|Year : 2017 | Volume
| Issue : 2 | Page : 81-85
Multidetector computed tomography scan for renal cell carcinoma: A review
Idorenyin C Akpayak1, Emmanuel O Igho2, Abdul J Salaam2, Samaila I Shuaibu1
1 Division of Urology, Surgery Department, Jos University Teaching Hospital, Jos, Nigeria
2 Radiology Department, Jos University Teaching Hospital, Jos, Nigeria
|Date of Web Publication||15-Nov-2017|
Idorenyin C Akpayak
Division of Urology, Surgery Department, Jos University Teaching Hospital, Jos
Source of Support: None, Conflict of Interest: None
Renal cell carcinoma (RCC) is the most common renal malignant tumour. Owing to its retroperitoneal location, RCC remains asymptomatic and non-palpable until advanced disease develops. Most cases are identified during radiological examination for other reasons. The management of RCC depends substantially on the effective use of imaging. This is true in all the stages of the RCC, from initial diagnosis to follow-up. This article sets to review the current knowledge about multidetector computed tomography (MDCT) scan and how it characterises the RCC. A search of PubMed database was made to locate the original and review articles in English that address the MDCT scan or RCC, without limit to publication date. Relevant articles and textbook chapters were reviewed, analysed and summarised. MDCT reveals the renal tumour, its extent, venous involvement, status of loco-regional lymph nodes as well as adrenal and liver extension. It is available and relatively affordable presently in some centres across the subregion. MDCT is an essential tool that has aided not only the early diagnosis of RCC, but also the staging and characterisation of the RCC.
Keywords: MDCT, renal cell carcinoma, surgery
|How to cite this article:|
Akpayak IC, Igho EO, Salaam AJ, Shuaibu SI. Multidetector computed tomography scan for renal cell carcinoma: A review. J Med Trop 2017;19:81-5
| Introduction|| |
Renal cell carcinoma (RCC) represents 3% of adult malignancies., There are various types of renal tumours,, but RCC is the most common renal malignant neoplasm, and it constitutes 80–85% of all the kidney tumours in adults., Its incidence is increasing globally.
Owing to its retroperitoneal location, RCC remains asymptomatic and non-palpable until advanced disease develops. Most cases are identified during radiological examination for other reasons. In modern era, computed tomography (CT) scan of the abdomen obtained for other reasons identifies early renal masses. Studies in our subregion have found that most RCC present in advanced stages.,,, In contrast, in Europe and America, most RCCs are diagnosed incidentally. Jayson and Sanders reviewed 131 consecutive patients who had nephrectomy for RCC and found that 61% of the patients were incidentally diagnosed. Additionally, in Europe, tumour stage is lower, and 5-year survival rate is better in incidentally diagnosed RCC.
The management of RCC depends substantially on the effective use of imaging. This is true in all the stages of the RCC, from initial diagnosis to follow-up. Abdominal radiograph and ultrasound can be used to detect the presence of renal mass, but ultrasound is operator dependent, and both imaging modalities are limited in complete characterisation of renal masses.
Magnetic resonance imaging (MRI) has the advantages of being non-invasive, delivers no radiation to the patient and gives information in any orthogonal anatomical planes with good inherent soft tissue resolution.,, Previously, with MRI using spin-echo sequences, respiratory and cardiac motions created motion artifacts that compromised image quality. Currently, MRI acquisition has become faster, providing more images in a single-breadth hold, reducing artefacts with the availability of 3 T MRI machines. This development has led to even greater imaging capabilities of MRI. But access, non-availability of the higher tesla MRI machine and cost remain strong impediments to its widespread use in our subregion.
CT scan has remained the most widely used imaging technique in the diagnosis and characterisation of RCC. With the development of multidetector computed tomography (MDCT), many of the limitations encountered with single-slice helical CT scan were overcome. MDCT reveals the renal tumour, its extent, venous involvement, status of loco-regional lymph nodes as well as adrenal and liver extension. It is available and relatively affordable presently in some centres across the subregion. This article sets to review the current knowledge about MDCT, and how it characterises the RCC.
| Materials and methods|| |
A search of PubMed database was made to identify the original and review articles in English that address the MDCT scan or RCC, without limit to publication date.
