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72 |
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Practical Urology: EssEntial PrinciPlEs and PracticE |
dysfunction, particularly in those with diabetic |
RCC |
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nephropathy, the administration of iodinated |
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contrast can lead to severe deterioration in |
Renal cell carcinoma (RCC) is the most common |
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renal function. In order to minimize the risk of |
malignant renal mass and accounts for 2–3% of |
|
contrast nephrotoxicity, the serum creatinine |
all human malignancies. |
|
should be checked before administration of |
Clinically, RCCs are often silent but may pres- |
|
iodine contrast in patients with suspected renal |
ent with hematuria, flank pain, or a loin mass. |
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impairment. Precautions should be taken in |
Increasingly RCCs are being detected as inci- |
|
high-risk patients to reduce the likelihood of |
dental findings during imaging for other |
|
contrast nephropathy. These include ensuring |
reasons. |
|
adequate hydration and the cessation of |
Renal carcinoma tends to metastasize pri- |
|
nephrotoxic drugs prior to administration of |
marily to regional lymph nodes,lung,and bones. |
|
contrast.4 |
Metastases to liver, pancreas, and brain are less |
|
Caution is also advisable in diabetic patients |
common. |
|
taking Metformin undergoing contrast- |
On ultrasound renal cell carcinomas can be |
|
enhanced studies. Metformin is excreted by |
echogenic, iso echoic, or echopoor relative to the |
|
the kidneys and in patients with renal dysfunc- |
surrounding renal parenchyma and are usually |
|
tion the administration of iodinated contrast |
associated with distortion of the normal renal |
|
leads to a small increase in the risk of lactic |
architecture (Fig. 5.3). Sensitivity for tumor |
|
acidosis. The serum creatinine should there- |
detection is low for tumors less than 2 cm in |
|
fore be checked in these patients and Metformin |
diameter. |
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should be withdrawn in those with renal |
CT is the preferred imaging modality for |
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impairment prior to the administration of |
renal tumor characterization and staging.6 The |
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contrast. Careful subsequent monitoring of the |
TNM staging of renal carcinoma is outlined in |
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renal function should be performed until the |
Table 5.1. The majority of renal cell carcinomas |
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administration of Metformin can be recom- |
are well-defined, rounded, or lobulated masses |
|
menced safely. |
which enhance heterogeneously, following con- |
|
Gadolinium-based contrast agents are com- |
trast injection (Fig. 5.4). Regional retroperito- |
|
monly used in MRI examinations. Allergic reac- |
neal lymph nodes larger than 8 mm are regarded |
|
tions to Gadolinium are relatively rare however |
as suspicious. Tumor growth into the ipsilateral |
|
recent reports suggests a link between certain |
renal vein is a feature of renal cell carcinoma |
|
Gadolinium based contrast agents and nephro- |
with occasional propagation into the IVC. |
|
genic systemic fibrosis (NSF). Clinical features of |
Pulmonary and skeletal metastases (usually of |
|
NSF include pain, pruritis and erythema later |
the lytic type) are well demonstrated by CT. |
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followed by thickening of the skin and subcuta- |
|
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neous tissues as well as life threatening fibrosis of |
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the internal organs. Patients with end stage renal |
|
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failure (GFR < 30 mL/min) are at higher risk of |
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developing NSF and implicated Gadolinium- |
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based contrast agents should not be used in this |
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patient subgroup.5 |
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Renal and Upper Tract Tumors
Renal masses can be benign or malignant. The most commonly encountered malignant renal mass is renal cell carcinoma. Other malignant tumors include transitional cell carcinoma, lymphoma, renal liposarcoma, and metastases. Benign renal tumors include oncocytoma and angiomyolipoma.
Figure 5.3. Ultrasound demonstrates a well-circumscribed echopoor mass arising from the midpole of left kidney in keeping with a renal cell carcinoma.
73
imaging of thE UPPEr tracts
Table 5.1. tnm staging of renal cell carcinoma
Primary tumor (t) |
|
t1 |
tumor < 7 cm mass confined |
|
to kidney |
t1a |
tumor < 4 cm |
t1b |
tumor >4–7 cm |
t2 |
tumor > 7 cm mass confined |
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to kidney |
t3a |
tumor invasion into adrenal |
|
gland or perinephric fat but |
|
not beyond gerotas fascia |
t3b |
tumor invasion into renal vein |
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or vena cava below |
|
diaphragm |
t3c |
tumor invasion into vena cava |
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above diaphragm |
t4 |
tumor invasion beyond gerotas |
|
fascia |
regional nodes (n) |
|
nX |
regional lymph nodes cannot |
|
be assessed |
n0 |
no regional node metastasis |
n1 |
metastasis in a single regional |
|
node |
n2 |
metastases in more than one |
|
regional node |
metastases (m) |
|
mX |
distant metastasis cannot be |
|
assessed |
m0 |
no distant metastasis |
m1 |
distant metastasis |
Figure 5.4. contrast ct shows a heterogenously enhancing lobulated mass arising from the right kidney indicating a renal cell carcinoma.
Benign Renal Tumors
The most frequently occurring benign renal tumors are oncocytoma and angiomyolipoma. Oncocytoma appears as a well defined enhancing mass, the presence of a central ‘scar’ is a well recognised feature but is not specific enough to allow differentiation from renal cell carcinoma.
