Postoperative Imaging

As laparoscopic techniques are newer than open ones, guidelines for postoperative imaging are less well established.

Patients are seen at four to six weeks after open partial nephrectomy for routine follow-up and have a physical examination, a serum creatinine level check, and an excretory urogram (37). Imaging with computed tomography or ultrasound is performed earlier in any patient who has clinical signs or symptoms of abscess, hematoma, urinary leak, or fistula.

Generally, a computed tomography scan with intravenous contrast is performed, and if a urine leak is of concern, delayed images should be obtained.

Postoperative surveillance for recurrent disease should be tailored to the initial pathological tumor stage (37).

■ All patients are evaluated annually with a review of history, physical examination, and blood tests including serum calcium, alkaline phosphatase, liver function tests, BUN, serum creatinine levels, and electrolytes.

■ Patients with T1 tumors do not require early postoperative imaging because there is a low risk of recurrent malignancy (38,39).

■ A yearly chest radiograph is recommended for patients with T2 or T3 tumors because the lung is the most common site of metastasis; low-dose chest computed tomography may also be used.

■ Patients with T2 tumors should have computed tomography every two years.

■ Patients with T3 tumors have a higher risk of developing local recurrence, especially during the first two postoperative years, and they should have a computed tomography every six months for two years, then at two-year intervals, if there is no documented tumor recurrence.

In patients who underwent nephron-sparing surgery and have compromised renal function, magnetic resonance imaging is a reasonable alternative to computed tomography, because the gadolinium contrast used does not pose a risk to renal function in patients with renal insufficiency.

The effectiveness of renal tumor ablation and laparoscopic partial nephrectomy has not yet been proven in long-term follow-up studies, and therefore, imaging protocols following the procedure are not standardized, varying among institutions. In our opinion, conservative surveillance is appropriate.

■ Patients who have had laparoscopic partial nephrectomy undergo follow-up abdominal and pelvic computed tomography and chest X-ray at six months, one year, and then at yearly intervals.

■ Patients who have had cryoablation undergo postoperative magnetic resonance imaging at one day, one month, six months, one year, and annually thereafter.

■ Contrast-enhanced computed tomography is the test of choice to search for tumor recurrence in those patients with a normal serum creatinine (40).

Contrast enhancement is important in detecting visceral organ metastases and local recurrence, but there is a risk of nephrotoxicity from iodinated computed tomography contrast in those patients who have had nephron-sparing surgery and have compromised renal function. magnetic resonance imaging is not generally used as a screening examination.

In patients who underwent nephron-sparing surgery and have compromised renal function, magnetic resonance imaging is a reasonable alternative to computed tomography, because the gadolinium contrast used does not pose a risk to renal function in patients with renal insufficiency.

Local recurrence after nephron-sparing surgery manifests as an enhancing mass at the resection site in the residual kidney (Fig. 19). Early on, postsurgical changes are significant after both laparoscopic partial nephrectomy and ablation and should not be confused for residual disease. These postsurgical changes can include perinephric fluid, fat necrosis, urine leak, scarring, or a defect at the operative site (Figs. 20 and 21). Hemostatic agents such as oxidized cellulose (Surgicel®a) may be present (41) and can mimic abscess formation (Fig. 22). After ablation, the mass progressively decreases in size over time (42,43) and eventually is seen as only a cortical defect (Fig. 23). Incomplete ablation is seen as a residual enhancement at the site of the mass. In our experience, enhancement or mass-like contour change suggests recurrent disease (44).

Metastatic disease can occur in regional lymph nodes or in distant sites. Lung, mediastinal, bone, liver, contralateral kidney, adrenal gland, and brain metastases are common, but metastatic disease can also be seen in the small bowel and peritoneal cavity (45). In this event, imaging reverts to the role of monitoring the treatment of metastatic disease.

FIGURE 19 ■ Recurrence at site of open partial nephrec-tomy. A 62-year-old woman had left open partial nephrectomy and right radical nephrectomy 2.5 years previously. Contrast-enhanced computed tomography shows round soft-tissue mass (arrow) abutting surgical clips and left renal vein (arrowhead).

FIGURE 19 ■ Recurrence at site of open partial nephrec-tomy. A 62-year-old woman had left open partial nephrectomy and right radical nephrectomy 2.5 years previously. Contrast-enhanced computed tomography shows round soft-tissue mass (arrow) abutting surgical clips and left renal vein (arrowhead).

aJohnson and Johnson, Arlington, TX.

FIGURE20 ■ Postoperative urine leak following partial nephrectomy. If entry into the collecting system is not identified and repaired at surgery, urine leaks can result. This patient has a perinephric fluid collection (A, arrow) after partial nephrectomy that fills in with contrast on a delayed scan (B).

