Biomedical subjects

R N White

Publications and source records attributed to R N White.

At least 19 recordsLinked to original sources

PubMed2000

Anatomy of the patent ductus venosus in the dog.

The biplanar umbilical vein portovenograms of 49 newborn puppies and the biplanar mesenteric vein portovenograms, obtained during surgery, of 42 adult dogs with left divisional intrahepatic portosystemic shunts consistent with a patent ductus venosus (PDV) were reviewed. On the basis of the combined surgical, postmortem and imaging data, the left divisional intrahepatic portosystemic shunts were consistent, each having a straight vessel which drained into a venous ampulla before draining into the caudal vena cava at the level of the diaphragm. The left phrenic vein and the left hepatic vein both entered the ampulla independently of the shunting vessel. The morphology of the ductus venosus in the pups was similar and consistent with the morphology of the left divisional intrahepatic PDV shunt of the adult dogs. It is concluded that this form of left divisional shunt is correctly named a PDV and is the result of the persistence of the fetal ductus venosus. From the surgical records it is concluded that all the shunts described as a PDV were attenuated by the direct manipulation of the ductus venosus before its entry into the ampulla.

Animals↗

PubMed2000

Concurrent torsion of the right cranial and right middle lung lobes in a whippet.

A four-year-old, entire male whippet was presented with a three-day history of lethargy, inappetence, occasional retching, a soft cough and intermittent episodes of haemoptysis. Clinical and laboratory findings, and thoracic radiographic and ultrasonographic studies suggested a diagnosis of lung lobe torsion. A concurrent lung lobe torsion of the right cranial and right middle lung lobes was confirmed at exploratory thoracotomy. Management included resection of both the affected lung lobes. No obvious underlying aetiology for the condition was apparent. The dog made a full recovery from the procedure and at the time of writing (11 months postoperatively) was reported to be well, exercising normally and showing no breathing abnormalities.

Animals↗

PubMed2000

Aortic and iliac thrombosis in six dogs.

Six dogs had signs of pelvic limb weakness, pain and collapse as a result of occlusion of the distal aorta and/or the iliac arteries by a thrombus. Antemortem diagnosis was made on the basis of clinical signs, angiography and ultrasonography. Five dogs had concurrent disease that probably predisposed to thrombosis, including hyperadrenocorticism (three dogs), neoplasia and cardiac disease. Two dogs died shortly after the episode of thrombosis. Dogs that survived the acute episode received aspirin in an attempt to prevent thrombosis occurring again and all regained pelvic limb function. For dogs that survived longer than one month after the acute episode, repeat thrombosis was uncommon; hence the prognosis was related to the underlying disease. Aortic and iliac thrombosis in dogs is an uncommon condition that usually arises secondarily to a predisposing disease process; it carries a more favourable prognosis than feline aortic thromboembolism.

Adrenocortical Hyperfunction↗

PubMed1999

The angiographic anatomy of the portal venous system in the neonatal dog.

The angiographic anatomy of the portal venous system in 50 dead, neonatal Labrador/Retriever type puppies is described. Angiography was performed by the injection of radioopaque contrast media through a catheter placed within the umbilical vein. In 49 pups the ductus venosus was a straight vessel arising from the left main portal vein and terminating in an ampulla into which the left hepatic and left phrenic veins entered prior to the ampulla entering the caudal vena cava. The diameter of the ductus venosus was significantly narrower (P<0.001) in pups born alive (n=10) when compared to stillborn individuals (n=39). No discreet narrowing of the ductus venosus indicating a sphincter was found, with closure appearing to be uniform along the vessel's length. A well-developed, patent portal venous system was present in the majority of individuals. One pup showed variation from the others studied having a vascular connection between the portal sinus and the vena cava within the liver. This may represent a normal variant of the ductus venosus, or may be an anatomical abnormality leading to the development of an intrahepatic portosystemic shunt. If this was an intrahepatic shunt, no concurrent ductus venosus was present.

Animals↗

PubMed1999

Management of a proximal pelvic limb skin laceration in a dog using a skin flap and an external fixator.

