Introduction

Total splenectomy is a commonly performed surgery in dogs and cats and is sometimes undertaken even in cases where preservation of a portion of the spleen is feasible. This disregards the important functions of the spleen and an increased susceptibility to some infectious diseases when the spleen is removed entirely.^1–8 Benign or traumatic lesions of the spleen may be amenable to partial resection, and splenic preservation is beneficial to the patient if the remnant spleen does not harbor any remaining pathology. Total splenectomy may sometimes be chosen over partial splenectomy because of the increased amount of time it takes to perform a traditional partial splenectomy or owing to concerns about hemostasis when a portion of the spleen is left behind. Reduction of surgical time can be achieved with modern surgical devices such as automated stapling devices and, if appropriate for this purpose, vessel-sealing devices rather than traditional suture and ligation. Bipolar vessel-sealing devices were originally designed for use exclusively in blood vessels; however, their clinical use is expanding. To the author’s knowledge, a technique for using these devices for splenic parenchymal resection in dogs and cats has yet to be described. The primary concern for the use of these devices on splenic parenchyma is hemostasis because these devices were not designed for use in this type of tissue. Successful and even advantageous use of these devices on other parenchymal organs has been described and suggests that further expansion of the application of these devices is possible.^9–13 Use of bipolar vessel-sealing devices may shorten surgical time, provide effective hemostasis, and allow preservation of the spleen for retention of its important functions and protective effects.

Case Reports

Case 4: Ben (2018)

Ben is an 8 yr old male neutered Havanese dog weighing 12.4 kg. He had a history of elevated liver enzymes for approximately 2 yr with no apparent clinical signs. A routine celiotomy was performed for liver biopsy. The liver was found to be nodular, and biopsy samples were obtained. The spleen had a 3 × 1 cm nodule in the mid-body, and partial splenectomy was undertaken using the vessel-sealing device^a (Figure 1). Examination of the bowel found multiple intraluminal masses in the jejunum with areas of adjacent scarring, and this was resected along with approximately half of the ileum to achieve adequate surgical margins. The vessel-sealing device was also used on mesenteric vessels attached to the area of resected bowel, and the abdomen was lavaged and closed routinely. Ben recovered well from his surgery and was discharged from the hospital the next day. Histopathology of the spleen was consistent with nodular lymphoid follicular hyperplasia, the liver histopathology was consistent with vacuolar hepatopathy, and the jejunal histopathology identified granulomatous enteritis with lymphangiectasia.

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Discussion

In all four cases included in this study, the patient was deemed suitable for partial splenectomy using a bipolar vessel-sealing device based on visual evaluation of the spleen and the lesion affecting the spleen. This includes a subjective evaluation of the thickness of the splenic parenchyma. This technique was reserved for patients of small size with isolated lesions. This required a judgment call to be made based on the clinical experience of the surgeon. The technique used is very simple because it requires only application of the bipolar vessel-sealing device directly to the parenchyma for tissue fusion until the positive feedback signal is received. The parenchyma is then cut using the cutting feature of the same device. Visual evaluation of hemostasis is likewise straightforward once the technique is completed.

Surgical resection of the spleen is indicated for diagnosis and/or treatment of splenic neoplasia, infiltrative disease, traumatic injury, and torsion and as a therapy for immune disorders.² Total splenectomy may take less time and be less technically challenging compared with partial splenectomy or splenorrhaphy if traditional suturing techniques are used.^1,2 Furthermore, one of the most common reasons for resection of the spleen is for diagnosis and treatment of splenic neoplasia.¹ Total splenectomy is often favored for this type of pathology to minimize the risk of recurrence or inadequate surgical margins requiring further surgical intervention. Nevertheless, partial splenectomy remains an important and potentially underused option, especially for trauma, abnormalities found incidentally during abdominal surgery, or isolated lesions where robust surgical margins could be obtained with partial splenectomy.

The important functions of the spleen in dogs and cats remains a compelling reason to preserve this organ where possible. The spleen has important immunologic and hematologic functions in addition to acting as a storage organ for 10–20% of circulating blood.^1,2 In humans, a syndrome known as overwhelming postsplenectomy infection can occur when the spleen is removed, characterized by a severe bacterial sepsis with a lifetime risk of about 5% in splenectomized patients with a mortality rate of 50–70%.¹⁴ This is related to the role of splenic macrophages in removing encapsulated bacteria; however, no similar syndrome has been identified in cats and dogs. In early development the spleen is a site of immune function development and maturation as well as red blood cell maturation.² In adult dogs and cats, the spleen aids in filtration of pathogenic microorganisms and antigenic particles.² The spleen is a site of erythrocyte pruning with older and damaged erythrocytes lacking the elasticity necessary to pass through the splenic sinus, resulting in their culling.¹ Young erythrocytes also spend time conditioning in the spleen to develop their characteristic cell membrane shape and composition prior to release into circulation.¹