The keywords used were renal cell malignancy, MDCT scan and surgery. Relevant articles and textbook chapters were reviewed, analysed and summarised after critique by all the authors.
Multidetector (also called multislice or multichannel or multiselection) computed tomography
MDCT is the most recent advance in CT technology and uses a multiple-row detector array instead of the single-row detector array used in the earlier version of the spiral CT. The earliest devices, developed in 1989, were called single-spiral computed tomography.
Approximately until the mid-1990s, CT images were obtained one slice at a time, with the patient table moving step-by-step through the gantry. Scans obtained using this older technique often required 30–40 min, and the patient held her or his breadth for every slice. MDCT allows faster data acquisition compared to a single detector CT with no loss of image quality. Very rapid data acquisition is made possible because of short gantry rotation time and the multiple detectors. Patients move rapidly through the gantry, and the examination can be completed in less than 5 min.
In 1980s, Kalender et al. developed MDCT, and since then, spiral CT scan machines have steadily increased the number of detectors (slices) they deploy. The prototype 16 multislice scanner was introduced in 2001 and in 2012, 128 multislice scanner was in the market. Presently, a 640 multislice CT scan is available. These can produce images in less than a second.
MDCT allows a faster data acquisition than single-detector CT, with no loss of image quality because of short gantry rotation intervals combined with multiple detectors at each level, providing increased coverage. This, along with short interscan delays, allows image acquisitions in multiple phases of renal parenchymal enhancement and contrast agent excretion in the collecting system after giving one bolus of intravenous contrast agent. Another advantage of MDCT is its improved spatial resolution, providing high-quality three-dimensional datasets of the renal vessels, comparable with conventional angiography and urography. The benefits outlined above also pose significant challenges, including selecting the optimal imaging sequences, controlling radiation exposure to the patient, and efficiently managing the increased data.
With the reconstruction of thin axial sections provided by MDCT, a near isotropic three-dimensional volume with sub-millimeter sized voxels can be constructed, that is well-suited for review on advanced 3D workstations. The review of axial images can be performed in cine mode, and in addition, sophisticated image reviewing on dedicated workstations allows a 2D multiplanar reformatting, maximal intensity projection and 3D volume rendering.
Multidetector computed tomography protocol
Using MDCT machine, the standard four-phase spiral CT has been recommended and is widely used in clinical practice for the characterisation of renal tumours. This multiphasic CT study includes pre-contrast, corticomedullary (CM), nephrogenic and excretory (delayed) phases, with a scan time of 30, 90 and 240 s for the CM, nephrogenic and the excretory phases, respectively.,, The initial un-enhanced scan before the phasic study should be a part of the protocol for the evaluation of RCC. It provides baseline to measure the enhancement after intravenous contrast.
A three-phase renal CT with the elimination of nephrogenic phase has been suggested to be the adequate protocol for the characterisation of RCC by some authors.
Songib et al., in their study titled: ‘Multiphasic renal CT in the evaluation of renal masses: is nephrogenic phase necessary?’, concluded that excluding nephrogenic phase from the standard four-phase renal CT protocol does not reduce the ability to detect and characterise renal lesions. Also, El-Esawy et al. also excluded the nephrogenic phase in the characterisation of solid renal masses using 64-slice MDCT.
Multidetector computed tomography in the diagnosis and surgical planning of renal cell carcinoma
It is essential to properly differentiate and characterise a renal mass once it is detected. The diagnostic criteria for RCC on CT include solid lesion or complex cystic mass with thick irregular septa, thick calcification or presence of solid component. MDCT scan gives an excellent characterisation of renal masses. Also, the reformatted images in multiple planes offer further details on arterial and venous collateral and extension of RCC to adjacent structures.
Renal masses do not have functioning renal nephrons, so following the injection of iodinated contrast, the masses exhibit varying degrees of enhancement depending on their vascularity.
The precontrast CT gives a baseline to measure the enhancement within the renal mass after the administration of intravenous contrast. Calcification, which is also seen in up to 30% of RCC, could be seen on pre-contrast CT. RCC usually have the enhancement values of more than 20HU. The enhancement suggests the presence of vascular tissue. The enhancement values are determined by the measurement of attenuation values with the renal mass before and after intravenous contrast injection in the different region of interest in the various acquisition sequences.
