Robert N. White

Objectives: To describe the signalment, clinical presentation, diagnostic findings, surgical management and outcomes of dogs undergoing surgical management for pleuroperitoneal diaphragmatic hernia. Materials and Methods: Medical records from seven referral hospitals were retrospectively reviewed to identify dogs diagnosed with pleuroperitoneal diaphragmatic hernia during the study period. Data collected included signalment, clinical presentation, diagnostic imaging findings, surgical findings, post‐operative complications and outcome. Complications were classified using the Clavien–Dindo grading system. Results: Twenty dogs met the inclusion criteria. Median age at surgery was 8.9 months (3.0 months to 10.2 years) and Cavalier King Charles Spaniels represented 30% (6/20) of cases. Seventeen dogs presented with clinical signs attributable to pleuroperitoneal diaphragmatic hernia, most commonly vomiting (45%, 9/20), tachypnoea (40%, 8/20) and dyspnoea (35%. 7/20), while three hernias were diagnosed incidentally. The stomach was the most frequently herniated organ (65%, 13/20), followed by the spleen (50%, 10/20) and small intestine (45%, 9/20). Hernias were most commonly located in the dorsolateral left crus of the diaphragm (80%, 16/20). Surgical enlargement of the defect to facilitate reduction of herniated viscera was required in 35% (7/20) of cases. Nineteen dogs underwent successful herniorrhaphy; one dog was euthanased intraoperatively because of extensive jejunal necrosis associated with mesenteric volvulus. Post‐operative complications occurred in 47% (9/19) dogs, and all dogs survived to discharge. One dog developed hernia recurrence. Clinical Significance: Pleuroperitoneal diaphragmatic hernia may present with acute respiratory and gastrointestinal signs or be identified incidentally during diagnostic imaging or surgery. Surgical correction is associated with favourable outcomes and a low recurrence rate.

Objectives: To determine the difference in complication rate, gastrointestinal grade and requirement for ongoing medical and/or surgical management following hiatal hernia repair in dogs with and without gastropexy.Materials and Methods: Clinical records were reviewed retrospectively for dogs that had undergone surgical hiatal hernia repair at two veterinary referral centres between April 2012 and March 2022. Pre‐operative grading of gastrointestinal signs and brachycephalic obstructive airway syndrome was performed. All dogs had an oesophagopexy and phrenoplasty. Referring primary veterinary practices and clients were contacted to obtain follow‐up information. Fisher's exact tests and Mann Whitney tests were used to assess pre‐ and intra‐operative similarities between groups. Wilcoxon signed rank tests were used to determine the changes in gastrointestinal grade at short‐ (6 months) follow‐up.Results: Forty‐one dogs which underwent oesophagopexy and phrenoplasty were included. Fifteen dogs had no gastropexy performed and 26 dogs had left‐sided gastropexy performed. Dogs that underwent gastropexy (n=8, 29%, 95% CI: 13 to 51%) were significantly more likely to require further surgery related to the initial surgery or persistence of gastrointestinal signs compared to dogs that had no gastropexy (n=0, 0%, 95% CI: 0 to 18%) . This difference was not significant when dogs which had further surgery to address brachycephalic obstructive airway syndrome were excluded. Gastrointestinal grade significantly improved for both groups at both short‐ and long‐term follow‐up. There was no significant difference in overall complication rate, gastrointestinal grade or requirement for further medical treatment between groups.Clinical Significance: A left‐sided gastropexy is not required for successful surgical repair of hiatal hernia in dogs provided oesophagopexy and phrenoplasty are performed.

Objectives: The aim of this study was to evaluate two unilateral laryngoplasty (arytenoid lateralisation) techniques for use in the surgical management of laryngeal paralysis in cats. Methods: Left cricoarytenoid abduction (lateralisation) was performed in 20 ex vivo cat larynges; 10 following complete cricoarytenoid disarticulation (group LAA-dis) and 10 following no cricoarytenoid disarticulation (group LAA-nodis). For both groups, left arytenoid abduction (LAA) was measured in the resting and postoperative larynges using image analysis software. Measurements were evaluated using the Mann–Whitney U-test. For both groups, dorsal images of the postoperative larynges were assessed visually for evidence of epiglottic coverage of the entrance to the larynx. Results: The mean percentage increase in LAA was 311.5% and 199.4% ( P <0.006) for group LAA-dis (complete cricoarytenoid disarticulation) and group LAA-nodis (no cricoarytenoid disarticulation), respectively. In both groups, there was no evidence of a lack of epiglottic coverage of the entrance of the larynx for any of the postoperative larynges. Conclusions and relevance: Placement of a single, tensioned suture between the muscular process of the left arytenoid cartilage and the caudolateral aspect of the ipsilateral cricoid cartilage (unilateral cricoarytenoid lateralisation) resulted in abduction of the left arytenoid cartilage and a corresponding increase in the area of the rima glottidis on the operated side. The clinical significance of the difference in outcome between left cricoarytenoid abduction following complete cricoarytenoid disarticulation and abduction following no cricoarytenoid disarticulation remains unclear, and both might be considered appropriate for the surgical management of laryngeal paralysis in the cat.

