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ORIGINAL ARTICLE
Clinical outcomes in cats with renal carcinoma undergoing
nephrectomy: A retrospective study
Shannon A. Kenny
1
| Matthew R. Cook
1
| Jennifer A. Lenz
2
|
Karl C. Maritato
3
| Katherine A. Skorupski
4
| Brandan G. Wustefeld-Janssens
5
|
MacKenzie A. Pellin
6
| Catrina J. Silveira
7
| Stan Veytsman
8
|
Laura E. Selmic
1
| Brian D. Husbands
1
1
Department of Veterinary Clinical Sciences,
The Ohio State University, Columbus,
Ohio, USA
2
School of Veterinary Medicine, University of
Pennsylvania, Philadelphia, Pennsylvania, USA
3
MedVet Cincinnati, Cincinnati, Ohio, USA
4
Department of Surgical and Radiological
Sciences, University of California at Davis,
Davis, California, USA
5
Department of Clinical Sciences, Colorado
State University College of Veterinary
Medicine and Biomedical Sciences, Fort
Collins, Colorado, USA
6
Department of Clinical Sciences, School of
Veterinary Medicine, University of Wisconsin,
Madison, Wisconsin, USA
7
Department of Small Animal Clinical Sciences,
College of Veterinary Medicine and Biomedical
Sciences, Texas A&M University, College
Station, Texas, USA
8
Department of Veterinary Clinical Sciences,
University of Minnesota, St. Paul,
Minnesota, USA
Correspondence
Shannon A. Kenny, DVM, The Ohio State
University College of Veterinary Medicine,
601 Vernon L. Tharp St., Columbus, OH,
43210, USA.
Email: shannon.a.kenny@gmail.com
Abstract
Renal carcinomas (RC) are uncommonly encountered in feline medicine. Limited
information regarding clinical presentation and postoperative outcomes is available.
The purpose of this multi-institutional, retrospective study was to describe the pre-
senting features and clinical outcomes of cats with RC undergoing nephrectomy.
Thirty-six client-owned cats were included. Medical records from participating
institutions were searched to identify cats that had a histopathologic diagnosis of
RC and underwent nephrectomy from January 2001 to October 2021. The most
common presenting complaints were weight loss (36.1%) and hyporexia (30.6%).
Based on preoperative imaging and intraoperative findings, eight cats had sus-
pected metastasis at the time of surgery (22.2%). Twenty-eight cats survived to dis-
charge (77.8%). Median progression free interval (PFI) could not be determined, as
only six cats developed suspected recurrence (16.7%) and seven cats developed
suspected metastasis (19.4%). The all-cause median survival time (MST) was
203 days (95% confidence interval [CI]: 84, 1379 days). When cases that died prior
to discharge were excluded, MST increased to 1217 days (95% CI: 127, 1641 days).
One-year, two-year, and three-year survival rates were all 40.4%. Neither renal
tumour histologic subtype nor the presence of preoperative azotemia, anaemia,
erythrocytosis, haematuria, or suspected metastasis at diagnosis were found to
influence survival. For cats surviving to discharge, prolonged survival times were
possible. Further studies are necessary to elucidate other potential prognostic fac-
tors, the utility of postoperative adjuvant treatment, and to identify cats at-risk of
mortality in the perioperative period.
KEYWORDS
carcinoma, feline, nephrectomy, renal
Received: 4 March 2023 Revised: 28 June 2023 Accepted: 30 June 2023
DOI: 10.1111/vco.12921
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
© 2023 The Authors. Veterinary and Comparative Oncology published by John Wiley & Sons Ltd.
Vet Comp Oncol. 2023;1–8. wileyonlinelibrary.com/journal/vco 1
1|INTRODUCTION
Primary renal neoplasia is infrequently observed in feline medicine
with an estimated prevalence of less than 1% of all cancers.
1,2
Exclud-
ing lymphoma, epithelial neoplasms constitute the majority of cases.
1,2
Of primary feline renal tumours, 60%–77% are epithelial, with renal
cell carcinoma (RCC) predominating; other epithelial tumours, includ-
ing transitional cell carcinoma, squamous cell carcinoma, renal ade-
noma, and renal oncocytoma are infrequently reported.
1–16
Additionally, primary renal hemangiosarcoma, leiomyosarcoma, myx-
oma, myxosarcoma, paraganglioma, and nephroblastoma have been
documented.