Angiomyolipoma (AML) is a benign renal tumor which consists of fat, muscle, and blood vessels. Multiple bilateral AMLs are associated with Tuberose Sclerosis. Angiomyolipomas are frequently seen as incidental lesions on ultrasound appearing as well-defined echogenic lesions. The presence of a fat containing renal mass on CT or MRI is considered diagnostic for AML (Fig. 5.5). Larger AMLs can undergo hemorrhage, and prophylactic embolization is a therapeutic option for lesions greater than 4 cm in diameter.
MRI is as sensitive as contrast-enhanced CT for the detection of renal tumors and is useful in the characterization of renal masses in those patients who cannot receive iodinated contrast media. MRI has an important role in the staging of advanced renal malignancy in defining the extent of inferior vena cava tumor thrombus extension associated with T3 disease6 (Fig. 5.6). MRI is preferable to CT in younger patients requiring repeated studies to follow up renal masses (e.g., patients with Von Hippel Lindau disease) in order to avoid repeated radiation exposure.
Transitional Cell Carcinoma
Transitional Cell Carcinomas (TCC) arise from the urothelium of the urinary tract. The commonest site is the urinary bladder, followed by the renal pelvis and ureter.
Clinically the commonest manifestation of TCC is microscopic or macroscopic hematuria. Flank pain may be due to “clot colic.” Tumors occurring at or below the level of the renal pelvis may cause hydronephrosis due to renal obstruction.
74
Practical Urology: EssEntial PrinciPlEs and PracticE
Figure 5.5. ct shows a large mass arising anteriorly from the |
Figure 5.7. iVU demonstrates extensive filling defect within the |
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left kidney. abundant fat within the mass is consistent with |
||
left pelvicalyceal system in keeping with transitional cell |
||
angiomyolipoma. |
||
carcinoma. |
||
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|
Figure 5.8. iVU demonstrates extensive lobulated filling defect |
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(arrow) within the distal right ureter consistent with transitional |
|
cell carcinoma. |
Figure 5.6. t3c renal tumor: mri scan demonstrates tumor |
“amputated calyx” or extend into the whole of |
thrombus in the right renal vein and supra diaphragmatic iVc |
the renal pelvis with extension into one or more |
extension into the right atrium (arrows). |
calyces. Ureteric tumors can expand the ureteric |
|
lumen and be surrounded by contrast, produc- |
Urinary cytology may be positive but is an |
ing the “goblet sign” (Fig. 5.8). |
Other causes of filling defects can mimic TCC |
|
unreliable method for TCC detection. |
and may therefore lead to diagnostic uncer- |
TCCs appear as solitary or multifocal filling |
tainty. Commonly encountered causes are listed |
defects on IVU (Fig. 5.7). The appearances can |
in Table 5.2, including pyeloureteritis cystica |
be subtle with only slight irregularity of the |
(Fig. 5.9). |
mucosa. Larger tumors can occupy a complete |
Small tumors are not usually detectable on |
calyx resulting in the appearance of an |
ultrasound. Larger TCCs can be identified as a |
75
imaging of thE UPPEr tracts
Table 5.2. nonmalignant causes of upper tract filling defects
thrombus
sloughed papilla
radiolucent calculus
Pyeloureteritis cystica
fungus ball
Figure 5.9. Pyeloureteritis cystica, submucosal cyst formation seen in association with chronic urinary tract infections. iVU shows multiple rounded filling defects (arrows) within the left renal pelvis and ureters in a duplex collecting system.
relatively echopoor mass within a calyx or renal pelvis (Fig. 5.10). Associated hydronephrosis may be a feature in obstructing lesions.
On CT,the diagnosis is made by the demonstration of an enhancing soft tissue mass within the renalcollectingsystemoruretericlumen(Figs.5.11 and 5.12). CT can usually distinguish between TCC and filling defects due to benign causes such as lucent stone and thrombus and is often used to clarify equivocal ultrasound or IVU appearances.
TCCs can enlarge and invade into renal parenchyma. More centrally situated tumors can invade beyond pelvic wall into the peripelvic fat and into adjacent retroperitoneal structures.7
Renal and proximal ureteric TCC typically spreads to para-aortic and paracaval lymph nodes whilst distal ureteric tumors spread to iliac and obturator nodes.
Figure 5.10. Ultrasound demonstrates a mass in the renal pelvis (arrow) causing slight hydronephrosis in keeping with transitional cell carcinoma.
Figure 5.11. ct demonstrates a soft tissue mass on the left renal pelvis. the tumor occupies the renal sinus and is demonstrating to be extending into the renal parenchyma indicating invasive transitional cell carcinoma.
Retrograde studies are useful in those patients with suspicion of upper tract TCCs where noninvasive imaging studies have been inconclusive and can be combined with ureteroscopy to evaluate an abnormal ureter or pelvicalyceal system. The technique involves placing a retrograde catheter within the ureter via a cystoscope and subsequently injecting iodinated contrast directly into the ureteric lumen and collecting system (Fig. 5.13). The images thus obtained can be scrutinized to establish whether any mucosal abnormality or filling defect is present.