Retrospective review of outcome following medical management of a congenital portosystemic shunt in 10 cats

Abstract

Case series summary

The objective of this case series was to describe the survival, cause of death, clinical signs and long-term quality of life (QoL) of cats treated medically for a congenital portosystemic shunt (CPSS). Signalment, clinical signs, imaging, medical management and reason for not pursuing surgical treatment were obtained using medical records from two referral centres. Long-term outcome was obtained using a health-related quality of life (HRQoL) owner questionnaire. A total of 10 owners completed a HRQoL questionnaire that included frequency of clinical signs relating to having a shunt, QoL, behaviour, improvement in body condition score (BCS), and date and cause of death (where applicable). Five (50%) cats died or were euthanased because of their shunt. The median follow-up time for all 10 cats (from birth to death or questionnaire completion if still alive) was 26.5 months (range 8 months to 15 years). The mean CPSS score was 30/124 (range 13–57) and all cats medically treated for their CPSS had ongoing clinical signs. QoL scores and BCS were assessed as improved by eight (80%) and nine (90%) owners, respectively, following medical management of a CPSS.

Relevance and novel information

This is the first case series description of cats managed medically for a CPSS, which demonstrates that all cats medically treated for a CPSS had ongoing clinical signs in the long term, albeit with improved QoL, and that half of cats treated medically can be expected to die because of their shunt. Although this study adds to the current body of knowledge of CPSS management in cats, ongoing research should be conducted to increase the sample size and compare long-term CPSS and QoL scores in healthy cats to groups of cats treated either medically or surgically for a CPSS.

Introduction

Medical management of a congenital portosystemic shunt (CPSS) may be used as preoperative stabilisation or as long-term treatment in cats when surgical intervention is considered unsuitable or impossible by clinicians or rejected by owners because of financial costs and/or surgical risks.^{1 –3} Medical management of a CPSS reduces systemic concentrations of toxins and ameliorates clinical signs of hepatic encephalopathy without treating underlying pathology. Studies suggest that surgical management of CPSS in dogs is associated with greater long-term survival and a better quality of life (QoL), with fewer clinical signs relating to having a shunt than medical management of signs.^{2 –5} However, there is a higher documented risk of life-threatening neurological complications after shunt surgery in cats.^{6 –10} There is currently minimal information regarding long-term medical treatment of cats with a CPSS. The aim of this case series was to describe the survival, cause of death, clinical signs and long-term QoL of cats treated medically for a CPSS.

Case series description

Data were collected from the medical records of cats diagnosed with a CPSS (on ultrasound and/or CT imaging) in two referral centres between January 2008 and February 2024 that did not undergo surgical shunt attenuation and were medically treated for clinical signs associated with having a CPSS (combination of modified diet, lactulose ± antibiotics) after discharge from the hospital. Cats that died during the initial presentation visit due to inability to stabilise the shunt medically were excluded. Cats were included if their owners consented to participation in the study and completed a health-related QoL (HRQoL) questionnaire (see Appendix 1 in the supplementary material) that included frequency of clinical signs relating to having a shunt, QoL, behaviour, improvement in body condition score (BCS), and date and cause of death (where applicable). The questionnaire was completed retrospectively by the owners at the time of follow-up for this study. Ethical approval for the study was granted by the Royal Veterinary College’s Social Science Research Ethical Review Board (reference URN – SR2024-0017) and the owners of selected cats were initially contacted via email or telephone. Participating owners only received the questionnaire after fully informed, signed consent.

