IN THIS NEWSLETTER:
One of the most frustrating problems for owners and veterinarians is dealing with the urinary-incontinent dog. This column will address management of the incontinent female dog, where problems such as infection and congenital urinary tract abnormalities (i.e., ectopic ureter) have been ruled out. Urinary incontinence is diagnosed when the dog develops lack of control of voluntary urination. Sphincter-mechanism incontinence is a functional incontinence, which must be distinguished from anatomical and neurological causes of incontinence. Assuming these other causes of incontinence have been eliminated, then we are left with dealing either pharmacologically or surgically with this incontinence. Many times sphincter-mechanism incontinence is first diagnosed post-ovariohysterectomy. The incontinence may be seen immediately after the hysterectomy or may develop several weeks to months later. Why this occurs is poorly understood, but may be related to an underlying anatomical problem or to the removal of estrogenic stimulation. Anatomical problems and estrogen stimulation may be inter-related in the development of incontinence in a previously normal animal, and a diagnostic work-up should be developed to assure there is not a concurrent anatomical problem. From a practical standpoint, the most diagnostically rewarding procedures are the positive contrast cystogram, and the double contrast, or air cystogram. Animals in which a trial with drug therapy fails to correct the incontinence should be evaluated next with these techniques for the identification of an intra-pelvic bladder location or an abnormal bladder neck and proximal urethra. Drug therapy is designed to increase the smooth muscle tone of the proximal urethra. The smooth muscle is under alpha adrenergic control, and to increase smooth muscle tone a drug trial with an alpha-receptor agonist should first be tried. Two drugs commonly used are phenylpropanolamine and ephedrine; phenylpropanolamine is preferred. Phenylpropanolamine should be tried at 1.5 mg/kg BID and at least two to three weeks given to assess effectiveness. If only partial improvement is seen, it may be beneficial to add estrogen to the phenylpropanolamine therapy; estrogen sensitizes alpha receptors whereas phenylpropanolamine stimulates them directly. The two drugs in combination may be synergistic. If drug therapy is unsuccessful, then surgery may be an option, especially when a pelvic bladder or a large, dilated bladder neck and proximal urethra are seen on the contrast studies. The goal of surgery is to increase tone in the proximal urethra in order to maintain closure pressure and continence. Procedures described in the literature include a ventral fascial sling, artificial sphincter placement, intra-urethral injection of Teflon, and colposuspension, to name a few. None of these has proven to be totally effective and all have complications which limit their use. Of all the techniques currently utilized, colposuspension as described by Holt is probably the most effective. This technique moves the bladder neck/proximal urethra into an intra-abdomenal location so that changes in intra-abdomenal pressure are transmitted to the bladder neck and urethra, rather than to the bladder alone. It also creates a mechanical increase in bladder neck and urethral tone. Colposuspension should be considered in dogs refractory to traditional drug therapy, or in dogs that become resistant to therapy.1,2
2. Holt PE. Urinary incontinence in the bitch due to sphincter mechanism incompetence: Surgical treatment. J Sm Anim Pract 1985; 26: 281-282.
Repair of the cruciate-deficient stifle joint is a common orthopedic condition presented to veterinarians in clinical practice. Trying to decide, and decipher amongst, the proper technique to use in individual cases is a challenge to all veterinarians with over 100 techniques for repair described in the literature. This newsletter will attempt to capsulize the major techniques and offer suggestions based upon our experience, and that of other veterinary surgeons, for selection of techniques. A new synthetic ligament replacement substance will also be described.
INTRA-ARTICULAR VS. EXTRA-ARTICULAR REPAIR
The two major techniques for repair of the cranial cruciate-deficient stifle are broadly classified into the extra-articular repair techniques and those involving an intra-articular reconstruction.
Intra-articular repair involves the use of autogenous tissue grafts or synthetic graft placed within the joint in a method approximating the natural course of the cranial cruciate. The cranial cruciate ligament is made up of two distinct bands of interweaving fibers; the anterior medial band (AMB) and the caudolateral part (CLP). The function of these two bands is to maintain tension against anterior drawer motion and internal rotation of the stifle during extension and flexion of the knee. Partial tears of the cruciate ligament are common and an understanding of the function of these two bands is paramount to proper diagnosis of partial tears. Both the AMB and CLP are tight with the knee in extension. With the knee in flexion, the CLP relaxes and the AMB maintains tension. Partial tears of the cruciate usually involve the AMB; I have seen only one partial tear which involved the CLP only. When there is a partial tear of the AMB, assessment of instability requires demonstration of drawer motion with the knee in partial flexion. Drawer motion will not be present in extension as the CLP is taut in extension and no drawer sign can be demonstrated. The drawer sign demonstrable in flexion will not be as pronounced as with a complete cruciate rupture and there will be a definite end-point to the drawer motion; typically only 5 mm or so of anterior drawer is evident. Lame dogs (particularly Rottweilers and Labradors where we see numerous cruciate ruptures) should always be palpated in flexion and extension, with sedation used if needed to overcome muscle tone.
An extra-articular repair with the stabilizing suture outside the joint, has become the technique of choice for many surgeons, regardless of dog body size, since results are predictably good. The drawback to extra-articular repair is that it relies on synthetic material which must be of sufficient strength to maintain joint stability during the early collagen cross-linking and stabilization phase of repair, which typically takes a minimum of 6 weeks. Extra-articular repair techniques, such as the Flo technique and DeAngelis-style suture placement, are described in numerous texts which should be consulted. I prefer to use monofilament suture, as problems are well-documented with multi-filament sutures such as Ethibond and Mersilene. The use of autoclaved Vetafil should be discouraged since the incidence of draining, fistulous tracts seems to be high.
