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Biomedical subjects

R Walshaw

Publications and source records attributed to R Walshaw.

At least 19 recordsLinked to original sources

Gastric dilatation-volvulus after splenic torsion in two dogs.

Two dogs developed gastric dilatation-volvulus 2 and 17 months, respectively, after splenectomy for treatment of splenic torsion. Splenic displacement and torsion may stretch the gastric ligaments, allowing increased mobility of the stomach. After splenectomy, an anatomic void may be created in the cranioventral part of the abdomen, contributing to the mobility of the stomach. Veterinarians treating dogs with isolated splenic torsion may wish to consider prophylactic gastropexy at splenectomy, to reduce the chance of future gastric dilatation-volvulus. Prophylactic gastropexy should be done only if the dog's hemodynamic status is stable enough to allow for performance of the additional surgery.

Animals

Effects of subcutaneous expansion on the mechanical properties of porcine skin.

The purpose of this study was to determine the effects of conventional and intraoperative tissue expansion on the biomechanical properties of skin. Two 200-cc silicone tissue expanders were inserted subcutaneously in each of six young pigs. One expander was inflated conventionally (4 weeks) and the other intraoperatively (three times within 1 hr). A skin specimen was excised from each expansion site and each contralateral control site and tested under tension to failure. The sites were closed and allowed to heal for 4 weeks at which time another biopsy specimen was taken from each site. Histological observations and biochemical analyses were conducted. Also, tangent modulus and ultimate stress were determined from the mechanical response of each specimen. Results indicated an initial decrease in stiffness and ultimate strength for conventionally expanded skin. The mechanism for this decrease could not be explained via our current biochemical and histological techniques. Mechanical properties for conventionally expanded skin, after healing, were not significantly different than controls. The mechanical properties for intraoperatively expanded skin were not significantly altered with respect to controls, either at initial expansion or after 4 weeks of healing. The tissue "generated" as a result of intraoperative expansion in the porcine model is likely tissue recruited from the surrounding skin.

Animals

Acute onset of hypokalemia and muscular weakness in four hyperthyroid cats.

Sudden onset of muscular weakness and ventroflexion of the neck were identified in 4 hyperthyroid cats. In each cat, the onset of clinical signs was associated with an acute decrease in serum potassium concentration. The cause for hypokalemia was undetermined, but could have resulted from deficits in total body potassium content or shifts of potassium from the extracellular space into the intracellular space. The 4 cats responded to administration of potassium. Hyperthyroid cats may be prone to disturbances in potassium homeostasis. Clinicians should be aware of potential changes in potassium homeostasis during the treatment of cats with hyperthyroidism.

Acute Disease

Stapling techniques in pulmonary surgery.

There are only a few reports in the veterinary literature describing the use of stapling equipment and techniques for pulmonary surgery. These reports indicate that complications associated with these procedures are minimal. Although pulmonary lobectomy procedures originally described independent isolation and ligation of the hilar vessels, it became apparent that, with the use of the smaller staples, especially the ones designed for vascular use, this was unnecessary. Therefore, en bloc hilar stapling is the procedure of choice. This makes the surgical procedure extremely quick to perform. Similarly, there is no indication to routinely oversew staple lines when performing a partial lobectomy. This is a tedious procedure and may actually increase the chance of air leakage. If point areas of leakage do occur, these can be independently occluded either with sutures or individual vascular clips. Selecting the correct size of TA stapler and staples to create the correct length of staple line is critical. It is important that all the tissue to be ligated lie comfortably within the staple line. It is better to use a stapler that is too long and collect the extra staples on a sponge than to use one that is too short that results in leakage from nonstapled tissue. In general, the 4.8-mm staples should not be used for pulmonary surgery in the dog and cat. They do not compress the tissue enough to prevent leakage. For most complete lobectomies, where the hilus of the lung can be adequately isolated, the TA 30 V3 is the stapler of choice. When performing a partial lobectomy, a longer stapler is often required. If a TA 55 or TA 90 is necessary, it should be used with 3.5-mm staples. Even though stapling techniques have made pulmonary surgical procedures safe, easy, and quick to perform, they are not totally free of problems and complications. Experience in the use of the equipment is essential, as is good surgical judgment as to when to use or not to use these techniques. The absence of reported clinical complications, either short- or long-term, attests to the success of these techniques.

Animals

Changes in renal function associated with treatment of hyperthyroidism in cats.

