38. Urolithiasis. Disorders of the urination Flashcards
Causes of urolithiasis (Crytals in the urine sediment)?
Causes Of Urolithiasis
CRYSTALS IN THE URINE SEDIMENT
Microscopic alterations; Some crystals form uroliths whilst others
dissolve
If there are visible stones in the UT, their composition cannot be
diagnosed based on crystals found in the sediment or in the urine.
Cysteine & urate crystals may warrant further workup
Sediment seen during imaging can be organic material – Blood; Pus;
Lipid
Pathogenesis?
PATHOGENESIS
Caused by an ↑ of supersaturated urine concentration
§ ↑ Protein & mineral-containing feed; ↑ Bacterial
production of NH4 of PO4 ions; ↓ Water intake; ↓ Tubular
resorption
§ Nidus (crystallisation centre) formation – May be organic
or inorganic
§ Urine stasis in the bladder
§ Ø Crystallisation inhibitors (Citrates; Glycosaminoglycans;
Pyrophosphates)
§ Always secondary to other diseases or problems: UTI;
Hepatopathy; Metabolic disease; Genetic disease
Occurrence: 90-95% in the urinary bladder
§ Struvite
§ Calcium oxalate
Clinical signs?
CLINICAL SIGNS
Dependent on the number, types & location of stones
§ Urinary bladder: Signs of cystitis;
§ Male dogs: Urethral obstruction; Postrenal uraemia; AKI
§ Ureter: Ø CSx; Pain; Haematuria; Hydronephrosis
§ Kidney: Ø CSx; Haematuria; Pyelonephritis; CRF in
bilateral cases
Struvite?
STRUVITE
40-60% of all uroliths; Alkaline/neutral urine
Predisposed: Females > Males; Dachshund; Poodle; Mini-schnauzer
Dog
Usually caused by UTI
Urease (from Staphylococcus/Proteus spp.) → Alkaline urine →
↑ NH4 concentration
Cat: Cases are usually sterile
Calcium oxolate?
CALCIUM OXALATE
~15-50% of all uroliths; ↑ in frequency of cases; Acidic urine
Acidic urine: Hypercalciuria;
↓ Urine citrate concentration (which acts as a crystallisation
inhibitor); ↑ Oxalate
Predisposed: Poodle; Mini-schnauzer; Yorkshire terrier
Urate?
URATE
Ammonium acid urate
§ ↑ Urate in urine: Dalmatian; English bulldog
§ ↑ Ammonium & urate in urine: Dogs with hepatic
insufficiency (PSS/Cirrhosis); UTI
§ ↓ Glycosaminoglycans in the urine
Cysteine?
CYSTEINE
Cystinuria: Inherited disorder of renal tubular transport + acidic urine Predisposed: Males; Middle aged dogs; Siamese cats
Diagnosis of urolithiasis?
Diagnosis of Urolithiasis
§ Radiography (contrast)
§ US; Stone analysis
§ Bacterial culture
§ Re-evaluation of patients
Treatment of urolithiasis?
Treatment Of Urolithiasis
Emergency urethral obstruction:
§ Catheterisation
§ Decompression of bladder
§ Treatment of AKI & its consequences
§ Surgical removal
§ Urohydropropulsion
§ Treat UTI
Diuresis induction
Treatment of struvite, calcium oxolate, urate and cysteine?
STRUVITE
§ Diet: ↓ Protein, Ca, Mg & P; ↑ Dietary salt for dissolution
§ If UTI is confirmed → Abx; Acidifier: NH4Cl/Methionine
§ Cats require life-long dietary prevention
CALCIUM OXALATE
§ Surgery is required (Ø Medical management available)
§ Diet: ↓ Protein; ↓ Nucleic acids; ↑ Dietary salt for
dissolution
§ Potassium citrate; Avoid excess alkalisation
URATE
Ø Associated with hepatic insufficiency
§ Diet: ↓ Purine; ↓ Nucleic acids; ↓ Added salts
§ Urine alkalisation; Xanthine oxidase; UTI treatment
CYSTEINE
§ Diet: ↓ Protein; ↓ Sodium (salt); Methionine for dissolution
& prevention
§ Urine alkalisation
§ Thiol-containing drugs: D-penicillamine/MGP/N-glycine
