Page 1368 - Cote clinical veterinary advisor dogs and cats 4th

690 Nephrolithiasis

obstruction, renal failure (acute or chronic), determine contribution of each kidney • Patients with CKD should be fed a suitable
to global GFR
or recurrent urinary tract infections. ○ Excretory urogram (p. 1101) or CT to diet (p. 167).
VetBooks.ir Differential Diagnosis confirm urolith location in kidney Possible Complications
• Nephrolith may lodge in ureter, causing
• Radiopaque renal opacities
○ Nephrocalcinosis
likely when calculi shrink (e.g., medical
○ Radiopaque intestinal content TREATMENT obstructive nephropathy, which is particularly
○ Mineralized lymph nodes Treatment Overview dissolution, lithotripsy).
○ Mineralized adrenal glands Incidentally discovered nephroliths often do not • Surgical trauma may further damage renal
○ Neoplastic mineralization require therapeutic intervention. Nephroliths parenchyma.
○ Other ectopic mineralization may remain stationary, pass into the bladder, • Some medical conditions may be worsened
• Clinical signs or become lodged in the ureter and result in by calculolytic diets (pp. 1014, 1016, and
○ Urolithiasis (ureters, bladder, urethra) renal dysfunction. Urinary tract obstruction 1019).
○ Feline lower urinary tract signs/disease should be relieved and uremia addressed directly. • Recurrence rates are high, especially for
(FLUTS/D) Whenever possible, measures to dissolve or calcium oxalate nephroliths.
○ Pyelonephritis or cystitis prevent urolith growth are undertaken.
○ Acute kidney injury Recommended Monitoring
○ Overt CKD Acute General Treatment • Routine monitoring (pp. 1014, 1016, and
○ Urinary tract neoplasia • Complete urinary tract obstruction is rare, 1019).
○ Prostatic disease but when present, it requires interventional • Repeated abdominal ultrasound or excretory
○ Causes of hematuria (p. 1229) (radiological, surgical, endoscopic) treatment. urography (contrast is potentially nephro-
• Address renal failure, including electrolyte toxic) should be considered in patients with
Initial Database and acid-base disorders (pp. 23, 167, radiolucent stones.
• CBC: often unremarkable and 169).
○ Normocytic, normochromic, nonregenera- • Address pyelonephritis (p. 849). PROGNOSIS & OUTCOME
tive anemia (if overt CKD)
○ Leukocytosis ± left shift (if pyelone- Chronic Treatment • Depends on urolith composition, degree
phritis) • Medical dissolution is possible for some of obstruction, remaining renal function,
• Serum biochemical profile: often unremark- types of nephrolithiasis (pp. 1014, 1016, concurrent infection, and ability to identify
able, but depending on degree of renal and 1019). and treat underlying cause
dysfunction and/or urinary obstruction, • Invasive intervention is not routinely • Surgical intervention does not address causa-
may reveal required, and benefit must be carefully tion; recurrence rates are high.
○ Azotemia weighed against risk.
○ Hyperphosphatemia • Indications for surgery (nephrotomy, PEARLS & CONSIDERATIONS
○ Hypokalemia/hyperkalemia pyelolithotomy, or nephrectomy)
○ Metabolic acidosis ○ Complete obstruction to urine flow Comments
• Urinalysis: may be unremarkable or reveal ○ Recurrent infection (nephrolith may be • Small nephroliths can be incidental findings
hematuria, proteinuria, pyuria, bacteriuria, nidus) requiring no therapy.
crystalluria, and/or isosthenuric urine ○ Marked, persistent renal hematuria • Medical management of nephroliths mirrors
• Urine culture and sensitivity (C/S) to rule ○ Progressive nephrolith enlargement (despite medical management of cystoliths of identical
out infection medical management) accompanied by composition.
• Blood pressure to rule out hypertension reduction in renal function or in a solitary
associated with CKD functional kidney Prevention
• Abdominal radiography: depending on • Lithotripsy (extracorporeal shock wave, laser, • Promote water consumption.
urolith composition, radiopaque density or electrohydraulic) • Identify and address risk factors.
apparent in one or both renal pelvises ○ Results in fragmentation or crushing of
○ Radiopaque: calcium phosphate, calcium calculi; may require multiple treatments, Technician Tips
oxalate, struvite; small uroliths are difficult depending on calculi shape, size, location, Nephroliths can cause kidney pain; avoid
to detect radiographically. and type abdominal pressure when picking up animals
○ Radiolucent: urate, cystine ○ Indications similar to those for surgical with renal pain.
○ Concurrent ureteral, cystic, or urethral intervention
calculi are sometimes present. ○ Shock wave availability limited (e.g., in Client Education
○ Enlarged or atrophied kidneys United States: Universities of Tennessee Strict adherence to dietary recommendations
• Ultrasound is a sensitive means of detection and Pennsylvania, Purdue, Tufts, Animal is crucial.
but may overestimate nephrolith size (acous- Medical Center in New York City); can
tic shadowing in renal pelvis, concurrent cause renal damage SUGGESTED READING
pyelectasia or hydronephrosis) ○ Laser lithotripsy more readily available Ross SJ, et al: A case-control study of the effects of
(several large referral centers) but tech- nephrolithiasis in cats with chronic kidney disease.
Advanced or Confirmatory Testing nique best suited to larger animals J Am Vet Med Assoc 230:1854, 2007.
• If nephroliths are recovered, quantitative AUTHOR: Adam Mordecai, DVM, MS, DACVIM
urolith analysis and culture Nutrition/Diet EDITOR: Leah A. Cohn, DVM, PhD, DACVIM
• If definitive therapy is anticipated • Diets to support dissolution or prevention
○ Nuclear scintigraphic or CT assessment of nephroliths, depending on stone type
of glomerular filtration rate (GFR) to (pp. 1014, 1016, and 1019)

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