A nine-year-old, spayed female crossbred dog sustained a traumatic skin lesion to the right proximal pelvic limb, extending to the extensor surface of the stifle. Surgical management of the wound included primary closure using a body skin flap fashioned from the right caudolateral abdominal wall. To achieve closure and prevent tension on the wound, the coxofemoral and stifle joints on the affected side needed to be immobilised in flexion. Flexion immobilisation of the stifle was achieved using the anatomical principle of muscle reciprocation. The ipsilateral tarsal joint was immobilised in flexion using a uniplanar-bilateral (type II) transarticular external skeletal fixator and this resulted in the automatic flexion of the stifle. The fixator was removed six weeks postoperatively when the wound had healed. There were no apparent complications associated with the fixator either during its use or in the longer term following its removal.

Animals↗

PubMed1998

Surgical treatment of intrahepatic portosystemic shunts in 45 dogs.

The surgical attenuation of an intrahepatic portosystemic shunt in 45 dogs is described. Twenty-nine (64 per cent) had left divisional shunts consistent with a patent ductus venosus (PDV), 15 (33 per cent) had central divisional shunts and one had a right divisional shunt. In the dogs with a PDV, the shunt vessel could be most easily manipulated at a posthepatic site, whereas in those with central and right divisional shunts the manipulation could be more easily made intrahepatically but sometimes involved demanding intravascular surgical techniques. Eight dogs (18 per cent) died during the surgery or shortly afterwards. Of the 37 dogs surviving longer term, 28 (76 per cent) became clinically normal and required no medication or diet control. In a further three animals the shunt was ligated completely only during a second surgical procedure. The remaining six dogs were euthanased because of clinical signs of encephalopathy which were either surgically or medically uncontrollable.

Animals↗

PubMed1998

Morphology of congenital intrahepatic portacaval shunts in dogs and cats.

The preoperative ultrasound images and biplanar operative mesenteric portograms of 28 dogs and six cats with congenital intrahepatic portacaval shunts were reviewed retrospectively. On the basis of the combined surgical, postmortem and imaging data, the shunts were classified according to their location within the liver and their shape. Thirteen dogs and four cats had a left-divisional shunt with a relatively consistent bent tubular shape that drained into the left hepatic vein. Another 13 dogs had a central-divisional shunt that took the form of a foramen between dilated portions of the intrahepatic portal vein and caudal vena cava. One cat with a central-divisional shunt had a tortuous vessel. The remaining two dogs and one cat had right-divisional shunts that were large, tortuous vessels. The morphology of a left-divisional shunt is compatible with patent ductus venosus, but the pathogenesis of central and right-divisional shunts is unknown. It is concluded that intrahepatic portacaval shunts in dogs and cats may be classified as left, central or right divisional. Ultrasound enables a preoperative morphological assessment that correlates well with the results of portography and may aid surgical planning.

Animals↗

PubMed1997

Skeletal muscle extra-aortic counterpulsation in dogs with dilated cardiomyopathy.

Skeletal muscle extra-aortic counterpulsation was performed in seven dogs with dilated cardiomyopathy. A left latissimus dorsi dynamic descending thoracic aortomyoplasty was used as the autologous counterpulsator. Pulse train stimulation in diastole was used to initiate contraction and fibre type transformation. Two of the dogs died within 48 hours of surgery. The device was successfully activated in the five remaining dogs, but in one individual it failed within 48 hours of activation. Serial echocardiographic examinations of dogs in which the device functioned successfully (n = 4) showed trends towards the decrease in the left ventricular systolic internal dimension, left ventricular diastolic internal dimension, E-point to septal separation and left atrial diameter in systole seven to 14 days following the procedure, although these changes failed to persist in the long-term. The results suggest that skeletal muscle for cardiac assistances such as extra-aortic muscle counterpulsation, might be a therapeutic option for dogs with cardiac failure due to dilated cardiomyopathy.

Animals↗

PubMed1997

Surgical management of subvalvular aortic stenosis and mitral dysplasia in a golden retriever.

