Introduction

Adrenalectomy is the treatment of choice for adrenal tumors in canines.^1–4 Surgical treatment of unilateral adrenal gland tumors has been well described in the veterinary literature, and unilateral laparoscopic adrenalectomy has been associated with favorable outcomes in selected cases of noninvasive adrenocortical and medullary tumors.^1,2,5,6 Reported criteria for selection of dogs to undergo laparoscopic adrenalectomy include the absence of vascular invasion into the caudal vena cava or invasion into adjacent organs, a diameter of < 5 cm, and the absence of periadrenal hemorrhage.⁶ Laparoscopic adrenalectomy has been found to be associated with low conversion rates, shorter surgery time, shorter hospitalization, and lower incidence of hypotension when compared with open celiotomy in 2 studies^2,6 where case characteristics were matched for comparison.

Bilateral adrenalectomy via open celiotomy has been infrequently reported in the veterinary literature.⁵ A study⁵ evaluating outcomes in dogs that underwent open bilateral adrenalectomy concluded that bilateral adrenalectomy is a viable treatment option for dogs with bilateral adrenal disease and that mortality may be lower than previously documented. In this aforementioned study,⁵ 8 of 9 dogs that survived the perioperative period had excellent long-term outcomes, ultimately dying of unrelated causes, and the resulting hypoadrenocorticism was routinely managed.

Bilateral, single-session, laparoscopic adrenalectomy (BSSLA) has not previously been reported in the veterinary literature. The purpose of this report is to describe perioperative characteristics and outcomes in dogs undergoing BSSLA. The aims of the study were to document the perioperative morbidity and mortality associated with BSSLA and to report short-term and long-term outcomes.

Materials and Methods

Medical records were searched for dogs that underwent BSSLA at 4 institutions between 2017 and 2022. Data collected included patient signalment, presenting clinical signs, physical examination findings, clinicopathologic results, diagnostic imaging results, and preoperative treatments. Operative data collected from medical records were reviewed, and surgical time, type and number of ports, order of adrenal gland removal, intraoperative surgical complications, need for conversion, total anesthesia time, and anesthetic complications were recorded where available. Postoperative data collected included tumor type from histopathology reports, postoperative adverse events, length of hospitalization, and details of short- and long-term follow-up where available in the medical records.

Owner consent for surgery was obtained for all dogs. Laparoscopic adrenalectomy was performed using a 3- or 4-portal transperitoneal technique on each side with the dog positioned in an oblique lateral recumbent position as previously described.^2,6–8 Briefly, a paramedian endoscopic portal was established lateral and caudal to the umbilicus. Depending on surgeon preference, 2 or 3 instrument portals were established in a triangulating pattern around the affected adrenal gland (Figure 1). The adrenal tumor and surrounding structures were identified (Figure 2). A vessel-sealing device (LigaSure; Medtronic) and other endoscopic instruments were used to dissect the adrenal tumor from its retroperitoneal attachments, leaving its final attachment. Finally, the vessel-sealing device was also used to seal and divide the phrenicoabdominal vein. The adrenal gland was placed into a specimen-retrieval bag (EndoCatch; Medtronic) and extracted through an enlarged portal incision. Following resection of the first gland, dogs were repositioned into the contralateral recumbency, and the laparoscopic technique was repeated.

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Port placement for laparoscopic adrenalectomy.

Citation: Journal of the American Veterinary Medical Association 261, 10; 10.2460/javma.23.03.0132

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Intraoperative view of the right kidney (A; white asterisk) and right adrenal tumor (black arrows) and the left kidney (B; white asterisk) and left adrenal tumor (black arrows) in dog 1.

Citation: Journal of the American Veterinary Medical Association 261, 10; 10.2460/javma.23.03.0132

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Surgical complications and adverse events were described and classified using the definitions proposed by Follette et al.⁹

Results

Six dogs were included in this study, with 3 being spayed females, 2 intact females, and 1 neutered male. Dogs included one of each of the following: Shih Tzu, Beagle, Basset Hound, Labrador Retriever, West Highland White Terrier, and mixed breed. The median age was 126 months (range, 96 to 133 months). The median weight was 14.75 kg (range, 6.2 to 34.2 kg; Table 1).

Presenting clinical signs prior to diagnosis included hyporexia (1), anxiety and restlessness (1), hypertension (2), polyuria and polydipsia (1), weakness and exercise intolerance (1), vomiting (1), and hypertensive retinopathy (1). In 1 dog, clinical signs were absent, and bilateral adrenal tumors were an incidental finding during abdominal ultrasonography performed to detect whether the dog had been previously spayed.