Information collected from medical records included breed, sex, date of birth, age at diagnosis, weight and BCS at presentation. The questionnaire was adapted from a previously published HRQoL questionnaire for dogs with CPSS. ¹¹ Owners were asked about the decision for medical management rather than surgical treatment for the CPSS and the details of any medical treatment the cat was receiving, either currently or at the last time they were alive. The remainder of the questionnaire was based on the clinical signs associated with having a CPSS, QoL, behaviour, improvement in BCS and outcome. For each clinical sign, owners were asked to rate the frequency on a scale of ‘never’, ‘less than once a month’, ‘monthly’, ‘weekly’ or ‘daily’. As per the 2019 study by Bristow et al, ¹¹ clinical signs were divided into three classes based on severity, with class 1 clinical signs multiplied by 3, class 2 clinical signs by 2 and class 3 clinical signs by 1 (Table 1). From this, an overall CPSS score was generated to assess the frequency and severity of clinical signs, with higher scores representing a more severely clinically affected cat. In addition, for each clinical sign, the impact on QoL was rated on a scale from 0 (‘not at all’) to 10 (‘could not be worse’). Behavioural questions addressed variables such as willingness to play and interact with owners, as well as observed improvements in general health and/or body condition, all of which were recorded on a scale from 0 (‘not at all’) to 10 (‘could not be more willing/improved’). Where applicable, owners were asked the date and known or presumed cause of death to determine survival time and whether the cause of death was related to the CPSS. Finally, owners were asked whether, if faced with the same situation again, they would opt for long-term medical management of a cat with a CPSS, by responding ‘Yes’, ‘No’ or ‘Not sure’. Long-term follow-up times were calculated from birth to death, or questionnaire completion in cats that were still alive. Survival times from birth to death were calculated for cats that died or were euthanased.

Table 1

Classification and scoring of clinical signs to produce a congenital portosystemic shunt score

Class	Clinical signs	Multiplication or increase of score
1	Seizures	3 × score
2	Headpressing, circling, disorientation, aggression, collapse, ataxia, lethargy, unresponsiveness, central blindness, hypersalivation	2 × score
3	Vomiting, diarrhoea, increased thirst, increased urination, haematuria, dysuria	1 × score
	Urolithiasis or urethral obstruction	+2 points if present
	Retarded growth	+4 points if present +2 points if owner unsure

A total of 10 cats with a CPSS from two centres were included in the study. They were medically managed for their clinical signs and their owners completed the HRQoL questionnaire. Seven cats were excluded because the CPSS was an incidental finding on imaging and the cats never required, nor received, medical or surgical treatment for their shunt. Three cats were excluded because they died or were euthanased at initial presentation for their CPSS owing to severe and deteriorating neurological signs. Two cats were excluded because their owners did not complete the HRQoL questionnaire.

The study population consisted of seven castrated males and three spayed females. There were six domestic shorthair cats, two domestic longhair cats, one British Blue and one Exotic Shorthair cat. Age at diagnosis was in the range of 4 months to 8 years (median 9.5 months). Six cats were aged less than 1 year at the time of diagnosis. The median time from birth to death, or questionnaire completion if still alive, was 26.5 months (range 8 months to 15 years). The median time between diagnosis and initiation of medical treatment to questionnaire completion and/or death was 14.5 months (range 6 weeks to 9 years).

The owners of eight (80%) cats elected to treat their cat medically because they wanted to avoid the risks associated with surgical treatment for the CPSS, alongside four owners (40%) wanting to avoid the high cost of surgery. Six (60%) owners reported that their cat responded well to medical management and five (50%) owners reported their cat was easy to medicate. Having a cat that was easy to medicate was one of the reasons they elected for medical management. One owner reported that they had intended on proceeding with surgical attenuation of their cat’s shunt once stabilised on medical management; however, the cat did not survive long enough to receive surgical treatment.

All cats in the study received oral lactulose and a modified diet as medical treatment for their shunt. Nine (90%) cats were fed a modified, restricted or hydrolysed protein prescription diet (Purina Hypoallergenic, Royal Canin Hepatic, Royal Canin Renal, Royal Canin Hypoallergenic). Of them, two (20%) cats also received a highly digestible diet (Royal Canin Sensitivity, Purina Digestible) in conjunction with their restricted-protein diet. One cat only received a highly digestible diet (Hill’s Prescription Digestive) so was not protein-restricted. In two cats, tuna was used as an additional protein source, given in conjunction with a prescription low-protein diet. One owner reported that their cat found the modified diet boring and so elected to rotate between different diets to generate some variety. Two owners reported challenges associated with feeding different diets to multiple cats in their household and an additional owner reported their cat would steal food from neighbouring cats and thus increase their frequency and severity of hepatic encephalopathy signs. Four (40%) owners reported their cats received antibiotics in conjunction with lactulose and a modified diet. None of the cats included in the study received levetiracetam, phenobarbitone or any other anti-seizure medication as part of their treatment regimen.