Songib et al. found that the optimum enhancement of RCC is best achieved in CM phase. He also noted that most renal malignant tumours particularly RCC are hypervascular and enhance early following intravenous contrast injection. In the studies by Sheir et al. and Kim et al. using morphological criteria as tumour size, calcification and cystic degeneration have minor role in differentiating between RCC histologic subtypes. Zhang et al. and Herts et al. found that the pattern of enhancement is the most reliable and most reproducible finding in the characterisation of RCC into subtypes. Clear cell RCC was found to enhance to a greater degree than the other histological subtypes. Kim et al. also reported that conventional RCC showed stronger enhancement than non-conventional RCCs in both the CM and excretory phases. They submit that the enhancement of 84HU in CM phase and that in 44HU in excretory phase were likely to be conventional RCC.
The nephrogenic phase has been found to be more sensitive in detecting smaller renal masses (<3 cm) than the CM phase could do.,, The increased detection of small renal masses has been attributed to higher attenuation values between the smaller renal lesions and the renal parenchyma. Szolar et al. compared the nephrogenic phase and CM phase in the evaluation of small renal masses. They found that the small renal masses have lower attenuation than the homogenously enhancing surrounding normal renal tissues in the nephrogenic phase of the CT. They concluded that small renal masses are better assessed in the nephrogenic phase of the CT.
Role of multidetector computed tomography in staging renal cell carcinoma
RCC staging reflects the extent of anatomic spread and involvement of the disease. It is considered the most important factor in predicting the clinical behaviour and outcome of RCC.
MDCT remains the most accurate imaging modality for the characterisation and staging of RCC with a reported accuracy of 85–95%.,, The presence of pseudocapsule suggests that the tumour is confined to the kidney. On MDCT, the most specific finding of extra-renal extension of RCC is the presence of enhancing nodule in the perinephric fat.
It could sometimes be difficult to differentiate between T2 and T3a tumours on MDCT. Perinephric stranding is not a reliable feature to differentiate between T1/T2 and T3a. This is because the perinephric stranding maybe caused by oedema, vascular engorgement or previous inflammation. The importance of differentiating between T3a/T2 tumours is that T3a requires radical nephrectomy while T1/T2 maybe satisfactorily treated with nephron-sparing procedures.Adrenal involvement is suggested by adrenal enlargement, displacement or non-visualisation. Sagalowsky found that these CT findings were noted in 24% of cases, and these patients required adrenalectomy.
The MDCT diagnosis of regional lymph node metastasis relies on regional node enlargement of more than 1 cm in the smallest diameter. In a series of 163 patients, this guideline resulted in a 4% false-negative rate. The study also revealed that the reactive (benign) lymph node enlargement was often due to extensive tumour necrosis or venous thrombosis. In some instances, the enhancement characteristics may help differentiate between benign and malignant lymph node enlargement. Metastatic lymph nodes may enhance while the benign ones do not, therefore nodal enlargement alone demonstrated on CT should not disqualify a patient from radical nephrectomy.
RCC frequently metastasise to the lungs, mediastinum, bones and liver and less commonly to the adrenal gland, the brain, pancreas, mesentery and abdominal wall. MDCT helps detect metastasise to these regions. Like the primary tumour, metastatic RCC deposits tend to be hypervascular.
Multidetector computed tomography in surgical planning
CT gives information that also facilitates surgical planning such as the extent of tumour and its location in the kidney, proximity to the renal collecting system and vessels, presence of fat planes between the tumour and other structures (e.g. liver, colon and posterior abdominal wall muscles), tumour extension into the renal vein or inferior vena cava and the level of this extension. The presence of intra-abdominal metastasis, the function of the contralateral kidney and the appearance of adrenal glands are also assessed.
MDCT helps determine the precise location of the renal mass, its relationship to the surface of the kidney, the collecting system and the renal vessels. The vascular anatomy may also be clearly displayed following the 3D reconstruction of MDCT images. This becomes very useful in planning nephron sparing surgery for small renal mass due to RCC.
| Conclusion|| |
MDCT is an essential tool that has aided not only the early diagnosis of RCC, but also the staging and characterisation of the tumour.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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