Congenital portosystemic shunts are abnormal vessels connecting the portal and systemic venous circulatory systems, diverting portal blood away from the liver.1 The incidence of CPSSs in cats examined at North American veterinary schools is reportedly 2.5/10,000 cats.1 Single CEPSSs are more commonly diagnosed in cats, although intrahepatic portosystemic shunts have been reported.1–6
Long-term medical treatment of CEPSSs has been associated with a poor outcome in cats.7,8 The goal of such treatment is to reduce production and absorption of ammonia and other toxicants from the gastrointestinal tract. Surgical treatment consists of complete or partial ligation of the shunt with nonabsorbable suture or gradual occlusion with an ARC or cellophane banding. The prognosis for cats with a CEPSS that undergo surgical attenuation of the shunt is reportedly fair to poor.5,9,10 Recently, 3 studies were conducted to assess the outcome of cats that underwent complete occlusion of a CEPSS by means of silk or polypropylene ligation5 or gradual shunt occlusion with ARCs.9,10 Associated long-term survival varied between 56%9 and 85%.5,10 The use of cellophane banding for gradual attenuation of a CEPSS has only been reported for 5 cats.11 The purpose of the study reported here was to retrospectively evaluate the long-term outcome of cats with a CEPSS that were surgically treated by means of cellophane banding.
Materials and Methods
Case selection—From January 2000 through March 2007, medical records of all cats with a diagnosis of CEPSS that underwent surgical attenuation at our institution were reviewed. A presumptive diagnosis of CEPSS was made on the basis of findings from the medical history, duration of clinical signs, hematologic and serum biochemical analysis, abdominal ultrasonography, and transcolonic nuclear scintigraphy imaging with technetium Tc 99m. A definitive diagnosis was made on the basis of shunt location as identified during exploratory celiotomy. Cats treated with an ARC or ligation were excluded from the study. Cats treated with cellophane banding without intraoperative attenuation were included.
Medical records review—For each cat, breed, age at surgery, body weight, and sex were recorded as well as results of preoperative hematologic and serum biochemical analyses, including SBA concentration measured 12 hours after food withholding and 2 hours postprandially. Also recorded were medical and dietary treatments (before and after surgery), results of abdominal ultrasonography, shunt fraction, and perioperative complications (eg, hemorrhage or hypotension). Hypotension was defined as mean arterial blood pressure < 60 mm Hg. Shunt fraction was calculated by the same board-certified radiologist in all cats. Postoperative complications during hospitalization (eg, euthanasia, signs of neurologic [eg, seizures, depression, or lethargy] or digestive [eg, inappetence, vomiting, or diarrhea] problems, or an abnormality in rectal temperature or serum glucose concentration) were considered short-term complications and recorded as such. Hypothermia was defined as a rectal temperature < 37.7°C (99.86°F).
Follow-up—Referring veterinarians or owners were contacted and asked about cat survival, results of the most recent serum biochemical analysis, and the presence of any abnormal clinical signs at the time of follow-up. Questions pertained to current cat status with respect to vomiting, diarrhea, inappetence, neurologic status (eg, ataxia, seizures, or blindness), behavior (eg, lethargy or signs of depression), polyuria, polydipsia, dysuria, and urolithiasis.
Statistical analysis—Data analysis was performed with commercially available statistical software.a Kaplan-Meier actuarial survival analysis was used to determine long-term survival. Cats that died of their disease were not censored, whereas cats that were lost to follow-up, died of causes unrelated to disease, or were alive at the time of the study concluded were censored at that point. Survival time was calculated from the time of surgery to the time of last follow-up. A log rank test was used to compare median survival times between cats with or without seizures before surgery. The Fisher exact test was used to evaluate whether the presence of seizures before surgery was associated with development of seizures after surgery. Significance was set at a value of P < 0.05. Data are summarized as median and range.