2,3,17–21
Larger studies evaluating feline RC are lacking.
Feline RCC has mainly been reported in middle-aged to older
cats.
1–5,10,22,23
Breed and sex predispositions have not been
reported.
3,4
Feline RCC is typically unilateral, with left and right kid-
neys affected at similar rates.
5
Cats often present with non-specific
signs such as lethargy, vomiting, weight loss, and abdominal pain.
3,4
Paraneoplastic polycythemia has been reported and generally resolves
following nephrectomy.
6,22–26
RCC has also been documented in cats
with concurrent polycystic kidney disease (PKD) and those undergo-
ing cyclosporine therapy for renal transplantation.
9,10
In the most comprehensive report of non-lymphomatous primary
renal tumours in cats, 19 cases were described, 13 of which were diag-
nosed as RCC.
3
Of the nine RCC cases with staging performed, five had
evidence of distant metastasis, including four with suspected pulmonary
involvement. In a histopathology and immunohistochemistry-focused
analysis of 12 cats with RCC, survival data were available for eight cats
(range: 28–2292 days), six of which were alive at the study's conclu-
sion.
4
However, details regarding case management and clinical out-
comes were not provided in either study.
Limited reports of feline renal transitional cell carcinoma (RTCC)
and renal squamous cell carcinoma (RSCC) have been described in
veterinary literature.
3,11–14
In the previously cited report of feline pri-
mary renal tumours, all three cats with RTCC had suspected metasta-
sis at diagnosis.
3
Additional RTCC case reports include: a cat with a
perinephric cyst; two cats with a history of chronic kidney disease
(CKD); and a young cat with ocular, pulmonary, and skeletal
metastases.
11–13
A solitary case report described a young cat with
RSCC and abdominal carcinomatosis.
14
Presently, there is limited information regarding the biologic
behaviour and postoperative outcomes in feline RC. The objective of
this multi-institutional, retrospective study was to describe the clinical
outcomes of cats with histologically confirmed RC undergoing
nephrectomy. Secondary aims included evaluating clinicopathologic
features at presentation and investigating potential prognostic factors
on disease progression and overall survival.
2|METHODS
A retrospective medical record search was performed to identify cats
with a histopathologic diagnosis of primary RC. This included cases of
RCC, RTCC, and RSCC. Medical records from 10 institutions were
collected from 1 January 2001, to 1 January 2022. To be included,
cats had to have undergone a complete or partial nephrectomy. Base-
line complete blood counts (CBC) and biochemical profiles were
required. Cases euthanized intra-operatively were eligible for inclu-
sion, provided histopathology was performed. Cases were excluded if
the mass was suspected to be non-renal in origin or if there was insuf-
ficient information available to determine if cats survived to
discharge.
Data abstracted from medical records included signalment, body
weight, presenting complaint, comorbidities, and baseline preopera-
tive laboratory findings (biochemistry profile, CBC, urinalysis, and
erythropoietin levels [EPO], when available). Erythrocytosis and anae-
mia were defined as a preoperative haematocrit greater than 60% and
less than 24%, respectively.
27,28
Cats with a preoperative creatinine
of 1.6 mg/dL or greater and a urine specific gravity of less than 1.035
were defined as having renal azotemia.
29
Gross haematuria was
defined as greater than 50 red blood cells per high power field. This
cut-off was used to account for potential traumatic cystocentesis.
30
Preoperative abdominal imaging (abdominal radiographs, abdomi-
nal ultrasound, or abdominal computed tomography [CT]) and thoracic
imaging (thoracic radiographs or thoracic CT) results were compiled.
The presence of suspected metastatic lesions was based on details
available in the imaging reports. For instance, if the radiologist men-
tioned sternal or abdominal lymphadenomegaly, cats were deemed to
have suspected metastasis; specific measurement cut-offs were not
employed. Median tumour size was based on the longest tumour mea-
surement described in imaging reports. Mitotic count from histopa-
thology reports was assessed when available.
Treatment data gathered included surgical procedure type (partial
or complete nephrectomy), presence of suspected intraoperative
metastasis, surgical complications, and use of systemic therapy (che-
motherapy or toceranib phosphate). Surgical adverse events were
characterized and graded, when applicable.
