Intercostal Approach for Right Adrenalectomy in Dogs
Natalia Andrade1, DVM, Luis R. Rivas1, Milan Milovancev2, DVM, Diplomate ACVS, Mary Ann Radlinsky1, DVM, MS, Diplomate ACVS, Karen Cornell1, DVM, PhD, Diplomate ACVS, and Chad Schmiedt1, DVM, Diplomate ACVS
1 Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, Georgia ,2 Department Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, Oregon and 3 Department of Small Animal Clinical Sciences, Texas A&M University, College Station, TX 77843.
Corresponding Author
Dr. Chad Schmiedt, DVM, Diplomate ACVS, Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, 501 DW Brooks Dr., Athens, GA 30602.
E-mail: cws@uga.edu
The current address for Luis Rivas is: Department of Small Animal Clinical Sciences, Texas A&M University, College Station, TX 77843.
Submitted February 2013 Accepted October 2013
DOI:10.1111/j.1532-950X.2013.12105.x
Objective: To describe an intercostal (IC) approach to the right adrenal (RA) gland in dogs.
Study Design: Cadaveric study and case series.
Animals: Dogs with right adrenal (RA) tumors (n = 11) and normal canine cadavers (6).
Methods: Cadavers had an IC (n=3) or paracostal (3) approach to the RA. The relative spatial position of the RA to the incision was evaluated. Medical records (June 2007-December 2012) of dogs that had an IC approach to the RA were reviewed. Perioperative data were recorded and described.
Results: In cadavers, the RA was closer to the cranial aspect of the surgical incision after an IC approach compared with a paracostal approach. The IC approach for right adrenalectomy was successfully performed in 11 dogs (6 adrenocortical carcinomas, 4 pheochromocytomas, and 1 osteosarcoma) with a mean anesthesia duration of 242 minutes and mean surgical of 144 minutes. Dogs had vascular invasion into the phrenicoabdominal vein (n = 11) and caudal vena cava (6). There were no significant intra- or postoperative complications. One dog was euthanatized intraoperatively. Median survival time for all dogs was 786 days.
Conclusions: The IC approach for right adrenalectomy offers superior exposure of the RA compared with a paracostal approach.
Adrenalectomy is performed for the treatment of functional adrenocortical tumors, tumors of the adrenal medulla (pheochromocytoma), and occasionally for pituitary-dependent hyperadrenocorticism resistant to medical management.1 The most common approach for open adrenalectomy is by ventral median celiotomy with an overall complication rate ranging from 15% to 51%.1-4 Reported complications associated with adrenalectomy in dogs include postoperative adrenal gland insufficiency, hemorrhage, hypotension, arrhythmias, pulmonary thromboembolism (PTE), pancreatitis, and acute renal failure.3,5 Poor surgical exposure may compound many of these complications, particularly the surgeon’s ability to prevent or address hemorrhage.
Major advantages of a ventral median approach are the ability to perform a full abdominal exploration, familiarity with the technique, and the associated anatomic perspective, as well as the surgeons’ ability to divide the abdominal wall through the linea alba, which prevents postoperative discomfort associated with muscular transection. For left-sided adrenalec- tomy, the ventral median approach provides adequate exposure
and surgical manipulation of the adrenal gland is relatively straightforward. For right-sided adrenalectomy, the ventral median approach provides poor exposure, and surgical manipu- lation of the adrenal gland by this approach is challenging.
The right adrenal gland is dorsolateral to the caudal vena cava and is often obscured by the liver, especially the caudate process of the caudate liver lobe. The hepatorenal ligament and the cranial pole of the right kidney, retroperitoneal membrane, and retroperitoneal fat further obscure the right adrenal. The liver, kidney, vena cava, pancreas, and duodenum must be retracted during the ventral approach. Achieving adequate exposure of the right adrenal gland is often difficult and requires assistance. Poor exposure may increase the risk for surgical complications such as hemorrhage, iatrogenic injury to the liver, pancreas, vena cava, and kidney.6
A paracostal approach for adrenalectomy has been described in a series of dogs, most of which had pituitary- dependent hyperadrenocorticism.6 A similar approach has been reported for thoracic duct ligation and cisterna chyli ablation.7 The reported advantages of the paracostal approach included adequate exposure of the adrenal glands, reduced risk of pancreatic injury, and a dorsally located incision which might result in fewer complications from wound healing problems common in dogs with hyperadrenocorticism.8 This
Presented in part at the University of Georgia Science Day, September 2012, Athens, GA, and presented at the 2013 ACVS Symposium in San Antonio, TX, October 24-26, 2013.
approach is not commonly used by veterinary surgeons for adrenalectomy1,2,9 perhaps because of lack of familiarity with the technique and adoption of chemotherapeutics as the standard of care for pituitary-dependent hyperadrenocorticism.
