September 21, 2008 1 Comment
The term “simple nephrectomy” describes the technique of removing the kidney from within Gerota’s fascia and in no manner is meant to indicate that the operation is technically easy. This procedure is usually performed in the setting of a nonneoplastic disease state but is the end operation after other therapies (including surgery) have failed, making this operation technically challenging.
Usually the indications for simple nephrectomy are for (a) trauma that is so severe that reconstruction is not possible, (b) a nonfunctioning kidney associated with hypertension or nephrolithiasis, or (c) a severe infectious process that cannot be cleared medically. The diagnostic studies, therefore, will depend on the clinical setting. Renal trauma and the diagnostic studies are discussed in Chapter 13.
The diagnosis of a nonfunctioning kidney is made by the absence of a nephrogram on excretory urogram or CT scan or by the absence of signal on a radionuclide scan in a kidney that is not obstructed. It is occasionally necessary to place a ureteral stent or a nephrostomy tube to relieve an obstruction so that lack of function can be documented by contrast or radionuclide study.
Severe infections such as xanthogranulomatous pyelonephritis or emphysematous pyelonephritis are often treated with simple nephrectomy. Patients with xanthogranulomatous pyelonephritis, an uncommon form of chronic renal infection, present with flank pain, fever, persistent bacteriuria, and flank mass. The CT reveals a renal mass associated with a calcification in the renal pelvis. The parenchyma is replaced by small water-density masses. Xanthogranulomatous pyelonephritis is often misdiagnosed preoperatively as renal cell carcinoma and correctly identified only after nephrectomy, by the pathologist. Emphysematous pyelonephritis is a complication of acute pyelonephritis in patients with diabetes. Patients with this condition present with severe pyelonephritis that does not resolve within the first 3 days of treatment. The diagnosis is made by a plain abdominal radiograph, which reveals small gas bubbles radiating in a radial distribution through the renal parenchyma.
INDICATIONS FOR SURGERY
Simple nephrectomy is indicated for nonneoplastic diseases of the kidney. The more common specific indications include severe trauma, renal infections (e.g., xanthogranulomatous pyelonephritis and emphysematous pyelonephritis), nonfunctioning kidneys with stru-vite stones or obstruction, renal vascular hypertension (when all attempts at medical and surgical therapy have failed), and renal fistula.
Alternatives to simple nephrectomy include partial nephrectomy, renal embolization, laparoscopic nephrectomy, and radical nephrectomy.
The right kidney is lower than the left kidney in 90% of patients as a result of downward displacement by the liver. The renal arteries run posterior to the renal veins, and the right renal artery runs posterior to the inferior vena cava. The renal arteries divide into segmental branches at the junction of the middle and final third of their course. This anatomic point is important to keep in mind if the vessels are divided close to the renal hilus, as in a subcapsular nephrectomy. The left renal vein receives tributaries from the phrenic vein, the adrenal vein, the gonadal vein, and occasionally the lumbar vein. The right renal vein usually receives no tributaries.
Anomalies of the renal vasculature are present in three-quarters of all patients.2 Departures from the anatomy presented in the textbooks usually involve supernumerary arteries rather than the veins. These additional arteries commonly supply the lower pole of the kidney.5
The preoperative evaluation has two purposes: to minimize risk and to determine the optimal incision. These two purposes are interrelated, and occasionally the primary reason for choosing one type of incision over another is to minimize risk to the patient. It is essential to document function in the contralateral kidney. For most cases, a serum creatinine and an IVP are adequate. In indeterminate cases, a nuclear renogram may be required to demonstrate sufficient renal function. The scout film of the IVP is useful for determining the level of a flank incision. Note which rib is superimposed on the middle of the lateral border of the kidney. An appropriate flank incision should be made at the level of this rib or above.
The surgeon should inquire about a history of pulmonary disease. The decubitus position with an elevated kidney rest can decrease the vital capacity by 20%. In the decubitus position, there is also preferential ventilation of the upper lung and perfusion of the lower lung, creating a ventilation–perfusion mismatch. A history of severe pulmonary disease will therefore favor an abdominal approach.
Exploration of the kidney in the setting of traumatic injury must be done through an abdominal approach. In an obese patient, a flank approach optimizes exposure and minimizes wound complications. Previous abdominal surgery also favors a flank approach. An extraperitoneal flank approach is preferable in a patient with a chronically infected kidney. In other cases, the choice of incision depends largely on the surgeon’s preference.
Subcostal Flank Incision
The patient is placed on the operating table so that the kidney rest is just cephalad to the anterior superior iliac spine. The patient is turned to the lateral decubitus position with his or her back toward the edge of the table. The contralateral leg is flexed and padded at the knee and ankle. The ipsilateral leg is appropriately padded with pillows and kept only gently flexed. The table is then flexed, and the kidney rest elevated. The patient should then be secured to the table with 2-inch tape over the patient’s hip. The patient should have an axillary roll placed to avoid brachial plexus injury, and upper extremities should be secured to arm board and sling support or Mayo stand. Some find a bean bag to be useful in holding the patient’s position. It is important to remember that the patient should be positioned with the table flexed before the bean bag is inflated.