31
When available, renal
values were reviewed postoperatively and at the time of last follow-
up. For systemic therapies, the drugs used and the dosing scheme
were abstracted.
Cytologic or histopathologic confirmation of metastatic lesions
was not required; instead, clinical suspicion based on imaging results
or exploratory surgical findings was admissible. Similarly, local recur-
rence was suspected if a new mass lesion was noted at the region of
the previously excised kidney on postoperative imaging. Additionally,
information regarding status at the time of last contact, date of death,
and cause of death was collected. If the cause of death was unclear, it
was assumed to be tumour-related. Clinical outcomes evaluated
included PFI and all-cause MST. PFI was defined as the time from sur-
gery to the first documented date of local tumour recurrence or
metastasis. MST was defined as the time between surgery and death
due to any cause.
Kaplan–Meier methodology was used to calculate the PFI and all-
cause MST with 95% CI. Cats were censored in the PFI analysis if they
did not develop local recurrence or metastasis by the date of last
follow-up or death. All-cause survival was evaluated, and cats were
censored if they were lost to follow-up or alive at last follow-up.
2KENNY ET AL.
14765829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vco.12921 by Lincoln Memorial University Distribution Center, Wiley Online Library on [24/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
Univariable Cox proportional hazards regression was performed to
assess for associations between PFI and MST. Variables assessed
included preoperative azotemia, anaemia, erythrocytosis, and haema-
turia, as well as tumour type, and presence of preoperative metastasis.
Statistical analysis was performed using commercially available soft-
ware (SAS version 9.4, SAS Institute Inc., Cary, NC; Prism 9, GraphPad,
San Diego, CA). A p-value of <.05 was considered statistically signifi-
cant for this analysis.
3|RESULTS
3.1 |Demographics and clinical signs
Medical records from 39 cats with histologically diagnosed RC were
reviewed. Three cases were excluded: two cats did not have a base-
line CBC or serum biochemistry and one cat had no perioperative
data, such that it was unclear if the cat survived to discharge or was
euthanized intraoperatively. In total, 36 cats were included. Most cats
were domestic shorthairs (n=25) and domestic longhairs (n=5).
Purebred cats included Ragdolls (n=2), an American Shorthair, a
Maine Coon, and a Russian Blue. One cat was described as a mixed
breed. There were 19 spayed females, one intact female, and 16 cas-
trated males. Median age at presentation was 11 years (range:
5–17 years) and median weight was 4.5 kg (range: 2.5–6.9 kg).
Presenting clinical signs were non-specific. The most common
complaints were weight loss (n=13) and hyporexia (n=12); three
cats presented with both. Six cats had vomiting, three had abdominal
pain, and two had difficulty defecating. There were five cats with uri-
nary signs, including polyuria (n=2), inappropriate urination (n=2),
and pollakiuria and stranguria (n=1). There were individual cases of
the following: paraparesis, melena secondary to duodenal ulceration, a
suspected foreign body, and dysphagia. One cat was presented for
renal transplant as part of chronic, bilateral PKD management. Thir-
teen cats had palpable renomegaly or abdominal mass effect detected
at presentation. Eight cats were incidentally diagnosed with RC when
renomegaly was discovered on physical examination (n=4), or
when erythrocytosis (n=2) or microscopic haematuria (n=2) were
identified on annual lab work. Presenting complaint was not provided
for one cat.
3.2 |Baseline clinicopathologic results
The median preoperative haematocrit was 38% (range: 9.5%–85%)
and the median red blood cell count was 9.3 K/μL(range:1.9–16.9 K/μL).
Five cats were anaemic with a median haematocrit of 20% (range:
9.5%–22%). Five cats had erythrocytosis with a median haematocrit of
72% (range: 62%–85%). Two of these cats had EPO levels evaluated, both
of which were within normal limits.
Nine cats had suspected renal azotemia. The median preoperative
blood urea nitrogen (BUN) and creatinine were 29 mg/dL (range:
14–68 mg/dL) and 1.9 mg/dL (range: 0.8–3.8 mg/dL), respectively. Thirty-
four cats had a preoperative urinalysis. The median preoperative urine
specific gravity was 1.034 (range: 1.008–1.055). Eleven cats had sus-
pected gross haematuria, one of which had concurrent bacteriuria. Five
cats had evidence of atypical or neoplastic epithelial cells in their urine.