We measured glomerular filtration rate (GFR) estimated by plasma disappearance of 99mTc-labeled diethylenetriaminepentaacetic acid, serum concentrations of thyroxine (T4), creatinine, and urea nitrogen, and urine specific gravity in 13 cats with naturally acquired hyperthyroidism before and 30 days after treatment by bilateral thyroidectomy, and in a group of 11 control cats. Mean (+/- SD) serum T4 concentration decreased from a pretreatment value of 120.46 (+/- 39.21) nmol/L to a posttreatment value of 12.15 (+/- 6.26) nmol/L (P < 0.0001; reference range, 10 to 48 nmol/L). Treatment of hyperthyroidism resulted in a decrease in mean (+/- SD) glomerular filtration rate, from 2.51 (+/- 0.69) ml/kg of body weight/min to a posttreatment value of 1.40 (+/- 0.41) ml/kg/min (P < 0.0001). Mean serum creatinine concentration increased from 1.26 (+/- 0.34) mg/dl to 2.05 (+/- 0.60) mg/dl (P < 0.01). Mean serum urea nitrogen concentration increased from 26.62 (+/- 6.83) mg/dl to a mean postthyroidectomy concentration of 34.92 (+/- 8.95) mg/dl (P < 0.01). All changes were significant. Two cats developed overt renal azotemia after treatment of hyperthyroidism. Our results provide further evidence that treatment of hyperthyroidism can result in impaired renal function. In addition, our results suggest that, in some instances, thyrotoxicosis might mask underlying chronic renal insufficiency.

Animals

Radiographic evaluation of esophageal function in Chinese Shar Pei pups.

Liquid barium esophagography was done in 29 clinically normal Chinese Shar Pei pups and observed fluoroscopically, beginning when they were approximately 3 months old and repeated periodically until they were at least 18 months old, if possible. Of these dogs, 69% had relatively slow stimulation of secondary waves, 48% had generalized poor esophageal tone or motility, and 38% had esophageal redundancy. Sequential studies revealed apparent improvement with age for those dogs initially showing slow motility, provided that redundancy was not also present. Another group of 9 Chinese Shar Pei pups had histories of either regurgitation or vomiting. Five of these had hiatal hernia and 2 had megaesophagus.

Animals

Treatment of left laryngeal hemiplegia in standardbreds, using a nerve muscle pedicle graft.

The efficacy of a nerve muscle pedicle (NMP) graft in restoring upper airway function was evaluated in exercising horses with induced left laryngeal hemiplegia. The NMP graft was created from the first cervical nerve and the omohyoideus muscle and transplanted into the left cricoarytenoideus dorsalis muscle. Seven adult Standardbreds were trained to exercise on a treadmill inclined at 6.38 degrees. With the horses at rest and exercising at 4.2 and 7.0 m/s, the following variables were recorded: peak inspiratory and expiratory transupper airway pressures (defined as the pressure difference between a lateral tracheal catheter and a mask catheter), peak inspiratory and expiratory air flow, inspiratory and expiratory impedance, tidal volume, minute ventilation, heart rate, and respiratory frequency. Measurements were made before left recurrent laryngeal neurectomy (LRLN), 28 days after LRLN, and 12, 24, and 52 weeks after the NMP graft (n = 5) or sham operation (n = 2). Before LRLN, exercise increased inspiratory and expiratory air flow and transupper airway pressure, whereas the impedance was unchanged. After LRLN, transupper airway inspiratory pressure and impedance were significantly greater and inspiratory air flow was significantly less than baseline values at 7.0 m/s. The sham operation did not improve airway function. Twelve weeks after insertion of the NMP graft, inspiratory impedance and inspiratory air flow were significantly different (improved) from LRLN values. Twenty-four weeks after insertion of the NMP graft, inspiratory impedance was not significantly different from LRLN values.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Subtotal colectomy for treatment of chronic constipation associated with idiopathic megacolon in cats: 38 cases (1979-1985).

Chronic constipation, nonresponsive to medical management and associated with idiopathic megacolon, was diagnosed in 38 cats from 1979 to 1985. All cats were treated by subtotal colectomy and enterocolostomy, in which the ileum or distal portion of the jejunum was joined to a 2- to 4-cm segment of distal portion of the colon preserved to accommodate an end-to-end anastomosis. After surgery, cats usually were depressed and anorectic, had tenesmus, and passed liquid tarry feces. In 37 cats 1 week to 3 months after surgery, character of the feces changed from diarrhea to soft semiformed or formed feces. One cat had severe diarrhea that was nonresponsive to diet change and pharmacologic treatment; the diarrhea resolved after 4.5 months. One cat developed a stricture of the enterocolostomy, which was relieved by 3 balloon catheter dilatations. All cats regained normal appetite, did not lose weight, and were not incontinent. Three cats had sporadic episodes of constipation and were easily treated. Results of histologic examination of the resected portion of colon in 23 cats were inconclusive.

