Page 596 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

574 PART IV Specific Malignancies in the Small Animal Patient

cardiomyopathy recently was described in dogs, and further stud- adrenal cortical tumors. 116–118 The adrenal gland is freed from all
ies are needed to determine if management of this condition affects surrounding tissues except for the phrenicoabdominal vein as it
enters the vena cava. The dorsolateral aspect of the phrenicoab-
190
morbidity or mortality in dogs with pheochromocytoma.

VetBooks.ir dominal vein should be isolated and ligated. For a thrombus that
does not extend beyond the hepatic hilus, Rummel tourniquets
Surgical Management of Adrenal Tumors
are placed around the vena cava cranial and caudal to the tumor
Before adrenalectomy every attempt should be made to deter- thrombus and on the contralateral renal vein. The Rummel tour-
mine whether an adrenal tumor is functional, whether evidence niquets are tightened, and a cavotomy is made at the level of the
of metastatic disease exists, and whether vascular invasion has phrenicoabdominal vein as it enters the vena cava. The length of
occurred. Patients with ADH also may be medically managed the venotomy should be limited to the diameter of the tumor
with trilostane or mitotane before surgery to mitigate metabolic thrombus, or just slightly longer than this. The tumor thrombus
derangements and potentially reduce the risk of thromboembolic is removed by gently sliding it out of the vena cava. The Satinsky
9
disease that can result from their prothrombotic state. Important clamps are placed tangentially across the cavotomy in a manner
components of the presurgical workup for a patient with an adre- that allows partial flow through the vena cava. Preplacement of a
nal tumor include blood pressure measurement, an ACTH stimu- small-gauge, nonabsorbable suture may facilitate placement of the
lation test as a preoperative baseline, CBC, serum biochemistry, Satinsky clamp and management of the venotomy. If stay sutures
and blood typing, with or without cross-matching, in preparation of 5-0 polypropylene suture material are used at the cranial and
for potential blood transfusion. Pretreatment with α-blockade has caudal extent of the proposed venotomy, the suture can be used
been recommended before surgery, because phenoxybenzamine to close the venotomy site. The Rummel tourniquets are released,
was shown in one study to improve the ST significantly in dogs and the venotomy site is sutured in a simple continuous pattern.
undergoing adrenalectomy. 175 However, the exact dosage and If further bleeding is noted, the Rummel tourniquets can be re-
number of days that dogs should be on this medication, and even engaged and the repair can be augmented with additional suture
the decision to pretreat, are somewhat controversial. This recom- as required. A recent publication reported phrenicoabdominal
mendation likely deserves re-examination, particularly because venotomy, rather than caval venotomy, for removal of adrenal
this also is an area of controversy in human medicine, 191 and the tumors with caval invasion. 120 This technique can be used for a
recommendation is not necessarily supported by findings in other relatively small caval thrombus, and it offers the advantage that
veterinary studies. 118 a cavotomy is not necessary. The tumor thrombus can be milked
Abdominal CT is a precise method for planning a resection into the phrenicoabdominal vein, and a Satinsky clamp can be
and for evaluating the extent of an adrenal mass and the presence placed between the thrombus and the vena cava. Rummel tourni-
of caval tumor thrombus. 134,135 CT also allows for further stag- quets still should be placed as a precaution, but engagement of the
ing of the lungs and the rest of the abdomen and will allow for Rummel tourniquets is not needed.
assessment of kidney and/or renal vein involvement, so that the Bilateral adrenalectomy first was reported in 1972 for the sur-
surgeon and owner can be prepared for possible nephrectomy. A gical management of canine Cushing’s disease. 199 Medical man-
recent study indicated that triple-phase contrast CT may aid in agement of Cushing’s disease has replaced surgical therapy in cases
preoperative diagnosis of the tumor type. 136 of PDH. However, the surgical management of bilateral adrenal
Blood loss from adrenalectomy can be significant and even tumors is possible and is no more challenging technically than
fatal, particularly in patients that have extensive invasion of the managing a unilateral tumor. The preoperative management is the
surrounding tissues or caudal vena cava. The patient should be same as for a unilateral adrenal tumor, with the exception that a
cross-matched and blood typed, and blood should be available for single patient may have both a pheochromocytoma and HAC,
transfusion intraoperatively and postoperatively. Dogs with HAC so this should be considered. The postoperative management
have a higher risk of being hypercoagulable. 192–194 Perioperative is slightly more challenging in cases of bilateral adrenalectomy
management of this potential complication is somewhat contro- because the patient becomes acutely Addisonian. However, this
versial and will vary among clinicians. When available, thrombo- can be managed with an appropriate dose of desoxycorticosterone
elastography (TEG) may be useful as a preoperative baseline and pivalate (DOCP) and a supraphysiologic dose of dexamethasone
postoperatively to monitor for evidence of hypercoagulability, to intraoperatively. In the short-term these patients need to be moni-
allow directed anticoagulant therapy when indicated. tored for signs of Addisonian crisis during recovery, and careful
The technical difficulty of adrenalectomy depends on the size attention should be paid to their fluid requirements, urine pro-
and invasiveness of the tumor. For small tumors with no inva- duction, and electrolytes. In the long-term these dogs essentially
sion, a ventral midline, flank, intercostal, or minimally invasive are treated as Addisonian patients and should be managed with
approach can be considered. 195–198 The approach used generally is DOCP injections approximately monthly and daily physiologic
based on the surgeon’s preference and experience. For large right- doses of prednisone. As with any Addisonian patient, the fre-
sided tumors, the right lateral abdomen also should be aseptically quency of DOCP injections and the dose of prednisone should
prepared in case the standard ventral midline approach needs to be be tailored to the patient. Similarly, the dose of prednisone should
extended to include a paracostal approach. A vessel sealing device be increased during times of stress. The reported success rate in
facilitates adrenalectomy. Hemaclips or ligaclips also should be a recent retrospective study of bilateral adrenalectomy was simi-
available to assist with hemostasis. lar to that reported with unilateral adrenalectomy when the acute
When caval invasion exists, the surgery requires a focused team. Addison’s disease was managed preemptively and appropriately. 119
Blunt dissection, electrosurgery, and the vessel sealing device are The perioperative mortality rate for adrenalectomy ranges
used to dissect the adrenal tumor from surrounding tissues. Con- from 15% to 37%. 116–118 Perioperative morbidity for adrenalec-
siderable neovascularization, and possibly invasion into the vascu- tomy also is high, with reported complications including gastro-
lature of the surrounding tissues, often is seen. Caval thrombus is intestinal (GI) problems, pancreatitis, hemorrhage, hypotension,
more common in cases of pheochromocytoma but can occur with electrolyte imbalances, renal failure, disseminated intravascular