Weird Case Files with Dr. Amy: Sawyer
A generalist’s perspective on Detrusor-Urethral Dyssynergia, among other things…
by Amy Lloyd, VMD
Case Files is a new column where we examine weird, inscrutable and illuminating cases our doctors have encountered. Today, we take a look at Sawyer, a 7-year-old Lab suffering from bilateral hip dysplasia and Detrusor-Urethral Dyssynergia.
I first met Sawyer when he was a puppy, a little more than 7 years ago. He first presented to me at about 9 months of age, when his people adopted him from a previous owner who said she didn’t have the time and energy for a young Lab.
The previous owner had had him neutered, but his vaccine series had not been completed and there was no documented history of routine parasite prevention.
He presented for a first exam to establish him as a patient, finish his vaccines, and start preventives. The only problem reported by the owner was that Sawyer seemed lazy – he was either unwilling or unable to jump up on the bed or sofa to be with them.
Initial SOAP, 11/21/13
S: BAR, sweet.
O: weight= 62 lbs., T= 101.7, P= 100, R= 28
- EENT: Eyes – clear and bright; no discharge, blepharospasm or scleral injection. Ears – clean, no swelling or erythema. Mouth – mm pink/moist, CRT < 2sec, no tartar, gingiva healthy, no oral ulcers; full adult dentition, but a portion of the deciduous right maxillary 3rd incisor appeared to be retained and overlapping the permanent tooth; oral exam somewhat limited by movement of patient. Nose – no discharge. Throat – no cough on tracheal palpation.
- CV/Resp: no murmur or arrhythmia, pulses strong and synchronous. Eupneic, normal bronchovesicular sounds all fields.
- Abdomen: soft, non-painful; no fluid wave or organomegaly noted on palpation.
- LN: no peripheral lymphadenopathy
- Integument: no evidence of ectoparasites; healthy coat, no skin lesions.
- M/S: lean, very poor muscle mass in hind end. Sits abnormally, with legs tucked backwards at the stifle, so he is sitting on his stifles with his lower legs and feet behind him. In a standing position, hocks are very straight. Both hind legs are weak, and his hind limb gait is stiff bilaterally. Very decreased range of motion both hips, and left hip palpably subluxated when checking range of motion.
- Neuro: Mentation appropriate, no ataxia, cranial nerve responses intact; proprioception difficult to assess – slightly slow in both hind limbs, but suspect more secondary to orthopedic abnormalities and pain than actual neurologic dysfunction.
- U/G/Anus: external MN genitalia normal in appearance, anus normal in appearance, normal anal tone, rectal not performed.
A: Retained deciduous incisor vs. fractured or malformed tooth
Decreased range of motion hips, bilateral, with poor muscle mass, stiff gait and palpable subluxation of left hip (Ddx: strong suspicion for hip dysplasia considering age and breed)
Slightly decreased CP’s of uncertain significance (r/o secondary to severe orthopedic abnormality vs. neurologic/spinal disease)
P: DHPP 1 of 2 (since he was only 12 weeks old at the time of his last DHPP)
Lepto 1 of 2 (since he hadn’t started it with the previous owner)
4DX: negative x 4
Fecal sent to lab
Discussed hip radiographs. Recommend do with sedation and can check tooth at the same time, as Sawyer is very busy for oral exam!
Discussed hip dysplasia at length, and suggested owner make appointment for orthopedic consult to be done after radiographs.
3 weeks later, we finished Sawyer’s vaccine series and did pre-op/pre-med bloodwork and urinalysis before starting an NSAID until Sawyer could have definitive treatment for his orthopedic disease.
The owners had also reported some possible PU/PD. Lab work was essentially non-remarkable, Sawyer was started on Previcox, and appointments were made for radiographs and dental evaluation under anesthesia, followed by an orthopedic evaluation with a local specialist who was capable of performing either total hip replacement or femoral head and neck osteotomy.
Radiographs and dental evaluation 12/27/13
Once Sawyer was fully sedated, it was obvious that his adult right maxillary 3rd incisor was fractured longitudinally, and it was very soft, friable and diseased. The fracture extended into the root of the tooth as well as the crown.