Animals

Neuromuscular pedicle graft for restoration of arytenoid abductor function in dogs with experimentally induced laryngeal hemiplegia.

Left laryngeal hemiplegia was induced by resection of the left recurrent laryngeal nerve in 12 dogs. A neuromuscular pedicle graft formed from the first cervical nerve and sternothyroideus muscle was transplanted after 1 week to the denervated cricoarytenoideus dorsalis muscle in 8 dogs. The remaining 4 dogs served as controls. Left arytenoid abduction was blindly evaluated by laryngoscopy with video photography at time 0, at 1 week, and at 19 weeks in all dogs. At 19 weeks, biopsy specimens of the left cricoarytenoideus dorsalis muscle and the neuromuscular pedicle were taken from 4 of the treatment dogs, and biopsy specimens of the left cricoarytenoideus dorsalis muscle were taken from the 4 control dogs. All biopsy specimens were blindly evaluated by histologic and histochemical examination. At 36 to 44 weeks, the remaining 4 treatment dogs, from which biopsy specimens had not been taken, were reevaluated by use of laryngoscopy with video photography. Complications and difficulties encountered during surgery included hemorrhage in the area of the cricoarytenoideus dorsalis muscle, location of a branch of the first cervical nerve that was long enough to prevent tension at the graft site, orientation of the muscle pedicle in the cricoarytenoideus dorsalis muscle without the use of an operating microscope, and preservation of the terminal portion of the first cervical nerve while forming the neuromuscular pedicle. Results of the arytenoid movement evaluations revealed improvement in arytenoid abductor function in the treatment group, compared with that in the control group at 19 weeks. Arytenoid abduction in the treatment group at this time, however, was still significantly decreased (P less than 0.05), compared with presurgical movement evaluations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Bacterial population and histologic changes in dogs with perianal fistula.

Ages of 44 dogs with perianal fistula, ranged from 6 months to 13 years (mean, 5.2 years). German Shepherd Dogs and Irish Setters were statistically (P less than 0.01) over-represented compared with those breeds in a canine hospital population (n = 22,047) for the same period. There was a 2:1 male-to-female ratio, with 38 (86.4%) of dogs sexually intact and 6 (13.6%) of dogs neutered. Eleven types of bacterial organisms were recovered from deep perianal tissues of which Escherichia coli, Staphylococcus aureus, beta-hemolytic streptococci, and Proteus mirabilus were most common. Organisms were not recovered from 7 dogs. Of 93 isolates, 88.3% were susceptible to gentamicin, 80.5% to cephalothin, 79.2% to chloramphenicol, and 74% to trimethoprim-sulfamethoxazole. Fifty-one biopsy specimens from 44 dogs were classified as having early, intermediate-, and late-stage lesions based on the amount of fibrosis, severity of the inflammatory response, and, if present, depth of sinus tracts. In most biopsy specimens, all 3 stages were represented in the same histologic section. In 45 specimens, most inflamed lesions were in the dermis of the zona cutanea. Hidradenitis was present in 22 biopsy specimens and was associated with the formation of epithelial-lined sinus tracts.

Anal Canal

Thyroid and immunologic status of dogs with perianal fistula.

Lymphocyte-proliferation responses, absolute lymphocyte counts, and thyrotropin-stimulation responses were determined in 33 dogs with perianal fistula; serum immunoglobulin values also were determined in 15 of the 33 dogs. Lymphocytes were stimulated with concanavalin A, pokeweed mitogen, and phytohemagglutinin and were cultured with medium containing normal pooled canine serum or fresh patient's autologous serum. Initially, lymphocytes from 9 dogs (27.3%) had depressed stimulation responses to greater than or equal to 1 phytomitogen, and 4 of the 9 dogs had absolute lymphopenia. One month after recovery in these 9 dogs, lymphocytes from 4 dogs (66.7%) had normal proliferation responses. Of immunoglobulin determinations in 15 dogs, serum IgA values were 32 to 185 mg/dl (mean, 69 +/- 10 mg/dl) and were low in 2 dogs (13%), and serum IgM values were 48 to 610 mg/dl (mean, 263 to 46 mg/dl) and were high in 8 dogs (53%). Serum IgG values were 1,050 to 3,220 mg/dl (mean, 2,339 +/- 165 mg/dl) and were high in 10 dogs (71%). After thyrotropin stimulation, 1 dog was considered hypothyroid. Neither pathogenesis nor prognosis of canine perianal fistula was clarified via immunoglobulin concentrations or absolute lymphocyte counts. Based on lymphocyte-proliferation assays, suppression of cell-mediated immunity was probably a result of perianal fistula, rather than a cause of the fistula.

