Page 463 - ONLINE PROCEEDING BOOK WSAVA 2017
P. 463

WSVA7-0549
HILL’S: NEPHROLOGY
CANINE AND FELINE NEPHROURETEROLITHIASIS
J. Bartges1
1The University of Georgia, Athens, GA, USA 30606
Objectives of presentation:
Following this presentation, the attendee should be able to
- describe role of nephroureterolithiasis with CKD
- outline diagnostic work-up for patients with nephroureterolithiasis
- describe complications associated with nephroureterolithaisis
- outline therapeutic approach to patients with nephroureterolithiasis
Introduction. Nephroureterolithiasis is being recognized more frequently; however, they account for < 2% of urolithiasis occurring in dogs and cats.(1) Many patients are asymptomatic and nephroureteroliths may not
be discovered until abdominal imaging is performed
for any reason. There appears to be an association
of nephroureterolithiasis with chronic kidney disease, especially in cats. Nephroureteroliths can lead to ureteral obstruction, deterioration of renal function, serve as a nidus for bacterial urinary tract infection, or cause hematuria or pain. Clinical signs, when present, include systemic signs associated with acute kidney injury (oftentimes associated with underlying chronic kidney disease), or vague signs such as abdominal pain, arched back, anorexia, or vomiting. Sometimes patients present for an abrupt change in behavior or
an acute onset of abdominal pain or vomiting when acute ureteral obstruction occurs. This may be mistaken for intervertebral disk disease or acute pancreatitis. Approximately 15% of cats with nephroureteroliths
had urocystoliths. When unilateral nephroureteroliths are present, they often occur in the larger and more functional kidney. Most (> 70%) of nephroureteroliths are composed of calcium oxalate, although struvite (particularly infection-induced) and other mineral types (such as urate and cysteine) do occur.
Treatment.(1) The decision to surgically treat nephroureteroliths can be dif cult to make. Not all nephroureteroliths require surgical treatment. In
one study, presence of nephroliths without ureteral obstruction was not associated with progression of chronic kidney disease. In another study, cats with ureteroliths that were managed surgically lived longer than cats with ureteroliths that were managed medically. If nephroureteroliths are composed of minerals amenable to medical dissolution (e.g. struvite, urate, and cysteine), then medical dissolution may be attempted. Indications
for surgical management of nephroureteroliths include ureteral obstruction, increase in urolith size and/or number despite appropriate medical treatment, recurrent or persistent urinary tract infection proven or presumed secondary to nephroureteroliths, compromise of renal function, recurrent or persistent clinical signs, or severe hematuria that is renal in origin.
Intervention. Surgical removal is not necessary for all upper urinary tract uroliths and may not be indicated
for relatively small, non-obstructive upper urinary tract uroliths as these may pass into the urinary bladder. It is unknown what a safe time period to allow for ureteroliths passing without resulting in irreversible renal damage. Renal function does not recover n dogs with unilateral ureteral ligation for 40 days. If a dog or cat is ill due
to ureteral obstruction, it is not appropriate to wait for the ureteroliths to pass or to medically manage them for a prolonged period of time if renal function is to be preserved. If bilateral upper urinary tract surgery
is required, the procedures should be staged with an approximate separation of 4 weeks in order to re- evaluate renal function and to allow recovery from the  rst procedure if possible. In general, the side with the most renal function should be operated  rst in order to preserve as much renal function as possible. Intervention is indicated if nephroliths are growing in size or number despite appropriate medical therapy or if ureteroliths are causing obstruction with presence of renal pelvic dilation of 5 mm>
Medical management. At present there is no means to medically dissolve calcium oxalate nephroliths. Infection- induced struvite, sterile struvite, urate, and cysteine uroliths may be dissolved by dietary modi cation and use of certain drugs. Medical dissolution therapy should not be attempted with ureteroliths unless urinary diversion (e.g. ureteral stent or subcutaneous bypass device)
is performed. Medical expulsion therapy may be tried
to facilitate passage of the ureteroliths into the urinary bladder. In human beings, alpha blocking agents have been shown to promote movement of ureteroliths into the bladder especially if the uroliths are in the distal
1/3 of the ureter; however, the effectiveness in dogs
and cats has not been evaluated. Glucagon has also been used to facilitate passage of ureteroliths after fragmentation by lithotripsy; however, it’s ef cacy and safety has not been reported in dogs and cats although it has been attempted. Alpha-blocking agents and anti- in ammatory drugs may facilitate passage with  uid therapy. Amitriptyline has been shown to relax ureteral smooth muscle and facilitate expulsion of ureteroliths in humans. Spontaneous passage of ureteroliths has been shown to occur. Ureteroliths have also been reported to move retrograde up to 4 cm in the ureter even back into
An Urban Experience
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