Biomechanical Evaluation of Different Numbers, Sizes and Placement Configurations of Ligaclips Required to Secure Cellophane Bands

Intercostal thoracotomy for surgical attenuation of portoazygos extrahepatic portosystemic shunts in three dogs: surgical technique and short-term outcomes

CASE HISTORIES

The medical records of three dogs, presenting to the surgery department at a tertiary private referral hospital (Cork, Republic of Ireland), were retrospectively reviewed. The patients presented for investigation of a 3-day history of progressive lethargy, decreased appetite and hindlimb weakness (Case 1); brachycephalic obstructive airway syndrome and the development of abnormal licking behaviours (Case 2); and a 2-month history of increased thirst with elevated alanine aminotransferase in serum (Case 3).

CLINICAL FINDINGS

Case 1 presented with tachycardia, hindlimb paraparesis and neck pain, while Case 2 presented with facial conformation abnormalities consistent with brachycephalic obstructive airway syndrome. General physical examination and neurological assessment were within normal limits for Case 3. Baseline serum biochemistry measurements, in all three patients, indicated elevated activities of alanine aminotransferase and alkaline phosphatase, as well as elevated concentrations of resting bile acids (BA), suggestive of an extrahepatic portosystemic shunt. Abdominal computed tomography (CT) angiography was performed, for each dog, which revealed the presence of a portoazygous shunt (PAS) with final insertion into the caudal azygos vein within the thorax.

TREATMENT AND OUTCOME

Abdominal CT angiography images were used for surgical planning and a right-sided intercostal thoracotomy was performed. The location of the thoracotomy was patient-specific and located cranial to the diaphragm, either at the point of PAS insertion into the azygos vein or one rib-space caudal to the insertion, as determined by pre-operative CT images. The intercostal thoracotomy provided good visualisation of the PAS and an appropriate surgical field for placement of a thin film band around the PAS. No surgical complications or post-attenuation seizures were observed. All patients appeared comfortable on oral analgesia and were discharged from the hospital by 48 hours after surgery. All patients demonstrated a clinical improvement when reassessed 6-8 weeks after surgery, and Cases 2 and 3 demonstrated a reduction of resting BA concentrations to within normal limits. The third patient (Case 1) had a considerable reduction in the concentration of resting BA from >140 µmol/L to 20 µmol/L (reference range 0-10 µmol/L) 6-8 weeks after surgery.

CLINICAL RELEVANCE

A right-sided intercostal thoracotomy can be considered for surgical management of PAS in dogs. While both intraoperative and short-term results appear promising, further prospective studies are required before this approach can be recommended as the preferred approach for PAS attenuation.

Feasibility of thoracoscopic attenuation of the azygos vein as a model for portoazygos shunts: A canine cadaveric study

OBJECTIVE

To evaluate the feasibility of thoracoscopic placement of three vascular attenuation devices by using the azygos vein as a model for portoazygos (PA) shunts and to describe the approach for thoracoscopic placement of these attenuation devices in small breed dogs.

STUDY DESIGN

Randomized, prospective, cadaveric study.

ANIMALS

Cadavers of 10 adult small breed dogs.

METHODS

Cadavers were placed in sternal recumbency with left dorsolateral obliquity, and three thoracoscopic ports were established in the right hemithorax at the mid-10th intercostal space and dorsal third of the ninth and 11th intercostal spaces. The caudal azygos vein was thoracoscopically isolated along three adjacent segments bordered by four intercostal arteries, beginning just cranial to the first intercostal artery visualized cranial to the diaphragm. Three attenuation devices including coated cellophane, uncoated cellophane, and a 5-mm ameroid constrictor were thoracoscopically placed around one segment in each dog. Minor port access modifications were required to improve working space and triangulation in three dogs. Ability to successfully place the device, time required for placement, endoscopic clip configuration, and complications associated with placement were recorded.

RESULTS

Median dog weight was 7.7 kg (range, 1.8-11). All attenuation devices were successfully placed thoracoscopically in all cadavers. No difference was detected in time required for placement between the ameroid constrictor and coated and uncoated cellophane (range, 2.3-33.8 minutes, P = .8).

