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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Anuria—lack of urine production
  • Oliguria—decreased urine production (<0.5 mL/kg/h, or <250 mL/h in a 500 kg horse)
  • Anuria or oliguria may be physiologic or pathologic
  • This chapter will focus on intrinsic renal failure causing anuria and oliguria

Pathophysiology!!navigator!!

N/A

Systems Affected!!navigator!!

Renal/urologic

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

Unknown

Geographic Distribution!!navigator!!

None

Signalment!!navigator!!

No age, sex, or breed predilection documented.

Signs!!navigator!!

  • No or insufficient urine production
  • Repeated posturing to urinate, with no urine production, in case of urinary tract obstruction
  • Abdominal distention in case of uroperitoneum
  • Edema when persistent anuria

Causes!!navigator!!

  • Physiologic oliguria—hyperosmolality; any disease process leading to renal hypoperfusion (e.g. dehydration, hypotension, low cardiac output)
  • Pathologic anuria/oliguria—intrinsic ARF; trauma to the lower urinary tract

Risk Factors!!navigator!!

  • Risk factors predisposing to ARF
  • For trauma to lower urogenital tract—birth trauma (e.g. dystocia) would increase the risk of urinary tract disruption and uroperitoneum in neonates and their dams; penile trauma is more common in breeding stallions

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Pathologic Anuria/Oliguria

  • Intrinsic AKI/ARF, terminal CKD, lower urinary tract disruption resulting in uroperitoneum, and urinary tract obstruction consequent to urolithiasis
  • Bladder displacement
  • Progressive abdominal distention should increase suspicion of uroperitoneum
  • Repeated posturing to urinate, with little urine passed, supports urinary tract obstruction

CBC/Biochemistry/Urinalysis!!navigator!!

  • Normal to high packed cell volume in most cases; mild to moderate anemia possible with terminal CKD
  • Moderate to severe increases in blood urea nitrogen (59–150 mg/dL; 18–54 mmol/L) and Cr (2.0–20 mg/dL; 177–1768 μmol/L)
  • Variable hyponatremia, hypochloremia, hyperkalemia, hypocalcemia, and hyperphosphatemia—hyperkalemia and hyperphosphatemia more common with intrinsic AKI/ARF; hyperkalemia most apparent with urinary tract disruption and development of uroperitoneum
  • Mild to moderate metabolic acidosis—dependent on the underlying disease process
  • Mild to moderate hyperglycemia—attributed to stress
  • USG—high (>1.035) with physiologic oliguria, low (<1.020) with oliguria due to intrinsic AKI/ARF; USG best assessed in urine collected during initial patient evaluation (before rehydration) or while the horse is not receiving fluids
  • Oliguria with intrinsic AKI/ARF may be accompanied by mild to moderate proteinuria, glucosuria, pigmenturia, and increased numbers of red blood cells and casts on sediment examination
  • Urine pH—normal to acidic, especially with concurrent depletion of body potassium stores

Other Laboratory Tests!!navigator!!

  • Fractional clearances (i.e. excretions) of electrolytes in cases of ARF/CKD
  • Increased urinary γ-glutamyltransferase to Cr ratio >25 in cases of ARF
  • Increased urine protein to Cr ratio in cases of CKD

Imaging!!navigator!!

Transabdominal and Transrectal Ultrasonography

  • Kidneys may be enlarged, with loss of detail of corticomedullary junction, in intrinsic AKI/ARF
  • Kidneys typically are reduced in size, with increased parenchymal echogenicity, in CKD
  • Accumulation of hypoechoic fluid in the peritoneal cavity in cases of uroperitoneum
  • Urinary calculi can be identified as hyperechoic structures associated with a shadow cone and distended proximal urinary tract

Urethroscopy/Cystoscopy

Endoscopy of the lower urinary tract is indicated when there is suspicion of lower urinary tract obstruction.

Diagnostic Procedures!!navigator!!

  • Abdominocentesis is indicated in cases of peritoneal effusion. Peritoneal Cr concentration over twice blood concentration in cases of uroperitoneum
  • Measurement of glomerular filtration rate and renal biopsies are indicated in case of CKD/chronic renal failure
  • Central venous pressure/arterial pressure measurements

Pathologic Findings!!navigator!!

See specific topics.

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • Treat anuria/oliguria as a medical emergency because persistent renal hypoperfusion may lead to ischemic AKI/ARF
  • If untreated, metabolic disturbances, most notably hyperkalemia, may lead to cardiac arrhythmias and death
  • Once the patient is stabilized (largely with supportive treatment in the form of IV fluid therapy), pursue further diagnostic evaluation to determine if surgical intervention (for correction of uroperitoneum or relief of obstruction) is needed
  • Proper recognition and treatment of all primary disease processes, usually on an inpatient basis for continuous fluid therapy, is warranted
  • Avoid nephrotoxic medications

Nursing Care!!navigator!!