The incision is made approximately 2 cm inferior to the 12th rib starting posterior to the angle of the 12th rib or at the inferior border of the paraspinous muscles. The incision usually is gently curved toward the umbilicus to the lateral edge of the rectus muscle. The latissimus dorsi and external oblique are divided with cautery, exposing the serratus posterior inferior and the internal oblique, which are then divided Figure 5-1). Often the subcostal nerve emerges from the fibers of the lumbodorsal fascia to extend along a course that is superficial to the transversus muscle. Careful proximal and distal dissection of this nerve will minimize the risk of injury. A small incision in the lumbodorsal fascia provides access to the retroperitoneum. The peritoneum is dissected medially off the transversalis fascia with blunt dissection. The transversus can then be divided with cautery or bluntly divided between the muscle fibers. Gerota’s fascia is identified beneath the paranephric fat and is then incised. The kidney is dissected free from the surrounding perinephric fat using blunt and sharp dissection. The renal pedicle can be approached anteriorly or posteriorly.
If additional exposure is required, the costovertebral ligament of the 12th rib can be divided bluntly or sharply, allowing for greater cephalad retraction.
Eleventh and 12th Rib Incision
If the kidney appears high in relation to the thoracic cage on preoperative radiographic studies, an 11th or 12th rib resection may be preferred. The patient is positioned as detailed above for the flank subcostal approach. The incision is made over the selected rib from the costovertebral angle over the tip of the rib medially to the edge of the rectus muscle (Figure 5-2).
Once the rib is exposed, the periosteum is incised along the length of the rib. The periosteum is dissected off the rib using the periosteal elevator and the Alexander periosteotome. The Doyen periosteal elevator is guided beneath the rib to complete the dissection posteriorly. Once free, the rib can be divided with a rib cutter, and the edges smoothed with a rongeur (Fig. 5-3).
The posterior periosteum is divided, exposing the fascial attachments of the pleura to the diaphragm Figure 5-4). These attachments are sharply incised so that the pleura can be reflected superiorly. The peritoneum is bluntly dissected from the deep surface of the transversalis fascia by sweeping it medially with the fingers. The medial extent of the incision, including the external oblique, the internal oblique, and the transversus, can now be completed. Gerota’s fascia is incised, and the kidney is dissected free from the surrounding peri-nephric fat using blunt and sharp dissection (Fig. 5-5).The flank incisions enhance the ease of a posterior approach to the pedicle without increasing the difficulty of the anterior approach.
Subcostal Abdominal Incision
The subcostal abdominal incision is preferred by some surgeons because of:
1.Early exposure of the renal pedicle
2.Lower risk of inadvertent pleurotomy
3.Decreased effect on ventilation in patients with pulmonary disease
The patient is positioned with the table break at the level of the 12th rib, and the operative side is elevated with a rolled sheet. The table is then flexed to maximize exposure.
The incision is typically two fingerbreadths below the costal margin with its medial extent being approximately two fingerbreadths below the xyphoid process. After the skin incision, the anterior rectus fascia is divided along with the rectus muscle and the external oblique. The superior epigastric artery is divided. The internal oblique is divided. The lumbodorsal fascia is incised laterally, and the peritoneum can be opened or bluntly stripped off the anterior abdominal wall. The transversus can then be divided with cautery or bluntly divided between the muscle fibers. If peritoneum is opened, one must reflect the colon medially to expose Gerota’s fascia, which is then incised. The kidney is dissected free from the surrounding perinephric fat using blunt and sharp dissection. The anterior approach to the renal pedicle is easier than the posterior approach when a subcostal abdominal incision is used.
Vertical Abdominal Incision
If a vertical abdominal incision is required for the evaluation of intraperitoneal structures (such as in a patient who has had abdominal trauma) or for a combined procedure, a simple nephrectomy can be performed through a midline incision. This incision is typically from the xyphoid process to the pubic symphysis. After incision of the skin and subcutaneous fat, the linea alba is identified and incised. The peritoneum can be identified beneath preperitoneal fat and is incised sharply and carefully to avoid bowel injury. The colon is reflected medially to expose Gerota’s fascia.
In a patient who has suffered renal trauma, it is important to obtain early vascular control by dissecting along the aorta for a left renal injury and along the inferior vena cava for a right renal injury. The dissection is carried superiorly to the level of the renal vessels. Vessel loops are placed around the renal artery and vein before exploration of the injured kidney.
The paramedian incision is helpful if an attempt will be made to stay extraperitoneal or if a two-layer closure is preferred. It is typically two fingerbreadths lateral to midline. The rectus muscle fibers are dissected off the linear alba and retracted laterally. If peritoneum is opened, one must reflect the colon medially. Gerota’s fascia is then incised, and the kidney is dissected free from the surrounding perinephric fat using blunt and sharp dissection.