Conventional paracostal approach results in persistently poor exposure on the right because it is too caudal for the more cranially positioned right adrenal gland.8 One option to improve exposure, is to combine ventral median and paracostal approaches; however, the increased exposure obtained is not over the right adrenal gland, which remains under the ribs and dorsal to the vena cava. Modification of the paracostal approach by performing an intercostal incision at the 12th intercostal space positions the dorsal aspect of the incision more cranially and improves exposure to the right adrenal gland. Because the dog is positioned in left lateral recumbency, the surgeon is able to expose structures dorsal to the vena cava without retracting the duodenum, pancreas, liver, kidney, and vena cava.
Our purpose is to describe an intercostal approach to the right adrenal gland developed in 6 normal cadavers and used in 11 dogs with adrenal tumors. We hypothesized that an intercostal approach will provide better surgical exposure to the right adrenal gland in cadavers and use of this approach will result in comparable or reduced surgical complications in dogs with right adrenal tumors.
MATERIALS AND METHODS
Cadaver Study
Adult, mixed breed, canine cadavers (n =6) obtained from dogs euthanatized for reasons unrelated to the study, were used.
Cadavers were positioned in left lateral recumbency and the right lateral aspect of the abdomen and thorax were prepared for surgery. Each dog was measured in the transverse plane from the spinal process to the umbilicus and in the sagittal plane from the cranial aspect of the iliac crest to the dorsocaudal surface of the last rib.
Dogs were alternately divided into 2 groups: paracostal approach group and intercostal approach group. For dogs in the paracostal group, a paracostal approach to the right adrenal gland was performed as described.3 For dogs in the intercostal group, an intercostal approach to the right adrenal gland was performed as described below.
Incision length and width of retraction within each group were standardized. The approach for the 1st dog in each group was performed by a surgeon to approximate as closely as possible the approach used in clinical patients. In that dog, the length and width of the incision were measured, and the size as a percentage of the sagittal and transverse measurements were calculated, respectively. For the remaining 2 dogs in each group, the length and width of the incision were made based on the percentages calculated from the first dog and the specific sagittal and transverse measurements of the cadaver.
The special relationship of the right adrenal to the surgical incision was determined by triangulating the cranial aspect of the body wall directly above (lateral to) the caudal vena cava, the lateral aspect of the caudal vena cava just below (axial to) the surgical incision, and the lateral aspect of the right phrenicoabdominal vein (Fig 1). The depth of the surgical field defined as the distance from the caudal vena cava vertically (laterally) to the body wall, the working length was the distance along a line from the cranial aspect of the incision directly over the caudal vena cava to the phrenicoabdominal vein, and the
Liver
h
Kidney
H
Adrenal gland
W
VC
Ao
working angle is the angle made by the intersection of the lines of depth of surgical field and working length. The horizontal length was also calculated as the (craniocaudal) distance between cranial aspect of the incision on the phrenicoabdo- minal vein measured along the vena cava.
After the intercostal or paracostal approach was made, the caudal vena cava, right adrenal gland, and phrenicoabdominal vein were identified, measurements (depth of the surgical field, working length, and working angle) were performed in duplicate and the mean was calculated.
Clinical Cases
Medical records (June 2007-December 2012) of dogs with adrenal masses admitted for surgery were reviewed. A dog was included if it had adrenalectomy through an intercostal approach. Data recorded were: date of surgery, age, body weight, breed, clinical signs, anesthesia duration, location of the affected adrenal gland, vascular invasion (phrenicoabdo- minal and vena cava), surgical duration, intra- and postopera- tive complications, survival time and, if alive, follow-up time.