3.3 |Imaging
All 36 cats had preoperative abdominal imaging. Abdominal ultra-
sound and abdominal CT were used exclusively in 29 cats and one
cat, respectively. Five cats had both abdominal ultrasound and radio-
graphs, while one cat had abdominal radiographs and abdominal CT
scan performed. Twenty-five cats imaged with abdominal ultrasound
had tumour measurements available; median tumour size was 4.6 cm
(range: 1.1–9 cm). Tumour size for the two cats with abdominal CT
was 2.9 and 5.3 cm. Urinary-related imaging abnormalities of interest
included: renal mass (n=26), chronic renal changes (n=8), hydrone-
phrosis (n=7), renomegaly (n=4), pyelectasia (n=3), hydroureter
(n=2), retroperitoneal effusion (n=1), bilateral, marked renal cysts
(n=1), and a mass effect in the retroperitoneal space (n=1). Addi-
tional pertinent imaging abnormalities reported included: scant to mild
peritoneal effusion (n=4), abdominal lymphadenomegaly (n=3),
splenic nodules (n=3), hepatic nodules (n=3), and pancreatic nod-
ules (n=1). One cat had no mention of urinary tract abnormalities;
instead, intestinal plication was noted. Imaging reports were unavail-
able for three cats.
Thirty-three of 36 cats had preoperative thoracic imaging.
Twenty-nine had thoracic radiographs, one had thoracic CT, and three
cats had both thoracic radiographs and CT. Imaging findings suspi-
cious for metastasis included pulmonary nodules (n=2), pleural effu-
sion (n=1), and sternal lymphadenopathy (n=1). Additional imaging
findings included: diffuse bronchial pattern (n=7), cardiomegaly
(n=3), bronchointerstitial pattern (n=2), suspected atelectasis
(n=2), a cystic mediastinal mass (n=1; historic finding that had not
progressed in 6 months), bilateral atrial enlargement (n=1), and peri-
bronchial infiltrates (n=1).
3.4 |Perioperative cytology
Twenty-six cats had ultrasound-guided fine needle aspirates of their
renal lesions prior to surgery. Neoplasia was suspected in the majority
of cases: carcinoma (n=6), epithelial neoplasia (n=5), malignant
neoplasia (n=2), and adenoma or low-grade carcinoma (n=1). Addi-
tional findings included: epithelial proliferation (n=2), epithelial cells
with atypical features (n=1), rare atypical cells with evidence of
necrosis (n=1), necrotic debris (n=1), macrophagic inflammation
(n=1), and no cytologic abnormalities (n=1). Two cats had non-
diagnostic samples, and reports were not available for three cats.
Intraoperative renal aspirates were performed in two cats. One
identified chronic inflammation and proteinaceous fluid, while the
other identified cystic fluid with dysplastic epithelial cells. Neither
were confirmatory for carcinoma.
KENNY ET AL.3
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3.5 |Surgery
RC was unilateral in all cases. Thirty-five cats underwent complete
nephrectomy and one had a partial nephrectomy. The partial nephrec-
tomy was performed in a cat with known bilateral renal insufficiency
as determined by a preoperative glomerular filtration rate study. A
renal transplant was recommended, but declined. A partial nephrec-
tomy to remove the 1.4 cm mass in the cranial pole of the right kidney
was attempted in order to preserve as much functional renal capacity
as possible; per the surgical report, 20% of the right kidney was
excised. Surgical procedures in addition to complete nephrectomy
included: adrenalectomy (n=2), splenectomy (n=1), partial liver
lobectomy (n=1), omental cyst removal (n=1), partial pancreatec-
tomy (n=1), necrotic lipoma removal (n=1), abdominal body wall re-
section (n=1), liver biopsy (n=2), and splenic biopsy (n=1).
Two cats underwent nephrectomy after a renal mass was inciden-
tally discovered. One cat with PKD had a renal mass discovered at the
time of renal transplant; the kidney had appeared severely cystic on
preoperative ultrasound, but neoplasia was not suspected at that time.
A second cat underwent an exploratory laparotomy for a suspected gas-
trointestinal foreign body. A 0.5 cm renal mass was incidentally
detected, removed, and submitted for histopathology; this was not
noted on preoperative abdominal ultrasound. For eight cases, the ratio-
nale for pursuing nephrectomy was unclear based on the available med-
ical records. This included three cats with hydronephrosis and two cats
with renomegaly that lacked a preoperative cytologic diagnosis of neo-
plasia, as well as the three cats without imaging reports.
