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Other Names: Kidney Stones, Urinary Calculi

Urolithiasis is an acquired degenerative kidney disease that occurs sporadically in chickens worldwide.It is characterized by focal mineralization of the kidneys and progressive obstruction of the ureters by uroliths (kidney stones). A normal, healthy hen's kidneys appear symmetrical in appearance, in shape, color, and weight. When hens develop kidney stones, if they get large enough or when large amounts accumulate, it can result in a blockage of the ureter that will cause the kidney tissue to atrophy; this can occur in one or both kidneys. As long as at least one third of the combined mass of a hen's kidneys are functional, she will still survive and continue to lay eggs. If kidney stones form and cause a blockage in both kidneys, it will lead to fatal renal damage which manifests as visceral gout (visceral urate deposition), followed by death.

The most common causes for previous documented outbreaks of urolithiasis in laying hens have been related to improperly mixed feed, feeding young chicks and pullets feed that is intended for egg laying hens, and water deprivation. There has also been suggested involvement of the nephropathogenic Infectious Bronchitis Virus (IBV).

Clinical Signs

Pale comb and wattles
Weight loss
Reduced muscle mass
Decreased egg production
Sudden death


  • History
  • Clinical signs
  • Urinalysis
  • Blood tests
  • Necropsy
  • Histopathology


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Apple cider vinegarAdd 1 tablespoon of apple cider vinegar to each gallon of fresh water (if hard water, add 2 tablespoons of vinegar per gallon of water), to aid in dissolving the stonesG Damerow 2015



  • Adding apple cider vinegar to the drinking water sporadically (1 tablespoon of apple cider vinegar to each gallon of fresh water. If hard water, add 2 tablespoons of vinegar per gallon of water)
  • Not feeding chickens feed intended for egg laying hens before start to lay eggs
  • Always providing chickens with multiple sources of fresh, clean water.
  • In the winter, providing a heated water source so that water does not freeze over.
  • Providing extra water during hot weather.
  • Biosecurity procedures to minimize risk of Infectious Bronchitis Virus.
  • Purchase quality poultry feed from a reputable feed manufacturer.

Scientific References

Age Range

Most frequently affects laying pullets and hens

Risk Factors

  • History of infectious bronchitis virus
  • Feeding chickens feed intended for egg laying hens before they start laying eggs or to roosters
  • Receiving excess dietary calcium, particularly if combined with low available dietary phosphorus.
  • Water deprivation
  • Mycotoxin contaminated feed
  • Gizzard erosions

Also Consider