Intraoperative complications were defined as complications while the dogs were anesthetized and postoperative complica- tions were defined as complications after recovery from general anesthesia. Dogs were evaluated at the time of suture removal by the surgeon or referring veterinarian. All owners were contacted by telephone to obtain follow-up information including whether the dog was alive, what medical problems had occurred after surgery, and any medications the dog was administered. Cause of death was ascertained. Survival time was defined as the time from surgery to death. Follow-up time ranged from 20 to 896 days, and no dogs were lost to follow-up.
Diagnostic Evaluation
Preoperatively, all dogs had a hematologic and serum biochemical profile, urinalysis, thoracic, and abdominal radio- graphs and abdominal imaging with ultrasonography, computed tomography (CT) or magnetic resonance imaging (MRI).
Anesthesia
Dogs were premedicated with hydromorphone (0.1 mg/kg subcutaneously) and midazolam (0.2 mg/kg subcutaneously) or hydromorphone (0.1 mg/kg subcutaneously) and acepromazine (0.05 mg/kg subcutaneously). Anesthesia was induced with propofol (4 mg/kg intravenously [IV]) or etomidate (1.5 mg/kg IV), dogs were intubated, and anesthesia was maintained with isoflurane or sevoflurane in 100% oxygen. Controlled ventila- tion was provided, and ECG, direct and indirect blood pressure, end tidal CO2 and pulse oximetry were monitored.
Surgical Technique
Dogs were positioned in left lateral recumbency (9), left oblique recumbency (1), or sternal recumbency (1). The right lateral
thorax and cranial abdomen were aseptically prepared for surgery. An incision was made between the 12th and 13th rib, beginning at the transverse vertebral process, and curved cranially at the distal margin of the 12th rib to follow the costal margin and extended to within 3-4 cm of the ventral midline (Fig 2). The external abdominal oblique, internal abdominal oblique, and transversus abdominis muscles were transected and retracted using a self-retaining retractor. The diaphragm was transected along the same line of exposure, leaving ~1-2 cm of its attachment to the 13th rib to facilitate closure.
The adrenal gland was identified cranial and medial to the kidney and dorsal to the vena cava (Fig 3). The phrenicoabdo- minal vein was ligated dorsally with monofilament, absorbable suture. Dissection was continued until the adrenal gland was completely free from retroperitoneal attachments. Hemostasis was achieved with bipolar electrocautery, a vessel sealing device (LigaSure™M, Valleylab, Tyco Healthcare, Boulder, CO), suture ligation, or hemoclips. The phrenicoabdominal vein was then ligated ventrally at its junction with the caudal vena cava with monofilament, absorbable suture. Cavotomy was performed using Rummel tourniquets when required, and a longitudinal lateral venotomy similar to that described for adrenalectomies through a ventral median approach.2,3 The diaphragm was closed using a simple continuous pattern with monofilament, nonab- sorbable suture. Abdominal muscles were apposed individually in a simple continuous pattern with monofilament, absorbable material, and the subcutaneous tissues and skin were closed. Pneumothorax was evacuated using a thoracostomy tube, which remained in place postoperatively.
Postoperative Care
Hydromorphone (0.05 mg/kg IV every 4-6 hours) or fentanyl (3-5 µg/kg/min IV) was administered for postoperative analgesia. Heart rate, respiratory rate and effort, temperature,
capillary refill time, and mental status were monitored closely for the first 24 hours to assess ventilatory status and for evidence of postoperative hemorrhage. Oxygen therapy and blood transfusions were given as required and recorded. All dogs were administered physiologic doses of dexamethasone (0.01-0.02 mg/kg/day IV) for the first 2 days postoperatively and thereafter given physiologic doses of oral prednisone for 10-14 days (0.1-0.2 mg/kg/day). For pain control dogs were administered tramadol (n = 11), buprenorphine (1) and fenta- nyl patch (1). Two dogs with systemic hypertension and suspected pheochromocytomas were administered phenoxy- benzamine until re-check at suture removal. Doxycycline was administered for a urinary tract infection in 1 dog and levothyroxine sodium for hypothyroidism in 1 dog.
Data Analysis
Median survival time was estimated using Kaplan-Meier estimation, and results were described using mean and range.