A 12-month-old neutered male golden retriever was presented with a history of lethargy and exercise intolerance. Clinical examination, electrocardiography, radiography and echocardiography supported a diagnosis of fixed subvalvular aortic stenosis with a Doppler pressure gradient of 77.5 mmHg. Surgical inspection also revealed gross structural abnormalities of the mitral valve consistent with mitral dysplasia. Intervention consisted of resection of the dysplastic mitral valve and the subvalvular aortic stenosis. The mitral valve was replaced with a bioprosthetic valve. Total cardiopulmonary bypass time was 65 minutes and aortic cross-clamp time was 55 minutes. A full recovery was made and 11 months postoperatively the aortic transvalvular gradient was 30 mmHg. At the time of writing, 12 months after surgery, the dog was clinically normal and requires no medication.

Animals↗

PubMed1997

Resolution of exfoliative dermatitis and Malassezia pachydermatis overgrowth in a cat after surgical thymoma resection.

A four-year-old, male neutered domestic shorthaired cat was presented with a two-week history of nasal and ocular discharge, generalised exfoliative dermatitis, intense pruritus, polydipsia, polyphagia, weight loss, intermittent hindlimb ataxia and lethargy. Cutaneous populations of Malassezia pachydermatis yeast organisms were found to be elevated. The generalised nature of the disease prompted survey radiography which revealed the presence of a cranial mediastinal mass which was subsequently resected and found to be a thymoma. Within six months of surgery, systemic and cutaneous signs had resolved and yeast counts had returned to normal, suggesting a causal relationship between the thymoma and the skin disease.

Animals↗

PubMed1997

Arteriovenous fistula involving the prepuce of a dog.

A nine-year-old male Ibizan hound had a network of large tortuous pulsating blood vessels on the prepuce that enlarged gradually over a five month period. A diagnosis of arteriovenous fistula was based on clinical signs, angiography and Doppler ultrasonography. Ligation of the major vascular supply to the fistula resulted in only temporary improvement. Definitive treatment was by wide excision, with penile amputation and scrotal urethrostomy.

Angiography↗

PubMed1997

Chronic caecal faecolithiasis in a dog.

A 14-year-old, spayed female Jack Russell terrier with a six month history of weight loss, lethargy, intermittent vomition and diarrhoea was diagnosed as having a chronic impaction of the caecum with mineralised faecal material. Diagnosis was based on the clinical findings and both survey and positive contrast radiographic studies. The diagnosis of caecal impaction was confirmed at surgery and a typhlectomy was performed with the aid of a linear stapler. Histopathology of the caecum confirmed the impaction to have resulted from faecolithiasis. The dog made a full recovery from the procedure, showing no recurrence of the clinical signs until euthanasia three months postoperatively for probable heart failure associated with mitral regurgitation.

Animals↗

PubMed1997

Naturally occurring xanthine urolithiasis in a domestic shorthair cat.

A five-year-old neutered male domestic shorthair cat was presented after three episodes of urethral obstruction and anuria requiring relief urethral catheterisation. A double contrast cystogram revealed the presence of multiple small cystoliths which were radiolucent on plain radiographs. A perineal urethrostomy and a cystotomy were performed to relieve the urethral obstruction and to remove the cystoliths. Quantitative analysis revealed the cystoliths to be composed of 100 per cent xanthine. Clinical history suggested the xanthinuria to be naturally occurring. Unfortunately, the cat was killed in a road traffic accident two months after the surgical procedure, preventing further long-term assessment.

Animals↗

PubMed1996

Surgical treatment of intrahepatic portosystemic shunts in six cats.

The surgical treatment of intrahepatic portosystemic shunts in six cats is described. The preoperative diagnoses were based on the results of abdominal ultrasonography, and mesenteric portography was used during surgery to confirm the diagnosis and establish the morphology of the shunting vessel. In four of the cats the shunt vessel passed through the left division of the liver, compatible with a patent ductus venosus (PDV), in one cat the shunt passed through the central hepatic division and in the other cat it passed through the right hepatic division. During surgery the shunt vessel was manipulated directly either intrahepatically, or post hepatically in the four cats with PDV. In five cats the shunt vessel was partially ligated, and in the other the vessel was completely ligated. The attenuation procedure produced a mean increase in mesenteric venous pressure of 17 cm H2O, with a range from 14 to 20 cm. All the cats recovered from the surgical procedure, but one developed neurological signs shortly after the operation and died from respiratory failure. Four of the cats were clinically normal and required no medication by one month after the operation. One cat required long-term medication to control its continued clinical signs.