Four of 6 dogs were pretreated with phenoxybenzamine prior to surgery. Dosages ranged from 0.2 to 0.6 mg/kg orally twice a day. Of these 4 dogs, 1 was also concurrently treated with amlodipine (0.1 mg/kg, PO, q 24 h). Two of six dogs that did not receive pretreatment with phenoxybenzamine prior to surgery were being treated with trilostane for management of hyperadrenocorticism.

The initial diagnosis of bilateral adrenal tumors was made with abdominal ultrasound in 5 of 6 dogs and with abdominal contrast-enhanced CT (CECT) alone in 1 of 6 dogs. Other abnormalities detected at the time of abdominal ultrasonography or abdominal CECT included mild biliary sludge and mild hepatomegaly (n = 1), splenic mass (1), and cystoliths (1). Additionally, all dogs included in this study had thoracic radiographs performed as part of preoperative staging, and no evidence of metastasis was present in any case.

All dogs included in this study underwent preoperative CECT. Contrast-enhanced CT was used to calculate maximal tumor diameter. Median maximal tumor diameter was 2.3 cm (range, 1.6 to 6.0 cm) for the left adrenal gland and 2.6 cm (range, 1.5 to 4.0 cm) for the right adrenal gland (Table 1). BSSLA was successfully performed in 5 of 6 dogs. Of the 5 dogs that successfully underwent BSSLA, median surgical time was 158 minutes (range, 75 to 180 minutes), and median anesthesia time was 264 minutes (range, 180 to 330 minutes). Three dogs underwent additional concurrent laparoscopic procedures (including laparoscopic liver biopsy [n = 1 dog], laparoscopic splenectomy [1 dog], and laparoscopic ovariectomy [1 dog]), which were included in total surgical and anesthesia times reported.

Histopathological evaluation of the 11 excised tumors revealed adrenocortical adenoma (6), adrenocortical carcinoma (2), pheochromocytoma (1), and undifferentiated tumors of adrenocortical origin (2; Table 1). In the 5 dogs that underwent BSSLA, the same tumor type was present in both adrenal glands. In the dog whose procedure was converted to open celiotomy following renal vein laceration, the single removed left-sided adrenal tumor was a pheochromocytoma, and a diagnosis from the contralateral tumor was not obtained, as it was left in situ.

High-grade intraoperative surgical complications were encountered in 2 dogs included in this study.⁹ Unrelenting hemorrhage was encountered in 1 dog following renal vein laceration during dissection of the left adrenal gland, which necessitated conversion to an open approach. Left adrenalectomy and ureteronephrectomy were performed at the time of open celiotomy, as the renal vein laceration was not repairable. The right adrenal tumor was left in situ. Intraoperative cardiac arrest occurred in 1 dog at the time of repositioning for the contralateral side due to iatrogenic pneumothorax. The cause of the pneumothorax was not identified but was suspected to be due to accidental diaphragm perforation during dissection of the right adrenal gland. Resuscitation was successful and, following owner consultation, a decision was made to move ahead with laparoscopic left adrenalectomy. The procedure was halted for 80 minutes for resuscitation, stabilization, and consultation with the owner. This time was not included in the total surgical time for this patient. No further anesthetic complications were encountered throughout the remainder of the procedure.

All dogs in this cohort recovered from surgery and survived to discharge. Postoperative complications reported included transient blindness for 18 hours in the dog that arrested during surgery (dog 6) and transient postoperative hypertension occurring 7 hours postoperatively (dog 1), which resolved with additional analgesics. The time spent in the hospital following surgery ranged from 45 to 96 hours, with a median postoperative hospital stay of 59 hours.

Histopathological evaluation of adrenal tumors removed in the dogs of this report revealed that 6 of 11 (55%) were adenomas, 2 of 11 (18%) were adrenocortical carcinoma, and 1 of 11 (9%) was a pheochromocytoma. Initial histopathology was inconclusive for the 2 tumors excised from dog 2 (Table 1). Immunohistochemistry was elected, and these tumors were ultimately diagnosed as undifferentiated adrenal cortical tumors; however, no further classification was obtained.

Postoperative follow-up was obtained in all 5 dogs that underwent BSSLA and ranged from 60 to 730 days, with a median follow-up time of 264 days. At the time of the last follow-up, 4 of 5 dogs were known to be alive, and no recurrence was noted. One dog was known to have been euthanized following development of aggressive mammary neoplasia 730 days postoperatively.