Perioperative surgical complications were reported.
31
One cat
experienced a Grade 4 intraoperative soft tissue injury upon acciden-
tal ureteral resection of the contralateral kidney. Ureteral reimplanta-
tion was performed without complication. A second cat had an
invasive renal tumour that required a 2 cm 2 cm body wall resec-
tion; the defect was repaired with surgical synthetic mesh (unknown
type and manufacturer). Grade 3 adhesions developed between the
mesocolon and surgical mesh and were surgically addressed 33 days
later. In the postoperative period, one cat experienced Grade 2 pneu-
mothorax and Grade 3 hypotension that resolved with supportive
care. An additional cat was described as having Grade 4 postoperative
complications, but details were not available. Three cats had Grade
5 postoperative complications. The first cat, who underwent partial
nephrectomy, experienced cardiopulmonary arrest during central
venous catheterization. The second cat, who had PKD and was under-
going concurrent renal transplant, developed several complications:
severe epidermal and dermal necrosis, suppurative dermatitis, and
necrotizing vasculitis caudal to the incision site; multifocal intravascu-
lar fibrin thrombi; acute tubular necrosis of the left transplanted kid-
ney; and seizures. Widespread acute inflammatory response was
strongly suspected, but sepsis was not confirmed. Theories surround-
ing the inflammatory response included dermal necrosis secondary to
postoperative thromboembolic disease to the skin with secondary
bacterial invasion, and/or primary necrotizing dermatitis resulting
from superficial trauma from urine scald with secondary bacterial
invasion. The third cat became acutely dyspneic and agonal 16 days
after surgery. A pulmonary thromboembolism was suspected, but nec-
ropsy was not performed.
3.6 |Histopathology
The left and right kidneys were affected with equal frequency. Histo-
pathology identified 29 cases of RCC, six RTCC cases, and one RSCC
case. Reporting techniques for mitotic count were variable. Twenty-
seven cases had numerical mitotic counts provided, but definitions of
high-powered fields differed by pathologist and institution. Two addi-
tional cases used qualitative descriptors of “occasional”and “few”
mitoses in lieu of a numerical count. Mitotic count was not provided
in the remaining seven histopathology reports.
3.7 |Metastasis
Between preoperative staging and intraoperative findings, eight
cats had suspected metastasis at the time of surgery. Six cats had
imaging findings concerning for metastasis, including: caudal
abdominal lymphadenomegaly (n=2), pulmonary nodule(s) (n=2),
pleural effusion (n=1), sternal lymphadenopathy (n=1), a body
wall lesion (n=1), and a retroperitoneal lesion (n=1). Of these
cases, one case had preoperative sampling of pleural effusion which
was consistent with suppurative effusion. Another cat had
ultrasound-guided aspirates of a pulmonary nodule, but this was
non-diagnostic. Two cats with suspected intraoperative metastasis
had no evidence of metastasis on preoperative abdominal ultra-
sound. This included a cat with bilateral adrenal nodules and a cat
with widespread hepatic nodules. The cat with adrenal nodules
underwent necropsy; the left adrenal gland was not identified post-
mortem, and the right adrenal gland was not given an anatomic
diagnosis. In contrast, the cat with widespread hepatic nodules had
histopathology-confirmed RC metastasis. The cat with a retroperi-
toneal mass effect on abdominal ultrasound instead had adrenal
and hepatic nodules at the time of surgery; these were confirmed
to represent RTCC metastasis on histopathology.
3.8 |Outcomes
Eight cats did not survive to discharge, with three cats euthanized
intraoperatively. Two cases were euthanized after advanced disease
was discovered intraoperatively. The first cat had widespread hepatic
metastasis and local tumour invasion into the aorta and phrenicoab-
dominal vein. The second cat, who was undergoing abdominal explor-
atory surgery for a suspected linear foreign body, was found to have a
perforated duodenum and an incidental small renal mass; the owners
declined duodenal resection and anastomosis and pancreatectomy, so
euthanasia was elected. A third cat was euthanized for unknown rea-
sons. The remaining five perioperative deaths included cardiac arrest
(n=2), intractable azotemia (n=1), seizures, acute tubular necrosis,
4KENNY ET AL.