The development of postattenuation neurologic signs (PANS) is a poorly understood and potentially devastating complication after surgical attenuation of congenital portosystemic shunts in dogs. Postattenuation neurologic signs include seizures but also more subtle neurologic signs such as depression, behavioral changes, tremors, and twitching. They most commonly occur within 7 days postoperatively and are typically unrelated to hyperammonemia, hypoglycemia, or electrolyte disturbances. This narrative review summarizes the findings of 50 publications from 1988‐2020 that report occurrence ofPANS. While most published reports included only dogs affected by postattenuation seizures (PAS), others included dogs with any form ofPANS. Overall,PANS(includingPAS) affected 1.6%‐27.3% of dogs, whereas incidence ofPASranged from 0%‐18.2%. The etiology ofPANSremains unknown; however, several theories have been proposed. Risk factors include preoperative hepatic encephalopathy, increasing age, and possibly certain breeds and extrahepatic shunt morphology. There is increasing evidence that prophylactic antiepileptic drugs do not preventPANS. Treatment is centered around controlling neurologic signs with antiepileptic drugs and providing supportive intensive care. The 30‐day survival rate in studies that included a minimum of four dogs affected byPANSwas 0%‐100% (median, 50.0%) and 0%‐75.0% (median, 37.5%) for those withPAS. Mortality associated withPANSwas typically related to occurrence of generalized seizure activity. Prognostic factors positively associated with short‐term survival included having a history of preoperative seizures and development of focal seizures only. If affected dogs survived to discharge, survival for several years was possible, and the majority of neurologic signs manifested as part of the phenomenon ofPANSappeared to resolve.

STRUCTURED SUMMARY: Objective: To re‐evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen.Material and Methods: A retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work‐up for a congenital extrahepatic portosystemic shunt.Results: In total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed.Clinical Significance: A precise pre‐treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field.

Objective To identify prognostic factors for short‐term survival of dogs that experience seizures within 7 days after surgical correction of single congenital extrahepatic portosystemic shunts (cEHPSS). Study design Multi‐institutional retrospective study. Sample population Ninety‐three client‐owned dogs. Methods Medical records at 14 veterinary institutions were reviewed to identify dogs that underwent surgical attenuation of a single cEHPSS from January 1, 2005 through February 28, 2018 and experienced postattenuation seizures (PAS) within 7 days postoperatively. Logistic regression analysis was performed to identify factors associated with 1‐month survival. Factors investigated included participating institution, signalment, shunt morphology, concurrent/historical conditions, presence of preoperative neurologic signs, presence of preoperative seizures, aspects of preoperative medical management, surgical details including method and degree of shunt attenuation, type of PAS (focal only or generalized ± focal), drugs administered as part of the treatment of PAS, and development of complications during treatment of PAS. Results Thirty (32.3%) dogs survived to 30 days. Seventy‐six (81.7%) dogs experienced generalized PAS. Factors positively associated with short‐term survival included having a history of preoperative seizures (P = .004) and development of focal PAS only (P = .0003). Most nonsurvivors were humanely euthanized because of uncontrolled or recurrent seizures. Conclusion Dogs that experienced PAS that had a history of preoperative seizures and those that experienced focal PAS only had significantly improved short‐term survival. Clinical significance The results of this study provide information that will help in the counseling of owners who seek treatment for PAS after surgical correction of cEHPSS. © 2020 The American College of Veterinary Surgeons.

