Ureteral and urethral obstruction Flashcards
What can cause ureteral obstruction in cats
ureterolithiasis, ureteral strictures, infection, dried solidified blood calculi, iatrogenic ureteral ligation, ureteral ectopia, retoperitoneal fibrosis after renal transplantation and neoplasia
What are the most common stones in cats?
Calcium oxalate
Persians and Himalayans pre-disposed to these
If there is an obstruction but no ultrasonographic or radiographic mineralisation, what should you consider?
Strictures
Blood calculi
What drugs can be part of medical management of ureteral obstruction?
Mannitol - not if oliguric
Prazosin - Alpha‐1 antagonist - ureteral relaxation
Frusemide
Amlodipine from smooth muscle relaxation - slow onset of action
How does extra corporeal shockwave lithotripsy therapy work?
consists of the generation of high-energy shockwaves by a lithotripter that are transmitted to the patient and allow fragmentation of uroliths
Can cause damage to renal parenchyma/ vascular endothelium/ adjacent tissues
Short-term complications are uncommon and often self-limiting and may include cutaneous bruising, renal hematoma, hematuria, cardiac arrhythmias, and pancreatitis.
When is ECSL recommended?
problematic nephroliths and ureteroliths measuring less than or equal to 1.5 cm in diameter in dogs.
In cases of obstructive ureteroliths, the obstruction must be relieved via ureteral stenting before performing ESWL in an effort to minimize loss of renal function
85% success rate
Not in cats due to fragments causing issues in tiny ureters
What non-invasive methods of cystolith removal are there?
voiding urohydropropulsion, cystoscopic-guided basket retrieval, cystoscopic-guided laser lithotripsy, and percutaneous cystolithotomy
Can all potentially cause bladder rupture so must have a negative urine culture first
What is cystoscopic guided basket retrieval?
can be used in dogs and female cats. In this technique, basket retrieval devices are used to grasp stones that are too big to be expelled via voiding urohydropropulsion but that are smaller than the urethral diameter. This technique is also commonly used following laser lithotripsy
Not recommended when there are lots of stones as requires repeated entry of the basket along the urethra which causes damage
What is laser lithotripsy?
transurethral cystoscopic evaluation of the lower urinary tract followed by intracorporeal laser lithotripsy in which uroliths are fragmented into smaller pieces and removed via voiding urohydropropulsion and/or basket retrieval. This treatment modality is indicated in dogs and female cats. It can be used to fragment uroliths of any type located in the urinary bladder or urethra
What medications can be used for medical treatment of urethral stones?
Amitriptyline - potent relaxant of urinary smooth muscle Phenoxybenzamine Prazosin Metoclop Cisapride
Also thoughts about glucagon infusions, NSAIDs or steroids to decrease oedema, Ca channel blockers used in humans
How good is ureteral obstruction recovery?
Inversely proportional to duration of obstruction
What are the common causes of urethral obstruction?
Approx 50% idiopathic, 30 urolithiasis, 18% urethal plugs
What is the possible stress cause of FIC?
Related to imbalance between sympathetic nervous system and the hypothalamic pituitary adrenal axis
Leads to impared blood flow and inflammatory mediators which cause oedema, smooth muscle spasm, pain
Pain can lead to escalation of smooth muscle dysfunction and urethral inflammation
What are some predisposing factors of blocked bladders/ FIC
body weight, inactivity, indoor, stress, male, edigree, longhair possibly, number of household cats
What causes post obstructive diuresis?
ADH resistance osmotic diuresis tubulr epithelial dysfunction medulary washout Increased natriuretic factors