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and probable sepsis secondary to skin necrosis with necrotizing vascu-
litis (n=1), and unknown cause (n=1).
Twenty-eight cats survived to discharge. Twenty-two cats had
follow-up imaging at varying times postoperatively (median 108 days;
range 37–1189 days). Restaging varied amongst cases. Suspected
recurrence and metastasis were identified in six and seven cats,
respectively. These were discovered concurrently in six cases. Sus-
pected metastatic sites included the intra-abdominal lymph nodes
(n=3), mesentery (n=1), ileum (n=1), omentum (n=1), contralat-
eral kidney (n=1), abdominal carcinomatosis (n=1), and cranial
mediastinum (n=1). Based on imaging findings, median time to recur-
rence was 84 days (range: 37–107 days) and median time to metasta-
sis was 105 days (range: 37–170 days). Confirmatory sampling was
only performed in two cases: one cat with a cranial mediastinal mass
and another with enlarged caudal abdominal lymph nodes. There was
no record of confirmatory sampling in cases with suspected local
recurrence.
Postoperative BUN and creatinine results were available in 24 cats.
The median time to first postoperative renal values recheck on bio-
chemistry was 9.5 days (range: 1–135 days) and to last recheck was
179 days (range: 1–1838 days). The median BUN at first postoperative
assessment was 33.5 mg/dL (range: 19–133 mg/dL) and creatinine was
2.0 mg/dL (range: 1.1–5.1 mg/dL). The median BUN and creatinine at
time of last follow-up were 44.5 mg/dL (range: 23–226 mg/dL) and
2.4 mg/dL (range: 1.3–11.8 mg/dL), respectively. For three cats, the first
postoperative assessment was also the time of last follow-up.
Necropsies were performed on three cats. One case had been
euthanized intraoperatively due to an unresectable renal mass. Bilat-
eral nephritis was identified and the renal mass invaded into the ipsi-
lateral adrenal gland and vasculature. The second case was the cat
with bilateral PKD that had undergone renal transplant and right
nephrectomy, concurrently. The cat was euthanized six days later for
severe inguinal epidermal and dermal necrosis, possible sepsis, and
generalized seizures. Histopathology confirmed the presence of a RC,
but no metastatic lesions were identified. The final cat developed
Horner's syndrome three months post-nephrectomy for RTCC. Nec-
ropsy identified a metastatic cranial mediastinal mass, perirenal mass,
and pulmonary and regional lymph node metastases.
All-cause MST was 203 days (95% CI: 84, 1379 days) (Figure 1).
The 1-year, 2-year, and 6-year survival rates were all 40.4%, while the
4-year and 5-year survival rates were 23.1% and 11.5%, respectively.
Given the limited number of cases that went on to develop recurrence
and metastasis, PFI could not be determined. Eleven cats were censored
from analysis. Six cats were still alive at the time of data collection at a
median of 807 days (range: 12–1838 days). The remaining five cats
were lost to follow-up at a median of 21 days (range: 12–247 days).
All-causeMSTforcatswithRCCwas84days(range:0–
3205 days). For cats with RCC surviving to discharge, MST was
251 days (range: 16–3205 days). Of note, five RCC cats were still
alive at the time of data collection at a median of 828 days (range:
373–1838 days). All-cause MST for cats with RTCC was 153 days
(range: 12–247days). The cat with RSCC lived 1day and did not
survive to discharge.
When cases surviving to discharge were analysed, all-cause MST
increased to 1217 days (95% CI: 127, 1641 days). Cause of death was
suspected to be RC-related in the majority of cases, including: chronic
kidney disease (n=2), anaesthetic complication during an omental
mass removal (n=1; no histopathology provided), suspected pulmo-
nary thromboembolism following postoperative air travel (n=1),
acute kidney injury, hyporexia, and weight loss (n=2). A single cat
with neurologic signs was assumed to be RC-related, as no necropsy
was performed, and central nervous system metastasis could not be
ruled-out. Cause of death was considered unrelated to RC in four cats:
mesenteric and jejunal hemangiosarcoma (n=1), complications of
hypertrophic cardiomyopathy (n=1), progressive renal azotemia sec-
ondary to lily toxicity (n=1), and gastrointestinal lymphoma (n=1).