Results
Cats—Congenital portosystemic shunts were diagnosed in 1 Birman and 8 domestic shorthair cats. Median body weight was 2.4 kg (5.3 lb; range, 1.4 to 4.6 kg [3.1 to 10.1 lb]). Median age was 16 months (range, 3.5 to 102 months). Seven cats were < 25 months old. Five cats were female (3 spayed), and 4 were male (2 castrated).
Presurgical findings—The most common clinical abnormalities in the study cats with a CEPSS at the initial evaluation were neurologic defects (ptyalism [n = 5 cats], seizures [4], and blindness [1]) and lethargy (5). Other abnormalities included urinary signs (n = 3 cats), copper-colored irises (2), and digestive signs (2). One of the 9 cats was brought to the hospital because it had a long recovery from anesthesia.
The median duration of clinical signs prior to diagnosis of CEPSS was 60 days (range, 4 to 90 days). Results of the CBC and serum biochemical analyses performed prior to surgery were summarized (Table 1). Preprandial SBA concentration was measured in only 2 cats. Seven cats were fed a low-protein diet before surgery, and 9 received medications including antimicrobials (amoxicillin-clavulanic acid [n = 5 cats], metronidazole [3], or enrofloxacin [1]), lactulose, or both. The median duration of this preoperative treatment was 7 days (range, 1 to 14 days). One cat had started to develop intermittent seizures 4 days prior to initial evaluation at the hospital; therefore, phenobarbital was administered 3 days preoperatively and postoperatively. No therapeutic blood phenobarbital concentration was recorded. One cat had intermittent seizure-like activity for approximately 2 months. This cat also had ptyalism and lethargy, and all of these clinical signs appeared to improve but remained mild with medical management (low-protein diet and antimicrobial treatment). One cat had a 2-month history of tremors, ataxia, and intermittent seizures. Another cat had a 3-month history of seizures, accompanied by copper-colored irises and ptyalism.
Median (range) values for results of hematologic and serum biochemical analyses in 9 cats with a CEPSS before shunt occlusion by cellophane banding.
Variable | Reference limits | Value |
---|---|---|
PCV (%) | 30–44 | 31 (23–44) |
Neutrophil count (X 103 cells/μL) | 2.5–12.5 | 8.0 (2.9–10.9) |
Albumin (mg/dL) | 2.8–4.2 | 2.8 (2.4–3.5) |
Alanine aminotransferase (U/L) | 25–120 | 84 (34–252) |
Alkaline phosphatase (U/L) | 11–61 | 119 (18–308) |
SUN (mg/dL) | 16–35 | 15 (9–39) |
Glucose (mg/dL) | 69–136 | 112 (87–160) |
Preprandial SBA (μmol/L)* | < 7 | 112 (4–194) |
Postprandial SBA (μmol/L) | < 15 | 112 (14–287) |
Values were available for only 2 cats.
Preprandial SBA concentration was measured 12 hours after food withholding; postprandial SBA concentration was measured 2 hours after a meal.
Abdominal ultrasonography aided detection of an extrahepatic portosystemic shunt in 4 cats and a suspected extrahepatic portosystemic shunt the other 5. Transcolonic nuclear scintigraphy was performed pre-operatively in 4 cats. Median shunt fraction was 59.5% (range, 50% to 86%).
Surgical findings—Placement of the cellophane band was performed as described elsewhere,11 except that the band was positioned in complete contact around the CEPSS and secured with titanium clips without any occlusion of the shunt.12 At surgery, all shunts were confirmed as extrahepatic. Two cats had a portoazygos shunt, and the remaining 7 had a portocaval shunt. In 4 of the 7 cats with a portocaval shunt, the shunt originated from the left gastric vein. In the other 3 cats, the shunt was joining the vena cava cranial to the liver.
All cats developed variable degrees of hypotension during surgery. Hypotension was treated by dobutamine administration in 8 cats, hetastarch administration in 5 cats, and blood transfusion in 1 cat. The cat that received the blood transfusion had excessive bleeding during shunt dissection. Liver biopsies were performed in all cats. Histologic analyses of biopsy specimens revealed portoarteriolar reduplication (n = 4 cats), arteriolar hyperplasia (3), lobular atrophy (1), and periportal fibrosis (1).
