scan. (B) Sagittal CTU maximum intensity projection images. CTU, computed tomography urography.
Mild prominence of collecting systems following cystectomy and incontinent diversions
after removal of stents might persist for variable periods of time; however, significant
pelvicaliectasis on surveillance scans might be an early indicator of recurrent disease.
However, less sinister reasons like parastomal hernia at the urostomy site, causing
extrinsic compression, or kinking of the stoma should be sought for.[39]
[41]
Imaging surveillance: Current consensus is to follow up patients postdefinitive management for four-monthly
CT scans during the first year, six-monthly until the third year, and annual imaging
thereafter. More stringent follow-up could be considered in patients with locally
advanced disease or lymph node involvement.[42]
An imaging algorithm of various types of urothelial cancers and management approaches
is summarized in [Fig. 13].
Fig. 13 Imaging algorithm and management strategies for urothelial cancers.
In conclusion, cancer care pathways continue to evolve with emerging imaging options,
and diagnostic and management strategies become more complex. Knowledge about complex
uro-oncology case scenarios, guidelines, pitfalls, and expected complications would
enable radiologists to deliver pragmatic opinions and contribute toward decision making
in multidisciplinary meetings.