CONCLUSION

Ameroid constrictors and thin film bands were consistently placed via thoracoscopy around the caudal azygos vein of small breed dogs.

CLINICAL SIGNIFICANCE

These results justify further investigation of thoracoscopic PA shunt attenuation in affected dogs.

Long-term clinical outcomes of dogs with single congenital extrahepatic portosystemic shunts attenuated with thin film banding or ameroid ring constrictors

OBJECTIVE

To compare long-term clinical outcomes of dogs with single congenital extrahepatic portosystemic shunts (CEHPSS) treated with thin film banding (TFB) consisting of polyolefin fiber or ameroid ring constrictor (ARC) placement in dogs.

DESIGN

Retrospective, two-center clinical study.

ANIMALS

Client-owned dogs (n = 123) with single CEHPSS undergoing gradual attenuation via TFB (n = 85) or ARC (n = 38).

METHODS

Medical records of dogs with CEHPSS were reviewed. Follow-up data were collected from the referring veterinarian and/or owner via standardized questionnaire. Data were analyzed to compare short-term mortality rate and long-term outcome (>6 months).

RESULTS

Dogs in the TFB group were older than dogs in the ARC group (median age, 19 vs 12 months, respectively; P = .01). There was no difference in survival to discharge between dogs in the TFB (81/85 [95.3%]) and ARC (37/38 [97.4%]; P > .99) groups. Preoperative levetiracetam was more frequently administered to dogs treated with TFB (64/85 [75.3%]) than to dogs treated with ARC (15/38 [39.5%;] P = .0002). Postoperative seizures were reported in 10 (8.1%) dogs; their prevalence did not differ between dogs treated with TFB (9/85 [10.6%]) and dogs treated with ARC (1/38 [2.6%]; P = .17). Median follow-up time for dogs treated with TFB (58.0 months, range 8-130) and ARC (63.3 months, range 7-138; P = .24) did not differ.

CONCLUSION

Gradual attenuation of a single CEHPSS with either TFB or ARC resulted in similar long-term clinical outcomes and low postoperative morbidity and mortality rates.

CLINICAL SIGNIFICANCE

Thin film banding (polyolefin fiber) offers an alternative leading to clinical outcomes similar to ARC in dogs with single CEHPSS.

Thin film occlusion of an intra-abdominal vein in cats

OBJECTIVE

To evaluate the occlusion of an intra-abdominal vessel as a model of an extrahepatic portosystemic shunt by thin film banding in a controlled setting and to document histologically the perivascular region's response to thin film banding after 8 weeks.

STUDY DESIGN

Experimental study.

ANIMALS

Six purpose-bred healthy domestic short hair cats.

METHODS

Thin film bands were placed around the external iliac vein, with a sham procedure on the contralateral vessel. Closure rates were monitored via computed tomographic angiography (CTA) every 2 weeks for a total of 8 weeks. After 8 weeks, the vessels were resected, if possible, and submitted for histopathologic evaluation.

RESULTS

All cats tolerated the procedure without surgical complications. Eight weeks after surgery, closure was evaluated as complete in one cat, marked in two cats, moderate in one cat, and mild in two cats according to CTA. Histological examination (in three cats) was consistent with chronic, multifocal, granulomatous inflammation with moderate fibrosis and collagen degeneration.

CONCLUSION

Venous occlusion was inconsistent and often incomplete 8 weeks after thin film banding of the external iliac vein despite the presence of moderate to abundant perivascular fibrous tissue.

CLINICAL SIGNIFICANCE

Vascular occlusion by thin film banding in cats is mainly incomplete after 2 months. This study supports the theory that high level of residual shunting may be expected in some cats after thin film banding.

Complications and outcome of cats with congenital extrahepatic portosystemic shunts treated with thin film: Thirty-four cases (2008-2017)

BACKGROUND

Congenital extrahepatic portosystemic shunts (CEHPSS) are rare in cats. Outcome after attenuation of CEHPSS with thin film has been described in a small number of cases.

OBJECTIVES

To describe the clinical presentation, postoperative complications, and outcome of cats treated with thin film to attenuate CEHPSS.