Postsurgical findings—Median duration of postoperative hospitalization was 2 days (range, 1 to 3 days). Seven of the 9 cats survived to 15 days after surgery. Three cats developed immediate postoperative complications (hypothermia or seizures, but no other abnormalities). Two cats, which had seizures before surgery, developed seizures afterward while in the hospital; these cats had not been treated specifically for their seizures prior to surgery and were euthanized at 2 and 3 days afterward because of the uncontrollable nature of the seizures. Medical management of postoperative seizures in 1 cat included diazepam administration; however, when the cat did not respond, a constant rate infusion of propofol was administered. In the other cat, only a constant rate infusion of propofol was used at a titration intended to keep the cat unconscious for 2 or 3 days. Assisted ventilation was not necessary during that period. After the propofol dose was reduced, persistent seizures were observed and the owner decided to euthanize the cat. The proportion of cats with seizure activity after surgery was not significantly (P = 0.72) higher for cats that already had seizures before surgery than for cats that did not have seizures at that time. The presence of seizures before surgery did not appear to influence the proportion of surviving cats (P = 0.31; Figure 1); however, the power to detect a difference in survival rates between cats with and without seizures was low (1 – β = 0.61).
Kaplan-Meier curve of survival time in cats with (dashed line; n = 4) and without (solid line; 5) seizure activity that subsequently underwent surgical attenuation of a CEPSS by means of cellophane banding. Survival times did not differ significantly (P = 0.31) between groups. Dots represent each cat.
Citation: Journal of the American Veterinary Medical Association 238, 1; 10.2460/javma.238.1.89
The lowest median blood glucose concentration measured postoperatively was 115 mg/dL (range, 82 to 157 mg/dL). Six cats received IV administration of crystalloid fluids with 2.5% dextrose to prevent hypoglycemia. The median lowest rectal temperature recorded after surgery was 37.8°C (100.04°F; range, 32.8° to 39.4°C [91.04° to 102.92°F]). While hospitalized, 3 cats developed hypothermia after surgery, including the 2 cats with postoperative seizures.
Postoperative treatment generally consisted of 4 weeks' treatment with antimicrobials (amoxicillin-clavulanic acid; n = 7 cats), a low-protein diet (7), and 6 weeks' to 6 months' treatment with lactulose (6). One cat continued to receive phenobarbital, which was administered 3 days preoperatively because of preoperative seizures. No neurologic signs were observed in this cat after surgery.
Follow-up findings—The median follow-up period was 150 days (range, 2 to 2,080 days) for all cats and 240 days for the 7 cats that survived the postoperative period. Two cats were lost to follow-up at 150 and 240 days after surgery. Four cats were still alive at the last follow-up. By the survival analysis, the 1, 2, and 3 year survival rate was 66% (Figure 2).
Kaplan-Meier curve of survival time in 9 cats that underwent surgical attenuation of a CEPSS by means of cellophane banding. Dots represent each cat.
Citation: Journal of the American Veterinary Medical Association 238, 1; 10.2460/javma.238.1.89
One month after surgery, 7 cats did not have any clinical signs typically associated with CEPSS. The postprandial SBA concentration was less than the upper reference limit (ie, < 15 μmol/L) in 5 cats by 3 months after surgery (Figure 3). One cat developed signs related to hepatic encephalopathy, seizures, and incontinence 1.5 months after surgery. These signs could not be medically managed, and the cat was euthanized 105 days after surgery. One cat had persistent ptyalism, considered a minor complication, > 3 years after surgery, although its postprandial SBA concentration was within reference limits 24 months after surgery. One cat had a cystotomy performed to remove biurate ammonium stones > 3 years after surgery but had no other clinical signs associated with the CEPSS. In that cat, the postprandial SBA concentrations were within reference limits when measured 1 and 3 months after the cellophane banding procedure.
