3-DIMENSIONAL VOLUME RENDERED COMPUTERIZED TOMOGRAPHY FOR PREOPERATIVE EVALUATION AND INTRAOPERATIVE TREATMENT OF PATIENTS UNDERGOING NEPHRON SPARING SURGERY:

Imaging in percutaneous nephrolithotomy

Image guidance is a critical factor for the performance of urologic interventions. Percutaneous minimally invasive procedures have been developed and are being used with constantly increasing frequency. Procedures such as percutaneous nephrolithotomy (PCNL) are not performed without any image guidance. Recent developments in medical imaging, such as three-dimensional radiographic fluoroscopy, CT, and magnetic resonance (MR) fluoroscopy, four-dimensional ultrasonography, and image fusion techniques, propose a new generation of image-guidance tools that promise to improve patient care. These developments have been used or have the potential to be used in PCNL and other urologic interventional procedures. Moreover, advanced needles and needle guidance systems provide a new perspective for the nephrolithotomy suite of the future. The current review presents existing imaging technology in PCNL and interventional urology as well as advanced imaging techniques that are being or are expected to be evaluated in PCNL practice.

The predictive value of helical computed tomography for collecting-system entry during nephron-sparing surgery

OBJECTIVES

To assess the ability of helical computed tomography (CT) including multiplanar reformatting and volume rendering (3D CT) to predict collecting system entry at surgery, as helical CT can be used to delineate renal tumour and normal renal anatomy before nephron-sparing surgery (NSS).

PATIENTS AND METHODS

Knowledge of the possibility of collecting system entry during surgery might either dissuade some surgeons from NSS in elective situations or influence the operative approach or ablative technology in cases where NSS is imperative, or prepare the surgeon for the possibility of collecting system repair. We reviewed all 3D CT (349 scans) obtained before NSS at our institution over three consecutive years. Tumour size, central tumour extension, and presence of calyceal involvement were prospectively recorded at the time of 3D rendering. Collecting system entry was analysed for these three CT variables, and for three clinical variables (tumour side, size and surgical approach) collected retrospectively from the medical records. Multivariate logistic regression was used to assess the sensitivity, specificity, and positive and negative predictive values.

RESULTS

Of 344 patients, 170 had collecting system entry reported at surgery. There were statistically significant associations between collecting system entry and central tumour location by CT (sensitivity 58.8%, specificity 80.5%, P < 0.001), calyceal involvement at CT (sensitivity 53.5%, specificity 78.2%, P < 0.001), and tumour size on CT of > 4 cm (sensitivity 39.4%, specificity 74.7%, P = 0.005). There were no significant associations with side or type of surgery (P > 0.83).

CONCLUSION

Helical CT is a reliable predictor of calyceal entry at surgery.

Three-Dimensional Planning of Percutaneous Renal Stone Surgery in a Horseshoe Kidney Using 16-Slice CT and Volume-Rendered Movies

Percutaneous management of calculi within horseshoe kidneys can be difficult because of the abnormal renal anatomy. We report our use of 16-slice CT scans to obtain three-dimensional (3D) volume-rendered (VR) movies of the pelvicaliceal system and stone for planning percutaneous renal stone surgery. The movie is formatted onto a disc, which can be played on a personal computer without additional software. This technique allows user-friendly 3D planning in the operating theatre. Unlike conventional two-dimensional images, the 3D VR movie provides a global appreciation for planning.

A prospective study of the predictive power of spiral computed tomographic angiography for defining renal vascular anatomy before live-donor nephrectomy

OBJECTIVE

To determine the accuracy of spiral computed tomography (CT) imaging of donor venous anatomy by comparing CT angiography (CTA) and operative findings, for both laparoscopic (LDN) and open donor nephrectomy.

PATIENTS AND METHODS

LDN presents unique surgical challenges, particularly with complex venous or arterial anatomy. The limitations of surgical access, poor visibility of the superior and posterior borders of the renal vein during LDN, and the variability of venous anatomy in this region, contribute to the difficulty of LDN, underlining the importance of imaging beforehand. Forty live donors (mean age 46 years, sd 11; 65% female) were assessed by CTA before donation. Scans were reported by the same radiologist. The number and diameter of 'predicted' renal arteries, veins and renal vein tributaries were documented. The donor kidney was removed by two consultant surgeons, and after back-table perfusion the same details were recorded and taken as the 'reference' findings. Tributaries of <1 mm diameter were not recorded. The right kidney was retrieved in seven patients; 25 of the 40 kidneys were retrieved by LDN and the other 15 by open surgery.