Objective To describe the implications of extrahepatic portosystemic shunt morphology for the chosen site of shunt closure in dogs and cats. Methods A retrospective review of a consecutive series of dogs and cats managed for congenital extrahepatic portosystemic shunts. Results In total, 54 dogs and 10 cats met the inclusion criteria, revealing five distinct shunt types: left gastrophrenic, right gastrocaval (types Ai, Aii and Aiii), splenocaval, colocaval and left gastro‐azygos. Without exception, findings of computed tomography angiography and direct gross observations at the time of surgery confirmed four consistent sites of communication between the anomalous shunting vessel and the systemic venous system: the caudal vena cava at the level of the epiploic foramen; the left phrenic vein at the level of the oesophageal hiatus; the azygos vein at the level of the aortic hiatus; and the caudal vena cava or iliac vein at the level of the 6th or 7th lumbar vertebrae. The use of intraoperative mesenteric portography was effective for confirming that at the time of surgery all portal tributary vessels were proximal to the point of shunt attenuation. Conclusions Findings confirmed that for the common types of extrahepatic portosystemic shunts there were only four consistent sites of communication between the shunt and the systemic venous system. This information supports the use of a systematic approach for the location and attenuation of shunts in dogs and cats.

In this essay we use clinical evidence and knowledge of anatomy to examine the relationship between blood flow and formation of congenital extrahepatic portosystemic shunts in dogs and cats. First we report on the clinical findings in a series of 50 dogs and 10 cats and then systematically review peer‐reviewed data on the detailed anatomy of shunts in dogs and cats. In dogs four types of shunt: spleno‐caval, left gastro‐phrenic, left gastro‐azygos and those involving the right gastric vein account for 94% of extrahepatic shunts. Cats also exhibit four types of shunt: spleno‐caval, left gastrophrenic, left gastro‐caval and left gastro‐azygos, and the first three of these account for 92% shunts in this species. Our findings lead us to propose that preferential blood flow influences the subsequent formation of one of a number of defined and consistent congenital extrahepatic portosystemic shunts in dogs and cats.

Objectives: Comparison of intra‐operative mesenteric portovenography and computed tomographic angiography for the documentation of the portal vasculature in patients with single extrahepatic portosystemic shunts.Methods: Retrospective study of patients with extrahepatic portosystemic shunts that underwent preoperative computed tomographic angiography and intra‐operative mesenteric portography. Studies were compared for identification of the intra‐ and extrahepatic portal vasculature.Results: Computed tomographic angiography demonstrated all four portal vein tributaries and sub‐tributaries. Intra‐operative mesenteric portography inconsistently demonstrated the cranial mesenteric vein, the gastroduodenal vein (12 of 49 dogs and 0 of 10 cats), splenic vein (46 of 49 dogs and 8 of 10 cats) and caudal mesenteric vein (3 of 49 dogs and 2 of 10 cats). Computed tomographic angiography showed the intrahepatic portal vein with shunts emanating from the left gastric vein, splenocaval shunts or shunts involving the left colic vein. It showed intrahepatic portal branching in 5 of 12 patients with shunts involving the right gastric vein. Intra‐operative mesenteric portography showed the intrahepatic portal vein in 29 of 59 patients but was outperformed by computed tomographic angiography in all cases except those patients with a shunt involving the right gastric vein.Clinical Significance: In cases that have undergone diagnostic preoperative computed tomographic angiography there is no indication for diagnostic intra‐operative mesenteric portovenography before ligation. In contrast, portovenography performed “after” temporary full ligation of the shunt provides clinical useful information and might be considered an integral investigation during shunt attenuation surgery.

OBJECTIVE: To describe the anatomy of congenital portosystemic shunts involving the left colic vein in dogs and cats.METHODS: Retrospective review of a consecutive series of dogs and cats managed for congenital portosystemic shunts. For inclusion a shunt involving the left colic vein with recorded intraoperative mesenteric portovenography or computed tomography angiography along with direct gross surgical observations at the time of surgery was required.RESULTS: Six dogs and three cats met the inclusion criteria. All cases had a shunt which involved a distended left colic vein. The final communication with a systemic vein was variable; in seven cases (five dogs, two cats) it was via the caudal vena cava, in one cat it was via the common iliac vein and in the remaining dog it was via the internal iliac vein. In addition, two cats showed caudal vena cava duplication.CLINICAL SIGNIFICANCE: The morphology of this shunt type appeared to be a result of an abnormal communication between either the left colic vein or the cranial rectal vein and a pelvic systemic vein (caudal vena cava, common iliac vein or internal iliac vein). This information may help with surgical planning in cases undergoing shunt closure surgery.