Animals

Naproxen-induced toxicosis in a dog.

Naproxen, a nonsteroidal anti-inflammatory drug, induced gastric ulceration and bleeding in a dog. Clinical signs included vomiting, anemia, melena, and weakness. The dog responded to a blood transfusion and supportive treatment (lactated Ringer's solution with added K+ and B vitamins, an antacid, and cimetidine). Naproxen had been given to the dog by the owner, as treatment for shoulder stiffness.

Animals

Radiotherapy of malignant nasal tumors in 67 dogs.

The nasal cavity of 67 dogs with malignant nasal neoplasia was treated with radiation. Preirradiation surgical cytoreduction of the tumor was done in 41 dogs. Fifty dogs were irradiated by use of 10 fractions over 22 days, and 17 dogs were given a similar total dose in 5 fractions over 35 days. The range of survival times (0.5 to 42 months), median survival time (8.5 months), and 1- and 2-year survival rates (38% and 30%, respectively) were better than those expected for other methods of treatment. Serious complications were few (4%). Survival times for dogs were determined on the basis of histologic tumor type and on the basis of megavoltage (cobalt or linear accelerator) vs softer deep radiation (cesium or orthovoltage) treatment, with or without cytoreductive surgery. Survival times of 10 dogs given softer radiation without surgery were shorter than those of 14 dogs that were given softer radiation and had cytoreductive surgery. Survival times of dogs that were given softer radiation and had surgery were similar to those of dogs that were given megavoltage radiation only. Cytoreductive surgery did not improve survival times for dogs that were given megavoltage radiation. Median survival time for 38 dogs with adenocarcinoma was 12 months, compared with 6 months for 14 dogs with squamous cell or undifferentiated carcinoma. Median survival time for 16 dogs with a variety of sarcomas was 11.2 months. Survival times of dogs with adenocarcinoma or sarcoma were significantly better (P less than 0.02 or 0.03) than for dogs with squamous cell or undifferentiated carcinoma. Necropsies were performed on 27 of 58 dogs that died or were euthanatized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma

Open peritoneal drainage for treatment of contaminated peritoneal cavity and septic peritonitis in dogs and cats: 24 cases (1980-1986).

The medical records of 22 dogs and 2 cats in which generalized peritonitis had been treated by open peritoneal drainage were reviewed. The age of the affected animals ranged from 5 months to 14 years. The causes of peritonitis were numerous, with the most common being leakage of gastrointestinal contents through spontaneous gastric or intestinal perforations and peritoneal contamination resulting from surgical complications. Bacteria were isolated from 18 (94.7%) of 19 specimens obtained for culturing at the time of diagnosis of peritonitis and from 8 (80%) of 10 specimens obtained for culturing at the time of final abdominal closure. Only 2 (25%) of 8 of the animals in which bacteria were isolated at the time of final abdominal closure died. The overall mortality was 33%. The mortality attributable to peritonitis or its direct complications was 21%. Open peritoneal drainage was tolerated well by all patients.

Animals

Cyclosporine pharmacokinetics in normal and pancreatectomized dogs.

Oral and i.v. cyclosporine (Cs) pharmacokinetics determined from radioimmunoassay (RIA) data were compared in normal and pancreatectomized dogs. An altered pharmacokinetics of Cs was observed in the pancreatectomized dogs that include: a 170% larger central compartment volume; a 34% greater total-body clearance; and lower steady-state average serum concentrations relative to the normals. Even though there were marked intersubject variations, both groups displayed a triexponential decline in Cs serum concentrations and disposition kinetics. Following 7 daily oral doses of commercial cyclosporine (CsA) (20 mg/kg) the Cs serum trough concentrations of the pancreatectomized dogs were consistently below 100 ng/ml, while those of the normal dogs were above 400 ng/ml. No alteration of CsA oral absorption was noted following pancreatectomy. This study suggests that frequent serum Cs concentration monitoring, with appropriate dosage adjustments, even in normals, is necessary to assure adequate drug levels. More significantly, the CsA dosage for pancreatectomized dogs should be several times greater to maintain serum concentrations comparable to normal dogs.

Animals