The CPSS scores demonstrated that ongoing clinical signs attributable to having a shunt were present in all the cats while receiving medical treatment (Table 2). All cats exhibited some form of neurological signs, including three (30%) cats that experienced seizures; however, despite this, none of the cats required anti-seizure medication as part of their treatment regimen. Eight (80%) owners reported that their cat was small/underweight for their breed, which was similar to information collected from the medical record where five (50%) cats presented with a BCS of 4/9, four (40%) cats presented with a BCS of 3/9 and one (10%) cat presented with a BCS of 2/9. However, despite the majority of owners reporting that their cat was still small/underweight, they also rated a median improvement in BCS of 7 (range 0–10) on medical management (Table 2). QoL scores were consistently higher on medical management than before treatment (Table 2). The median results of owners’ scores of general improvement, activity levels, willingness to play and willingness to interact with owners were 6.5, 5, 6 and 9.5, respectively (Table 2). When owners were asked if they would elect for medical management of a cat with CPSS again, five (50%) reported that they would, two (20%) reported they were unsure and three (30%) reported that they would not elect for medical management again and instead would choose surgical attenuation.

Table 2

Follow-up time, congenital portosystemic shunt (CPSS) score, quality of life (QoL) score before and after medical management, improvement in body condition score (BCS), improvement generally and behavioural parameters of CPSS cats on medical management

Variable	Score
CPSS score (max 124)	30 (13–57)
QoL before treatment	3.5 (0–7)
QoL after treatment	7.5 (1–9)
Body condition improvement	7 (0–10)
General improvement	6.5 (2–10)
Activity	5 (2–10)
Willingness to play	6 (2–10)
Willingness to interact with owners	9.5 (4–10)

Data are median (range)

Six (60%) cats were euthanased, five because of severe or worsening neurological signs caused by the CPSS and one euthanasia was unrelated to the shunt (due to uncontrollable hyperthyroidism). Therefore, the mortality rate for cats in this study directly attributable to their shunt was 50%. The median survival for all the cats that were euthanased was 20.5 months (range 8 months to 15 years). Four (40%) cats were still alive at the time of questionnaire completion, with a median time of 35.5 months (range 12 months to 68 months). Overall median time, from birth to euthanasia or questionnaire completion, for all 10 cats was 26.5 months (range 8 months to 15 years).

Discussion

In this study, the mortality rate of 50% – with cats being euthanased because of their shunt after long-term medical management – is lower than the 89% long-term mortality rate reported in dogs. ² This is new and useful information for owners contemplating treatment options for cats with a CPSS and should be considered alongside the risks of surgery, including the increased occurrence of life-threatening post-attenuation neurological signs (PANS) in cats compared with dogs.^9,10 Although a larger sample of cats is required to corroborate this finding, this could be problematic, given that the search period for this study spanned 16 years in two centres.

Despite 50% of cats ultimately being euthanased because of their CPSS, the overall median survival time from birth for all the cats (including those euthanased) was still relatively long at 26.5 months (range 8 months to 15 years), which is lower but similar to the median survival time of 836 days (approximately 27.5 months) reported in dogs managed medically for a CPSS. ² It is important to note that while on medical management, all cats exhibited neurological clinical signs attributable to their CPSS, typically intermittent disorientation, ataxia, hypersalivation and/or lethargy. Furthermore, three cats experienced seizures. Despite these ongoing clinical signs, owners consistently scored improved QoL for cats after medical management and 50% of owners would choose medical management again for a cat with a CPSS. There is currently no published information on CPSS scores or QoL scores for cats managed medically or surgically for a CPSS, nor dogs treated medically for a CPSS; therefore, comparisons cannot be made between different treatment groups, nor compared with control populations. However, the median CPSS score for cats following medical management in this study was 30.5/124 (range 13–57), which is vastly higher than the 3/110 (range 1–10) reported for dogs with a surgically attenuated extrahepatic shunt. ¹¹ Similarly, the median QoL score for cats treated medically in this study was 7.5/10 (range 1–9), which is lower than the 9.6/10 (range 8.9–10) reported for dogs treated surgically for their CPSS. ¹¹ This extrapolation would suggest that surgical treatment of a CPSS is likely to produce a better long-term QoL with fewer clinical signs; however, the disparity between species and sample sizes makes firm conclusions problematic. It is also important to recognise that after starting medical management, QoL is unlikely to revert to ‘normal’ as the underlying pathology persists; however, the increase in QoL scores from a median of 3.5 before treatment to a median of 7.5 after medical treatment shows that considerable improvement in QoL is still possible with medical management of CPSS in cats.