3.9 |Prognostic factors
Potential prognostic factors evaluated are summarized in Table 1. All-
cause MST for cats with preoperative anaemia (p=.38), erythrocyto-
sis (p=.14), azotemia (p=.60), and haematuria (p=.97) were not
significantly different than cats without those abnormalities. There
was no significant difference in MST between cats with suspected
metastasis at the time of surgery (36 days) versus those without
(203 days; p=.09). There was no significant difference in MST
between cats with RCC (127 days) and RTCC (153 days; p=.21).
3.10 |Systemic therapy
Eight cats received postoperative systemic therapy. Agents used
included mitoxantrone (n=3), toceranib phosphate (n=1), cyclo-
phosphamide (n=1), toceranib phosphate followed by cyclophospha-
mide (n=1), gemcitabine (n=1), and a chemotherapy agent that was
FIGURE 1 Kaplan–Meier curve depicting overall survival time
for the 36 cats undergoing nephrectomy (203 days, 95% CI:
84–1379 days). Tick marks represent censored cats.
KENNY ET AL.5
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not reported (n=1). A final cat received chlorambucil followed by a
multi-drug protocol (cyclophosphamide, vincristine, prednisolone,
L-asparaginase) to treat gastrointestinal lymphoma. Details regarding
dosing and tolerability were limited.
4|DISCUSSION
To the authors' knowledge, this is the first case series to investigate
the presenting signs and clinical outcomes of cats with RC undergoing
nephrectomy. Study demographics echoed the current body of litera-
ture: cats were middle-aged to older with no breed or sex predilec-
tion.
1–5,10,22,23
Clinical signs were nonspecific with weight loss,
hyporexia, and vomiting being most common. Renal tumours were
incidentally detected in eight cats when a palpable mass was identi-
fied on routine examination or when haematuria or erythrocytosis
were detected on laboratory work. This highlights the importance of
routine health screenings and minimum database assessment in
middle-aged to older cats.
Preoperative metastatic rates in this population were lower than
previously reported (22%). This contrasts with the Henry et al. study
where nine of 14 (64%) staged cases had distant metastasis, including
all three (100%) RTCC cases.
3
This, in part, can be explained by our
study design, as nephrectomy was an inclusion criterion. Since owners
and veterinarians may be less willing to pursue surgery for cats with
metastatic disease, the lower incidence of metastasis could be a result
of selection bias. Likewise, since few cases had preoperative sampling
beyond their renal masses, metastatic lesions may have been missed
or ascribed to other disease processes. Although the presence of pre-
operative metastasis was not prognostic for survival ( p=.09), the
potential influence of study design and incomplete preoperative stag-
ing make it a topic worthy of further exploration.
Histopathology findings were congruent with the current litera-
ture, as RCC was most common, followed by RTCC. A single cat with
RSCC was identified. Tumour subtype had no bearing on survival out-
come, though RTCC and RSCC numbers were low. While mitotic
count was initially of interest, inconsistent reporting and definitions of
high-power fields prevented reliable comparisons. In dogs with RCC,
survival times decrease as mitotic index increases
32
; this has not been
evaluated in cats. Ideally, future studies would include histopathology
review to not only confirm diagnosis and tumour subtype, but also, to
report mitotic count uniformly. This could reveal histopathologic fea-
tures of prognostic importance.
In the present study, all-cause MST was 203 days. Substantial peri-
operative mortality (22%) was noted, as three cats were euthanized at
the time of surgery and five cats died or were euthanized prior to dis-
charge. Two cases euthanized intraoperatively had unanticipated locor-
egional disease, which emphasizes the need for sensitive preoperative
staging. Since the remaining causes of perioperative mortality varied,
patient risk factors in this period remain undefined.
TABLE 1 Univariable Cox
proportional hazard analysis of potential
prognostic factors for cats with renal
carcinoma undergoing nephrectomy.
Prognostic factor
Median overall
survival (days) p-value
Preoperative anaemia
a
.38
Present (n=5) 203
Absent (n=31) 102
Preoperative erythrocytosis
b
.14
Present (n=5) 1379
Absent (n=31) 84
Preoperative azotemia
c
.60
Present (n=9) 786
Absent (n=22) 75
Preoperative haematuria
d
.97
Present (n=11) 102
Absent (n=21) 127
Suspected metastasis at
time of surgery
.09
Present (n=8) 36
Absent (n=28) 203
Histopathology subtype .21
RCC (n=29) 127
RTCC (n=6) 153
Abbreviations: RCC, renal cell carcinoma; RTCC, renal transitional cell carcinoma.
a
Preoperative haematocrit <24%.
b
Preoperative haematocrit >60%.
c
Preoperative creatinine of ≥1.6 mg/dL and urine specific gravity <1.035.
d
Preoperative urinalysis with >50 red blood cells per high power field.