  • Fluid therapy is a large part of supportive treatment
  • Peritoneal drainage and urinary catheterization to remove urine from the abdomen is part of the treatment of uroperitoneum

Activity!!navigator!!

Stall rest.

Client Education!!navigator!!

N/A

Surgical Considerations!!navigator!!

Surgical intervention is indicated for uroperitoneum and urolithiasis. See specific topics.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Fluid therapy to correct renal hypoperfusion—after initial measurement of body weight, correct estimated dehydration with isotonic (0.9%) saline or another potassium-poor electrolyte solution over 12–24 h; monitor closely for subcutaneous and pulmonary edema (i.e. increased respiratory rate and effort); conjunctival edema may develop rapidly in horses with intrinsic oliguric to anuric AKI/ARF; use maintenance fluid therapy judiciously in animals that are not clinically dehydrated; if hemorrhage is contributing to hypovolemia and renal hypoperfusion, initial treatment with hypertonic saline and/or a blood transfusion may have value
  • Severe hyperkalemia (>7.0 mEq/L) or cardiac arrhythmias—treat with agents that decrease serum potassium concentration (e.g. sodium bicarbonate (1–2 mEq/kg IV over 5–15 min)), or counteract the effects of hyperkalemia on cardiac conduction (e.g. calcium gluconate (0.5 mL/kg of a 10% solution by slow IV injection))
  • Furosemide—this diuretic may be administered 2 times (1–2 mg/kg IV or IM) at 1–2 h intervals; if effective, urination should be observed within 1 h after administration of the second dose; if ineffective, discontinue
  • Based on recent evidence in critically ill human patients the routine use of mannitol or dopamine in equine patients with oliguria is no longer recommended

Contraindications!!navigator!!

Avoid all nephrotoxic medications unless specifically indicated for the underlying disease process, and then modify dosage accordingly.

Precautions!!navigator!!

  • Monitor response to fluid therapy closely—as little as 40 mL/kg of IV fluids (20 L to a 500 kg horse) may produce pulmonary edema
  • Reassess dosage schedule of drugs eliminated by urinary excretion; consider discontinuing all nephrotoxic medications (especially gentamicin, tetracycline, and NSAIDs)

Possible Interactions!!navigator!!

Use of multiple anti-inflammatory drugs (e.g. corticosteroids and one or more NSAIDs) will have additive negative effects on renal blood flow; avoid combined administration in azotemic patients.

Alternative Drugs!!navigator!!

None

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Assess clinical status (emphasizing hydration), urine output, and body weight frequently for the first 3 days
  • Assess magnitude of azotemia and electrolyte and acid–basis status at least daily for the first 3 days of treatment
  • Consider placing a central venous line to maintain central venous pressure <8 cmH2O in more critical patients and neonates

Prevention/Avoidance!!navigator!!

See specific topics.

Possible Complications!!navigator!!

  • Severe hyperkalemia accompanied by cardiac arrhythmias and death
  • Pulmonary and peripheral edema; conjunctival edema may be dramatic

Expected Course and Prognosis!!navigator!!

Dependent on underlying cause. Poor prognosis if diuresis is not rapidly restored.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Colic; enterocolitis
  • Pleuritis; peritonitis; septicemia
  • Exhausted horse syndrome—multiorgan failure

Age-Related Factors!!navigator!!

Neonates afflicted with hypoxic–ischemic multiorgan damage or septicemia may be at increased risk of anuric/oliguric AKI/ARF.

Zoonotic Potential!!navigator!!

Leptospirosis has infectious and zoonotic potential; avoid direct contact with infective urine.

Pregnancy/Fertility/Breeding!!navigator!!

None

Synonyms!!navigator!!

None

Abbreviations!!navigator!!

  • AKI = acute kidney injury
  • ARF = acute renal failure
  • CKD = chronic kidney disease
  • Cr = creatinine
  • NSAID = nonsteroidal anti-inflammatory drug
  • USG = urinary specific gravity

Suggested Reading ⬆ ⬇

Bayly WM. Acute renal failure. In: Reed SM, Bayly WM, Sellon DC, eds. Equine Internal Medicine, 4e. St. Louis, MO: Elsevier, 2017:923–930.

Schott HC. Chronic kidney disease. In: Reed SM, Bayly WM, Sellon DC, eds. Equine Internal Medicine, 4e. St. Louis, MO: WB Saunders, 2017:930–946.

Author(s) ⬆

Author: Harold C. Schott II

Consulting Editor: Valérie Picandet