Intra-articular repair techniques typically involve the use of an autogenous fascial graft placed through the joint to mimick the accurate anatomical placement of the cranial cruciate ligament. The classic Paatsama technique is the basis of most current modifications such as Arnoczky's over-the-top repair. Fascia lata, and bone-tendon-bone grafts are currently commonly used. Difficulty in proper tensioning of these grafts, graft failure, and destruction of the graft by the "hostile" joint environment in chronic cases is a drawback to intra-articular repair. The advantage of intra-articular repair is that it, theoretically, maintains an anatomical, tension-free range of motion in the knee throughout the full course of stifle flexion and extension. A new synthetic material made of Gore-Tex is currently available to veterinarians for intra-articular repair. This material and the procedure for implantation can be acquired by contacting WL Gore and Associates at 800-437-2771. Clinical trials have been done and results are encouraging, although there is a significant learning curve to obtain consistent results.
Our office will be closed the week of May 27th. Our receptionist will
be here to answer the phone and make appointments, or you may leave a message
on the recorder to schedule surgeries for the next week. I will return
in the office on June 3rd. Dr. Tangner in Oklahoma City has offered to
cover for us in emergency surgical situations. I hope this does not cause
an inconvenience to anyone.
With the advent of a new year, I would like to thank everyone for their support over the last two years, and wish you a happy, healthy 1996.
Many of the cases we have seen involve some sort of neoplastic lesion. Although some anti-cancer therapies are not available (e.g. radiation therapy) locally, or are not feasible, chemotherapy of selected tumors is often valuable in addition to, or in place of, surgical therapy. One of the more commonly recommended anti-cancer drugs is Adriamycin. The following information will hopefully be of use to you in your administration of this potent anti-neoplastic agent.
Butterfly and similar type catheters have proven unsatisfactory for Adriamycin administration in the dog. Since extravasation is potentially one of its most serious side effects, an indwelling plastic catheter (i.e., Sovereign or Gelco) should be used. Special attention should be paid to aseptic technique prior to IV catheterization of immunosuppressed patients. The goal of catheterization is a clean venipuncture; do not use a vein that has had a recent venipuncture or catheter. Since Adriamycin reacts with heparin and corticosteroids to form a precipitate, plain 0.9% NaCl should be used for catheter flushes.
The Adriamycin should be administered in a minimum of 2 cc/# of 0.9% NaCl over a 30 to 45 minute period. Occasional administration reactions in the dog include head shaking (i.e., ringing in the ears), mild anaphylaxis (i.e., swelling of eyelids and lips), urticaria, rarely acute severe anaphylaxis, and rarely nausea and vomiting. Anaphylaxis is managed by administration of corticosteroids, antihistamines, and fluid therapy; other reactions can usually be managed by decreasing the rate of drug administration. The chance of anaphylaxis increases slightly with subsequent administrations but is still probably under 10%. If anaphylaxis occurs, it will be during administration of the drug. Delayed anaphylaxis is rarely seen. The catheter should be thoroughly flushed prior to removal to prevent drawing residual Adriamycin through the subcutaneous tissue.
The recommended dosage of Adriamycin is 30 mg/m2 at three week intervals to a total cumulative dose of 150 mg/m2. To calculate the body surface area (m2 area), conversion tables are available in several veterinary textbooks (i.e., Ettinger).
Additional side effects of Adriamycin include diarrhea, hair loss, bone marrow suppression, and cardiac toxicity. Hair loss associated with AD is somewhat breed dependent. Dogs with continually growing hair coats seem to be the most severely affected. Hair growth will resume once the drug is discontinued, but it may be thinner, finer, and a different color. Shaved hair will regrow poorly until the drug is withdrawn. Gastrointestinal upset can occur in varying degrees, with the most severe symptoms usually seen in smaller patients. Problems begin 24-48 hours post-administration and usually last 24-48 hours. In most cases the side effects are self limiting and can be managed by dietary adjustments. Owners should be instructed to contact the clinic if the signs are severe or protracted. Myelosuppression following AD administration is not uncommon. The greatest WBC depression is seen at about ten days post treatment. Most animals will have bone marrow recovery by the time they re-present at three weeks, but a CBC should be done to rule out severe myelosuppression. A neutrophil count of less than 2,500 cells/ul necessitates drug withdrawal. In these patients, CBCs should be performed weekly until the neutrophil count again exceeds 2,500 and drug therapy can be resumed.
Trimethoprim sulfa should be given to animals whose neutrophil count is less than 2,00 cells/ul, or in any animal with signs of sepsis or local infection. Cardiomyopathy is a late occurring side effect of Adriamycin. At a total cumulative dose of 240 mg/m2 about 10-20% of dogs will develop cardiotoxicity. Although rare, cardiomyopathy can occur at total doses as low as 120 mg/m2. Pre-existing cardiac disease has not seemed to significantly increase the chances of cardiac toxicity. At the recommended dose, the risk of cardiac toxicity does not outweigh the potential therapeutic advantages.
If you have any further questions or problems, please do not hesitate to call Dr. Dean at (918) 665-0508.
NEW SERVICE AVAILABLE
We have recently purchased a fiberoptic endoscope in response to requests
for endoscopy in selected cases. If you have a case you feel would be a
candidate for endoscopy, please give us a call.