The tooth was surgically extracted and then hip radiographs were performed. The radiographs confirmed severe bilateral hip dysplasia with extremely shallow acetabula, bilateral subluxation, and bilateral remodeling of the femoral heads. By far, to this day, Sawyer’s hip dysplasia was the worst I have personally seen.
Both FHO and total hip replacement were discussed with the owners, and the patient was continued on Previcox until his appointment with the orthopedic surgeon about 10 days later.
I had a long referral relationship with the orthopedic surgeon and called her to discuss the case in advance, including describing the way Sawyer sat, and discussing my knowledge of the owners, their expectations, and their level of commitment to their pets.
I remember the surgeon specifically asking me if I thought they wanted him to be perfect, or if they just wanted him to be happy and functional, and me saying that I knew these owners well enough to know that happy was more important than perfect.
If the owners decided on total hip replacement, the surgery would have to wait until Sawyer was fully grown. If they elected FHO, the surgeon could do the surgery now, at 10 months of age, and Sawyer could stop compensating, start feeling comfortable and gain some strength and muscle mass.
The final decision, which all of us agreed was best for this patient, was bilateral FHO. When Sawyer’s incisions were completely healed and he was released by the surgeon, he started rehabilitation, including hydrotherapy and stretching exercises.
Over a relatively short period of time, he was able to run and jump, and he learned to sit like a “normal” dog. His owners had a second home on a lake, and Sawyer loved to jet ski and jump into the lake off the dock, as you can see below, which never fails to make me smile when I think of how lucky he was to find THIS particular family, who gave him everything he needed to live a happy life!
One year later
When Sawyer was about 2, his story started to get even more interesting. When he was at the lake with his family, sometimes he would develop severe dysuria and what seemed to be a functional urethral obstruction. They would take him to the local ER, no cause would be found, he would be catheterized easily, his bladder emptied, and he would be sent home.
He had also had a similar episode following his FHO surgery, but at the time, it was thought to be because of post-op pain or secondary to medications. The owners had often noted that he would dribble urine a little, or that it would take him longer to urinate than other dogs they had, but they accepted that he was different from other dogs, and they didn’t worry until he was in pain.
When I examined him during this period, he had a palpably enlarged bladder, had had a few episodes of needing to be catheterized, and had developed a urinary tract infection at one point as well.
He was initially sent for ultrasound to rule out any structural abnormality. When nothing was found, and the episodes of dysuria continued, I started to discuss detrusor-urethral dyssynergia with the owners, although I had never seen it before.
We did medication trials of prazosin first, which did not help, followed by tamsulosin, which did help, but not enough. At that point, not feeling comfortable with any further trial-and-error, I referred them to Penn Vet, my go-to for anything that I think is particularly strange.
At Penn, he had bloodwork, urinalysis, urine culture, a focal urinary ultrasound, and a neurology consult. Two days after that, he had a cystourethrogram and cystourethroscopy. No abnormalities were found, and he was diagnosed with idiopathic detrusor-urethral dyssynergia.
Diazepam was added to the tamsulosin, and when he was still moderately symptomatic, bethanechol was added after that. He has been on tamsulosin q 24 hrs, bethanechol q 12 hrs and diazepam q 8 hrs since 2016.
He gets regular bloodwork and urine monitoring, and has had urinary tract infections secondary to not completely emptying this bladder…and he still has a great life! Like I said, he has some pretty special owners!
In almost 23 years of practice, I have never seen another dog quite like Sawyer, and I am grateful for all he has taught me, and for the fact that he put idiopathic detrusor-urethral dyssynergia on my radar, and now I can share that knowledge with others who have not been lucky enough to meet Sawyer.
Before him, I had only seen disorders of micturition secondary to cauda equina injury, IVDD with or without surgery, or atonic bladder from over-stretching after urethral obstruction.
Urination is initiated under conscious control, based on nociceptive sensors that detect stretch in the bladder sending sensory information through their associated afferent nerves to the brain, and voiding begins under what is most commonly voluntary control. For voiding to occur, simultaneous contraction of some muscles and relaxation of others must follow.