Postprandial SBA concentrations at various measurement points in 5 cats (identified by number) that underwent surgical attenuation of a CEPSS by means of cellophane banding. Concentrations were considered clinically unremarkable when < 15 μmol/L.
Citation: Journal of the American Veterinary Medical Association 238, 1; 10.2460/javma.238.1.89
Discussion
In the present study, cats surgically treated for CEPSS by gradual attenuation of the shunt via cellophane banding and that survived the short-term postoperative period (ie, 15 days) had a fair to good prognosis. Four of the 7 cats surviving the short-term postoperative period did not have clinical signs related to persistent shunting or multiple acquired extrahepatic shunts, whereas 1 cat had persistent ptyalism and another underwent cystotomy for removal of ammonium biurate stones > 2 years after the cellophane banding procedure.
The sample of cats in our study was similar to that in other studies1–3,9,10 of other cats with a CEPSS with regard to age, clinical signs at the time of initial evaluation, clinicopathologic findings, and site of the shunts. Clinical signs in affected cats are usually observed by 6 months of age1,2,8,13; however, in our study, some cats developed clinical signs at 1 year of age. In our study, male and female cats were equally represented; however, in the literature, male cats seem to be overrepresented among those with a CEPSS.3,9,10 All CPSSs were extrahepatic in our study; 2 were portoazygos shunts, and 4 originated from the left gastric vein. Portoazygos shunts were identified in 47% cats in another study,10 whereas only 22% of the cats had the same condition in the present study.
Abdominal ultrasonography confirmed the presence of a CEPSS in 4 of the 9 study cats. In other studies,2,10 the same method was used to identify a CEPSS in 47% to 50% of affected cats. Per rectal scintigraphy, which can be used to measure the shunt fraction, is another screening tool for the diagnosis of portosystemic shunts.14,15 In the study reported here, 1 cat that was euthanized during the postoperative recovery period had the highest shunt fraction (86%) among the 4 cats in which shunt fraction was evaluated, and the other 2 cats with a poor prognosis did not undergo preoperative scintigraphy. Because results of shunt-fraction measurement can be variable and operator dependent,14,15 the same board-certified radiologist made these measurements in our study. Other researchers have reported a median shunt fraction of 82% in 12 cats with a CEPSS, and in their study, 9 it was not a prognostic indicator. Postoperative nuclear scintigraphy was used in the management of CPSSs in 5 surgically treated cats, of which 1 cat had no change in its shunt fraction, although its neurologic clinical signs improved.15
The proportion of cats that develop complications after surgical manipulation of a CEPSS via various different techniques is high, with the most detrimental complication being the development of uncontrollable seizures.1,5,9–11 In our study involving cellophane banding, one-third of cats developed postsurgical complications. In a study10 involving placement of an ARC, postoperative complications developed in approximately three-quarters of cats, whereas complications developed in one-third of cats in another study.9 Thirty-seven percent of cats in yet another study5 developed postoperative neurologic signs after surgical manipulation of their CEPSS. In our study, 2 cats developed seizures after the cellophane banding procedure and were subsequently euthanized because of the poor prognosis. Hypoglycemia could be considered a contributing factor for the development of seizures16; however, in our study, none of the cats became hypoglycemic, although 6 received dextrose after surgery. Hypothermia has also been reported as a risk factor for complications in dogs that have undergone portosystemic shunt attenuation.17 The 2 cats that developed seizures after surgery in our study were hypothermic at 1 point in the postoperative period, and 1 of these cats was severely hypothermic (rectal temperature, 32.8°C). Neurologic abnormalities appeared to be a consequence of hepatic encephalopathy in those cats because they already had seizures before surgery. The presence of seizures before surgery did not appear to have an effect on the likelihood of developing seizures after surgery or the likelihood of survival. We could not evaluate the effect of presurgical treatment of seizure-susceptible cats with phenobarbital or potassium bromide because only 1 cat was treated preoperatively with phenobarbital and the blood concentration of that drug was not measured.