For the cadaver study, the variables measured for the 2 groups were compared using a 2-tailed, Student’s t-test with significance set at P <. 05. Statistical analysis was performed with software (Graphpad Prism v5.03 for Windows, Graphpad Software, San Diego, CA [Kaplan-Meier estimation] or Microsoft Excel [Student’s t-test], Microsoft Corporation, Redmond, WA).
RESULTS
Cadaver Study
The 2 surgical approach groups were not significantly different in cadaver size, depth of surgical field, or working length; however, the working angle and horizontal length were significantly less in the intercostal group (Table 1).
Clinical Cases
Eleven dogs (5 neutered males, 6 spayed females; median age, 10 years [range, 6-13 years]; median weight, 26.1 kg [range, 16.2-65.6 kg]) met the inclusion criteria. Breeds were Labrador Retriever (n=3), mixed breed (3), 1 each of Great Dane, Corgi, Rottweiler, Border Collie, and West Highland White Terrier.
Clinical Signs
Clinical signs included lethargy (n=4), polydipsia/polyuria (4), polyphagia (3), inappetance (2), hypertension (2), elevation in liver enzymes (2), hemoabdomen (2), tachycardia (2), hematuria (1), vomiting (1), proteinuria (1), weight loss (1), aggression (1).
Diagnostic Test Findings
Abnormal laboratory results included increased alkaline phosphatase (n =5), increased alanine aminotransferase (4), hyperbilirubinemia (2), hypermagnesemia (2), thrombocyto- penia (2), proteinuria (2), leukocytosis (2), hyperlactatemia (2), prolonged partial thromboplastic time and activated partial thromboplastic time (1), hypokalemia (1), hypercholesterol- emia (1) increased serum creatinine (1), increased blood urea
| Paracostal Group (n=3) | Intercostal Group (n=3) | ||||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | P-Value | |
| Transverse circumference (cm) | 30.6 | 2.0 | 30.8 | 2.7 | 1 |
| Sagittal length (cm) | 12 | 1.4 | 12.6 | 1.8 | .7 |
| Depth of field (cm) | 7.2 | 0.5 | 7.2 | 0.6 | .9 |
| Working length (cm) | 8 | 0.5 | 7 | 0.4 | .1 |
| Working angle (0) | 30.5 | 1.2 | -1.1 | 1.1 | <. 01 |
| Horizontal length (cm) | 5 | 0.9 | -0.2 | 0.5 | .01 |
Transverse circumference: distance from the spinal process to the umbilicus; sagittal length: distance from the cranial aspect of the iliac crest to the proximal caudal surface of the last rib; depth of field: distance from the caudal vena cava vertically (laterally) to the body wall; working length: distance from the cranial aspect of the incision to the phrenicoabdominal vein; working angle: angle made by the intersection of the lines of depth of surgical field and working length; horizontal length: distance between the cranial aspect of the incision on the phrenicoabdominal vein measured along the vena cava. Negative values mean the phrenicoabdominal vein was caudal to the cranial aspect of the incision.
nitrogen concentration (1), metabolic acidosis (1), hypopro- teinemia (1), hypochloridemia (1), hyperkalemia (1), hypona- tremia (1), regenerative anemia (1).
Five dogs were tested for hyperadrenocorticism (low dose dexamethasone test [n = 2], adrenocorticotrophic stimulation test [3]); 3 had results consistent with hyperadrenocorticism.1
No evidence of metastatic disease was identified on thoracic radiographs, and abdominal radiographs were not specific for the diagnosis of adrenal neoplasia. Six dogs had abdominal ultrasonography, 4 CT, and 1 MRI. Neoplastic invasion of the phrenicoabdominal vein was observed in all dogs. Neoplastic invasion of the caudal vena cava was identified preoperatively in 5 dogs (2 CT, 2 ultrasonography, 1 MRI) and confirmed at surgery and in 1 other dog that had been evaluated preoperatively with abdominal ultrasonography.
Surgical Findings
Ten adrenal tumors were removed and 1 dog was euthanatized intraoperatively at the owner’s request because the tumor was considered nonresectable. None of the dogs died from anesthetic or surgical complications. Median surgical time was 144 minutes (range, 121-208 min) and median anesthesia time, 242 minutes (range, 210-289 min). Intraoperative com- plications included hypotension (systolic < 80 mm Hg [n=4]), hypothermia (<98ºF; 2), mild blood loss (<10% blood volume; 3), and serious blood loss (>10% blood volume; 1) necessitating red blood cell transfusion.
