[Laparoscopic Urology] Laparoscopic Kidney Cyst Decoding

Simple renal cysts, also known as acquired renal cysts, are a common kidney disease, affecting about one-quarter of adults. Their pathogenesis is not fully understood. They often occur in isolation or on one side, and are more common in men. They mostly protrude from the surface of the kidney, but can also be located in the deep cortex or medulla. When located in the renal pelvis or renal sinus, they are called parapelvic cysts.

Clinical Manifestations: Most patients are asymptomatic. When the cyst compresses the kidney and renal pelvis, symptoms such as hypertension, lower back pain, and hydronephrosis may occur. If infection or bleeding occurs, symptoms such as fever, lower back pain, and hematuria may appear.

Diagnosis: Ultrasound is the preferred diagnostic method. CT, MRI, and cyst aspiration are used to further differentiate between malignant transformation and other lesions.

Treatment: For cysts less than 5 cm in diameter without significant compression of the renal parenchyma or renal pelvis, and without infection, malignancy, or hypertension, regular follow-up is sufficient. For cysts larger than 5 cm in diameter, or even those less than 5 cm but compressing the renal pelvis causing hydronephrosis, or with confirmed malignant transformation of the cyst wall, surgical treatment is required. Currently, laparoscopic renal cyst decortication is the gold standard for surgical treatment. When the cyst is severely infected, or compresses the kidney causing severe renal function impairment, or has become malignant, the affected kidney must be removed.

Surgical Key Points and Experiences

01. Patient Position

The "folding knife position" is the most commonly used surgical position, following the traditional open posterior approach. Its advantage is easy placement of the trocar, but its disadvantage is that the surgeon's visual axis, operational axis, and center of gravity are separated, leading to fatigue over time. Academician Guo Yinglu's improved "Guo's position" avoids these disadvantages. The key points are: head as far forward as possible, hips as far back as possible, lower back directly facing the lumbar bridge, and body perpendicular to the ground.

02. Trocar Placement

Generally, the trocar is placed 2cm above the highest point of the iliac spine. The operating ports for both hands are located 1-2cm below the anterior axillary line and the tip of the 12th rib. An isosceles triangle is optimal for the three ports, with a distance of approximately one fist between them. This can be adjusted appropriately according to the surgical area and the patient's height and waist width; a few anatomical landmarks should not be mechanically memorized.

03. Establishing the Retroperitoneal Cavity

The main methods are the "endoscopic method" and the "balloon dilation method."

The "endoscopic method" involves using a trocar through the observation port to enter the extraperitoneal fat layer. After pneumoperitoneum dilation, the retroperitoneal space is expanded using the endoscope. The difficulty lies in controlling the trocar puncture depth. The general principle is the same as percutaneous nephrolithotomy: err on the side of shallower rather than deeper insertion. Multiple attempts are acceptable, aiming to see the "spider web" tissue beneath the muscle. The endoscope is then placed against the top wall, while the other hand remains close to the skin to guide its movement. A "fiber dissection" sensation can be felt. With practice, the retroperitoneal space can be expanded in one go. After locating the puncture point with a long needle, the trocar is inserted for both hands.

The "pneumoperitoneum dilation method" uses either a homemade or commercially available pneumoperitoneum. The procedure involves taking a trocar 1-2 cm below the 12th rib, making a 2-3 cm incision in the skin, and using large curved forceps to penetrate and dilate the deep external oblique aponeurosis. A two-layer "breakthrough sensation" is generally felt. Then, the index finger is inserted along the incision into the extraperitoneal fat space for dissection, and a pneumoperitoneum is inserted for dilation, generally until the iliac crest depression is full.

Establishing the retroperitoneal cavity is the most crucial step; failure to do so signifies the failure of the retroperitoneal laparoscopic surgery, often becoming a major obstacle for beginners. There is no inherent superiority of one method over the other—the laparoscopic approach or the balloon dilation method—they can complement each other. When the laparoscopic approach fails, the balloon dilation method can be used, and vice versa.

Relatively speaking, the laparoscopic approach is more suitable for retroperitoneal laparoscopic renal cyst decortication because it involves a smaller incision. If the surgeon is confident, only a 5mm trocar can be placed in either hand's operating port, requiring only one suture post-surgery. Of course, mastering both methods is best; the method you are most comfortable with is the most suitable.

04. Dissection of Extraperitoneal Fat

This is the most easily overlooked step. Many people consider fat removal a waste of time, but it involves dissection and hemostasis, fundamental techniques in laparoscopy, providing invaluable practical experience for beginners.

First, locate the avascular layer between the extraperitoneal fat and Gerota's fascia. This layer is usually visible after dissecting the fat (see video for details). Obese patients should not be impatient to avoid damaging the peritoneum and other tissues by dissecting too deeply. Dissect along the avascular layer from top to bottom, clockwise or counterclockwise, paying particular attention to the iliac fossa area, as the limited space makes it easy to lose this layer.

After dissecting the fat, for the "balloon method," large pieces of fat can be directly grasped with oval forceps; for the "endoscopic method," fat can be removed with "spoon forceps," or scissors can be used to cut the fat and then suction it away. Some surgeons have also innovatively used a prostate shredder to remove fat.

05. Locating the Cyst: Incise the Gerota fascia near the psoas major muscle. Free the dorsal side of the kidney along the retrorenal space between the psoas major muscle and the perirenal fat capsule. Free the ventral side of the kidney along the anterior space between the peritoneum and the perirenal fat capsule. The anterior and retrorenal spaces are relatively avascular. If fat-feeding vessels are encountered, they can be pre-stopped and then detached. Then, incise the renal fat capsule and locate the cyst according to the preoperative CT scan. Completely remove the cyst wall about 5 mm from the renal parenchyma. The chance of cyst recurrence can be reduced by applying iodine or suturing the remaining cyst wall.