RESULTS

In all, 48 actual renal arteries were identified at nephrectomy; of these, 47 were predicted by CTA. Likewise, 41 actual renal veins were found at nephrectomy, 40 of which were predicted. The overall accuracy of spiral CTA in predicting the presence or absence of renal vein tributaries was 83% for gonadal and adrenal veins, and 75% for lumbar veins. There were seven false-negative lumbar veins found at nephrectomy; in these cases the CTA films were retrospectively examined, and five of these seven veins were identified. The predicted renal vein tributary diameter correlated poorly with the measured diameter at nephrectomy.

CONCLUSIONS

Assessing potential renal donors before surgery with spiral CTA provides an accurate prediction of the presence or absence of the gonadal and adrenal vein, but is less accurate for predicting lumbar veins. This is especially pertinent as the posterior lumbar tributaries have the most intra-individual variation, and are the most difficult to display and control at LDN. This highlights the need for meticulous dissection of the renal vein, particularly along its posterior wall.

Outcome of nephron-sparing surgery: elective versus imperative indications

INTRODUCTION

The increase in the detection of renal tumors incidentally in earlier stages has enhanced the enthusiasm for nephron-sparing surgery (NSS).

PATIENTS AND METHODS

We performed NSS in 76 patients (53 male, 23 female) with a mean age 52.3 between December 1988 and September 2001. Patients were sub-classified into 2 groups as elective or imperative indication group. They were compared regarding surgical technique, time of surgery, pathological analysis, complications, and disease free status.

RESULTS

Elective indication group (group I) with a normal contralateral kidney consisted of 50 patients, whereas there were 26 patients in the imperative indication group (group II). Tumors were incidentally detected in 63%; 74% in group I and 42% in group II. Although the mean diameter of the tumor was slightly higher in group II (39.1 vs. 36.3 mm), this difference did not reach statistical significance (p > 0.05). The partial nephrectomy was performed more frequently compared to enucleation in group I (90 vs. 69%, p = 0.050). However, the mean operation time as well as the mean clamping time did not differ significantly between the two groups (p > 0.05). In the histological evaluation tumors were benign in 16 (21%) and malignant in 60 patients. All of the patients but one with renal cell carcinoma had stage T1-T2 disease. Major complications were observed in 14 (18%) and 12 were from group II. Complication rate was significantly higher in group II (p = 0.000). Of 60 patients with renal cell carcinoma, 2 died of unrelated causes. One patient died with multiple visceral metastases. One patient was lost to follow-up. In the remaining 56 patients with a mean follow-up of 37.1 months (1-152), local recurrence or distant metastases were not detected. Serum creatinine levels have remained almost the same compared to preoperative levels (1.2 +/- 0.6 vs. 1.5 +/- 0.9). Overall and cancer-specific survivals were 100 and 100% in group I, 85 and 95% in group II, and 94 and 98% for the entire patient population, respectively.

CONCLUSION

NSS is an effective and reliable treatment in low stage renal tumors. It prevents unnecessary nephrectomy in benign lesions that could not be diagnosed preoperatively. However, the patients who underwent NSS with elective indication outcome with better results, compared to those with imperative indication.

Nephron-sparing surgery for renal cell carcinoma

Nephron-sparing surgery (NSS) provides effective curative therapy for patients with localized renal cell carcinoma. In patients with imperative indications, it represents an alternative to renal replacement therapy. For selected patients with systemic comorbidities that threaten global renal function, NSS preserves unaffected nephrons with excellent cancer-specific survival. Elective partial nephrectomy for patients with a small (< or = 4 cm), unifocal tumor and a normal contralateral kidney is associated with a low risk (0%-3%) of local recurrence and cancer-specific survival rates of 90%-100%. Comparisons between radical and partial nephrectomy demonstrate equivalent cancer control over five years. Minimally invasive techniques of NSS are feasible but await improved technologies and long-term outcome data before they become fully acceptable treatment options.

Image-guided therapy in urology

Technological breakthroughs have advanced the fields of urology, radiology, and minimally invasive surgery. Today, the various imaging modalities are increasingly applied to guiding therapy. Among the procedures now in use or under development are percutaneous cyst drainage or sclerotherapy; tissue ablation with high-intensity focused ultrasound, cold, heat, or photon radiation; and conformal radiation and brachytherapy. As current limitations are overcome, image-guided therapy will expand.

Three-dimensional CT of the genitourinary tract

The applications of three-dimensional (3D) CT techniques encompass a spectrum from calculus disease to preoperative planning. With proper selection of display windows and levels, accurate measurement of stone size can be achieved, along with volumetric information. A CT scan with reconstruction may help guide the direction of an endopyelotomy incision away from crossing vessels. The benefits of 3D CT in the evaluation of living renal donors include lower cost and decreased patient morbidity. In renal allograft recipients and other patients, the study may be used to investigate hypertension. Also, 3D CT is invaluable in planning nephron-sparing surgery for renal masses. The ultimate role of this modality rests in the hands of clinicians who can benefit from them and the radiologists who must provide the high-quality images and the interpretive expertise.