Laparoscopic Renal Procedures: Renal Cystectomy, Biopsy, and Nephropexy

MICHAEL MADDOX

BENJAMIN R. LEE

INTRODUCTION

Laparoscopic Management of Renal Cystic Disease

Simple cysts are a commonly encountered and often incidental finding on abdominal imaging studies. These are acquired lesions postulated to develop from diverticula of the distal convoluted tubule and collecting duct. Previous autopsy reports indicate that 50% of people older than age 50 years have renal cysts (1). With the advent and increased use of spiral computerized tomography (CT), more contemporary studies show an overall prevalence of 41% in the adult population with an increase to more than 60% by age 80 years (2).

DIAGNOSIS

Historically, the diagnosis of renal cysts was made by intravenous urography with tomography. However, ultrasound (US) and CT have supplanted intravenous urography as the primary diagnostic tools for renal cystic disease. Bosniak is credited with describing a spectrum of complexity to renal cystic lesions based on characteristics on abdominal CT. Magnetic resonance imaging (MRI), with its superior contrast resolution compared to CT, may help distinguish between benign and malignant complex cystic lesions. Further, since the introduction of the Bosniak classification of renal cysts, MRI has been validated as a surrogate for CT scan regarding the applicability of the Bosniak classification scheme (3).

The majority of renal cysts are asymptomatic and thus an incidental finding on imaging. However, a small subset of patients may present atypically with a palpable mass, obstructive symptoms, infections, or pain thought to be related to hemorrhage into the cyst or distension of the renal capsule. Cysts associated with autosomal dominant polycystic kidney disease (ADPKD) may manifest as hypertension or renal insufficiency.

BOSNIAK CLASSIFICATION

Prudent to any discussion of management of renal cystic disease is the Bosniak classification scheme. Distinguishing simple renal cysts from solid renal masses with cross-sectional imaging is not difficult. However, cystic lesions of the kidney are heterogeneous entities covering a wide spectrum from benign simple cysts to cystic renal cell carcinomas (RCCs). In fact, 5% to 7% of RCC are cystic, often demonstrating a slower growth rate and more favorable pathologic characteristics compared to solid RCC (4).

Bosniak (5) first described his classification of renal cysts in 1986, in which the lesion’s morphology and enhancement characteristics were assessed and lesions were placed into four categories (I to IV) with increasing concern for malignancy. The consensus among urologists and radiologists is that Bosniak I cysts are simple cysts requiring no further follow-up with minimal risk of malignancy, whereas Bosniak IV cysts are complex and managed surgically as a presumed malignancy. However, there is considerable interobserver variability in distinguishing Bosniak II and Bosniak III lesions (6). Bosniak later modified the scheme to include a fifth category of Bosniak IIF to help narrow the gap between II and III renal cysts (7). The current classification is summarized in Table 8.1. CT images of the five Bosniak subclassifications are shown in Figure 8.1A-E.

Malignancy Risk by Bosniak Class

The goal of the Bosniak classification was to provide a reproducible and universal description of cystic renal lesions in order to guide therapy. However, the majority of studies attempting to characterize pathologic outcomes by Bosniak classification are retrospective case series and limited by small patient numbers. In addition, preoperative attempts to assess the risk of malignancy based on cytologic evaluation of cyst fluid have not proven to be helpful with only 14% of known cystic RCC having a positive preoperative cytology (8).

A number of studies have quantified the malignancy risk of renal cystic lesions. These studies should be interpreted with some caution because many have used radiographic surveillance with stability of the lesion to define benignity. Koga et al. (9) pooled data from five studies including their own to assess the percentage of lesions that were ultimately malignant based on their CT Bosniak classification. All of these studies included used a pathologic correlate to the imaging findings. Malignancy rates were 2%, 27%, 60%, and 90% for Bosniak I, II, III, and IV, respectively (8,9,10,11,12).

It is important to understand that there is no absolute malignancy risk for all subclasses of renal cysts but rather a continuum in which the imaging characteristics should be interpreted in the context of the clinical situation on an individual patient basis.

SIMPLE CYSTS

It is generally agreed on that simple renal cysts (Bosniak I) are acquired lesions. These cysts are more common in men than women with an incidence ratio of approximately 1.4:1 (2).
Terada et al. (13) demonstrated the propensity of these cysts to increase in size and quantity with age. With this progression, a subset of these patients will develop symptoms without other discernible etiologies on imaging. If these patients fail conservative measures with anti-inflammatory agents and narcotic analgesics, they may benefit from further intervention.