Animals↗

PubMed1996

Ultrasonographic diagnosis of congenital portosystemic shunt in 14 cats.

Twenty-four cats with clinical and, or, clinicopathological signs compatible with portosystemic shunting were examined prospectively using two-dimensional grey-scale, duplex and colour-flow Doppler ultrasonography. Diagnosis of congenital portosystemic shunt was subsequently confirmed in 14 cats using operative mesenteric portography and surgery. Of the 14 affected cats, nine were purebred; eight were male and six female. The mean age at the time of diagnosis was nine months (range four to 27 months). Ultrasonographic evidence of a small liver was present in seven cats (50 per cent); visibility of intrahepatic portal vessels was reduced in three (21 per cent). An anomalous blood vessel was identified ultrasonographically in each cat; in 10 cats (71 per cent) the vessel was observed to originate from the portal vein and drain into the caudal vena cava. Abnormally variable portal blood flow was present in eight of the 10 cats in which it was measured. At surgery, six shunts were intrahepatic and eight extrahepatic; the ultrasonographic diagnosis of intra- versus extrahepatic shunt was correct in 13 cats (93 per cent). No anomalous blood vessels or abnormalities affecting the portal vein were detected ultrasonographically in any of the 10 cats that did not have congenital portosystemic shunting. Hence, the accuracy of ultrasonography for diagnosis of congenital portosystemic shunting in this series was 100 per cent.

Animals↗

PubMed1996

Per rectal portal scintigraphy in the diagnosis and management of feline congenital portosystemic shunts.

Five cats with a congenital portosystemic shunt (CPSS) were examined using transcolonic portal scintigraphy before and after surgical ligation of the shunting vessel. The mean shunt index before surgery was 52 per cent (range 45 to 61 per cent). Repeat portal scintigraphy, six to eight weeks after surgery, indicated a significant reduction in shunt index (mean 13 per cent, range 5 to 25 per cent) in four cats. In one of these cats a marked reduction in the shunt index, as determined by scintigraphy, preceded normal fasting blood ammonia. In the fifth cat there was no significant change in the shunt index, fasting serum bile acids and blood ammonia six months after surgery, although its clinical signs of hepatic encephalopathy had improved. Portal scintigraphy is useful in the diagnosis of CPSS and enables a quantitative assessment of the effects of surgery and may be a more accurate indicator of the degree of shunting after surgery than blood ammonia and serum bile acids.

Ammonia↗

PubMed1996

Review of the technique and complications of median sternotomy in the dog and cat.

The surgical and medical records of 67 dogs and nine cats which underwent median sternotomy over a five-year period were reviewed. The indication for median sternotomy and the short and longer term complications were recorded. Twenty-six of the dogs died or were euthanased within 48 hours of the surgery as a consequence of the pre-existing disease or complications of the intrathoracic surgical procedure. A further four dogs were enthanased between 48 hours and 14 days following confirmation of neoplastic processes. Thirty-seven dogs were alive at 14 days: of these, seven dogs (19 per cent) experienced short-term wound complications, including haemorrhage, wound infection, thoracic limb neurological deficits and excessive postoperative discomfort. Of the 37 dogs alive for longer term follow-up, eight dogs (22 per cent) experienced wound complications, including haemorrhage, sternal fracture, sternal osteomyelitis and delayed wound healing. No complications were noted in the cats.

Animals↗

PubMed1996

Treatment of acquired myasthenia gravis associated with thymoma in two dogs.

Two cases of myasthenia gravis associated with thymoma are reported. Both were female German shepherd dogs and the thymoma was surgically resected. Aspiration pneumonia secondary to persistent megaoesophagus was a complication in both cases. The myasthenia gravis did not resolve, but there was a more satisfactory control of clinical signs with anticholinesterase treatment. Corticosteroid therapy was used in one case, but the resulting polydipsia increased the incidence of regurgitation, resulting in recurrent episodes of aspiration pneumonia.

Adrenal Cortex Hormones↗