Postoperative Complications and Median Survival Time
No dogs died during the postoperative hospitalization period. Postoperative complications included, hypoxemia (hemoglo- bin O2 saturation < 94%; n =5), hypertension (systolic >180 mm Hg; 2), urinary tract infection (1), incisional infection (1),
100
Percent survival
80
60
40
20
0
0
250
500
750
1000
1250
Survival (days)
hemorrhage needing a packed red blood cell transfusion (1), seizure (1), aspiration pneumonia (1), and premature ventricu- lar contractions (1).
All dogs that survived surgery were discharged (median hospitalization, 4 days; range, 3-8 days). None of the dogs was lost to follow-up. Median survival time was estimated at 786 days (Fig 4). At the time of writing, 5 dogs were alive; 1 was found dead, 1 arrested after surgery for a kidney biopsy, and 3 were euthanatized because of “old age” according to owners.
Histopathology Findings
Four adrenal masses were diagnosed as pheochromocytoma and 6 were adrenal cortical carcinoma. The dog that was euthanatized intraoperatively had osteosarcoma of the right adrenal gland and spindle cell sarcoma in the liver and caudal vena cava.
DISCUSSION
An intercostal approach for right adrenalectomy was success- fully performed in 11 dogs with right adrenal tumors. We found this approach provided excellent exposure to the right adrenal and associated vasculature, with comparable anesthetic and surgical times to those reported for the ventral median approach.1º In the cadaver study, the working angle was significantly less than for the paracostal technique. The right adrenal gland was frequently within the frame of the incision compared with the paracostal technique where the adrenal gland was always substantially cranial to the cranial aspect of the incision. This improved exposure can have substantial benefits in complicated resections or when confronted with intraoperative hemorrhage.
Although our reported clinical cases are relatively low, the complication rate and perioperative mortality were lower or comparable to previous reports.1,2,6,9-12 Hypoxemia (hemo- globin O2 saturation <94%) was the most common postopera- tive complication and occurred in 5 dogs. Hypoxemia was likely caused by inefficient ventilation because of thoracotomy or left-sided atelectasis, rather than PTE, a reported complica- tion with ventral median adrenalectomy, because the hypox- emia resolved with O2 therapy and/or evacuation of the iatrogenic, postoperative pneumothorax.5 Unfortunately, data on blood CO2 concentrations were not available to further define these events.
Another potentially life-threatening complication of ventral median adrenalectomy is pancreatitis, believed to be caused by pancreatic trauma from surgical retraction.º None of our dogs developed this complication, perhaps because this approach abrogates the requirement of duodenal and pancreatic retraction and thereby prevents or minimizes trauma to the pancreas and other right cranial abdominal organs. Further, the incision is located in an intercostal space, a nondependent area, which might be beneficial in dogs with functional adrenocorti- cal neoplasia and delayed wound healing.8
A disadvantage of an intercostal approach is an inability to perform complete abdominal exploration compared with a ventral median approach. Thus coaxial preoperative abdominal imaging
(e.g. CT or MRI) is imperative. Fortunately, coaxial imaging of the abdomen is becoming more commonplace, especially in dogs with right adrenal disease, allowing a more comprehensive evaluation of all abdominal organs. This improvement in preoperative staging reduces reliance on exploratory celiotomy and allows more focused and optimized surgical procedures.13
The intercostal approach requires abdominal muscle transection, possibly increasing postoperative pain and the need for additional analgesia, which might represent another disadvantage. Although supportive data were not obtained to compare pain, duration of hospitalization was comparable to other studies.1º The requirement for intraoperative ventilation and thoracostomy tube placement to re-establish negative intrathoracic pressure makes surgery and anesthesia slightly more complex.
We found the intercostal approach for right adrenalectomy a viable surgical option for resection of the adrenal gland with or without involvement of the vena cava. It provides excellent access to the right adrenal gland with acceptable complication rates and clinical outcomes.
DISCLOSURE
The authors report no financial or other conflicts related to this report.
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