TABLE 8.1 BOSNIAK RENAL CYST CLASSIFICATION

I	A benign simple cyst with a hairline thin wall that does not contain septa, calcifications, or solid components. It measures water density and does not enhance.
II	A benign cyst that may contain a few hairline thin septa in which “perceived” enhancement may be present. Fine calcification or a short segment of slightly thickened calcification may be present in the wall or septa. Uniformly high attenuation lesions <3cm (so-called high-density cysts) that are well marginated and do not enhance are included in this group. Cysts in this category do not require further evaluation.
IIF	Cysts that may contain multiple hairline thin septa or minimal smooth thickening of their wall or septa. Perceived enhancement of their septa or wall may be present. Their wall or septa may contain calcification that may be thick and nodular, but no measurable contrast enhancement is present. These lesions are generally well marginated. Totally intrarenal nonenhancing high-attenuation renal lesions >3cm are also included in this category. These lesions require follow-up studies to prove benignity.
III	“Indeterminate” cystic masses that have thickened irregular or smooth walls or septa in which measurable enhancement is present. These are surgical lesions, although some will prove to be benign (eg. Hemorrhagic cysts, chronic infected cysts, and multiloculated cystic nephroma), some will be malignant, such as cystic renal cell carcinoma and multiloculated cystic renal cell carcinoma.
IV	These are clearly malignant cystic masses that can have all the criteria of category III, but also contain enhancing soft-tissue components adjacent to, but independent of, the wall or septum. These lesions include cystic carcinomas and require surgical removal.
Reprinted with permission from Israel GM, Bosniak MA. An update of the Bosniak Renal Cyst Classification System. Urology 2005;66:484-488. Copyright © 2005 Elsevier Inc. All rights reserved.

Some apply a percutaneous approach initially to assess for relief of symptoms with aspiration to demonstrate a causal relationship. Aspiration alone has shown a significant recurrence rate between 41% and 78% (14,15,16). Addition of a sclerosing agent at the time of percutaneous aspiration may improve recurrence rates, but these are still unacceptably high ranging between 32% and 100% (5,17). It should be mentioned as well that percutaneous sclerosing agents are contraindicated in parapelvic cysts due to the risk of injury to the collecting system.

Laparoscopic cyst decortication (LCD) offers a more definitive management of symptomatic simple cysts without the morbidity of open surgical decortication. Roberts et al. (18) reported their results of laparoscopic ablation of 32 patients, 11 with parapelvic, and 21 with parenchymal cysts. All patients were symptomatic at the time of intervention. They showed at a mean follow-up of 18.1 months, all patients were without symptom recurrence, and only one patient experienced a radiographic recurrence without symptoms. The complication rate was 13% with one major complication (ureteral stricture) and three minor complications (ileus, intraoperative diaphragm injury repaired without consequence, and a transient peroneal nerve palsy) (18).

In one of the largest series of LCD of simple renal cysts, Atug et al. (19) demonstrated a durable response at a mean follow-up of 58 months. Using pre- and postoperative patientreported pain scales, the mean scores were 7.66 reduced to 1.21 following surgery. The 91.1% of patients were symptom-free, whereas four patients (8.8%) reported some alleviation of their symptoms. Radiographic success was 95.5% in this series with two of the partial responders developing asynchronous de novo cysts (19).

Okeke et al. (20) investigated their experience with LCD compared to sclerotherapy. At 17 months of follow-up, all patients undergoing decortication were without symptoms, whereas the sclerotherapy cohort had a 100% recurrence of symptoms (20). Laparoscopic cystectomy is proven to be a safe, efficacious, and durable treatment modality for patients with symptomatic simple renal cysts.

AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE

Although most simple cysts are sporadic/acquired, ADPKD invariably is responsible for a significant proportion of patients with symptomatic renal cysts. ADPKD affects between 300,000 and 600,000 Americans (21). It is the fourth most common cause of renal failure comprising approximately 10% of all dialysis patients (22). Enlarged cysts compress the renal parenchyma and vasculature, resulting in renal capsular distention and an ischemic activation of the renin-angiotensinaldosterone system resulting in pain and hypertension (23,24). Therefore, a majority of these patients will become symptomatic and may ultimately require therapeutic intervention.

The urologic literature describing LCD for ADPKD is composed primarily of retrospective case series with many of them having a heterogeneous mix of patients with simple cysts and cysts as a result of ADPKD. We will review the largest series of patients undergoing laparoscopic management of exclusively ADPKD patients.

In a comprehensive review of all relevant series using LCD for ADPKD, Millar et al. (25) addressed the outcomes for pain, hypertension, and renal function. Despite the variable degree of improvement and duration, LCD consistently offers an improvement in chronic pain in the ADPKD population
following LCD. Although some studies report an encouraging trend toward improvement in postoperative blood pressure, the literature does not consistently confirm the benefit of LCD for management of hypertension. Finally, the majority of patients can expect an insignificant change in postoperative renal function following LCD, but the authors caution that significant preoperative renal insufficiency may pose a greater risk of postoperative deterioration of renal function (25).