All cats that died at presentation for their CPSS and all cats where a CPSS was diagnosed as an incidental finding were excluded from our study. These excluded cases are interesting as they demonstrate the vast variability of feline CPSS and indicate that surgical or medical treatment may not always be required, appropriate or possible. Therefore, our study of medical management only analysed a very specific subset of cats with a CPSS. The median age of 9.5 months at diagnosis in this study was similar to other studies of cats managed surgically, where the median age at presentation was approximately 8–9 months.^8,9,12 However, in this study, three (30%) cats were diagnosed over 2 years of age, with the oldest being 8 years. In these cases, milder clinical signs associated with the shunt were reported as being exhibited earlier in life; however, it took several years for a correct diagnosis to be made and medical treatment initiated. These late diagnoses also indicate the varied presentations and spectrum of disease in feline CPSS and it could be speculated that late clinical presentations represent less severe shunts, which may be more amenable to good outcomes under medical management.

All cats in this study received lactulose as part of their medical management. Most cats were fed hydrolysed, hepatic or renal reduced-protein diets or a combination thereof. The optimal diet for cats with CPSS remains understudied but the literature suggests that severe protein restriction, as in hepatic and renal diets alone, is contraindicated in dogs or cats with CPSS, except in cases of severe hepatic encephalopathy when temporary protein restriction may be required for initial stabilisation.^13,14 The importance of feeding as much good-quality protein that can be tolerated without becoming encephalopathic has also been documented. ¹⁴ Clinical signs associated with hepatic encephalopathy are less severe, and survival times extended, in patients given highly digestible protein diets, particularly of vegetable or dairy origin, compared with meat-based protein products;^{15 –17} however, these studies focus mostly on canine and human patients. The lack of information regarding optimum diets for feline patients, together with the small sample size and variability of diets observed in this study, makes conclusions regarding the impact of highly digestible protein diets on CPSS scores and survival times impossible and indicates an important area for further research.

Owner-based questionnaires face several documented limitations. One study described potential bias in owner responses after seeing statistically better QoL scores in postoperative CPSS dogs compared with healthy controls. ¹¹ The same study also considered the possibility of attention bias, where owners notice and remember ‘abnormal’ episodes more regularly than ‘normal’ behaviour, which could contribute to increased CPSS scores, as well as the potential for recall bias, where owners may be more generous with QoL assessments owing to dramatic post-treatment improvements, compared with owners of healthy, non-CPSS animals. In this study, the lack of a control cohort makes reliable interpretation of CPSS and QoL scores difficult to assess. The very small sample size of this study prohibits parametric statistical analysis, which means internal validity and result reliability cannot be assured. The relative rarity of CPSS in cats alongside favouring of surgical treatment makes small sample sizes inevitable. The limitations associated with carrying out retrospective research include data being limited to information retrieved from medical records. This study only included cats diagnosed with a CPSS that met specific inclusion criteria, which means the results may not be applicable to every case of feline CPSS. Nevertheless, this study provides additional information for owners and veterinarians regarding outcomes of medical management of feline CPSS to inform discussions of treatment options.

Conclusions

Median QoL scores improved after medical management of cats with a CPSS and overall median follow-up extended to 26.5 months. However, all cats had ongoing clinical signs and 50% of cats were euthanased because of their shunt. In future, additional cats with medically managed CPSS should be recruited prospectively to increase the sample size and enable stronger conclusions regarding changes in CPSS and QoL scores, cause of death and median survival for cats treated in this way. Furthermore, the HRQoL questionnaires should be administered to cohorts of both surgically treated and healthy cats, to allow for a comparison between treatment options and with a control group. Finally, dietary options, specifically the addition of highly digestible protein sources rather than traditional restricted-protein diets, should also be investigated to explore whether the same benefits reported in dogs are seen in cats with a CPSS.

Supplemental Material

Appendix 1

Portosystemic shunt quality of life questionnaire: after medical management.