In dogs, the role of the spleen as a contractable reservoir for red blood cells has been well established.^1,3,4 There is evidence that canine total splenectomy eliminates exercise-induced polycythemia, reduces exercise-induced oxygen uptake, and decreases the ability of the lungs to diffuse carbon monoxide.^3,4 Cardiac output, blood pressure, and exercise capacity are all decreased in splenectomized dogs.^3,4

A long-term study of beagles found that splenectomized dogs showed a consistent, prolonged increase in red blood cell transit time, which in this study was used to approximate increased erythrocyte deformability.⁵ In case reports of Babesia canis infections in dogs, previous splenectomy has been associated with an increased severity in clinical signs and, in some cases, rapid mortality.⁶ Infection with Mycoplasma haemocanis has also been found to cause worse clinical signs in dogs who have undergone total splenectomy.⁷ In 2004, a canine hemorrhagic shock study had to be cancelled after an outbreak of Mycoplasma caused significant morbidity in the study population after they underwent total splenectomy.⁸Mycoplasma infection in splenectomized dogs has been reported to be difficult to treat, with some cases remaining polymerase chain reaction positive despite months of antibiotic treatment.^7,8

Given the important role of the spleen, it is reasonable to choose partial splenectomy when neoplasia is not strongly suspected or appears confined to a small portion of the spleen. In dogs, splenic neoplasia is common, but one study of dogs found that over half of splenic lesions were non-neoplastic.^2,15 A contemporaneous study in cats found that neoplasia accounted for 37% of splenic lesions.¹⁶ This leaves a significant number of cases potentially suitable for partial splenectomy.

Traditional subtotal splenectomy technique involves isolation of the resectable portion and ligation of adjacent hilar vessels.¹ This causes a line of demarcation to appear in the splenic parenchyma, creating a convenient boundary for tissue division. The parenchyma should then be crushed with the fingertips, clamped, and excised. A time-consuming process of suturing the splenic capsule follows.¹ This process can be shortened by eliminating the need for clamping or suturing when a bipolar vessel-sealing device is used. Alternatively, stapling devices can be used to decrease surgical time. Thoracoabdominal staplers apply staggered lines of stainless-steel staples to the splenic parenchyma to achieve hemostasis prior to resection. Thoracoabdominal staplers come with a variety of staple leg lengths that should be chosen according to the thickness of the spleen. The stapler is positioned to the desired line of resection, then squeezed shut to apply the staples in a linear fashion, and the spleen is resected near the stapled line. When available, these devices may shorten surgical time, but hemostasis may be inadequate if inappropriate staple leg length is chosen.³

Bipolar vessel-sealing devices function by emitting bipolar electrothermal energy to induce collagen and elastin fusion within a compressed area of tissue.¹⁷ Feedback to the device allows it to sense the density of the tissue and regulate the amount of energy emitted accordingly to limit damage to adjacent tissues.¹² Advantages of this device over traditional suture-based hemostatic techniques include shorter surgical times and more effective hemostasis.^18,19 Comparison with other hemostatic devices such as the harmonic scalpel have shown vessel-sealing devices to achieve comparatively better burst pressure and shorter sealing time with relatively low thermal spread.^17–19 Furthermore, this device has been shown to retain functionality after repeated sterilization, making it financially viable in a veterinary setting.²⁰ They are also readily usable in laparoscopic procedures. With the growing popularity of these devices has come research into their use in other tissues. Recently published research has described use of vessel-sealing devices in partial pancreatectomy in both dogs and cats,^9,10 lung lobe biopsy in dogs,¹¹ and soft palate resection in dogs.¹² Astudy in dogs undergoing partial pancreatectomy for insulinoma using a vesselsealing device on the pancreatic parenchyma compared with the traditional suture-fracture method found that using the vesselsealing device shortened both surgery and hospitalization times and resulted in fewer cases of postoperative pancreatitis.¹⁰ In cats, vessel-sealing devices were evaluated for use in ovariohysterectomy on patients with pyometra in a 2017 study. The vessel-sealingdevicewas used on thesuspensory ligament,pedicle,and uterine body; however, patients with a uterine body measuring greater than 0.9 cm were excluded. The authors experienced no complications in the 10 cats ultimately included in the study, and they concluded that vessel-sealing devices are suitable for feline ovariohysterectomy with pyometra.¹³

Conclusion

Given their ability to shorten surgical time and improve hemostasis when properly used, further studies investigating the full spectrum of applications for which the vessel-sealing device is suited are needed. Patient selection is likely to be an important component of success with this therapy. Although hemostasis was well controlled in all patients included in this study, using a bipolar vessel-sealing device on a larger spleen could result in adverse bleeding events, and establishing an objective size cutoff for both dogs and cats would be helpful. In this study, the largest patient included had a body weight of 12.4 kg, and no adverse bleeding was noted in the splenic parenchyma. This may indicate that the technique is suitable for patients around 12 kg or less; however, further investigation may augment this figure. Further studies comparing traditional partial splenectomy with this new technique including determining appropriate patient selection, total surgical time, and short- and long-term outcomes would be beneficial.