Anesthesia Case of the Month

Successful surgical removal of a pheochromocytoma in a mare via trans‐costal approach

“…This was most likely the result of catecholamine release after pressure was applied to the adrenal gland and should be expected if surgical excision is attempted and further cautions against attempting removal with the horse under standing sedation. Although this has not directly been documented in horses, these observations may explain the severe haemodynamic complications reported in horses positioned in dorsal recumbency undergoing exploratory celiotomy for colic‐like signs that had an undiagnosed pheochromocytoma at the time of surgery 11,22,23,24 …”

“…Furthermore, as pheochromocytomas are an adrenal‐associated tumour, the anatomy of the retroperitoneal space was carefully considered prior to surgical intervention. The retroperitoneal space is located behind the parietal peritoneum, extending from the diaphragm cranially to the perineum caudally and contains the kidneys, adrenal glands, proximal ureters, aorta, caudal vena cava and their associated vasculature 23,30 . Nephrectomy is one of the most commonly performed surgeries pertaining to the retroperitoneal space in horses, and has been described using a ventral midline celiotomy, 24,31 a trans‐costal laparotomy, 25,32 and via a hand‐assisted minimally invasive technique 26,33 .…”

“…A trans‐costal technique generally offers good exposure to the kidney and has also been described for bilateral adrenalectomy in a population of healthy ponies 13 . Minimally invasive techniques may offer reduced morbidity, however, until recently, the retroperitoneoscopic anatomy in the horse was not comprehensively described 23,30 . In the study by Pujol et al, 23,30 the adrenal gland and the axial aspect of the left kidney were adequately visualised in 10 equine cadavers, although the absence of active blood flow and haemorrhage represent limitations as to whether these findings can be accurately translated to an in vivo setting.…”

“…Although this has not directly been documented in horses, these observations may explain the severe haemodynamic complications reported in horses positioned in dorsal recumbency undergoing exploratory celiotomy for colic-like signs that had an undiagnosed pheochromocytoma at the time of surgery. 11,22,23,24 Because catecholamine-induced changes in blood pressure and heart rate were anticipated in this case, anaesthetic management preemptively included constant rate infusions of lidocaine as an antiarrhythmic and dexmedetomidine as an anti-arrhythmic/antisympathetic agent. 25,26 Additionally, intravenous magnesium is commonly used as a catecholamine blocker and anti-arrhythmic in human pheochromocytoma surgery and was also included in the protocol, though its use for this purpose in horses has not been reported previously.…”

“…The retroperitoneal space is located behind the parietal peritoneum, extending from the diaphragm cranially to the perineum caudally and contains the kidneys, adrenal glands, proximal ureters, aorta, caudal vena cava and their associated vasculature. 23,30 Nephrectomy is one of the most commonly performed surgeries pertaining to the retroperitoneal space in horses, and has been described using a ventral midline celiotomy, 24,31 a trans-costal laparotomy, 25,32 and via a hand-assisted minimally invasive technique. 26,33 A trans-costal technique generally offers good exposure to the kidney and has also been described for bilateral adrenalectomy in a population of healthy ponies.…”