In benign adrenal tumors the usual technique is minimally invasive adrenal surgery(either via transabdominal or retroperitoneoscopic access).
Factor suggesting malignant growth must be recognized and considered early because in these malignant tumors open surgery is still preferred over minimally invasive techniques.
After curative resection of the primary and if there are no confirmed other metastases, the preferred technique in synchronous and metachronous metastasesof lung cancer, malignant melanoma and renal cell carcinoma still is open surgery.
Since infiltrating and organ invading tumors are exclusion criteria for minimally invasive surgery, most authors oppose endoscopic resection of adrenal metastases. Very few cases have been published to date. In the absence of metastases, definite differentiation between benign and malignant tumors is rarely possible before surgery, even by histopathology.
The risk of malignancy for tumors less than 4cm in diameter is estimated at about 2%. However, in tumors larger than 6cm the risk is about 25%.
At present, endoscopic resection of adrenal tumors larger than 6cm is under intense discussion. Several small studies demonstrated a higher rate of local recurrence and capsular injury in patients with tumors larger than 6cm who had undergone laparoscopic adrenalectomy. Two somewhat larger studies concluded that by itself tumor size does not contraindicate endoscopic surgery.
While Naja et al. in their study demonstrated a longer duration of surgery (210 minutes versus 175 minutes) and heavier bleeding (about 200mL versus 30mL) in patients with tumors larger than 6cm, they nevertheless concluded that safe laparoscopic adrenalectomy is still possible even in large tumors.
For tumors sized 5cm - 11cm and tumors smaller than 5cm, the retrospective analysis by Zorro et al. of 178 laparoscopic adrenalectomies did not find any difference in the duration of surgery, severity of bleeding and complication rate.
The authors emphasized that the choice of surgical technique should be governed by the presence or absence of invasive growth and not by the size of the tumor. Unfortunately, the authors of both studies did not analyze the oncological results.
However, good patient outcome does not depend on meeting all criteria of oncological radicality but rather on avoiding injury to the tumor capsule and tumor cell dissemination.
Pheochromocytoma
The old assumption of a 10% rate of malignancy in pheochromocytoma has been revised recently and today is estimated at about 5%. The objective of the various imaging modalities employed, e.g., CT, MRI, 123J-MIBG-PET and 18F-DOPA-PET, is the early detection of malignant neoplasias and synchronous hereditary tumors.
Until now, pheochromocytomas have been described as “10% tumors”, since 10% are bilateral, 10% exhibit malignant growth, 10% are hereditary in nature, and - leaving aside the official nomenclature - 10% are extra-adrenal in location. This rule of thumb is not coherent because in bilateral pheochromocytoma genetic disposition must be assumed. However, since not all familial cases exhibit synchronous bilateral pheochromocytomas, the number of actual hereditary cases must be higher than 10%.
Technique
Fundamentals of dissection in laparoscopic adrenalectomy (see Brunt 2006):
- The plane of dissection remains strictly extracapsular.
- Never grasp the adrenal directly but rather its periadrenal fat or bluntly push it aside.
- Seal the suprarenal vein with clips. The arterial branches and other suspensory structures may be transected by electrocoagulation or with the Ultracision®.
- Remove the specimen in a retrieval bag.
Standard approaches are transperitoneal accessand retroperitoneoscopy. Transperitoneal access offers the benefit of a larger space for dissection, less problems when having to convert to open surgery in case of complications, and better familiarity of most surgeons with the intraperitoneal anatomy.
The transperitonealapproach is limited by and runs the risk of extensive adhesions from previous surgery and the bigger danger of injuring intraabdominal organs.
The major benefit of retroperitoneoscopy on the prone patient is the option of being able to perform a bilateral procedure with having to reposition the patient.
Since there is no standard decision tree of when to perform transperitoneal laparoscopy or retroperitoneoscopy, this decision is primarily governed by the surgeon’s experience. The recommendation to undergo adrenalectomy in specialized centers arises from the fact that mastery requires a learning curve of about 30 such procedures.
To date, the question whether transabdominal laparoscopic access is better than the retroperitoneoscopic approach is still under discussion.
Papaya et al. compared the anterior transperitoneal approach with lateral transperitoneal access in large right-sided tumors (larger than 5cm; N = 40). The groups did not differ in their blood loss and complications. Lateral access prolonged the duration of surgery by 9 minutes.
However, the authors concluded that the anterior approach should be preferred because of its better access to the vessels and larger space for dissection.
In special cases function sparing partial adrenalectomymay have its place helping to avoid adrenal failure with its need for life-long cortisol replacement therapy.
It is a possibility, particularly in certain bilateral disorders such as non-malignant pheochromocytoma as part of a MEN 2a syndrome, and in patients with unilateral tumors who already have lost their contralateral adrenal gland to previous surgery or trauma.
Hormone production
Comparative quantitative measurements of catecholamines released perioperatively in open and laparoscopic surgery for pheochromocytoma demonstrated even for these patients less intraoperative and postoperative stress in laparoscopic surgery than in standard open technique.
Later studies by other authors confirmed these data and showed that, compared with open surgery, the intraoperative CO2insufflation and laparoscopic tumor dissection did not release more catecholamines and neither did it put additional stress on the cardiovascular situation of the patients.
Nevertheless, it is recommended to first gather adequate experience with the laparoscopic resection of non-hormone producing adrenal tumors, as well as tumors producing aldosterone or cortisol, before turning to laparoscopic adrenalectomy in patients with pheochromocytoma.
A core requirement for low-risk surgery in pheochromocytomas is adequate preoperative alpha blocking with phenoxybenzamine, which usually should be gradually increased in dosage to 3-5mg/kg body weight/day. Paragangliomas solely secreting dopamine are special cases.
It is reasonable to preoperatively treat patients with Conn syndrome with spironolactone, an aldosterone antagonist. Particularly in the presence of marked hypokalemia, this pretreatment is quite helpful in avoiding the severe elevation in the potassium level immediately after surgery. In primary hyperaldosteronism the patients are pretreated over a period of about 6 weeks with spironolactone 200mg - 300mg before surgery; depending on the blood pressure this dose may be upped to 400mg.
Patients with Cushing syndrome usually do not require antihormone treatment except for disease specific metabolic urgency.
Intraoperative and postoperative hormone replacement therapy with hydrocortisone must be instituted in all unilateral resections where the underlying disorder has suppressed the contralateral adrenal, and in all bilateral adrenalectomies. Once oral diet has been restarted switch the hydrocortisone to cortisol and fluorocortisol.
Specific anatomical features
Right adrenalectomy is regarded as technically more challenging than the left sided resection. The reason for this is the short right suprarenal vein which runs far posteriad and is anatomically hard to access. In case of bleeding close to the inferior cava the situation quickly gets out of hand.
In 20% to 30% of cases there are anatomical variants (doubling, crossing over or junction with accessory posterior hepatic veins, junction at the angle of inferior vena cava with right renal vein). Unlike on the right side, the course of the left suprarenal vein draining into the left renal vein is much easier to expose, and there are far fewer anatomical variants. In most cases a small phrenic vein (inferior phrenic vein running on the left crus of the diaphragm) drains into the suprarenal vein, with the latter serving as landmark.