The proportion of cats that die after surgical treatment of a CEPSS is highly variable. In the present study, 2 of 9 cats died in the immediate postoperative period, which is a proportion higher than that reported for other studies2,10,11 and may be attributable to the uncontrollable seizures in the affected cats. For example, 4% to 11% of cats reportedly died in the immediate postoperative period after surgical attenuation of a CEPSS via silk or polypropylene ligation.1,5 In those studies, cats that died had signs of portal hypertension or deteriorating neurologic status after surgery. In cats treated with an ARC, the proportion of cats that die after surgery reportedly ranges from 0% to 4.5%.9,10 In another study11 in which cellophane banding was used in 5 cats, none died soon after surgery. Our comparatively high mortality rate was likely attributable to the uncontrollable seizures in the 2 cats that died.
Two-thirds of our study cats survived for at least 3 years after cellophane banding. One cat was euthanized 105 days after surgery because of uncontrollable seizures that started 90 days after surgery. This cat did not have any other signs of neurologic disorder before the seizures developed. Therefore, it is unknown whether the seizure activity was related to shunting of blood around the liver. For the survival analysis, the seizures were considered related to the shunt attenuation.
Long-term outcome associated with the surgical treatment of CPSS in cats appears highly variable, with proportions of surviving cats ranging from 56% to 100%.5,9–11 The study11 with the 100% survival rate involved 5 cats treated with cellophane banding in which clinical signs improved with time. Two of the 5 cats had improvement of their clinical signs even with development of acquired shunting or no attenuation of the shunt. On the other hand, use of ARCs has been associated with long-term survival rates of 85%10 and 56%,9 whereas 83% of cats treated with surgical ligation reportedly survive.5
The most common cause of death or euthanasia in cats is often associated with neurologic dysfunction that cannot be controlled. Similar to findings in our study, cats appear to be at risk of developing intractable seizures several months after surgery, even when results of serum biochemical analysis or scintigraphy are unremarkable.5,9,10 One month after surgery in our study, the surviving 7 cats did not have any clinical signs. Postprandial SBA concentrations were within reference limits 3 months after surgery in the 5 cats in which SBA were measured, indicating that the shunts were likely attenuating. Results of postoperative per rectal scintigraphy or portovenogram were not available for any of those cats. Such diagnostic tools would have been of great value in the cats with seizures 90 days after surgery, persistent ptyalism, or biurate ammonium stones 2 years after the initial surgery. The retrospective nature of our study did not allow this type of evaluation.
Limitations to our study included the small number of cats and the retrospective nature of the study. Although all of the cats evaluated for CEPSS at our institution after January 2000 were treated with cellophane banding, in general, few cats are evaluated at veterinary hospitals for portosystemic shunts. A multi-institutional study would be valuable for further exploration of the effectiveness of cellophane banding for attenuation of CEPSSs; however, this procedure is not commonly used in cats because there are some doubts regarding its efficacy. Our study showed that cellophane banding effectively alleviated most of the clinical signs in cats treated for a portosystemic shunt. Because the median follow-up period after surgery was 240 days, it is possible that if the period was longer, more cats might have developed complications because complications can develop up to years after surgery. However, death due to the disease was no longer a factor 4 months after surgery.
Regardless of the limitations, our study showed that the prognosis of cats surgically treated for CEPSSs via gradual occlusion by cellophane banding without intraoperative attenuation was fair to good if they survived the immediate postoperative period. Findings also suggested that in the immediate postoperative period, cats should be monitored closely for neurologic dysfunction.
ABBREVIATIONS
ARC | Ameroid ring constrictor |
CEPSS | Congenital extrahepatic portosystemic shunt |
CPSS | Congenital portosystemic shunt |
SBA | Serum bile acids |
JMP, SAS Institute Inc, Cary, NC.
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