Manejo Cirúrgico de Shunts Esplenofrénicos em Três Gatos

Resumo

Background: Portosystemic shunts are abnormal vessels that communicate with the portal and systemic venous circulation, causing bypass of blood from the gastrointestinal tract to the liver. Cats with portosystemic shunts may show clinical signs of neurological, gastrointestinal, and urinary tract diseases. The diagnosis is mainly based on computed tomography, and both medical and surgical treatment are recommended for patients with portosystemic shunts. However, the prognosis of long-term medical treatment without surgical management is unsatisfactory in cats. For surgical management of the shunting vessel, surgical correction using a gradual occlusion device, such as an ameroid ring constrictor, is indicated to redirect portal blood into the liver. However, surgical approaches for extrahepatic splenophrenic shunts require careful consideration since the terminating part of the shunting vessel is embedded in the central tendon of the diaphragm. This study presents the outcomes of ameroid ring constrictor placement on the shunting vessel caudal to the diaphragm in 3 cats with splenophrenic shunts.
Cases: All 3 patients showed hypersalivation during the physical examination. On serum biochemical analyses, all patients showed increased ammonia and postprandial bile acid concentrations, indicating a portosystemic shunt. Based on blood tests, radiography, ultrasonography, and computed tomography, an extrahepatic splenophrenic shunt originating from the splenic vein and entering the caudal vena cava at the level of the diaphragm was diagnosed. Placement of an ameroid ring constrictor caudal to the diaphragm was performed to gradually attenuate the shunting vessel. In Case 3, additional cystostomy was performed to remove the urinary bladder calculus. All 3 cats recovered uneventfully from anesthesia. In Case 1, the ultrasonographic examination conducted during the postoperative period revealed mild abdominal effusion, which spontaneously resolved within a few days. In Case 3, the patient showed seizure activity, which resolved spontaneously. The clinical signs in all patients disappeared after surgery. Follow-up studies were performed on days 7, 14, 28, and 56 after surgery. All cats recovered after surgery without major complications.

Discussion: Portosystemic shunts are generally classified as intrahepatic or extrahepatic. In cats, a single extrahepatic shunt originating from the left gastric vein and entering the caudal vena cava is the most frequent type of congenital portosystemic shunt. Intrahepatic portosystemic shunt in cats is much less described, but the most commonly reported type is the left divisional vessel. Ligation of the shunting vessel around the vessel as close to its insertion into the caudal vena cava as possible is generally recommended. If the ligation is placed between the tributaries and portal vein, the tributary still acts as a shunting vessel, resulting in hepatofugal flow. However, if the ligation is placed between the tributaries and caudal vena cava with complete occlusion, the tributary no longer acts as a shunting vessel, resulting in hepatopetal flow. In patients with a splenophrenic shunt, the shunting vessel terminates in the middle of the diaphragm, making it difficult to isolate the shunting vessel without any attachment to the surrounding tissues. Therefore, in the current study, the ameroid ring constrictor was placed caudal to the diaphragm. As shown in the current study, placement of the ameroid ring constrictor in the splenophrenic shunt in 3 cats yielded satisfactory outcomes.
Keywords: ameroid ring constrictor, cat, splenophrenic shunt.