Detrusor-urethral dyssynergia, also known as reflex dyssynergia, is a disorder of the voiding phase of micturition in which relaxation of the urethral sphincter may be absent or incomplete. The bladder detrusor muscle reflex may be initiated, then immediately followed by urethral sphincter contraction/spasm, resulting in functional urethral obstruction.
Normal initiation and completion of the voiding phase of micturition (i.e., fully emptying the bladder) involves coordination between contraction of the detrusor muscle of the bladder and relaxation of the urethral sphincter, which requires both stimulation of parasympathetic innervation and inhibition of sympathetic innervation at the same time.
In patients with detrusor-urethral dyssynergia, urinary voiding is initiated normally, but the urethral sphincter contracts involuntarily, interrupting the flow of urine, and causing urinary retention due to functional outflow resistance. The result is incomplete emptying of the urinary bladder, and pain for the patient as they strain against a functional obstruction.
The syndrome is considered to be idiopathic, but it may involve a loss of inhibitory signal to the pudendal and hypogastric nerves secondary to lesions in the reticulospinal tract, Onuf’s nucleus (a distinct group of neurons in the sacral spinal cord), or the caudal mesenteric ganglion.
Sawyer’s case of Detrusor-Urethral Dyssynergia
Patients with detrusor-urethral dyssynergia usually have a history of starting to urinate, then developing a thin stream, intermittent stream, or no stream at all.
When I have watched Sawyer urinate, you can see his abdominal muscles straining to help him to urinate, but his stream is variable, and his family reports that some days he is better than others. As it has been with Sawyer, it is typically easy to pass a urinary catheter in these patients.
Because they do not completely empty their bladder, these patients can also develop overflow incontinence periodically, and Sawyer’s owners do report that sometimes he leaks or dribbles urine. While the syndrome is uncommon, it is most commonly reported in male, large to giant breed dogs of varying ages.
While no neurologic lesions for Sawyer’s clinical signs were identified when he was at Penn, the neurologist did report that occasional muscle spasms were noted in Sawyer’s right quadriceps and cranial tibial muscles, and that hopping on his hind limbs was slightly decreased bilaterally.
I do wonder if, along with his severe hip dysplasia, there could also be lumbosacral stenosis or another abnormality, either an inherited defect or an abnormality caused by the compensatory posture Sawyer adopted during his first 10 months of life because of his severe hip dysplasia, that might have led to some nerve impingement, and the scientist in me would love for him to have an MRI, although it would not change Sawyer’s ability to urinate, or his comfort level.
The peripheral nerves involved in normal micturition, which are (1) sacral parasympathetic nerves (pelvic nerves, arising from S2 spinal cord segments), (2) thoracolumbar sympathetic (hypogastric nerves, arising from L1-4 spinal cord segments), and (3) sacral somatic nerves (pudendal nerves, arising from S1-2 spinal cord segments) arise from the caudal spine.
With a history of such severe hip dysplasia, it seems possible that caudal spinal stenosis could be more likely than it would be in another dog. Neurogenic bladder dysfunction has been reported in humans with spinal stenosis, as well as with acute and chronic cauda equina syndrome.
Regardless of potential cause, medical management in these dogs includes a smooth muscle relaxant (phenoxybenzamine, prazosin or tamsulosin), a skeletal muscle relaxant (typically diazepam), and sometimes bethanechol, which stimulates parasympathetic cholinergic receptors to elicit contraction of the detrusor muscle of the urinary bladder.
My favorite thing about Sawyer, though, is that after 7 years and all the things I and other veterinarians have done to him, he is still the happiest dog I know, always excited to see me, and always looking for treats! I am so grateful that I still get to see him as an IndeVet!
He recently came to see me at one of our partner practices for routine lab work to continue his medications. Since he was used to seeing me in my former mobile clinic and he was not used to seeing me in a mask, at first he didn’t recognize me. When he heard my voice, he started running around the room, running through my legs, and looking for treats 😊
These are the days that I know I am blessed and lucky to do this job!
Amy Lloyd, VMD, is an area medical director for IndeVets.