ANIMALS

Thirty-four cats with CEHPSS were identified from the database of 3 institutions over 9 years.

METHODS

Retrospective study. Medical records were reviewed to identify cats with a diagnosis of a CEHPSS that underwent surgical attenuation. Congenital extrahepatic portosystemic shunts were suspected from clinical signs, clinicopathologic findings, and diagnostic imaging, and confirmed at exploratory laparotomy. Cats treated with thin film band attenuation were included. Postoperative complications and follow-up were recorded.

RESULTS

Complications were recorded in 11 of 34 cats. Deaths related to CEHPSS occurred in 6 of 34; 4 cats did not survive to discharge. Persistent seizures were the cause of death in 4 cats. Seizures were recorded in 8 of 34 cats after surgery; all these cats received preoperative antiepileptic drugs. Serum bile acid concentrations normalized in 25 of 28 of the cats for which data was available. Three cats had persistently increased serum bile acid concentrations and underwent a second exploratory laparotomy. One had a patent shunt, the other 2 had multiple acquired portosystemic shunts. Median follow-up was 8 months (0.5-84 months).

CONCLUSIONS AND CLINICAL IMPORTANCE

Congenital extrahepatic portosystemic shunts attenuation using thin film in cats carries a good short- and mid-term prognosis if they survive the postoperative period. Seizures were the most common cause of death.

The chemical and ultra-structural analysis of thin plastic films used for surgical attenuation of portosystemic shunts in dogs and cats

The objective of the study was to (1) characterize and compare the chemical composition at the surface, subsurface and in the bulk of thin plastic films used for portosystemic shunt attenuation in their native state and after plasma exposure. (2) Assess the presence, concentration and location of irritant compounds (e.g dicetyl phosphate) within the films. Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-ray Photoelectron Spectroscopy (XPS) and dynamic Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were used to analyze thirteen thin plastic films. Sample thickness was visualized and measured using Scanning Electron Microscopy (SEM). Sample thicknesses were compared using a one-way ANOVA. XPS reported low phosphorous concentrations (surrogate marker of dicetyl phosphate) between 0.01 and 0.19% wt at the sample surfaces (top 10 nm). There were significant differences between film thicknesses (P < .001) observed by SEM. The ATR-IR and ToF-SIMS identified four distinct surface and bulk chemical profiles: 1) Cellophane, 2) Polypropylene, 3) Modified Cellophane, and 4) Unique. Following plasma immersion for 6 weeks, samples showed little change in film thickness or chemical composition. This study confirmed that films used to attenuate portosystemic shunts were commonly not pure cellophane, with significant variations in surface and bulk chemistry. Suspected irritant compounds were not readily identifiable in significant proportions. Pronounced variability existed in both the thickness and chemical composition of these films (surface vs. bulk). The present findings lead to a legitimate question about the reproducibility of shunt occlusion when using thin plastic films from different origins.

Recanalisation of a congenital extrahepatic portosystemic shunt previously attenuated with cellophane banding in a cat

Case summary

A congenital extrahepatic portosystemic shunt was attenuated with commercial roll cellophane banding in a cat and postoperative liver changes were monitored using CT angiography (CTA). The patient clinically improved after cellophane banding, characterised by resolution of hepatic encephalopathy, weight gain, reference interval (RI) bile acid stimulation tests, as well as CTA-documented increased liver size, increased hepatic vasculature and shunt attenuation. Six months later the cat re-presented with recurrence of clinical signs and increased bile acids. CTA confirmed recanalisation of the shunt. Shunt attenuation was repeated using pure cellophane banding and nearly complete closure of the shunt was later documented by CTA. Seven months later, recanalisation was again documented via CTA and associated with clinical signs and increased bile acids. Complete ligation of the shunt was achieved using a polypropylene ligature and a titanium ligating clip. At long-term follow-up, the cat was clinically well, and bile acids and biochemistry were within the RIs.

Relevance and novel information

This is the first report of CTA-documented recanalisation of an extrahepatic portosystemic shunt previously attenuated with cellophane banding. Recanalisation should be considered as a differential for recurrence of hepatic encephalopathy following cellophane banding.