After Gerota’s fascia is incised and the kidney is dissected free from surrounding perinephric fat, the renal artery should be identified. One must keep in mind possible aberrant vessels, particularly lower-pole branches. The renal artery can usually be identified during posterior dissection of the pedicle. Ligation of the artery before the vein prevents renal congestion and is thus preferred. Two size-0 silk ties are placed proximally, and a single silk is placed distally. The artery is divided with scissors; a scalpel is used when there is minimal distance between the proximal and distal ligatures. To minimize the possibility that the proximal tie will slip off the arterial stump, some surgeons place a suture ligature distal to the 0 silk ties.
The ureter is quickly identified by blunt dissection in the fat inferior to the kidney. It is divided between ligatures or clips. The connective tissue and lymphatics are dissected off the kidney, revealing the renal vein. On the left, particular attention is paid to the gonadal vein, inferior adrenal vein, and lumbar venous branches. These branches are divided between silk ties if distal to the area dissected. The renal vein is doubly ligated, as was the artery.
The adrenal gland can be dissected off with sharp dissection, taking care to clip all vessels. If the nephrectomy is secondary to an infectious process, a drain is left in the posterior flank.
In patients undergoing simple nephrectomy for stone disease or for infection, previous surgery or chronic inflammation can make dissection very difficult. In these cases, it is advantageous to come down to the capsule, incise it, and continue the dissection under the capsule to the hilus. It is important to remember that the renal vessels have already divided into several branches once they reach the renal hilum and to continue searching for additional arterial branches once the apparent main branch has been divided.
There are differing opinions on the best technique for closure of a flank wound, although there is general agreement that the abdominal portion of a flank wound should be closed in two layers. The bean bag is deflated, the kidney rest is lowered, and the flexion is taken out of the table. The closure should be initiated at each end of the incision and continued toward the middle of the incision. Anteriorly, the internal oblique is closed with a running PDS suture. In the posterior portion of the wound, the inferiorly reflected periosteum is approximated to the periosteum and intercostal muscle of the superior rib. When the rib has been resected, the periosteum and intercostal muscles above and below the rib are approximated. The latissimus dorsi fascia is then closed in continuity with the external oblique fascia using a running PDS suture. A single-layer closure is often sufficient over the ribs. A single running PDS suture closing the fascia of the external oblique and continuing posterior to close the fascia of the latissimus dorsi has resulted in one hernia in approximately 700 donor nephrectomies at our institution.
The operative mortality of nephrectomy for benign disease is less than 1%.4
The most common intraoperative problem is hemorrhage, especially of the renal vein and vena cava. It is important to avoid blind clamping and suture ligatures that can lead to an arteriovenous fistula.6 The proper strategy is to gain control by direct pressure on the vena cava with sponge sticks, followed by optimization of exposure. The surgeon can then use a running 5-0 vascular suture to repair the vessel. Blind clamping can also lead to duodenal injury in a right nephrectomy. It is important to reflect the duodenum medially before division of the vessels from an anterior approach. The superior mesenteric artery is vulnerable to injury during a left nephrectomy.
Unintentional laceration of the parietal pleura is common and can usually be repaired without placement of a chest tube. The edges of the pleura are approximated with a running absorbable suture. A red rubber catheter is placed through the laceration into the pleural cavity before the suture is tied. The end of the catheter is placed in a basin of water. The anesthesiologist gives the patient a deep breath; air is expelled from the pleural cavity; the catheter is removed; and the suture is tied. After such a maneuver, it is important to obtain a chest x-ray in the recovery room. A small pneumothorax will be reabsorbed without sequelae. A larger pneumothorax may benefit from aspiration of air from the pleural cavity using a large luer lock syringe, a stopcock, and an intravenous angiocath. Because the pulmonary parenchyma is not injured, it is rarely necessary to insert a chest tube. Inability to reapproximate the pleural edges in an airtight fashion may necessitate placement of a chest tube. Atelectasis is common after a simple nephrectomy even if the pleural cavity has not been entered.
A flank bulge is common after a nephrectomy through the flank approach, especially if the subcostal nerve has been injured. The nerve lies below the internal oblique muscle and above the transversus abdominus muscle. Careful identification, proximal and distal dissection, and gentle retraction of the nerve can minimize this problem. Flank bulges must be distinguished from incisional hernias, which are rare. A fascial defect is usually palpable in patients with a hernia.
Generally, the patients recover from simple nephrectomies uneventfully and remain in the hospital for less than a week, depending on the indication for the nephrectomy, the comorbidities, and the patient’s preoperative status. Success rates with improved control of hypertension are as high as 86% in patients with unilateral atherosclerotic disease of the renal artery.1 Many of these patients continue to require antihypertensive medications, although at lower doses. The success in the treatment of xanthogranulomatous pyelonephritis approaches 100%. In contrast, patients with emphysematous pyelonephritis have a mortality rate as high as 43% despite aggressive intervention with nephrectomy.3