3D reconstruction of CT scans aid in preoperative planning for sarcomatoid renal cancer: A case report and mini-review

1 Introduction

Contrast-enhanced multi-slice computed tomography (MSCT) is one of the most commonly used imaging modalities for preoperative decision-making regarding urological tumours, including kidney cancer [2–4]. It provides comprehensive and accurate information about the mass size and invasion [5, 6]. Contrast-enhanced MSCT is a four-phase investigation modality which produces a series of images in non-enhanced, arterial, venous and excretory modes. Modern MSCT scanners allow for 3D reconstruction of an area of interest to be performed for every single phase [7–9]. At present, 3D reconstruction of CT scans is extensively used in clinical practice to assess renal tumours to assist treatment planning [10, 11]. Moreover, 3D-printed models appear to be useful for better decision-making in the clinical setting [12]. There is evidence that the 3D reconstruction of CT scans can facilitate intraoperative navigation via augmented reality to improve surgical accuracy during partial nephrectomy, which, in turn, can help surgeons better determine tumour margins [13]. However, there is limited data on 3D reconstruction of CT scans in patients with advanced renal tumours invading the liver. Combining all phases into a 3D image would enable better understanding and interpretation of the preoperative imaging data, and lead to carefully-weighted decision-making in cases with a congenital defect, tissue damage or for complex malignant tumours [14–17]. This case report aims to evaluate the feasibility and effectiveness of 3D imaging based on a series of scans for preoperative planning in a rare case of sarcomatoid renal cancer which directly invaded the liver tissue.

2 Case presentation

A 59-year-old male presented with a 12-month history of intermittent left flank pain without irradiation, frequency, urgency or haematuria. He had no family history of cancer, alcohol abuse or liver disease. Abdominal ultrasound showed a large mass in the right kidney. All routine laboratory tests were within the normal range, and a dipstick test was negative. Renal scintigraphy revealed no abnormalities. However, a contrast-enhanced CT scan revealed a middle segment lesion (75×93×87.5 mm) in the hilum of the right kidney invading the sixth segment of the liver and Gerota’s fascia (Fig. 1).

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Fig.1

Contrast-enhanced multi-slice computed tomography showing a kidney tumour invading the sixth segment of the liver (indicated by a dotted arrow).

Several paracaval lymph nodes were detected, but there was no evidence of bone metastases on whole-body bone scintigraphy. Therefore, the tumour of the right kidney was staged as T4N2M0. However, CT scans did not provide data on whether the tumour was amenable to surgery in terms of the patient’s anatomy. Thus, a preoperative 3D reconstruction of CT scans was performed to assist surgical decision-making. In order to simulate the consequences of surgery, the four phases of the MSCT were combined to obtain a 3D image of the right kidney and the affected section of the liver.

MSCT examinations were performed with a 320-detector row CT-system (Aquilion Multi; Toshiba Medical Systems, Japan). Images acquired with 1-mm slice thickness were reconstructed in multiple planes. Amira version 5.4 (Konrad-Zuse-Zentrum, Berlin) software was used to generate 3D CT models of the patient’s liver and kidneys. The four-phase abdominal CT images included: (1) pre-contrast scans, (2) arterial scans (shortly after the contrast reaches the renal arteries), (3) parenchymal scans (50 to 60 s after the arterial phase), and (4) excretory scans (7 min after the arterial phase). Images were collected in a DICOM format. The 3D tools in the commercial software have various functions, enabling an IT specialist to build 3D kidney and liver models. In addition, the software tools allowed the margins of the kidney and liver to be freed from adjacent organs with similar attenuation. Structures with different attenuation values could be added or removed from the model.

4 Results

Adjusting the degree of transparency within the kidney and liver parenchyma by applying various software filters allowed us to obtain detailed information about intra-liver and intra-parenchymal structures, the renal pedicle, and renal and liver vessels at every angle. This, in turn, enabled us to determine the actual borders of kidney tumour invasion into the liver. Colour coding was performed by an IT specialist based on attenuation and gradient. This 3D modelling revealed that three segments (segments 6, 7 and 8) of the liver were affected, closer to the lateral contour of the liver (Fig. 2A). Adjusting the tissue transparency revealed that the seventh segment of the liver was the most affected area (depth of invasion was 31.18 mm) (Fig. 2B).

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Fig.2

A. Liver tissue modified using a transparency filter, showing lateral contour invasion. 1, aorta; 2, vena cava inferior; 3, right kidney; 4, kidney tumour and affected liver tissue; 5, the liver. B. The seventh segment of the liver was found to be most affected by the renal tumour (depth of invasion was 31.18 mm). C. Use of a transparency filter for the liver tissue (purple colour), showing several branches of segmental liver arteries at the site of tumour invasion (dotted arrow). D. Distance to the major arterial hepatic branch (14.9 mm) revealed by the 3D CT scan.