Discussion

In this small cohort of dogs, BSSLA resulted in a low perioperative complication rate and favorable outcomes. These findings are in accordance with a previous study⁵ on outcomes following bilateral adrenalectomy (single session or staged) via open celiotomy. Appropriate case selection is of critical importance when indications for BSSLA are being determined. In the dogs of this study, BSSLA was only performed when modest-sized tumors with no vascular invasion were found, in accordance with the criteria proposed by Mayhew et al⁶ for unilateral laparoscopic adrenalectomy.

Due to the perioperative risks and mortality associated with adrenalectomy, appropriate preoperative endocrinological interrogation and preoperative therapy are recommended, as previously reported.^8,10,11 Phenoxybenzamine, an adrenergic α-receptor blocking agent, is used to manage hypertension associated with pheochromocytomas.^8,10,11 Preoperative administration of phenoxybenzamine is shown to increase survival in dogs undergoing adrenalectomy for pheochromocytomas.^8,10,11 In this cohort of dogs, 4 of 6 received phenoxybenzamine prior to surgery. Although only 1 of 6 had histopathology consistent with pheochromocytoma, pretreatment with phenoxybenzamine was likely administered due to preoperative hypertension or the inability to definitively rule out pheochromocytoma prior to surgery. Minimal alterations in blood pressure were noted in the operative period in this cohort of dogs and may have been a result of pretreatment with phenoxybenzamine or, more likely, based on histopathological evaluation, due to the benign origin of the vast majority of adrenal tumors removed from the dogs in this study.

In the dogs of this report, a standard 3- or 4-port technique was used to perform unilateral laparoscopic adrenalectomy in lateral recumbency as previously described,^2,6,7 and then the dog was repositioned into contralateral recumbency, and laparoscopic adrenalectomy was repeated on the opposite side. The need for repositioning of the dog and repeating aseptic surgical preparation along with introduction of portals prolonged anesthesia time. Mean surgical time for BSSLA in the dogs of this study (158 minutes total/79 minutes per side) was similar and lower than 2 previous reports^2,6 of unilateral laparoscopic adrenalectomy that found median surgical times of 69.8 and 90 minutes, respectively. A laparoscopic approach that does not require repositioning of the dog and allows for access to both adrenal glands would be desirable to minimize anesthesia time in cases of bilateral adrenal tumors.

Overall, the peri- and postoperative complication rates for the dogs included in this report were low, and the frequency and type of complications encountered in this report are consistent with previous reports^2,6 of unilateral adrenalectomy. Inadvertent diaphragm perforation during adrenal gland dissection was suspected in the dog that developed an intraoperative pneumothorax. This complication has not been reported in open adrenalectomy, and thus the risk is likely higher in laparoscopic procedures; however, the overall risk is low. The longer anesthesia time required for BSSLA did not result in a higher incidence of anesthetic complications in this study; however, the sample size in this study is limited. Further studies would be required to determine whether complication rates for BSSLA compare to unilateral laparoscopic adrenalectomy and to further support single-session procedures over staged procedures.

Postoperative outcomes for the dogs included in the study were excellent. At the time of last follow-up, none of the dogs that successfully underwent BSSLA had known recurrence or significant complications related to their procedures. One dog is known to have been euthanized for an unrelated cause, and the remainder were known to be alive at the time of last follow-up. No complications associated with the procedure or difficulties managing postoperative Addison disease were reported in this cohort of dogs.

In human medicine, bilateral adrenalectomy is most often considered a treatment option for hyperadrenocorticism that is refractory to medical management.¹² Due to the significantly longer expected life span in humans when compared with canines, bilateral adrenalectomy is often considered as a last resort due to the need for lifelong mineralocorticoid. One study¹¹ comparing open versus laparoscopic single-session, bilateral adrenalectomy in humans found that BSSLA had longer surgical times but shorter postoperative hospital stays when compared with open procedures. Thus, high-risk anesthetic candidates may benefit from staged procedures.¹¹ Based on the findings of this study, we suspect that laparoscopic bilateral adrenalectomy may have similar advantages and disadvantages in canine patients; however, further studies are needed.

Limitations of this study were the retrospective nature and small number of dogs undergoing BSSLA. Anesthetic case management and perioperative case management were variable between cases, and therefore, low-grade complications may be underreported. Additionally, no dogs in this report underwent successful BSSLA for bilateral adrenal medullary tumors (pheochromocytoma); therefore, further studies are needed to determine whether the findings of this report hold true for this tumor type.