Ureterolith

From Dog
(Redirected from Ureterolithiasis)

Ureteroliths are a ureteral disease of dogs characterized by urinary crystals (uroliths) located within the urinary system between the renal pelvis and urinary bladder.

Ureteroliths are composed of similar minerals as those located elsewhere within the urinary system, but their location within the ureter distinguishes them from uroliths and nephroliths.

However, it is not uncommon for dogs to have nephrolithiasis, ureterolithiasis and urolithiasis[1]. Bilateral ureteroliths also occur but are more rare.

These crystals frequently cause unilateral ureteral obstruction, resulting in retrograde increases in intraureteral pressure[2] with consequent hydroureter, acute renal injury, nephromegaly and death of the affected kidney[3].

Types of ureteroliths include:

  • Calcium oxalate (most common)[4]
  • Struvite
  • Calcium phosphate
  • Struvite, calcium phosphate and calcium oxalate aggregates[5]

Clinical signs are variable, but consistent symptoms include acute abdominal pain, vomiting and depression.

Blood tests may reveal azotemia, hyperkalemia and leucocytosis.

Diagnosis is based on presenting clinical signs, blood tests, abdominal radiographic evidence of mineral deposits within the ureter(s) and excretory urography[6].

A differential diagnosis would include ectopic ureter[7], congenital ureteral stenosis[8], hydronephrosis, ureteral adenocarcinoma and renal parasites (e.g. Dioctophyme renale, Pearsonema plica and Schistosoma japonicum).

Ureteroliths are initially managed medically with intravenous fluid therapy, use of diuretics such as mannitol and prazosin or tamsulosin, but in the majority of cases, surgical intervention is indicated because the time required will result in excessive kidney damage.

Many canine patients have concurrent cystitis and broad-spectrum antimicrobials are also indicated[9].

Surgical intervention depends on financial constraints and many are managed with ureterectomy or neoureterocystostomy via exploratory laparotomy. Due to the negative effects of urine on wound healing[10] and the risk of uroabdomen, alternative methods of therapy should be considered such as the placing of ureteral stents[11], extracorporeal shock wave lithotripsy[12] or subcutaneous ureteral bypass[13].

Placement of double-pigtail ureteral stents could obviate complications associated with ureterectomy such as leakage, structure or re-obstruction. Stents are placed via endoscopy, interventional fluoroscopy or laparotomy. Complications of this procedure include proliferative fibrosis at the ureterovesicular junction, cystitis, dysuria, stent migration and stent occlusion.

Serial monitoring of individual cases is recommended in uncomplicated cases, using diagnostic imaging, hematological testing and treatment with furosemide and intravenous fluids.

Spontaneous retrograde movement of these ureteroliths may occur, with movement anteriorly back into the renal pelvis or passing into the urinary bladder, obviating the need for surgical intervention[14].

Complications such as ureteral stricture, ureteral stenosis and chronic renal disease are possible in recurrent cases.

References

  1. Houston DM et al (2012) 2,8-dihydroxyadenine uroliths in a dog. J Am Vet Med Assoc 241(10):1348-1352
  2. Biancani P et al (1976) Time course of ureteral changes with obstruction. Am J Physiol 231:393–398
  3. Mayhew PD et al (2013) Experimental and Clinical Evaluation of Transperitoneal Laparoscopic Ureteronephrectomy in Dogs. Vet Surg Feb 1
  4. Low WW et al (2010) Evaluation of trends in urolith composition and characteristics of dogs with urolithiasis: 25,499 cases (1985-2006). J Am Vet Med Assoc 236:193-200
  5. Snyder DM et al (2005) Diagnosis and surgical management of ureteral calculi in dogs: 16 cases (1990-2003). N Z Vet J 53(1):19-25
  6. Secrest S et al (2013) Effects of furosemide on ureteral diameter and attenuation using computed tomographic excretory urography in normal dogs. Vet Radiol Ultrasound 54(1):17-24
  7. Anders KJ et al (2012) Ectopic ureters in male dogs: review of 16 clinical cases (1999-2007). J Am Anim Hosp Assoc 48(6):390-8
  8. Lam NK et al (2012) Endoscopic placement of ureteral stents for treatment of congenital bilateral ureteral stenosis in a dog. J Am Vet Med Assoc 240(8):983-990
  9. Kyles AE et al (2005) Management and outcome of cats with ureteral calculi: 153 cases (1984-2002). J Am Vet Med Assoc 226:937-944
  10. Adin CA & Scansen BA (2011) Complications of upper urinary tract surgery in companion animals. Vet Clin North Am Small Anim Pract 41(5):869-888
  11. Fu WJ et al (2012) Comparison of a biodegradable ureteral stent versus the traditional double-J stent for the treatment of ureteral injury: an experimental study. Biomed Mater 7(6):065002
  12. Adams LG (2013) Nephroliths and ureteroliths: a new stone age. N Z Vet J Feb 13
  13. Berent AC (2011) Ureteral obstructions in dogs and cats: a review of traditional and new interventional diagnostic and therapeutic options. J Vet Emerg Crit Care 21:86-103
  14. Dalby AM et al (2006) Spontaneous retrograde movement of ureteroliths in two dogs and five cats. J Am Vet Med Assoc 229:1118-1121