In addition, renal tumour invasion in several branches of the right segmental liver arteries was clearly identified using a tissue transparency filter (Fig. 2C). This knowledge is of great importance for the surgeon when performing an atypical liver resection. Importantly, 3D modelling enabled the surgeon to accurately estimate the depth of invasion of the renal tumour into the seventh segment of the liver, in addition to the distance to the major arterial hepatic branch (Fig. 2D). Using preoperative 3D data, we performed a nephrectomy and atypical resection of segments 6 to 8 of the liver.

The renal tumour mass appeared to invade the lower segments of the liver and the anterior parietal peritoneum (Fig. 3A), which was detected during an open procedure. An atypical hepatic resection of the sixth, seventh and eighth segments was performed, followed by a radical nephrectomy (Fig. 3B). Surgical incisions were closed by additional suturing and ligation of the hepatic vessels. Haemostatic gauze was used to cover the liver incision bed (Fig. 3C).

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Fig.3

A. Ring kidney tumour mass (long thin arrow) invaded the lower segments of the liver (short thick arrow) and anterior parietal peritoneum. B. Atypical hepatic resection (arrow) after partial nephrectomy. C. Haemostatic gauze (arrow) placed on the liver incision.

Clinically, the patient had a T4N2M0 renal tumour, diagnosed based on the TNM renal tumour classification. The diagnosis was verified by histological examination. Histopathological investigation of right kidney, liver and lymph tissue samples confirmed a clear cell renal cell carcinoma with sarcomatoid features (Fig. 4).

The surgical margin on the liver was negative, and no metastases to veins, lungs or other organs were detected by means of abdominal and chest contrast-enhanced CT. Despite the fact that sarcomatoid histology is considered a poor prognostic factor, the patient is alive and well 17 months after surgery.

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Fig.4

Micrograph of renal cell carcinoma with sarcomatoid features (arrows), G3, at 200X magnification.

Renal cell carcinoma (RCC) is the most common type of kidney cancer in adults, responsible for up to 95% of cases [18]. RCC originates in the lining of the proximal convoluted tubule. As a rare type of kidney cancer, sarcomatoid RCC has been fully characterised. However, it remains a poorly treatable and highly lethal form of kidney cancer [19]. Although it accounts for only 5% of RCCs, the aggressive nature and advanced stage of presentation makes sarcomatoid RCC fairly common to practitioners who manage patients with metastatic disease. X-ray imaging plays an important role in the diagnosis, staging and follow-up of renal cell cancer. In addition, 3D CT scans can aid in the diagnosis of kidney tumours that directly invade the liver, and can help surgeons decide whether a patient is amenable to surgery. In the case described here, the depth of invasion and distance to the major arterial hepatic branch were accurately estimated, allowing for precise planning of the procedure.

A series of clear images undoubtedly assist in pre-surgery planning for advanced renal tumours. In addition, 3D CT scans help identify the borders of atypical liver resection, allowing the removal of affected liver segments in the depths of the liver tissue. The advantages of 3D CT reconstruction over axial sections include: (1) 3D reconstruction provides more comprehensive and detailed information for precise and accurate measurements when compared to 2D imaging; (2) modern software allows rotation of 3D images and adjustment of the degree of transparency, facilitating acquisition of data for the area of interest. Based on the images obtained by 3D CT, a radical nephrectomy, not preservation surgery, was considered in this patient. Without these 3D CT images, misinterpretation of preoperative imaging data could have led to inadequate decision-making and the development of various complications. Importantly, a CT imaging protocol with ≤1 mm slice thickness is necessary as slices greater than 1 mm thick are not suitable for 3D reconstruction.

It is challenging to identify the origin of tumours in cases where tumours simultaneously appear in the kidney and liver using regular X-ray imaging technology alone, particularly for cases of renal tumours which lack specific clinic features. In the CT angiography, the contrast often accumulates earlier in the liver vessels than in the kidney [20]. In our patient, the contrast appeared in the liver, then subsequently invaded the kidney tumour within the liver. However, even in cases where the renal tumour invades the liver, it may be difficult to determine the original tumour source based on the preoperative data [21]. Clinically, liver cancer rarely invades the kidney, although renal tumours have been known to directly invade the liver [1, 21–26].

In addition, most liver metastases originate from colon or colorectal cancers. More than half of people diagnosed with colorectal cancer develop secondary liver cancer. Pathological examination is critical for the final diagnosis. In this case, sarcomatoid RCC at stage T4 was confirmed by pathologic assessment. Although the renal tumour was found to have invaded the liver, 3D imaging helped surgeons produce a surgical plan consisting of nephrectomy and liver-sparing surgery. Nephron-sparing surgery is not advisable in cases of RCC stage T4 tumours.

6 Conclusions

3D reconstruction of CT scan angiography represents a useful tool for differential diagnosis of the original tumour, allowing visualisation of the renal mass compared to the secondary metastasis of the liver tumour, especially in patients with a high-grade sarcomatoid RCC tumour located in the upper or middle segment of the kidney. Presumably, if 3D reconstruction of CT scans had not been performed, the patient would not have been considered a good candidate for surgical treatment, which might have led to unfavourable oncological outcomes.

Conflict of interest

The authors have no conflicts of interest to disclose.