6KENNY ET AL.
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With 1-year, 2-year, and 3-year survival rates of 40.4%, durable
survival outcomes were possible in a subpopulation of cats. Namely,
for cats surviving to discharge, all-cause survival rose to 1217 days.
Since five of these cats were censored alive at a median of 807 days,
potential for long-term outcome may be greater yet. Our findings
echo that of Matsumoto et al. who reported survival times ranging
from 1287 to 2292 days in three cats with RCC.
4
Cause of death was considered unrelated to RC in three cats. For
the remaining cases, insufficient details, restaging, or necropsies
meant cause of death was undetermined. This was particularly true
for cats euthanized for CKD (1379 and 1826 days after nephrectomy)
or after acute kidney injury (death due to renal failure following lily
toxicity 253 days after nephrectomy). While CKD is a common dis-
ease of geriatric cats, it is impossible to differentiate cases that were
de novo versus secondary to nephrectomy. Preoperative GFR studies
and consistent, standardised assessment of postoperative renal values
and urine specific gravity would improve our understanding of ongo-
ing renal function in this population.
None of the preoperative and tumour-related variables evaluated
were prognostic for survival. Although RC subtype was not prognos-
tic, the 10 cats with MST in excess of 1 year all had RCC. Given the
limited number of cases of RTCC and RSCC identified, a Type II error
may have influenced results. Future studies are needed to elucidate
the clinical course of RTCC and RSCC and their biologic behaviour.
Postoperative systemic therapies were used in eight cats and dif-
fered by case. Assertions regarding the utility of systemic therapy
could not be extrapolated from this cohort. It remains to be seen if
chemotherapy has value in the postoperative setting, if specific histo-
pathology findings should prompt systemic therapy, and which agents
or dosing schemes are efficacious.
Like many veterinary retrospective studies, the current study had
several limitations. As an uncommon tumour type, a small number of
cases were accrued despite a 20-year study period and 10 participating
institutions. As a multi-institutional study, preoperative staging
approaches, histopathology reporting, and postoperative management
differed. In particular, preoperative sampling of potential metastatic
lesions was inconsistent, leaving the true metastatic rate at diagnosis
unknown. Likewise, perioperative and long-term renal monitoring var-
ied, and a large proportion of cats were lost to follow-up. Additionally,
there was no uniform restaging scheme, sampling of suspected meta-
static and recurrent lesions was limited, and necropsies were rarely per-
formed. Collectively, this likely led to underreporting tumour recurrence
and metastasis. Thus, accurate PFI for feline RC remains undetermined.
In conclusion, nephrectomy is a suitable treatment option for cats with
RC. While an unknown subset of cats appears at-risk in the perioperative
period, cats that survive to discharge can have prolonged survival times.
Additional studies are necessary to identify cases at risk in the perioperative
period and those likely to develop early recurrence or metastasis.
ACKNOWLEDGEMENTS
The authors would like to thank Dr. Alycen Lundberg (University of
Illinois) and Dr. Ariel Schlag (Western College of Veterinary Medicine)
for their contributions to abstracting cases.
FUNDING INFORMATION
The authors have no financial support to disclose.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the
corresponding author upon reasonable request.
ORCID
Matthew R. Cook https://orcid.org/0000-0003-1825-2161
Katherine A. Skorupski https://orcid.org/0000-0003-0324-445X
Brandan G. Wustefeld-Janssens https://orcid.org/0000-0001-8458-
1735
MacKenzie A. Pellin https://orcid.org/0000-0002-1094-8909
Laura E. Selmic https://orcid.org/0000-0001-6695-6273
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How to cite this article: Kenny SA, Cook MR, Lenz JA, et al.
Clinical outcomes in cats with renal carcinoma undergoing
nephrectomy: A retrospective study. Vet Comp Oncol. 2023;
1‐8. doi:10.1111/vco.12921
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