FIGURE20 ■ Postoperative urine leak following partial nephrectomy. If entry into the collecting system is not identified and repaired at surgery, urine leaks can result. This patient has a perinephric fluid collection (A, arrow) after partial nephrectomy that fills in with contrast on a delayed scan (B).

FIGURE 21 ■ Postoperative hemorrhage following partial nephrectomy. The mass (arrow) in (A) was resected laparoscopically; the patient complained of left flank pain following the surgery and had a low hemoglobin concentration. Postoperative, unenhanced computed tomography scan (B) shows a perinephric hematoma (thin arrows).

FIGURE 21 ■ Postoperative hemorrhage following partial nephrectomy. The mass (arrow) in (A) was resected laparoscopically; the patient complained of left flank pain following the surgery and had a low hemoglobin concentration. Postoperative, unenhanced computed tomography scan (B) shows a perinephric hematoma (thin arrows).

Surgicel Mri

FIGURE22 ■ Oxidized cellulose (Surgicel®) mimics abscess at laparoscopic partial nephrectomy site. This patient presented to emergency department with flank pain after laparoscopic partial nephrectomy and had a normal white blood cell count. (A) Contrast-enhanced computed tomography demonstrates ovoid collection with scattered gas foci at partial nephrectomy site (arrow). No intervention was performed. (B) Computed tomography six months later shows resolution of collection with minimal residual low attenuation (arrow).

FIGURE22 ■ Oxidized cellulose (Surgicel®) mimics abscess at laparoscopic partial nephrectomy site. This patient presented to emergency department with flank pain after laparoscopic partial nephrectomy and had a normal white blood cell count. (A) Contrast-enhanced computed tomography demonstrates ovoid collection with scattered gas foci at partial nephrectomy site (arrow). No intervention was performed. (B) Computed tomography six months later shows resolution of collection with minimal residual low attenuation (arrow).

Partial Nephrectomy Mri

FIGURE23 ■ Normal findings after left renal cell carcinoma cryoablation. (A) Computed tomography scan before ablation shows a small anterior carcinoma. (B) One month after cryoablation, gadolinium-enhanced T1-weighted two-dimensional gradient echo magnetic resonance imaging shows no enhancement at the cryoablation site. Low signal intensity perinephric changes (arrows) merge imperceptibly with the ablated renal parenchyma. (C) Four and one-half years after ablation, gadolinium-enhanced T1-weighted three-dimensional gradient echo magnetic resonance imaging shows only cortical scar at ablation site. Source: From Ref. 46.

FIGURE23 ■ Normal findings after left renal cell carcinoma cryoablation. (A) Computed tomography scan before ablation shows a small anterior carcinoma. (B) One month after cryoablation, gadolinium-enhanced T1-weighted two-dimensional gradient echo magnetic resonance imaging shows no enhancement at the cryoablation site. Low signal intensity perinephric changes (arrows) merge imperceptibly with the ablated renal parenchyma. (C) Four and one-half years after ablation, gadolinium-enhanced T1-weighted three-dimensional gradient echo magnetic resonance imaging shows only cortical scar at ablation site. Source: From Ref. 46.

SUMMARY

■ The development of multislice computed tomography scanners that can rapidly obtain thin slice image data, advancements in magnetic resonance imaging software design and coil technology, the emergence of sophisticated three-dimensional rendering methods, and the development of laparoscopic ultrasound probes have now allowed the radiologist to participate in the planning of laparoscopic surgery, guiding its performance, and then following patients for possible complications or tumor recurrence.

■ The laparoscopic urologist must have an accurate understanding of the renal parenchymal and vascular anatomy and tumor location to preserve normal renal tissue and, thus, preserve renal function.

■ Accurate surgical planning information helps to minimize postoperative complications, such as urinary leak or renal infarct, and to maximize preserved renal parenchyma.

■ Computed tomography is considered the gold standard for detection, diagnosis, and staging of renal cell carcinoma.

■ Magnetic resonance is reserved for problem solving or for those patients with renal insufficiency or a history of severe allergy to iodinated contrast.

■ Three-phase computed tomography protocols are the state-of-the-art for imaging the kidneys and provide all the necessary information for surgical planning for laparoscopic surgery. Thin slices are employed.

■ A thorough discussion between the radiologist and the referring urologist regarding their surgical approach and surgical planning needs is recommended.

■ The ability of intraoperative ultrasound to localize a renal mass during laparoscopic partial nephrectomy is invaluable.

■ Guidelines for postoperative imaging after laparoscopic procedures are still evolving.

■ Magnetic resonance imaging is a reasonable alternative to computed tomography for the postoperative follow-up of patients with compromised renal function.

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